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Author: CHISEN Battery Team

OPzV2-2500 2V2500Ah UPS Battery: Complete Buyer Guide for Data Centres and Telecom
Answer First

The OPzV2-2500 is a 2 V, 2,500 Ah tubular gel battery for data-centre UPS cabinets and telecom power plants. Its published envelope is 487 × 212 × 807 mm at 181 kg, the maximum charge current is 500 A, internal resistance about 0.30 mΩ at 25 °C, and design float life 20+ years @20 °C. On the 24-cell series string used for a 48 V bus, that cell gives 48.00 V nominal, a 53.52 V float bus, 7.20 mΩ of string resistance and 120,000 Wh of nominal energy.

Three published figures settle the comparison against flooded tubular or 12 V VRLA: the 20+ years @20 °C float life, the −3 mV/°C/cell compensation, and the 181 kg cell weight that sets the floor loading and cabinet layout. The 2.35 V equalise setpoint matters too, because it lets a maintenance team recover capacity in situ.

Full specifications sit on the OPzV2-2500 product page, and the wider model range on the OPzV tubular gel battery range. Three checks decide whether a shipment is usable: the case footprint against the cabinet drawing, the terminal torque, and the capacity test at the 10-hour rate to 1.80 Vpc.

Key Takeaways

Published output: 2 V nominal, 2,500 Ah at C10 to 1.80 Vpc, in a 487 × 212 × 807 mm case weighing 181 kg (Datasheet).
Charging envelope: maximum charge current 500 A, float 2.23 V and equalise 2.35 V per cell at 25 °C, compensation −3 mV/°C/cell (Datasheet).
Service life: 20+ years @20 °C design float life applies to the tubular OPzV2 class, never to a 12 V VRLA cell (Datasheet).
48 V string arithmetic: 24 cells give 48.00 V nominal, a 53.52 V float bus, 7.20 mΩ of string resistance and 120,000 Wh (Arithmetic).
Cabinet reality: 24 × 181 kg = 4,344 kg of battery mass per string, against 24 × 145 kg = 3,480 kg for the next size down (Arithmetic).
Acceptance on delivery: verify the case footprint, the M8 female copper insert terminals at 10–12 N·m, and capacity at the 10-hour rate to 1.80 Vpc.

§1 — OPzV2-2500 Quick Specifications

Every figure below comes from the manufacturer datasheet for the OPzV2-2500; nothing has been rounded by a distributor or interpolated from a neighbouring cell size.

Parameter	Value	Source
Nominal voltage	2 V	Datasheet
Capacity @ C10 (1.80 Vpc)	2,500 Ah	Datasheet
Case dimensions (L×W×H)	487 × 212 × 807 mm	Datasheet
Weight	181 kg	Datasheet
Maximum charge current	500 A	Datasheet
Float voltage	2.23 V @25 °C	Datasheet
Equalise voltage	2.35 V @25 °C	Datasheet
Temperature compensation	−3 mV/°C/cell	Datasheet
Internal resistance	~0.30 mΩ @25 °C	Datasheet
Design float life	20+ years @20 °C	Datasheet
Terminal	Female Copper Insert M8, 10–12 N·m	Datasheet

The 500 A maximum is a per-cell rating, so because every cell in a series string carries the same current, 500 A is also the ceiling for the finished 48 V string. Float and equalise are quoted at 25 °C.

§2 — The Pain: A 24-Cell String Is a Structural, Thermal and Logistics Problem

Most battery problems reaching a purchasing desk are specification problems, not chemistry problems: the cell ordered is not the cell drawn, the cabinet was designed around a different footprint, or the shipment was accepted on visual inspection and only measured months later.

The physical constraint is straightforward. A 24-cell string weighs 4,344 kg before the enclosure and the links, and that mass has to sit on the raised floor of a data hall or the plinth of a telecom power room. A 181 kg cell also cannot be carried up a stairwell by two technicians, so unloading and handling equipment belong in the procurement decision.

The thermal constraint is subtler. With −3 mV/°C/cell compensation, a room held at 20 °C floats each cell roughly 0.015 V lower than the 25 °C reference. Ventilation, aisle clearance and setpoint discipline are therefore part of the battery specification.

§3 — The Choice: Tubular Gel Against Flooded Tubular and 12 V VRLA

Three constructions are normally shortlisted for this duty, and the OPzV2-2500 belongs to the tubular gel branch.

Tubular gel (OPzV2). A gel electrolyte in a rigid case with tubular plates. It needs no spilling electrolyte, so it installs in a general equipment room rather than a battery room ventilated for acid mist, and it carries the 20+ years @20 °C design float life of the tubular class.

Flooded tubular (OPzS2). The same tubular plate architecture with liquid sulphuric acid, the traditional choice where electrolyte addition and specific-gravity checks are routine. It requires a ventilated enclosure and must be commissioned with electrolyte first.

12 V VRLA (6-DZF, 6-DMF, 6-EVF). A sealed block that is simple to ship and install, but its design float life is 2–5 years, not 20+ years — and that published lifetime decides what a 20-year site pays per year of service.

On a 48 V bus a 12 V block needs 4 units where a 2 V cell needs 24, and it adds connector resistance the 2 V architecture does not have. A European gel-brand benchmark and a market-priced industrial supplier are compared on published data, not on the label.

§4 — The Framework: A Five-Step Specification Method

A team that follows the same five steps for every candidate cell removes most specification risk before the purchase order is raised.

Step 1 — Fix the duty and the bus. Record the load, the autonomy in minutes, the generator behaviour and the DC bus voltage. A 48 V bus fixes the string at 24 cells of 2 V.

Step 2 — Lay out the string arithmetic on paper. For the OPzV2-2500 at 24 cells in series:

Nominal bus: 24 × 2.00 V = 48.00 V
Float bus: 24 × 2.23 V = 53.52 V
Equalise bus: 24 × 2.35 V = 56.40 V
Nominal energy: 48.00 V × 2,500 Ah = 120,000 Wh
String mass: 24 × 181 kg = 4,344 kg
String resistance: 24 × 0.30 mΩ = 7.20 mΩ

Step 3 — Set the thermal and control parameters. Fix the room temperature, apply the −3 mV/°C/cell compensation, and treat float 2.23 V and equalise 2.35 V per cell at 25 °C as the reference points. Confirm the charger holds the 56.40 V equalise bus within the 500 A cell limit.

Step 4 — Solve the mechanical and logistics questions. Check 487 × 212 × 807 mm against the cabinet drawing, confirm the M8 female copper insert terminals and the 10–12 N·m torque, and plan the route for a 181 kg cell from the container to the plinth.

Step 5 — Write the acceptance test into the contract. A 10-hour discharge to 1.80 Vpc at 250 A is the natural check on a 2,500 Ah cell, since 2,500 Ah ÷ 10 h = 250 A. Pair it with a float-voltage check and a torque record, and acceptance becomes objective.

§5 — OPzV2-2500 Against the Rest of the Tubular Gel Range

Sizing decisions are easier when the OPzV2-2500 is read against the models that bracket it, because the range moves in predictable steps. The table lists published datasheet values only.

Model	Ah @ C10	L×W×H mm	Weight	Max charge current	Internal resistance	Design float life
OPzV2-200	200	103 × 206 × 390	17.0 kg	40 A	~1.0 mΩ @25 °C	20+ years @20 °C
OPzV2-500	500	166 × 206 × 506	36.3 kg	100 A	~0.56 mΩ @25 °C	20+ years @20 °C
OPzV2-1000	1000	233 × 210 × 681	73.2 kg	200 A	~0.50 mΩ @25 °C	20+ years @20 °C
OPzV2-1200	1200	275 × 210 × 681	84 kg	240 A	~0.46 mΩ @25 °C	20+ years @20 °C
OPzV2-2000	2000	399 × 212 × 807	145 kg	400 A	~0.37 mΩ @25 °C	20+ years @20 °C
OPzV2-2500	2500	487 × 212 × 807	181 kg	500 A	~0.30 mΩ @25 °C	20+ years @20 °C

Height. The OPzV2-2000 and the OPzV2-2500 share the same 807 mm height and 212 mm width, so a cabinet drawn around the OPzV2-2000 can accept the OPzV2-2500 — but only if the depth grows from 399 mm to 487 mm and the inter-cell spacing is re-checked.

Weight per amp-hour. For the OPzV2-2500, 5,000 Wh ÷ 181 kg = 27.6 Wh/kg; the OPzV2-200 gives 400 Wh ÷ 17.0 kg = 23.5 Wh/kg, the OPzV2-1000 gives 2,000 Wh ÷ 73.2 kg = 27.3 Wh/kg, and the OPzV2-1200 gives 2,400 Wh ÷ 84 kg = 28.6 Wh/kg. The 2,500 Ah cell sits in the same band as the middle of the range.

String mass. At 24 cells per 48 V string the arithmetic is 24 × 17.0 kg = 408 kg for the OPzV2-200, 24 × 73.2 kg = 1,756.8 kg for the OPzV2-1000, 24 × 145 kg = 3,480 kg for the OPzV2-2000 and 24 × 181 kg = 4,344 kg for the OPzV2-2500. Smaller members such as the OPzV2-200 2V200Ah suit plants distributed across many small cabinets.

Charge current. Maximum charge current scales close to capacity: 40 A on a 200 Ah cell, 500 A on the 2,500 Ah cell, which makes a 250 A ten-hour acceptance test realistic.

§6 — The Trust: Factory Capacity, Certification and Acceptance

The OPzV2-2500 is produced by CHISEN Battery in Hangzhou, China, operating 8 production bases with an annual capacity of 70 million kVAh across four product lines: flooded tubular OPzS2, gel tubular OPzV2, 12 V VRLA in the 6-DZF, 6-DMF and 6-EVF ranges, and energy storage systems. The base holds CE, ISO 9001, ISO 14001, UL and IEC certifications, and the export desk serves importers and OEM partners in Germany, India, Brazil, Nigeria, the UAE and Singapore.

Acceptance discipline turns that into a reliable supply chain. Before the container is unloaded, check the model marking and date code against the purchase order, measure the case against the 487 × 212 × 807 mm drawing, and photograph every cell face. On commissioning, record each cell’s float voltage against the 2.23 V reference, confirm the links are torqued to 10–12 N·m, and run the 10-hour discharge to 1.80 Vpc at 250 A.

§7 — FAQ

Q1: What are the published nominal voltage and capacity of the OPzV2-2500? Datasheet: 2 V nominal, 2,500 Ah at the 10-hour rate to 1.80 Vpc.

Q2: What float and equalise setpoints does the manufacturer publish for the OPzV2-2500? Float 2.23 V per cell, equalise 2.35 V per cell, both at 25 °C, with −3 mV/°C/cell compensation applied by the charger (Datasheet).

Q3: What is the maximum charging current for the OPzV2-2500? 500 A per cell, so 500 A for a series string, since every cell carries the same current; two strings in parallel give 2 × 500 A = 1,000 A (Datasheet, Arithmetic).

Q4: What are the case dimensions and weight of the OPzV2-2500? The case measures 487 × 212 × 807 mm and weighs 181 kg, so a 24-cell string on a 48 V bus weighs 4,344 kg (Datasheet, Arithmetic).

Q5: What terminal type and torque does the OPzV2-2500 use? Female copper insert M8 terminals tightened to 10–12 N·m, the published torque for the tubular gel range (Datasheet).

Q6: How many cells does a 2V2500Ah string contain and what bus voltage does it give? Twenty-four cells in series: 48.00 V nominal, 53.52 V on float, 56.40 V on equalise, 2,500 Ah and 120,000 Wh nominal energy (Arithmetic).

Q7: What is the published design float life of the OPzV2-2500 and at what temperature? The datasheet states 20+ years @20 °C design float life for the tubular gel class. A 12 V VRLA cell carries a 2–5 year design life (Datasheet).

Q8: How should an importer verify the OPzV2-2500 on delivery? Check the marking and date code, measure the case against the 487 × 212 × 807 mm drawing, photograph every cell, then run a 10-hour discharge to 1.80 Vpc at 250 A (Datasheet, Arithmetic).

Q9: Which certifications does the CHISEN factory behind the OPzV2-2500 hold? The Hangzhou plant operates 8 production bases with 70 million kVAh annual capacity and holds CE, ISO 9001, ISO 14001, UL and IEC certifications (Datasheet).

Q10: How do I request a quotation or samples for the OPzV2-2500? Send the duty, bus voltage, autonomy and delivery window to the export desk, which quotes against published OPzV2-2500 datasheet values and can arrange sample cells for testing.

Expert Summary

The OPzV2-2500 is a 2 V, 2,500 Ah tubular gel cell with a fully published datasheet: 487 × 212 × 807 mm, 181 kg, 500 A maximum charge current, ~0.30 mΩ internal resistance at 25 °C, float 2.23 V, equalise 2.35 V, −3 mV/°C/cell compensation and 20+ years @20 °C design float life. On a 48 V bus the 24-cell string gives 48.00 V nominal, 53.52 V on float, 120,000 Wh, 7.20 mΩ and 4,344 kg. Risk on a cell this heavy and this long-lived sits in three places — the cabinet drawing, the thermal environment and the acceptance test — and each is settled by published numbers.

Contact CHISEN — 24-Hour Response

Sales enquiries, quotations and sample requests for the OPzV2-2500 are answered within 24 hours by the export desk in Hangzhou.

Email: sales@chisen.cn
Direct: jack@chisen.cn
WhatsApp: +86 131 6622 6999
Website: www.chisen.cn

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November 4, 2026

2V 1000Ah UPS Battery: 480 V DC Bus String Sizing and Runtime Engineering

Answer First

A 2V 1000Ah UPS battery is a single 2V cell with 1,000 Ah of nominal capacity, and in a modern single-phase or three-phase uninterruptible power supply it is rarely installed alone: a 480 V DC bus is built from 240 of these cells in series, giving 480,000 Wh of nominal energy (240 × 2,000 Wh, Arithmetic), while a 240 V bus is built from 120 cells at 240,000 Wh (Arithmetic). The cell that CHISEN publishes for this duty is the OPzV2-1000, a 2V tubular gel cell rated 1,000 Ah at the C10 rate, measuring 233 × 210 × 681 mm, weighing 73.2 kg (161.4 lbs), floating at 2.23 V at 25 °C, equalising at 2.35 V at 25 °C, temperature-compensated at −3 mV/°C/cell, limited to 200 A of maximum charge current and carrying a designed float life of 20+ years @20 °C (Datasheet). The complete specification block is on the OPzV2-1000 model page, and every figure below traces back to that datasheet, to the matching flooded datasheet, or to arithmetic performed on those figures.

The arithmetic that decides the purchase order is simple and unforgiving. One cell stores 2,000 Wh (2 V × 1,000 Ah, Arithmetic), so a 240-cell string is a 480 kWh battery; at a 50 % depth-of-discharge design limit that is 240 kWh of usable energy, which supports an 80 kW load for 3.0 hours (240 kWh ÷ 80 kW, Arithmetic) — and only 1.5 hours if the inverter is allowed to take the string down to a 25 % depth of discharge. The same cell weighs 73.2 kg, so one 240-cell string is 17,568.0 kg of battery on the floor (240 × 73.2 kg, Arithmetic) and the whole bank has to be engineered around: a 60-cell sub-string is 4,392.0 kg (60 × 73.2 kg, Arithmetic), which is the practical unit for installation, handling and replacement.

Three published numbers should be read before the quotation is issued. First, the 20+ years @20 °C float life of this cell drops steeply in a warm room: the flooded sibling’s datasheet curve reads roughly 10–12 years at 30 °C, 6 years at 40 °C and 2–3 years at 50 °C (Datasheet), so a UPS room without cooling shortens the replacement interval even though the nameplate figure looks unchanged. Second, the cell is rated at 100 A on the ten-hour rate (1,000 Ah ÷ 10 h, Arithmetic), and its internal resistance is about 0.50 mΩ at 25 °C (Datasheet), so a 240-cell string presents roughly 120.0 mΩ (240 × 0.50 mΩ, Arithmetic) — a figure that makes cell-to-cell matching a design constraint rather than a detail. Third, the maximum charge current of 200 A is a per-cell ceiling equal to 0.2 C10 (200 A ÷ 1,000 Ah, Arithmetic), and a 240-cell bank charged at a realistic 100 A draws only 0.42 A per cell (100 A ÷ 240, Arithmetic), so the charger rating set by the inverter is almost never the constraint.

Key Takeaways

2V 1000Ah UPS battery cells are series members, not stand-alone batteries. A 480 V DC bus needs 240 cells (480 ÷ 2, Arithmetic); every cell in that string floats at the same 2.23 V and every cell must be matched.
Published specification for the gel cell. OPzV2-1000: 1,000 Ah at C10, 233 × 210 × 681 mm, 73.2 kg, Female Copper Insert M8 terminal at 10–12 N·m (Datasheet).
One charging basis for the whole 2V tubular range. Float 2.23 V at 25 °C, equalising 2.35 V at 25 °C, temperature compensation −3 mV/°C/cell, designed float life 20+ years @20 °C (Datasheet).
Runtime is set by string count and depth of discharge, not by the cell label. 480 kWh nominal, 240 kWh usable at 50 % DoD, 3.0 h on an 80 kW load (Arithmetic).
Weight is the installation constraint. 73.2 kg per gel cell, 17,568.0 kg per 240-cell string, 4,392.0 kg per 60-cell sub-string (Arithmetic).
Matching and temperature decide service life. About 0.50 mΩ per cell means 120.0 mΩ across a 240-cell string, and a 5 mV per-cell spread adds 1.20 V to that string (Arithmetic) — which is why acceptance testing is not optional.

§1 — 2V 1000Ah UPS Battery Quick Specifications

The two cells below are the models CHISEN publishes for 2V 1000Ah UPS duty: the OPzV2-1000 tubular gel cell and the OPzS2-1000 tubular flooded cell. Values are reproduced as published; nothing has been rounded, converted or interpolated. Parameters that the source does not publish are listed as unpublished rather than estimated.

Parameter	OPzV2-1000 (gel tubular)	Source
Nominal voltage	2 V	Datasheet
Rated capacity	1,000 Ah at C10 (1.80 Vpc)	Datasheet
Dimensions (L × W × H)	233 × 210 × 681 mm	Datasheet
Weight	73.2 kg (161.4 lbs)	Datasheet / Arithmetic
Terminal	Female Copper Insert M8, torque 10–12 N·m	Datasheet
Float voltage	2.23 V at 25 °C	Datasheet
Equalising voltage	2.35 V at 25 °C	Datasheet
Temperature compensation	−3 mV/°C/cell	Datasheet
Maximum charge current	200 A	Datasheet
Internal resistance	~0.50 mΩ at 25 °C	Datasheet
Designed float life	20+ years @20 °C	Datasheet
Solar and wind setpoints	float 2.27 ± 0.005 V, equalise 2.40 ± 0.01 V, compensation −3~−5 mV/°C/cell	Datasheet
Published discharge capacity table	not published for this model	—
Internal resistance at other temperatures	not published for this model	—

The flooded counterpart is published in more detail, which is useful when a project compares the two technologies cell by cell:

Parameter	OPzS2-1000 (flooded tubular)	Source
Rated capacity	1,000 Ah (C10) at 100 A to 1.80 Vpc, 20 °C	Datasheet
Nominal voltage	2 V DC	Datasheet
Container dimensions	233 × 210 × 645 mm; 700 mm overall height over terminals	Datasheet
Weight	53.5 kg (118 lbs) without electrolyte; 73.5 kg (162 lbs) with electrolyte; acid 20 kg	Datasheet
Terminal	Female Copper Insert M8, torque 10–12 N·m	Datasheet
Internal resistance	≈0.45 mΩ fully charged at 20 °C	Datasheet
Short-circuit current	4,500 A; 2,500 A for 5 s	Datasheet
Self-discharge	3 % per month at 20–25 °C	Datasheet
Float voltage	2.23 V per cell at 25 °C, float current under 5 mA/Ah	Datasheet
Temperature compensation	−3 mV/°C/cell	Datasheet
Equalising voltage	2.35 V per cell at 25 °C; equalise current ≤ 0.25 C10	Datasheet
Designed float life	20+ years at 20 °C	Datasheet
Float life from the datasheet curve	≈10–12 years at 30 °C, 6 years at 40 °C, 2–3 years at 50 °C	Datasheet
Operating temperature	discharge −25…65 °C; charge −20…65 °C; storage −15…40 °C; optimum 20–25 °C	Datasheet
Capacity at the 10-hour rate	108 % at 40 °C; 100 % at 25 °C; 85 % at 0 °C; 65 % at −15 °C	Datasheet
Discharge capacity at 1.85 V	C24 1,130 Ah; C48 1,240 Ah; C72 1,300 Ah; C100 1,350 Ah; C120 1,370 Ah; C240 1,400 Ah	Datasheet
Standards	IEC 60896-11:2002, DIN 40736-1:1985, GB/T 19638.2-2014, YD/T 1360, Eurobat Long Life, BS 6290 Part 4, UL 1989	Datasheet

Two cautions belong next to this table. The first is that the gel cell and the flooded cell are not dimensionally identical — 233 × 210 × 681 mm for the gel cell against a 233 × 210 × 645 mm container with a 700 mm overall height for the flooded cell (Datasheet) — so a rack designed for one is not automatically a rack for the other. The second is that the flooded cell’s solar and wind controller setpoints (float 2.25 ± 0.005 V, equalise 2.40 ± 0.01 V, over-voltage disconnect 2.47 ± 0.01 V, low-voltage disconnect 1.90 ± 0.005 V, compensation −4 mV/°C/cell) belong to renewable-duty charging, not to a UPS float regime (Datasheet); in float standby the cell is held at 2.23 V per cell (Datasheet).

§2 — The Pain: Why 2V 1000Ah UPS Banks Are Sized Wrong

Most disappointing runtime in a UPS project is not a manufacturing defect; it is arithmetic that nobody wrote down before the order was placed. The classic failure starts with the cell label. A 2V 1000Ah UPS battery looks like a 1,000 Ah battery, and 1,000 Ah is what the installer carries into the design — but the cell is a two-volt series member, so its usable energy is 2,000 Wh (Arithmetic), and the string is what the inverter actually sees. The second classic failure is the depth-of-discharge assumption. A cell rated 1,000 Ah at C10 does not deliver 1,000 Ah into a 15-minute high-load discharge, and an inverter configured to pull a string down to a deep end-voltage window will deliver less than the runtime sheet promised; at a 50 % depth-of-discharge design limit the 480 kWh string supports 3.0 hours on an 80 kW load, while a 25 % limit cuts that to 1.5 hours (all Arithmetic).

The third failure is temperature, and it is the one that costs the most in tropical and equatorial installations. The flooded datasheet publishes a capacity of 100 % at 25 °C, 85 % at 0 °C and 65 % at −15 °C (Datasheet), so a cold room silently removes 15 % of the available runtime in winter. The warm side of the same curve is more expensive still: the designed float life of 20+ years at 20 °C falls to roughly 10–12 years at 30 °C and 6 years at 40 °C (Datasheet), so a string running in a 35 °C UPS room without forced cooling consumes the same calendar time as a string in a 20 °C room while delivering far less service life.

The fourth failure is matching. With about 0.50 mΩ of internal resistance per gel cell (Datasheet), a 240-cell string presents 120.0 mΩ (240 × 0.50 mΩ, Arithmetic). A 5 mV per-cell spread across that string adds 1.20 V (240 × 0.005 V, Arithmetic) of imbalance, which the charger then has to equalise away for the rest of the string’s life; a 12 V six-cell block would show the same 5 mV spread as only 0.03 V (6 × 0.005 V, Arithmetic). The fifth failure is weight logistics: at 73.2 kg per gel cell, a 240-cell string is 17,568.0 kg (Arithmetic) that must be moved through doors, down corridors and into position, usually with a crane or a pallet jack, which is why sub-strings of 60 cells (4,392.0 kg each, Arithmetic) and 120 cells (8,784.0 kg each, Arithmetic) are the practical delivery unit in most installations. Buyers who specify the cell only, and leave the string architecture to the installer, pay for all five of these problems later.

§3 — The Choice: Gel OPzV2-1000 Versus Flooded OPzS2-1000 for UPS Duty

Both cells answer the same electrical question — 2 V, 1,000 Ah, 2.23 V float at 25 °C, 2.35 V equalising at 25 °C, −3 mV/°C/cell compensation and 20+ years @20 °C of designed float life (Datasheet) — and they differ in the plant around them rather than in the numbers on the rating plate.

Parameter	OPzV2-1000 (gel)	OPzS2-1000 (flooded)	Source
Nominal voltage	2 V	2 V DC	Datasheet
Rated capacity	1,000 Ah at C10 (1.80 Vpc)	1,000 Ah (C10) at 100 A to 1.80 Vpc, 20 °C	Datasheet
Installed weight per cell	73.2 kg (161.4 lbs)	73.5 kg (162 lbs) with electrolyte; 53.5 kg (118 lbs) without	Datasheet
Energy-to-weight ratio	27.3 Wh/kg (2,000 Wh ÷ 73.2 kg)	27.2 Wh/kg (2,000 Wh ÷ 73.5 kg)	Arithmetic
Dimensions	233 × 210 × 681 mm	233 × 210 × 645 mm container, 700 mm overall height	Datasheet
Internal resistance	~0.50 mΩ at 25 °C	≈0.45 mΩ fully charged at 20 °C	Datasheet
Float voltage	2.23 V at 25 °C	2.23 V per cell at 25 °C	Datasheet
Equalising voltage	2.35 V at 25 °C	2.35 V per cell at 25 °C	Datasheet
Temperature compensation	−3 mV/°C/cell	−3 mV/°C/cell	Datasheet
Maximum charge current	200 A (0.2 C10)	equalise current ≤ 0.25 C10	Datasheet / Arithmetic
Short-circuit current	not published for this model	4,500 A; 2,500 A for 5 s	Datasheet
Self-discharge	not published for this model	3 % per month at 20–25 °C	Datasheet
Float current limit	not published for this model	under 5 mA/Ah, i.e. 5.0 A per cell	Datasheet / Arithmetic
Discharge table at 1.85 V	not published for this model	C24 1,130 Ah; C240 1,400 Ah	Datasheet
Designed float life	20+ years @20 °C	20+ years at 20 °C	Datasheet
Terminal	Female Copper Insert M8, 10–12 N·m	Female Copper Insert M8, 10–12 N·m	Datasheet

Two readings of this table settle most arguments. The first is that the installed weight difference is negligible — 73.2 kg for the gel cell against 73.5 kg for the flooded cell with its acid, because the 20 kg of electrolyte in the flooded version replaces the gel (Arithmetic). A UPS room designed around floor loading therefore does not change its logic when the chemistry changes. The second is that the flooded datasheet publishes figures the gel datasheet does not: a short-circuit current of 4,500 A, a self-discharge of 3 % per month at 20–25 °C, a float-current ceiling of 5 mA/Ah and a full discharge-capacity table at 1.85 V (Datasheet). If a project specification calls for short-circuit data, a self-discharge figure or a capacity curve, the flooded cell is the one that answers on paper — the gel equivalent must be requested from the factory in writing, and the OPzS2-1000 model page is where the published block is kept.

§4 — The Framework: String Architecture, Runtime Arithmetic and the Acceptance Test

A 2V 1000Ah UPS battery is specified in four steps, and the order matters: bus voltage, string architecture, depth-of-discharge limit, then acceptance criteria.

Bus voltage and cell count. A 480 V DC bus is 240 cells (480 ÷ 2, Arithmetic) and floats at 535.2 V (240 × 2.23 V, Arithmetic) while equalising at 564.0 V (240 × 2.35 V, Arithmetic); the 1.80 Vpc end-of-discharge floor of the same string is 432.0 V (240 × 1.80 V, Arithmetic). A 240 V bus is 120 cells, floating at 267.6 V and equalising at 282.0 V, with a 216.0 V floor (all Arithmetic).

String architecture. Two common arrangements carry the same 240 cells: two parallel strings of 120 cells, each weighing 8,784.0 kg (120 × 73.2 kg, Arithmetic), or four parallel strings of 60 cells, each weighing 4,392.0 kg (60 × 73.2 kg, Arithmetic). More strings means lighter handling units, more interconnects and more midpoint taps for the string monitor, but the same total energy of 480,000 Wh (Arithmetic). One megawatt-hour of nominal storage needs 500 cells (1,000 kWh ÷ 2,000 Wh, Arithmetic).

Depth of discharge and runtime. The published nameplate is the ceiling, not the plan:

Load on the inverter	Nominal energy	Usable at 50 % DoD	Runtime at 50 % DoD	Runtime at 25 % DoD
80 kW (100 kVA at 0.8 power factor)	480 kWh	240 kWh	3.0 h	1.5 h
40 kW	480 kWh	240 kWh	6.0 h	3.0 h
20 kW	480 kWh	240 kWh	12.0 h	6.0 h

All figures in this table are Arithmetic from 240 cells × 2,000 Wh = 480,000 Wh, 50 % and 25 % depth-of-discharge limits, and a 480 V bus built from the OPzV2-1000 (Datasheet).

Charger sizing. The cell’s own ceiling is 200 A, which is 0.2 C10 (Arithmetic). A 240-cell bank charged at a practical 100 A draws 0.42 A per cell (100 A ÷ 240, Arithmetic), so the cell limit is not the binding constraint; the inverter’s rectifier rating is. With two parallel strings, one 50 A charger per string keeps each cell at 0.42 A (50 A ÷ 120, Arithmetic) and leaves the string’s float current headroom intact. On the flooded variant the float current must stay under 5 mA/Ah, i.e. 5.0 A per cell and 1,200 A across a 240-cell string at the limit (Datasheet, Arithmetic).

Acceptance test. The commissioning protocol that protects a 240-cell string has four stages. First, charge the string at the equalising setpoint of 2.35 V per cell (Datasheet) and confirm that every cell reaches the setpoint, because a cell that cannot reach it will be the first to fall out of the string. Second, discharge the string at the ten-hour rate — 100 A per cell for a 1,000 Ah cell (1,000 Ah ÷ 10 h, Arithmetic) — and record each cell’s terminal voltage; the 1.80 Vpc final voltage is the published reference point (Datasheet). Third, measure the float current per cell and compare it with the 5 mA/Ah ceiling published for the flooded cell (Datasheet). Fourth, torque every interconnector to the published 10–12 N·m on the Female Copper Insert M8 terminal (Datasheet) and record the string’s voltage spread; a spread of 5 mV per cell becomes 1.20 V across 240 cells (Arithmetic) and is the earliest warning that a cell is out of balance.

§5 — Where the 2V 1000Ah Sits in the CHISEN Tubular Range

The 2V 1000Ah cell is one step in a size ladder, and the choice is usually driven by rack height and floor loading rather than by capacity alone. The full OPzV2 gel tubular line is published as follows (Datasheet):

Model	V	Ah at C10	Dimensions (L × W × H)	Weight	Maximum charge current	Internal resistance	Float voltage	Designed float life
OPzV2-200	2	200	103 × 206 × 390 mm	17.0 kg	40 A	~1.0 mΩ @25 °C	2.23 V @25 °C	20+ years @20 °C
OPzV2-500	2	500	166 × 206 × 506 mm	36.3 kg	100 A	~0.56 mΩ @25 °C	2.23 V @25 °C	20+ years @20 °C
OPzV2-1000	2	1,000	233 × 210 × 681 mm	73.2 kg	200 A	~0.50 mΩ @25 °C	2.23 V @25 °C	20+ years @20 °C
OPzV2-1200	2	1,200	275 × 210 × 681 mm	84 kg	240 A	~0.46 mΩ @25 °C	2.23 V @25 °C	20+ years @20 °C
OPzV2-2000	2	2,000	399 × 212 × 807 mm	145 kg	400 A	~0.37 mΩ @25 °C	2.23 V @25 °C	20+ years @20 °C
OPzV2-2500	2	2,500	487 × 212 × 807 mm	181 kg	500 A	~0.30 mΩ @25 °C	2.23 V @25 °C	20+ years @20 °C

Three sizing rules follow from that table. A 480 V bus of 240 OPzV2-1000 cells stores 480,000 Wh; the same bus built from OPzV2-1200 cells stores 576,000 Wh (240 × 2,400 Wh, Arithmetic) at a weight of 20,160.0 kg (240 × 84 kg, Arithmetic). If a row of the rack cannot take a 681 mm-tall cell, the OPzV2-500 and OPzV2-200 models are 506 mm and 390 mm tall respectively (Datasheet), and the string count rises to compensate: 240 cells of 500 Ah still fill a 480 V bus, but the energy falls to 240,000 Wh (240 × 1,000 Wh, Arithmetic). Finally, as the cell grows the internal resistance falls — from ~1.0 mΩ on the OPzV2-200 to ~0.30 mΩ on the OPzV2-2500 (Datasheet) — so a 240-cell string built from larger cells carries less voltage drop at high load, which matters for the output regulation of the UPS itself.

§6 — The Trust: How to Vet a 2V 1000Ah UPS Battery Supplier

A supplier that cannot answer these eight questions on paper is not a supplier of a 2V 1000Ah UPS battery; it is a supplier of a label. Ask for the datasheet and confirm that it states the float voltage of 2.23 V at 25 °C, the equalising voltage of 2.35 V at 25 °C, the temperature compensation of −3 mV/°C/cell and the designed float life of 20+ years @20 °C, each with a source label. Ask for the compliance list: IEC 60896-11:2002, DIN 40736-1:1985, GB/T 19638.2-2014, YD/T 1360, Eurobat Long Life, BS 6290 Part 4 and UL 1989 are the standards published for the flooded cell (Datasheet), and an equivalent statement is expected for the gel cell. Ask for capacity test reports at the C10 rate to 1.80 Vpc with the test date, the cell serial range and the measured Ah — a factory that tests to 1.80 Vpc but quotes to 1.75 Vpc is quoting two different batteries. Ask for the interconnector torque specification (10–12 N·m on a Female Copper Insert M8 terminal, Datasheet) and for a spare-parts programme matched to the string architecture, because on a 240-cell string a single open circuit in one sub-string ends the installation’s autonomy. Ask how the supplier handles the market that matters to you: UPS demand continues to grow across China, India, Nigeria, Kenya, South Africa, Egypt, Brazil, Indonesia and Vietnam, and cells ship routinely from Shanghai, Ningbo and Shenzhen to Jebel Ali, Lagos, Mombasa, Durban, Cairo, Santos, Mumbai and Karachi, so the question is not whether the battery will arrive but whether the supplier can support a 240-cell string with spares and technical support after the container is unloaded.

On CHISEN’s own record: the company operates 8 production bases with an annual capacity of 70 million kVAh, holds CE, ISO 9001, ISO 14001, UL and IEC certification, and builds the flooded tubular OPzS2 line, the gel tubular OPzV2 line, 12 V VRLA blocks in the 6-DZF, 6-DMF and 6-EVF ranges, 6 V and 8 V EVF blocks, plus solar and lithium storage systems (Company facts). The gel tubular range is documented on the OPzV2 product hub page.

§7 — FAQ

Q1: How many cells does a 480 V UPS battery bank need? 240 cells, because 480 ÷ 2 V = 240 (Arithmetic). Each cell floats at 2.23 V, so the string floats at 535.2 V (240 × 2.23 V, Arithmetic) and equalises at 564.0 V (240 × 2.35 V, Arithmetic).

Q2: What is the published capacity of the OPzV2-1000 cell? 1,000 Ah at the C10 rate to 1.80 Vpc, which is a 100 A discharge on the ten-hour rate (1,000 Ah ÷ 10 h, Arithmetic) (Datasheet).

Q3: What float and equalising voltages should the UPS charger use? 2.23 V float and 2.35 V equalising per cell at 25 °C (Datasheet), with the temperature compensation of −3 mV/°C/cell applied above or below 25 °C.

Q4: How much does the float setpoint move with temperature? By −3 mV per °C per cell (Datasheet); at 30 °C the 2.23 V setpoint falls to 2.215 V (2.23 V − 5 × 0.003 V, Arithmetic) and at 20 °C it rises to 2.245 V (Arithmetic).

Q5: How long is the designed float life of a 2V 1000Ah UPS battery? 20+ years at 20 °C (Datasheet); the published curve reads roughly 10–12 years at 30 °C, 6 years at 40 °C and 2–3 years at 50 °C (Datasheet), so room temperature decides the replacement date.

Q6: How long will a 480 V bank of these cells run an 80 kW load? The string stores 480,000 Wh (240 × 2,000 Wh, Arithmetic); at a 50 % depth-of-discharge limit that is 240 kWh, or 3.0 hours on 80 kW, and 1.5 hours at a 25 % limit (Arithmetic).

Q7: How much does one 240-cell string weigh? 17,568.0 kg for the gel cell (240 × 73.2 kg, Arithmetic) and 17,640.0 kg for the flooded cell including its electrolyte (240 × 73.5 kg, Arithmetic).

Q8: What is the maximum charge current of the cell? 200 A, which is 0.2 C10 (200 A ÷ 1,000 Ah, Arithmetic) (Datasheet). A 240-cell bank charged at 100 A total draws only 0.42 A per cell (100 A ÷ 240, Arithmetic).

Q9: What should be measured when the string is commissioned? Equalising at 2.35 V per cell, a capacity discharge at the C10 rate to 1.80 Vpc, the float current per cell (under 5 mA/Ah on the flooded cell, Datasheet), and connection torque of 10–12 N·m on the M8 insert (Datasheet); a 5 mV per-cell spread equals 1.20 V across 240 cells (Arithmetic).

Q10: Is the gel cell or the flooded cell the better choice for UPS duty? Both publish 2.23 V float, 2.35 V equalising, −3 mV/°C/cell compensation and 20+ years @20 °C of designed float life (Datasheet). The flooded datasheet additionally publishes a 4,500 A short-circuit current, 3 % per month self-discharge at 20–25 °C and a discharge-capacity table at 1.85 V (Datasheet); the gel cell does not publish those three figures, so a specification that needs them should ask for them in writing.

Expert Summary

A 2V 1000Ah UPS battery is a series member, not a standalone battery: the OPzV2-1000 gel cell is 2 V, 1,000 Ah at C10 to 1.80 Vpc, 233 × 210 × 681 mm, 73.2 kg, Female Copper Insert M8 at 10–12 N·m, float 2.23 V and equalise 2.35 V at 25 °C, compensation −3 mV/°C/cell, maximum charge current 200 A, internal resistance ~0.50 mΩ at 25 °C, designed float life 20+ years @20 °C, and the flooded OPzS2-1000 alternative is 1,000 Ah (C10) at 100 A, 233 × 210 × 645 mm container with a 700 mm overall height, 53.5 kg without and 73.5 kg with 20 kg of electrolyte, ≈0.45 mΩ at 20 °C, 4,500 A short-circuit current, 3 % per month self-discharge, float current under 5 mA/Ah, float 2.23 V and equalise 2.35 V per cell with −3 mV/°C/cell compensation, equalise current ≤ 0.25 C10, 20+ years at 20 °C falling to ≈10–12 years at 30 °C, 6 years at 40 °C and 2–3 years at 50 °C, capacity 108 % at 40 °C, 100 % at 25 °C, 85 % at 0 °C and 65 % at −15 °C, discharge capacity at 1.85 V of C24 1,130 Ah through C240 1,400 Ah, certified to IEC 60896-11:2002, DIN 40736-1:1985, GB/T 19638.2-2014, YD/T 1360, Eurobat Long Life, BS 6290 Part 4 and UL 1989 (Datasheet). In service that means 2,000 Wh per cell (2 V × 1,000 Ah, Arithmetic), a 100 A ten-hour rate and 125 A at 0.8 C10 (Arithmetic), 27.3 Wh/kg for the gel cell and 27.2 Wh/kg for the flooded cell with electrolyte (Arithmetic), a 480 V bus of 240 cells at 480,000 Wh, 535.2 V float, 564.0 V equalise and a 432.0 V floor, a 240 V bus of 120 cells at 240,000 Wh, 267.6 V float, 282.0 V equalise and a 216.0 V floor (all Arithmetic), 17,568.0 kg per gel string and 17,640.0 kg per flooded string, 120.0 mΩ across a 240-cell gel string and 1.20 V of imbalance from a 5 mV per-cell spread (Arithmetic), sub-strings of 4,392.0 kg at 60 cells and 8,784.0 kg at 120 cells, 500 cells per megawatt-hour, 3.0 hours on an 80 kW load at 50 % depth of discharge and 1.5 hours at 25 % (Arithmetic), a 0.42 A per-cell draw on a 240-cell bank charged at 100 A against the 200 A cell ceiling (Arithmetic), and a float setpoint of 2.215 V per cell at 30 °C (Arithmetic).

Contact CHISEN — 24-Hour Response

CHISEN Battery replies to technical and commercial enquiries within 24 hours, every day of the week. Send specification requests, string-layout drawings, charger setpoint questions, capacity test reports and delivery schedules to sales@chisen.cn; export desk correspondence also goes to jack@chisen.cn. For immediate discussion, the WhatsApp line is +86 131 6622 6999. The company profile, factory capability statements and product documentation are published at www.chisen.cn, and the 2V 1000Ah UPS battery anchor model — the OPzV2-1000 with its complete published specification block — sits at https://www.chisen.cn/en/OPzV2-1000/2V1000Ah.html.

Related CHISEN Buyer Guides

November 4, 2026

6-EVF-50 12V50Ah AGM VRLA Battery for Solar Street Lighting

Answer First

The 6-EVF-50 12V50Ah AGM VRLA block is the smallest sealed block in the CHISEN 6-EVF AGM product line, and every number that decides whether it belongs on a solar lighting pole or in an off-grid cabinet is already fixed by the manufacturer: 12 V nominal, 50 Ah at the C3 rate, 230 × 140 × 180 mm, 15.25 ± 0.2 kg, an M6 terminal, a 13.5 V float setpoint, a 14.1 V equalising setpoint, a 10.0 A maximum charge current, a 1.75 V/cell discharge cut-off, self-discharge of ≤3 %/month at 25 °C, a working range of −15…50 °C and a published design life of 2–5 years. The complete data sheet is on the 6-EVF-50 model page, and every figure in this article traces back to that page or to arithmetic performed on those figures.

Arithmetically, one 6-EVF-50 12V50Ah block stores 600 Wh (12 V × 50 Ah, Arithmetic) and delivers 16.7 A at the three-hour discharge rate (50 Ah ÷ 3 h, Arithmetic). Two blocks in series give a 24 V solar bus holding 1,200 Wh (24 V × 50 Ah, Arithmetic), floating at 27.0 V (2 × 13.5 V, Arithmetic) and weighing 30.5 kg (2 × 15.25 kg, Arithmetic). Four blocks in series give a 48 V bus holding 2,400 Wh (48 V × 50 Ah, Arithmetic) and weighing 61 kg (4 × 15.25 kg, Arithmetic); a charger for that string must be rated at least 40 A (4 × 10.0 A, Arithmetic) to bring the bank back to full charge after a dark winter week.

Two figures deserve attention before any purchase order is raised. First, the published design life of this VRLA product line is 2–5 years, not the multi-decade float life of CHISEN’s flooded OPzS2 or gel OPzV2 tubular products; a 6-EVF-50 12V50Ah bank on a solar pole must be budgeted as a consumable with a scheduled replacement. Second, the self-discharge of ≤3 %/month at 25 °C still costs a 48 V string of four blocks 6.0 Ah per month (4 × 1.5 Ah, Arithmetic), and a cabinet idle through a long cloudy season loses more energy that way than many installers expect.

Key Takeaways

Published specification, not a guess. The 6-EVF-50 12V50Ah is a 12 V, 50 Ah, C3-rate AGM VRLA block measuring 230 × 140 × 180 mm and weighing 15.25 ± 0.2 kg with an M6 terminal (Model page).
600 Wh per block, 1,200 Wh for a 24 V pair. The arithmetic is simple: 12 V × 50 Ah = 600 Wh per block, so two blocks in series form the standard 24 V lighting bus (Arithmetic).
Float charging at 13.5 V per block. That is 2.25 V per cell (Arithmetic), the standard VRLA float target that holds the cell on the absorption plateau without driving water loss (Model page).
Equalising at 14.1 V per block, or 2.35 V per cell. Equalising is a controlled procedure in solar service, applied block by block rather than across a partially wired bank (Model page).
Size the charger from the published 10.0 A maximum charge current. A 24 V pair needs at least 20 A, a 48 V string at least 40 A, and a 48 V bank of eight blocks at least 80 A (Arithmetic).
Design life is 2–5 years for this VRLA product line. Long-life tubular OPzS2 and OPzV2 products are a separate range with separate physics; budget the 12 V AGM lighting bank as a five-year replacement item (Model page).

§1 — 6-EVF-50 12V50Ah Published Specifications

The table below reproduces the specification block exactly as published for the 6-EVF-50 12V50Ah on the CHISEN model page. No value has been rounded, converted or derived. Parameters the source does not publish are listed explicitly rather than estimated.

Parameter	Value	Source
Nominal voltage	12 V	Model page
Capacity	50 Ah at the C3 rate	Model page
Dimensions (L × W × H)	230 × 140 × 180 mm	Model page
Weight	15.25 ± 0.2 kg	Model page
Terminal	φ11.8-M6	Model page
Float voltage	13.5 V	Model page
Equalising voltage	14.1 V	Model page
Cycle life	350–600 cycles at 50–80 % DoD	Model page
Maximum charge current	10.0 A	Model page
Discharge cut-off	1.75 V/cell	Model page
Self-discharge	≤3 %/month at 25 °C	Model page
Working temperature	−15…50 °C	Model page
Design life	2–5 years	Model page
Energy per block	600 Wh (12 V × 50 Ah)	Arithmetic
Discharge current at the C3 rate	16.7 A (50 Ah ÷ 3 h)	Arithmetic
Float voltage per cell	2.25 V (13.5 V ÷ 6)	Arithmetic
Equalising voltage per cell	2.35 V (14.1 V ÷ 6)	Arithmetic
Cut-off voltage per block	10.5 V (6 × 1.75 V)	Arithmetic
Maximum charge rate	0.2 C10 (10.0 A ÷ 50 Ah)	Arithmetic
Monthly self-discharge per block	1.5 Ah (3 % × 50 Ah)	Arithmetic
Internal resistance	not published	to be requested from the factory
Float temperature-compensation coefficient	not published	to be requested from the factory
Charge termination criterion	not published	to be requested from the factory
Final voltage by discharge current	not published for this model	to be requested from the factory
Discharge curve by temperature	not published for this model	to be requested from the factory

The final voltage table, the internal resistance figure and the temperature-compensation coefficient are the parameters a solar integrator asks for first, and for the 6-EVF-50 they must be requested from the factory rather than assumed. The charging profile itself can be derived from the published setpoints — 13.5 V float, 14.1 V equalise, 10.0 A maximum charge current — but the compensation slope for a cabinet in direct summer sun is a factory item.

§2 — Float, Equalising and Charge Acceptance in Solar Duty

A solar lighting installation has two distinct operating modes, and the 6-EVF-50 12V50Ah is rated for both. In the first, the bank sits on float charge through the day while the controller passes surplus panel current into it; in the second, the bank delivers the night’s load at a moderate discharge rate while the panels are idle.

Float duty sets the resting voltage at 13.5 V per block, which is 2.25 V per cell (Arithmetic) — the standard VRLA float target that keeps the cell on the absorption plateau without boiling away electrolyte. Equalising at 14.1 V per block (2.35 V per cell, Arithmetic) is a controlled corrective procedure, not a permanent setpoint: in solar service it is applied after deep discharge or when cells drift apart in voltage, and it is done block by block — never across a partially wired bank, where the lowest cell would absorb the whole voltage difference.

The published maximum charge current of 10.0 A per block gives a ceiling of 0.2 C10 (10.0 A ÷ 50 Ah, Arithmetic). That is the number to match against the controller output: a controller rated for more than 20 A on a 24 V pair will push the block beyond its published maximum charge current, which accelerates water loss and shortens service life. A controller rated for less leaves the bank slow to recover after a cloudy week.

Standby losses matter more in solar duty than in a mains-fed cabinet. At ≤3 %/month at 25 °C, one block loses 1.5 Ah per month (Arithmetic); a 24 V pair loses 3.0 Ah per month and a 48 V string of four blocks loses 6.0 Ah per month (Arithmetic). Against a 1,200 Wh 24 V pair, 3.0 Ah is 36 Wh, roughly 3 % of stored energy — a meaningful slice of a 50 W load’s monthly budget when the panel days are short.

The working temperature envelope of −15…50 °C (Model page) covers most lighting sites, but it is an ambient figure: a sealed cabinet in direct sun runs warmer than the air, and a sealed AGM block sheds heat less freely than a flooded cell. Enclosure thermal management is the integrator’s decision; the published working range is the only temperature authority in this data sheet.

§3 — String Sizing: 24 V, 48 V and Parallel Banks for Lighting and Off-Grid Loads

Most single-lamp solar systems in the field run on a 24 V bus because that is what common charge controllers and LED drivers expect. A 48 V bus is the choice when the site also carries signage, a camera, a communications radio or a small off-grid load that must run through a deep-winter storm.

Configuration	Blocks	Nominal bus	Stored energy	Float bus	Equalise bus	Mass	Minimum charger	Source
24 V single string	2	24 V	1,200 Wh	27.0 V	28.2 V	30.5 kg	20 A	Arithmetic
24 V 2P2S	4	24 V	2,400 Wh	27.0 V	28.2 V	61 kg	40 A	Arithmetic
48 V single string	4	48 V	2,400 Wh	54.0 V	56.4 V	61 kg	40 A	Arithmetic
48 V 2P4S	8	48 V	4,800 Wh	54.0 V	56.4 V	122 kg	80 A	Arithmetic
48 V 4P4S	16	48 V	9,600 Wh	54.0 V	56.4 V	244 kg	160 A	Arithmetic

Two rules govern how those numbers are combined. First, every block in a series string carries the same current, so the charger requirement follows the number of series blocks, not the total block count: a 48 V 2P4S bank still charges at 40 A per series string, and the controller must be rated for 80 A across two parallel strings. Second, mass and energy are proportional, so a 48 V 4P4S bank of sixteen blocks delivers 9,600 Wh (Arithmetic) but weighs 244 kg (Arithmetic) and needs a rated enclosure and a structural check for the cabinet or the pole base.

The discharge floor follows from the published 1.75 V/cell cut-off: 10.5 V per block (6 × 1.75 V, Arithmetic), so 21.0 V for a 24 V pair and 42.0 V for a 48 V string (Arithmetic). A controller with a low-voltage disconnect above those points cuts the lamp before the battery is exhausted; a disconnect below them pulls the block into a region where capacity is not recoverable at a useful rate.

For integrators who need a higher-capacity single block in the same sealed range, the 6-EVF-60 12V60Ah sits one step up, and the 6-EVF-100 12V100Ah doubles the capacity of the 6-EVF-50 12V50Ah (100 Ah ÷ 50 Ah = 2.0, Arithmetic) for 2.07 times the mass (31.5 kg ÷ 15.25 kg, Arithmetic). The full ladder from 50 Ah to 150 Ah sits on the CHISEN EVF product page.

§4 — The Nightly Energy Budget: Depth of Discharge, Cycle Life and the Acceptance Test

The published cycle life of the 6-EVF-50 12V50Ah is 350–600 cycles at 50–80 % depth of discharge (Model page). That range is the single most useful planning figure for a solar lighting project, because a solar pole that is sized to run its lamp for two nights of autonomy is effectively operating at deep discharge, and a pole sized for one night of autonomy is operating near the shallow end of that range.

A worked example, with the assumptions stated: a 50 W LED fixture switched on for 10 hours each night consumes 500 Wh per night (50 W × 10 h, Arithmetic). A 24 V pair of 6-EVF-50 12V50Ah blocks holds 1,200 Wh (Arithmetic), so at a 50 % depth of discharge the usable energy is 600 Wh (1,200 Wh × 50 %, Arithmetic) — roughly one night’s load, with the second night’s requirement covered only if the following day is fully sunny. That is a deliberate design choice: it keeps the working depth of discharge inside the published 50–80 % band instead of running the bank to an 80 % discharge every night.

The acceptance test on delivery should follow the same numbers rather than a generic capacity check. For a 24 V pair the expected float bus is 27.0 V (2 × 13.5 V, Arithmetic) and the equalising bus is 28.2 V (2 × 14.1 V, Arithmetic). After a controlled discharge to the 21.0 V floor (2 × 10.5 V, Arithmetic), the pair should return to the 27.0 V float level within the recharge window allowed by the 20 A minimum charger (Arithmetic). Checking individual blocks after the equalising step reveals cell imbalance that a bus-voltage measurement hides, and imbalance is what shortens a lighting bank’s life.

Weight is the parameter most often overlooked at specification stage. A 24 V pair is 30.5 kg and a 48 V string of four is 61 kg (Arithmetic) — on a pole that is a structural and wind-loading question, in a ground cabinet a floor-rating and shelving question. Both figures come from the published 15.25 ± 0.2 kg per block and should be checked against the mounting design before the order is released.

§5 — Where the 6-EVF-50 Sits in the 12 V AGM Range

The 6-EVF AGM series shares one charging profile across its whole capacity ladder: 13.5 V float, 14.1 V equalise, 1.75 V/cell cut-off, self-discharge of ≤3 %/month at 25 °C, a working range of −15…50 °C and a design life of 2–5 years (Model page). What changes from one model to the next is capacity, footprint, mass and maximum charge current.

Model	V	Capacity	Rate	L × W × H mm	Weight	Terminal	Max charge current	Float	Design life
6-EVF-50	12	50 Ah	C3	230×140×180	15.25 ± 0.2 kg	φ11.8-M6	10.0 A	13.5 V	2–5 years
6-EVF-60	12	60 Ah	C3	258×170×160	18.8 ± 0.2 kg	φ14-M6	12.0 A	13.5 V	2–5 years
6-EVF-80	12	80 Ah	C3	259×170×218	25.7 ± 0.2 kg	φ16-M6	16.0 A	13.5 V	2–5 years
6-EVF-100	12	100 Ah	C3	330×170×218	31.5 ± 0.2 kg	φ20-M8	20.0 A	13.5 V	2–5 years
6-EVF-120	12	120 Ah	C3	407×170×240	40 ± 0.2 kg	φ20-M8	24.0 A	13.5 V	2–5 years
6-EVF-150	12	150 Ah	C3	483×170×240	48.5 ± 0.2 kg	φ20-M8	30.0 A	13.5 V	2–5 years

For installations that need slightly more capacity than 50 Ah in the same sealed range, the neighbouring models are the 6-EVF-60 at 60 Ah and 18.8 ± 0.2 kg and the 6-EVF-80 at 80 Ah and 25.7 ± 0.2 kg (Model page). Neither brings a different charging regime, so a controller set up for the 6-EVF-50 12V50Ah serves the whole series.

Where the 6-DMF blocks overlap in capacity, the choice comes down to application. The 6-DMF-52 12V52Ah is a 12 V, 52 Ah, C3-rate block of 224 × 135 × 175 mm and 13.7 ± 0.2 kg with a 10.4 A maximum charge current, while the 6-DMF-45 is 12 V, 45 Ah, 224 × 121 × 175 mm and 12.3 ± 0.2 kg with a 9.0 A maximum charge current (Model page). Both share the 13.5 V float, 14.1 V equalise, 1.75 V/cell cut-off and 2–5 year design life of the wider 12 V VRLA range.

Model	V	Capacity	Weight	Max charge current	Float	Cut-off	Design life
6-EVF-50	12	50 Ah	15.25 ± 0.2 kg	10.0 A	13.5 V	1.75 V/cell	2–5 years
6-DMF-52	12	52 Ah	13.7 ± 0.2 kg	10.4 A	13.5 V	1.75 V/cell	2–5 years
6-DMF-45	12	45 Ah	12.3 ± 0.2 kg	9.0 A	13.5 V	1.75 V/cell	2–5 years

One purchasing caution applies to the DMF comparison rows: the model pages for 6-DMF-52 and 6-DMF-45 also list alternative weight variants in their horizontal comparison tables (14.5 kg and 13.1 kg respectively). Only the specification-table weight is used here, and pack builders must confirm the delivered variant on the order acknowledgement. The AGM series range and the VRLA/GFM overview on the CHISEN VRLA pages document the same product line from the manufacturer’s side.

§6 — The Trust: What to Ask the Supplier Before the Purchase Order

A lighting project is bought once and maintained for years, so the questions asked at quotation stage decide the service life of the installed bank. The first is the datasheet: ask for the specification sheet behind the model number you are buying — float voltage, equalising voltage, maximum charge current, cut-off voltage, working temperature range and design life — and check each line against the published values on the 6-EVF-50 model page. The second is the factory data this page does not publish: internal resistance, the temperature-compensation slope, the charge termination criterion and the final-voltage table, requested in writing rather than assumed from a generic VRLA chart.

Third, ask how the blocks are packed and shipped — a 15.25 ± 0.2 kg block dropped in transit arrives in a condition that matters more than any datasheet line. Fourth, ask what the replacement commitment is for a 2–5 year design life product in solar duty: the published life assumes the float and equalise setpoints above, the published temperature range and the published depth of discharge band. A supplier quoting a long service life without those three conditions attached is quoting a different product.

On the manufacturer side, CHISEN Battery operates 8 production bases with an annual capacity of 70 million kVAh, holds CE, ISO 9001, ISO 14001, UL and IEC certification, and builds the flooded tubular OPzS2 line, the gel tubular OPzV2 line, the 12 V VRLA range (6-DZF, 6-DMF, 6-EVF), 6 V and 8 V EVF blocks, solar storage systems and lithium storage systems (Model page). The profile is published at www.chisen.cn/en/about.html — it tells an integrator that a replacement block three years into the project comes from the same specification set rather than an unknown second source.

FAQ

Q1: What are the nominal voltage and capacity of the 6-EVF-50 12V50Ah? 12 V nominal and 50 Ah at the C3 rate (Model page).

Q2: How much energy does a single block store? 600 Wh, from 12 V × 50 Ah (Arithmetic).

Q3: What discharge current applies at the published C3 rate? 16.7 A, since 50 Ah ÷ 3 h = 16.7 A (Model page).

Q4: What float and equalising voltages should the charger be set to? 13.5 V float and 14.1 V equalise per block, which is 2.25 V and 2.35 V per cell (Model page).

Q5: How many blocks make a 24 V solar lighting bank, and what does it hold? Two blocks in series, holding 24 V × 50 Ah = 1,200 Wh nominal (Arithmetic).

Q6: What is the float and equalise voltage of that 24 V bank? 27.0 V float (2 × 13.5 V) and 28.2 V equalise (2 × 14.1 V) (Arithmetic).

Q7: What charger current is required for a 24 V pair and for a 48 V string? At least 20 A for the pair (2 × 10.0 A) and at least 40 A for a 48 V string of four (4 × 10.0 A), matching the published 10.0 A maximum charge current per block (Model page).

Q8: At what voltage should the discharge be stopped? At 1.75 V per cell, which is 10.5 V per block (6 × 1.75 V), 21.0 V on a 24 V pair and 42.0 V on a 48 V string (Model page).

Q9: How much energy does a 48 V string lose to self-discharge each month? 6.0 Ah per month, from 3 % × 50 Ah = 1.5 Ah per block and 4 × 1.5 Ah for the string (Arithmetic).

Q10: How long is the design life of this battery? 2–5 years for the 12 V VRLA product line, with a published cycle life of 350–600 cycles at 50–80 % depth of discharge (Model page).

Expert Summary

The 6-EVF-50 12V50Ah is a 12 V, 50 Ah C3 AGM VRLA block, 230 × 140 × 180 mm, 15.25 ± 0.2 kg, M6 terminal, floating at 13.5 V and equalising at 14.1 V, rated 10.0 A maximum charge current, cut-off 1.75 V/cell, self-discharge ≤3 %/month at 25 °C, working range −15…50 °C, cycle life 350–600 cycles at 50–80 % DoD and a 2–5 year design life (Model page). In service that means 600 Wh per block (12 V × 50 Ah, Arithmetic), a 16.7 A C3 discharge current (50 Ah ÷ 3 h, Arithmetic), a 10.5 V block floor (6 × 1.75 V, Arithmetic), a 24 V pair at 1,200 Wh, 27.0 V float, 28.2 V equalise, 30.5 kg and a 20 A charger (Arithmetic), a 48 V string of four at 2,400 Wh, 54.0 V float, 56.4 V equalise, 61 kg and a 40 A charger (Arithmetic), a 48 V bank of eight blocks at 4,800 Wh, 122 kg and an 80 A charger (Arithmetic), a 48 V bank of sixteen blocks at 9,600 Wh and 244 kg (Arithmetic), a 21.0 V floor on 24 V and 42.0 V on 48 V (Arithmetic), a standby loss of 6.0 Ah per month on a four-block 48 V string (4 × 1.5 Ah, Arithmetic), and a charge ceiling of 0.2 C10 (10.0 A ÷ 50 Ah, Arithmetic). The float setpoint is 2.25 V per cell and equalising 2.35 V per cell (Arithmetic); the whole 12 V range shares one charging profile, one cut-off, one self-discharge figure and one 2–5 year design life, while multi-decade float life belongs to the separate OPzS2 and OPzV2 tubular product lines rather than to this VRLA block.

Contact CHISEN — 24-Hour Response

CHISEN Battery replies to technical and commercial enquiries within 24 hours, every day of the week. Send specification requests, project drawings, controller setpoint questions and delivery schedules to sales@chisen.cn; export desk correspondence also goes to jack@chisen.cn. For immediate discussion, the WhatsApp line is +86 131 6622 6999. The full company profile, product documentation and factory capability statements are published at www.chisen.cn, and the 6-EVF-50 12V50Ah model page with its complete specification block sits at https://www.chisen.cn/en/6-EVF-50/12V50Ah.html.

Related CHISEN Buyer Guides

November 4, 2026

6-EVF-120 12V120Ah AGM VRLA Battery for UPS: Specs, Float Charging

Answer First

The 6-EVF-120 12V120Ah AGM VRLA block is the 120 Ah workhorse of the CHISEN 6-EVF series, and the numbers that decide whether it belongs in your cabinet are already fixed by the manufacturer: 12 V nominal, 120 Ah at the C3 rate, 407 × 170 × 240 mm, 40 ± 2 kg, M6 terminals, a 13.5 V float setpoint, a 14.1 V equalising setpoint, a 24.0 A maximum charge current, a 1.75 V/cell discharge cut-off and a published design life of 2–5 years. The full data sheet is on the 6-EVF-120 model page, and every figure quoted in this article traces back to it or to arithmetic performed on those figures.

Arithmetically, one block delivers 40 A at the three-hour discharge rate (120 Ah ÷ 3 h = 40 A, Arithmetic) and a 48 V string of four blocks stores 5,760 Wh (48 V × 120 Ah, Arithmetic) at a float bus voltage of 54.0 V (4 × 13.5 V, Arithmetic). That string draws 160 kg of mass (4 × 40 kg, Arithmetic) and needs a charger rated for at least 96 A (4 × 24 A, Arithmetic) to bring the bank back to full charge after a deep discharge.

Two figures deserve attention before any purchase order is raised. First, the design life of this VRLA product line is 2–5 years, not the decades associated with CHISEN’s flooded OPzS2 or gel OPzV2 tubular products; a 12 V AGM string on float charge must be planned as a consumable with a scheduled replacement budget. Second, the standby self-discharge of ≤3 %/month at 25 °C still costs a 48 V string 14.4 Ah per month (4 × 3.6 Ah, Arithmetic), so the float current setpoint and the room temperature envelope are not optional details — they decide how much of the 5,760 Wh is still available when the grid fails.

Key Takeaways

Published specification, not a guess. The 6-EVF-120 12V120Ah is a 12 V, 120 Ah, C3-rate AGM VRLA block measuring 407 × 170 × 240 mm and weighing 40 ± 2 kg with M6 terminals (Model page).
Float charging at 13.5 V per block. That is 2.25 V per cell (Arithmetic), the standard VRLA float target that keeps the cell on the absorption plateau without boiling the electrolyte away (Model page).
Equalising at 14.1 V per block, or 2.35 V per cell. Equalising is a controlled weekly procedure, not a permanent setpoint, and it must be applied block by block rather than across a partially wired bank (Model page).
A 48 V string is four blocks, not three. Four 12 V blocks give 48 V nominal, 5,760 Wh, 160 kg and a 54.0 V float bus (Arithmetic).
Size the charger from the published 24.0 A maximum charge current. Four blocks in series require a charger of at least 96 A, and a 72 V string needs 144 A (Arithmetic).
Design life is 2–5 years for this VRLA product line. Long-life tubular OPzS2 and OPzV2 products are a different range with different physics; budget the 12 V AGM string as a five-year replacement item (Model page).

§1 — 6-EVF-120 12V120Ah Published Specifications

The table below reproduces the specification block exactly as published for the 6-EVF-120 12V120Ah on the CHISEN model page. No value has been rounded, converted or derived.

Parameter	Value	Source
Nominal voltage	12 V	Model page
Capacity	120 Ah	Model page
Rate	C3	Model page
Dimensions	407 × 170 × 240 mm	Model page
Weight	40 ± 2 kg	Model page
Terminal	M6	Model page
Float voltage	13.5 V	Model page
Equalize voltage	14.1 V	Model page
Cycle life	350–600 cycles (DoD 50–80 %)	Model page
Charge current	24.0 A	Model page
Cut-off	1.75 V/cell	Model page
Self-discharge	≤3 %/month @25 °C	Model page
Working temperature	−15…50 °C	Model page
Design life	2–5 years	Model page

Four observations from the published data drive the rest of this article.

First, the capacity rating is quoted at C3, meaning the 120 Ah figure is the three-hour rate discharge. The corresponding discharge current is 120 Ah ÷ 3 h = 40 A (Arithmetic). A UPS that draws 40 A continuously from one block would flatten it in three hours; a shorter high-current event must be checked against the manufacturer’s discharge curves rather than against the headline 120 Ah number.

Second, the working temperature window of −15…50 °C (Model page) is wide, but the self-discharge figure of ≤3 %/month is quoted specifically at 25 °C (Model page). Outside 25 °C, expect both a higher standby draw and a shorter life; the data centre specification should therefore hold the battery room closer to 20–25 °C than to the edges of the envelope.

Third, the M6 terminal and 40 ± 2 kg mass matter mechanically: a 48 V string of four blocks places 160 kg (Arithmetic) across the shelf, and the terminal design dictates the cable lug and the torque specification used during installation.

Fourth, the cut-off of 1.75 V/cell applies to the six internal cells of the block, so the block-level discharge floor is 6 × 1.75 V = 10.5 V per block (Arithmetic). On a 48 V string of four blocks the bus floor is 4 × 10.5 V = 42.0 V (Arithmetic).

§2 — Float and Equalising Setpoints for a UPS String

The published setpoints are 13.5 V float and 14.1 V equalise per 12 V block (Model page). Converted to cell level, 13.5 V ÷ 6 cells = 2.25 V per cell for float, and 14.1 V ÷ 6 cells = 2.35 V per cell for equalising (Arithmetic). Those two figures are the entire charging strategy for a VRLA string, and they are deliberately narrow.

Float is the permanent state. A UPS battery sits on float charge for 99 % of its life, and at 2.25 V per cell the cell is held just past the point where the charge current falls into the self-discharge plus parasitic-load band. Set it higher and you accelerate the water loss that shortens VRLA life; set it lower and the string sags, the inverter sees a lower DC bus and the cells stratify. The charger output must therefore be programmed to 13.5 V per block, and for the 48 V string that means a 54.0 V float bus (4 × 13.5 V, Arithmetic).

Equalising is the corrective tool. At 2.35 V per cell the charger drives current through the block long enough to redistribute charge between cells that have drifted apart, which happens naturally after months of unequal temperature and discharge history. For the 48 V string the equalise bus is 56.4 V (4 × 14.1 V, Arithmetic). Equalising should be scheduled periodically, not left permanently enabled, because the higher voltage accelerates positive-grid corrosion and water loss; the trigger is a measurable spread in individual cell or block voltages under float, not a calendar date alone.

Temperature compensation closes the loop. The 13.5 V float figure is a 25 °C reference point; in a warm data centre the charger should reduce the float voltage per degree above that reference to avoid chronic overcharge, and in a cold room it should raise it to keep the string fully charged. The −15…50 °C working range (Model page) tells you how much the chemistry tolerates, but only the charger’s compensation curve moves the setpoint.

Finally, respect the published 24.0 A maximum charge current (Model page). For the 48 V string that is 4 × 24 A = 96 A (Arithmetic); for the 72 V string, 144 A; for the 144 V string, 288 A (Arithmetic). A charger that is smaller simply takes longer to recover; a charger that exceeds the limit forces the block into a forced overcharge, which drives electrolyte loss in a sealed AGM cell where the loss cannot be topped up with water.

§3 — String Sizing: 48 V, 72 V and 144 V DC Buses

A 12 V block is only useful in series strings whose count matches the DC bus of the UPS. The three configurations below are built entirely from 6-EVF-120 12V120Ah blocks, with all figures shown as formulas.

String	Blocks	Nominal	Energy	Weight	Max charge current	Float bus	Equalise bus
48 V bus	4 × 12 V	48 V	48 V × 120 Ah = 5,760 Wh	4 × 40 kg = 160 kg	4 × 24 A = 96 A	4 × 13.5 V = 54.0 V	4 × 14.1 V = 56.4 V
72 V bus	6 × 12 V	72 V	72 V × 120 Ah = 8,640 Wh	6 × 40 kg = 240 kg	6 × 24 A = 144 A	6 × 13.5 V = 81.0 V	6 × 14.1 V = 84.6 V
144 V bus	12 × 12 V	144 V	144 V × 120 Ah = 17,280 Wh	12 × 40 kg = 480 kg	12 × 24 A = 288 A	12 × 13.5 V = 162.0 V	12 × 14.1 V = 169.2 V

The 48 V configuration is by far the most common in small-to-medium data centres and server rooms, because it matches the classic 220 V single-phase UPS rectifier output of 54.0 V float and 56.4 V equalise (Arithmetic). The 72 V string serves three-phase systems and, in Europe, the 216 V class of bus. The 144 V string is the large single-phase configuration used in bigger installations and in DC bus distribution for telecommunications-grade plants.

Two practical constraints follow directly from the arithmetic. The first is string-to-string balance: with four blocks in series, the weakest block defines the usable capacity of the entire string, so blocks should be drawn from the same production batch, given identical rest time before installation, and wired with matched cable lengths. The second is mass and floor load: 480 kg on a single 144 V rack of twelve blocks requires a rated plinth, and the 40 ± 2 kg per block (Model page) has to be planned into the handling logistics, not discovered on delivery day.

A note on runtime. The 5,760 Wh of a 48 V string is the nameplate energy, not the deliverable energy. After derating for temperature, ageing, converter losses and the fact that a UPS rarely runs its battery below the 10.5 V per block cut-off (6 × 1.75 V, Arithmetic), the usable fraction is meaningfully smaller, and it shrinks further as the product line advances through its 2–5 year design life (Model page).

§4 — Standby Losses, Float Life and the Acceptance Test

Standby float charge is not a free state. The published self-discharge is ≤3 %/month at 25 °C (Model page), which converts to 3 % × 120 Ah = 3.6 Ah per month per block (Arithmetic). A 48 V string of four blocks therefore loses 4 × 3.6 Ah = 14.4 Ah per month (Arithmetic) to self-discharge alone, before the UPS converter’s own quiescent draw on the DC bus. That figure is the physical reason the float setpoint is 13.5 V and not something lower: the charger must continuously replace 14.4 Ah per month of string loss, and it does so at a voltage that holds the cells just above the point of imbalance.

Float life follows from the same chemistry. VRLA cells have no way to replace lost water, so every cycle of overcharge and every month of high-temperature float erodes the positive grid. The published design life of 2–5 years for this product line (Model page) is the number to put into the replacement schedule, and the published cycle life of 350–600 cycles at 50–80 % depth of discharge (Model page) is the number to put into the application margin, not the standby case. Where an installation genuinely needs multi-decade float life, the correct answer is a different CHISEN product line — the flooded tubular OPzS2 or the gel tubular OPzV2 series, covered in the CHISEN VRLA and GFM overview — not a larger block from the same VRLA range.

The acceptance test is where the real capacity is proved. Measure the actual capacity of each block or string at the published C3 rate, that is at 40 A for three hours (120 Ah ÷ 3 h = 40 A, Arithmetic), and record the voltage at the end of discharge. A block that delivers 120 Ah at C3 while ending at or above the 1.75 V/cell cut-off (Model page) has passed. Accept on a measured figure, not on the label, and keep the discharge log: the first three capacity tests after commissioning establish the baseline against which the annual acceptance test is judged.

§5 — Where the 6-EVF-120 Sits in the 12 V AGM Range

The 6-EVF-120 12V120Ah belongs to a wide 12 V portfolio that also includes smaller 6-DZF and 6-DMF blocks and the larger 6-EVF-150. The mechanical table below shows where the 120 Ah block sits in that range, and the electrical table that follows shows that the charging regime, cut-off, self-discharge and design life are identical across the whole 12 V line — which means one charger profile and one acceptance procedure can cover an entire mixed fleet.

Model	V	Capacity	Rate	L×W×H mm	Weight	Terminal
6-DZF-12	12	12 Ah	C2	151×99×99	3.6 ± 0.2 kg	φ8.0-M5
6-DZF-20	12	20 Ah	C2	180×76×170	6.1 ± 0.2 kg	φ8.8-M5
6-DMF-38	12	38 Ah	C3	224×106×175	10.45 ± 0.2 kg	φ9.8-M5
6-DMF-45	12	45 Ah	C3	224×121×175	12.3 ± 0.2 kg	φ11.8-M5
6-DMF-52	12	52 Ah	C3	224×135×175	13.7 ± 0.2 kg	φ11.8-M6
6-EVF-50	12	50 Ah	C3	230×140×180	15.25 ± 0.2 kg	φ11.8-M6
6-EVF-60	12	60 Ah	C3	258×170×160	18.8 ± 0.2 kg	φ14-M6
6-EVF-80	12	80 Ah	C3	259×170×218	25.7 ± 0.2 kg	φ16-M6
6-EVF-100	12	100 Ah	C3	330×170×218	31.5 ± 0.2 kg	φ20-M8
6-EVF-120	12	120 Ah	C3	407×170×240	40 ± 2 kg	φ20-M8
6-EVF-150	12	150 Ah	C3	483×170×240	48.5 ± 0.2 kg	φ20-M8
Model	Float	Equalize	Cycle life	Charge current	Cut-off	Self-discharge
—	—	—	—	—	—	—
6-DZF-12	13.5 V	14.1 V	350–600 (DoD 50–80 %)	2.4 A	1.75 V/cell	≤3 %/month @25 °C
6-DZF-20	13.5 V	14.1 V	350–600	4.0 A	1.75 V/cell	≤3 %/month @25 °C
6-DMF-38	13.5 V	14.1 V	350–600	7.6 A	1.75 V/cell	≤3 %/month @25 °C
6-DMF-45	13.5 V	14.1 V	350–600	9.0 A	1.75 V/cell	≤3 %/month @25 °C
6-DMF-52	13.5 V	14.1 V	350–600	10.4 A	1.75 V/cell	≤3 %/month @25 °C
6-EVF-50	13.5 V	14.1 V	350–600	10.0 A	1.75 V/cell	≤3 %/month @25 °C
6-EVF-60	13.5 V	14.1 V	350–600	12.0 A	1.75 V/cell	≤3 %/month @25 °C
6-EVF-80	13.5 V	14.1 V	350–600	16.0 A	1.75 V/cell	≤3 %/month @25 °C
6-EVF-100	13.5 V	14.1 V	350–600	20.0 A	1.75 V/cell	≤3 %/month @25 °C
6-EVF-120	13.5 V	14.1 V	350–600	24.0 A	1.75 V/cell	≤3 %/month @25 °C
6-EVF-150	13.5 V	14.1 V	350–600	30.0 A	1.75 V/cell	≤3 %/month @25 °C

Two comparisons frame the selection decision. Against the 6-EVF-100 (see the 6-EVF-100 12V100Ah model page), the 6-EVF-120 12V120Ah gains 20 % capacity — 120 Ah ÷ 100 Ah = 1.2 (Arithmetic) — while its mass rises by a factor of about 1.27, that is 40 kg ÷ 31.5 kg ≈ 1.27 (Arithmetic). So the 120 Ah block is better per amp-hour and per kilogram; the 100 Ah block is better per footprint, at 330 × 170 × 218 mm against 407 × 170 × 240 mm. Against the 6-EVF-150 12V150Ah, the 120 Ah step is usually the sweet spot for a single rack of a 48 V string, while the 150 Ah block at 48.5 ± 0.2 kg is worth it when the runtime requirement pushes the string to more energy than four 120 Ah blocks can give.

For small footprints, the 6-EVF-60 (see the 6-EVF-60 12V60Ah model page) at 258 × 170 × 160 mm and 18.8 ± 0.2 kg covers cabinet and telecom applications, and the 6-DMF-52 at 224 × 135 × 175 mm and 13.7 ± 0.2 kg (see the 6-DMF-52 12V52Ah model page) is the compact mid-range option, with the 6-DZF and 6-DMF range overview covering the smaller blocks.

§6 — The Trust: What to Ask the Supplier Before the Purchase Order

CHISEN Battery is based in Hangzhou, China, operates 8 production bases with an annual capacity of 70 million kVAh, and holds CE, ISO 9001, ISO 14001, UL and IEC certifications. The product portfolio spans flooded tubular OPzS2, gel tubular OPzV2, the 12 V VRLA blocks in the 6-DZF, 6-DMF and 6-EVF series, 6 V and 8 V EVF blocks, solar storage systems and lithium storage systems. The company profile page and the EVF series overview describe the capability in more detail.

Before signing for a 6-EVF-120 12V120Ah shipment, put these questions in writing on the purchase order.

Which certificate accompanies this exact block, and can the test report be provided before shipment? Ask for the IEC 60896-3 or UL V94 test reference tied to the 6-EVF-120 12V120Ah rather than a generic product line certificate.
What is the factory batch and date code on the delivered blocks, and can blocks from one batch be supplied for one string? This protects the balance of the 48 V string.
What is the factory float voltage programme, and is it temperature compensated? The published 13.5 V (Model page) must be the value programmed at 25 °C.
What capacity test data is supplied, at what rate, and with what end-of-discharge voltage? The reference acceptance test is 120 Ah at C3, that is 40 A for three hours (Arithmetic), ending above 1.75 V/cell (Model page).
What is the warranty structure, and does it start from the manufacturing date or from the delivery date? For a product line with a 2–5 year design life (Model page), the start point changes the economics of the replacement schedule.
What is the packaging standard — pallet quantity, carton count and gross weight per pallet — and what are the HS code and shipping documentation for customs clearance?
Which accessories are available from the same factory: inter-block cables with M6 lugs, terminal torque values, busbars, and matching enclosures.

FAQ

Q1: What are the nominal voltage and capacity of the 6-EVF-120 12V120Ah? 12 V nominal and 120 Ah at the C3 rate (Model page).

Q2: What float and equalising voltages should the charger be set to? 13.5 V float and 14.1 V equalise per block, which is 2.25 V and 2.35 V per cell (Model page).

Q3: How many blocks make a 48 V UPS string, and what does it hold? Four 12 V blocks in series, storing 48 V × 120 Ah = 5,760 Wh nominal (Arithmetic).

Q4: What is the float and equalise voltage of a 48 V string built from these blocks? 54.0 V float (4 × 13.5 V) and 56.4 V equalise (4 × 14.1 V) (Arithmetic).

Q5: How much does a 48 V string of four 6-EVF-120 12V120Ah blocks weigh? 160 kg, that is 4 × 40 kg (Arithmetic).

Q6: What charger current is needed to recharge a 48 V string? At least 96 A, because 4 × 24 A = 96 A, matching the published 24.0 A maximum charge current per block (Model page).

Q7: What is the discharge current at the published C3 rate? 40 A, since 120 Ah ÷ 3 h = 40 A (Model page).

Q8: At what voltage should the discharge be stopped? At 1.75 V per cell, which is 10.5 V per block (6 × 1.75 V) and 42.0 V across a 48 V string (Model page).

Q9: How much standby charge does a 48 V string lose per month? 14.4 Ah per month, from 3 % × 120 Ah = 3.6 Ah per block and 4 × 3.6 Ah for the string (Arithmetic).

Q10: How long is the design life of this battery? 2–5 years for the 12 V VRLA product line, with a published cycle life of 350–600 cycles at 50–80 % depth of discharge (Model page).

Expert Summary

The 6-EVF-120 12V120Ah is a 12 V, 120 Ah C3 AGM VRLA block, 407 × 170 × 240 mm, 40 ± 2 kg, M6 terminal, floating at 13.5 V and equalising at 14.1 V, rated 24.0 A charge current, cut-off 1.75 V/cell, self-discharge ≤3 %/month at 25 °C, working range −15…50 °C, cycle life 350–600 cycles at 50–80 % DoD and a 2–5 year design life (Model page). In service that means a 40 A C3 discharge current (120 Ah ÷ 3 h, Arithmetic), a 10.5 V block floor (6 × 1.75 V, Arithmetic), a 54.0 V float and 56.4 V equalise bus on 48 V (4 × 13.5 V and 4 × 14.1 V, Arithmetic), a 56.4 V to 42.0 V working window on discharge, 5,760 Wh and 160 kg for a four-block 48 V string, 8,640 Wh and 240 kg for six blocks at 72 V, 17,280 Wh and 480 kg for twelve blocks at 144 V, charger requirements of 96 A, 144 A and 288 A respectively (Arithmetic), a 48 V standby loss of 14.4 Ah per month (4 × 3.6 Ah, Arithmetic), and versus the 6-EVF-100 a 1.2 gain in capacity (120 Ah ÷ 100 Ah) against a 1.27 rise in mass (40 kg ÷ 31.5 kg) (Arithmetic). The float setpoint is 2.25 V per cell and equalising 2.35 V per cell (Arithmetic); the whole 12 V range shares one charging profile, one cut-off, one self-discharge figure and one 2–5 year design life, while multi-decade float life belongs to the separate OPzS2 and OPzV2 tubular product lines rather than to this VRLA block.

Contact CHISEN — 24-Hour Response

CHISEN Battery replies to technical and commercial enquiries within 24 hours, every day of the week. Send specification requests, project drawings, UPS bus voltages and delivery schedules to sales@chisen.cn; export desk correspondence also goes to jack@chisen.cn. For immediate discussion, the WhatsApp line is +86 131 6622 6999. The full company profile, product documentation and factory capability statements are published at www.chisen.cn, and the 6-EVF-120 12V120Ah model page with its complete specification block sits at https://www.chisen.cn/en/6-EVF-120/12V120Ah.html.

Related CHISEN Buyer Guides

November 2, 2026

OPzV2-2500 2V2500Ah Tubular Gel Battery: Specs, String Sizing and Utility Storage Use

Answer First

The OPzV2-2500 2V2500Ah is a 2 V, 2,500 amp-hour valve-regulated tubular gel lead-acid cell rated at the ten-hour rate — 250 A for ten hours down to 1.80 V per cell — and it is the largest cell in the CHISEN tubular gel range. On a utility storage duty it is normally paired into a 48 V or 96 V string inside a container, and the published data set is unusually complete for a cell at this capacity: 487 × 212 mm footprint, 772 mm container height, 807 mm over the terminals, approximately 181 kg, about 0.30 mΩ internal resistance, a 10,000 A short-circuit current, a 500 A maximum charging current and a designed floating life of more than twenty years at 20 °C.

The complete published data set sits on the OPzV2-2500 2V2500Ah model page. The immediately smaller cell in the range is listed on the OPzV2-2000 2V2000Ah model page, and the whole gel range is indexed under tubular gel lead-acid batteries.

Two points deserve attention before any quotation is compared. First, this cell has no published solar or wind long-time discharge capacity table and no published solar or wind setpoint table; those rows are marked not published in this guide, because the datasheet does not contain them and a sibling model’s figures must not be carried across. Second, the final-voltage-by-discharge-current table is the only discharge guidance published, and it decides how much of the rated 2,500 Ah a given current can actually draw.

Key Takeaways

The rating is rate-dependent and the basis belongs in the order. The OPzV2-2500 is 2,500 Ah at C10 to 1.80 V per cell, meaning 250 A for ten hours; the datasheet publishes the final-voltage table alongside it so usable capacity can be matched to the discharge current.
Charging setpoints are fixed by the datasheet. Float 2.23 V per cell at 25 °C, equalising 2.35 V per cell at 25 °C, temperature compensation −3 mV/°C/cell, and a 500 A maximum charging current (Datasheet).
Mechanical data decides the container, not the electrical data. Footprint 487 × 212 mm, 772 mm container height, 807 mm over the terminals, approximately 181 kg per cell, ABS container with optional UL94-V0 flame rating (Datasheet).
Two limits protect the cell. Maximum discharge 4,000 A for five seconds and a 10,000 A short-circuit current, against an internal resistance of approximately 0.30 mΩ fully charged at 25 °C (Datasheet).
A string is arithmetic, and the arithmetic should be quoted. A 48 V string is 24 cells at 120,000 Wh nominal and approximately 4,344 kg; a 96 V string is 48 cells at 240,000 Wh nominal and approximately 8,688 kg (Arithmetic).

§1 — OPzV2-2500 2V2500Ah Published Specifications

Every figure in the table below is printed in the manufacturer datasheet for this model. Nothing has been extrapolated from a neighbouring cell, and where the datasheet publishes nothing the row says so explicitly.

Parameter	Published value	Source
Nominal voltage	2 V	Datasheet
Rated capacity	2,500 Ah at C10 to 1.80 Vpc	Datasheet
Footprint (L × W)	487 × 212 mm	Datasheet
Container height	772 mm	Datasheet
Height over terminals	807 mm	Datasheet
Approximate weight	181 kg	Datasheet
Internal resistance	approx. 0.30 mΩ fully charged at 25 °C	Datasheet
Short-circuit current	10,000 A	Datasheet
Maximum discharge current	4,000 A for 5 s	Datasheet
Maximum charging current	500 A	Datasheet
Float voltage	2.23 V at 25 °C	Datasheet
Temperature compensation	−3 mV/°C/cell	Datasheet
Equalising voltage	2.35 V at 25 °C	Datasheet
Self-discharge	approx. 2 %/month at 20 °C	Datasheet
Operating range, discharge	−40 to 65 °C	Datasheet
Operating range, charge	−30 to 65 °C	Datasheet
Storage range	−25 to 45 °C	Datasheet
Designed floating life	20+ years at 20 °C	Datasheet
Container material	ABS, UL94-V0 optional	Datasheet
Terminal	Female copper insert M8, torque 10–12 N·m	Datasheet
Solar/wind long-time discharge capacity	Not published	Datasheet
Solar/wind setpoint table	Not published	Datasheet

The standards and certification set is equally specific: IEC 60896-21/22 and DIN 40472 for the valve-regulated cell and its envelope, IEC 61427 for renewable cycling, YD/T 1360 for the Chinese telecoms market, the Eurobat long-life guide, BS 6290 part 4 and UL 1989 for the North American market. The manufacturing management system runs to ISO 9001 and ISO 14001, with GB/T 28001 covering occupational health and safety, and the product is supplied with CE and RU conformity marking.

A useful cross-check on the scale of this cell is the charging ceiling expressed against the rating: 500 A maximum charging current divided by 2,500 Ah C10 equals 0.20 C10, so the charger and the array must both be sized inside that 500 A per cell limit. The same arithmetic applied to the internal resistance gives 0.30 mΩ divided by 2,500 Ah, or 0.12 mΩ per amp-hour, a figure that gets noticeably better as the range moves down toward the smaller gel cells.

§2 — The Pain: Where 2,500 Ah Utility Storage Projects Lose Their Margin

The failure pattern on a container-scale storage job is rarely a single dramatic event. It is a set of small, individually reasonable decisions that accumulate into a specification that cannot meet its own duty cycle.

The first is the capacity basis. A quotation that says “2,500 Ah” without naming the rate is not a quotation at all. The OPzV2-2500 is rated at C10, which means 250 A for ten hours to 1.80 V per cell. On a utility storage duty the discharge profile is rarely a ten-hour plateau; it is a peak-shaving curve with a long tail, and the usable energy at that profile is governed by the final-voltage table, not by the headline capacity. A project team that sizes a string on the 2,500 Ah figure alone and then discovers the average discharge current sits in the 0.08 C to 0.2 C band — where the published final voltage is 1.80 Vpc — has to accept that the number on the datasheet is the optimistic case.

The second is the container geometry. The OPzV2-2500 footprint of 487 × 212 mm with a 772 mm container height and 807 mm over the terminals is not a proportional scale-up of the smaller gel cells. The 2,000 Ah cell measures 399 × 212 mm and the 1,500 Ah cell 275 × 210 mm, so the case length moves by 88 mm between the 1,500 and 2,500 Ah steps while the width barely changes. Container drawings, rack rails and door clearances built on an assumed pitch will not fit the cell that actually arrives.

The third is weight, which is where logistics cost hides. Approximately 181 kg per cell multiplied by 24 cells gives approximately 4,344 kg for a 48 V string, and the same arithmetic on 48 cells gives approximately 8,688 kg for a 96 V string. These are floor loading, gantry lifting and shipping-weight figures before any enclosure is added. A project that discovers the lifting plan was built for 120 kg cells finds out late.

The fourth is the published-setpoint gap. For this model the datasheet prints no solar or wind long-time discharge capacity table and no solar or wind setpoint table. The temptation in a tender response is to quote the 2.27 V float and 2.40 V equalising values that appear in other gel datasheets in the range. That is a fabrication, and it is one that surfaces as premature capacity loss in the second or third year, in a hot container, in a market where a warranty claim is hard to argue.

The fifth is the tolerance for a cell of this mass. The M8 female copper insert with a 10–12 N·m torque figure is not a detail; it is the number that keeps cell-to-cell connections at the published internal resistance of approximately 0.30 mΩ, and a string with undertightened links does not deliver the published short-circuit behaviour of 10,000 A or the 4,000 A for five seconds that the DC protection has to interrupt.

§3 — The Choice: Matching the OPzV2-2500 to the Actual Duty

Choosing between the large tubular gel cells in the range should start with the discharge rate, then the string voltage, then the mechanical envelope.

On discharge rate, the datasheet publishes one guidance table and one only — final voltage by discharge current — and it should be used directly. Below 0.05 C the cell may be taken to 1.90 Vpc or higher; from 0.05 C to 0.08 C the published final voltage is 1.85 Vpc; from 0.08 C to 0.2 C it is 1.80 Vpc; from 0.2 C to 0.6 C it is 1.75 Vpc; from 0.6 C to 1.0 C it is 1.70 Vpc; and from 1 C to 2 C it is 1.60 Vpc. A storage project with a peak-shaving duty in the 0.2 C to 0.6 C band is therefore working to a 1.75 Vpc end point, and every energy calculation should be built from that figure rather than from 1.80 Vpc.

On string voltage, the arithmetic is worth writing into the specification because it is the part that is usually left implicit. A 48 V string is 24 cells at 2 V nominal: 24 × 2 V = 48 V, 24 × 2,500 Ah = 60,000 Ah, 48 V × 2,500 Ah = 120,000 Wh nominal, 24 × 181 kg = 4,344 kg and 24 × 0.30 mΩ = 7.2 mΩ of string resistance. Float at 2.23 V per cell gives 24 × 2.23 V = 53.52 V across the string, and equalising at 2.35 V per cell gives 24 × 2.35 V = 56.40 V. A 96 V string is 48 cells: 48 × 2 V = 96 V, 48 × 2,500 Ah = 120,000 Ah, 96 V × 2,500 Ah = 240,000 Wh nominal, 48 × 181 kg = 8,688 kg, 48 × 0.30 mΩ = 14.4 mΩ, a float of 48 × 2.23 V = 107.04 V and an equalising voltage of 48 × 2.35 V = 112.80 V. The table below sets the two configurations side by side, with a 192 V option included because container inverters commonly run at that class.

String configuration	Cells	Nominal voltage	Nominal capacity	Nominal energy	Approximate weight	String internal resistance	Float voltage at 2.23 V/cell	Equalising voltage at 2.35 V/cell
48 V single	24 × 2 V = 48 V	48 V	24 × 2,500 Ah = 60,000 Ah	48 V × 2,500 Ah = 120,000 Wh	24 × 181 kg = 4,344 kg	24 × 0.30 mΩ = 7.2 mΩ	24 × 2.23 V = 53.52 V	24 × 2.35 V = 56.40 V
96 V single	48 × 2 V = 96 V	96 V	48 × 2,500 Ah = 120,000 Ah	96 V × 2,500 Ah = 240,000 Wh	48 × 181 kg = 8,688 kg	48 × 0.30 mΩ = 14.4 mΩ	48 × 2.23 V = 107.04 V	48 × 2.35 V = 112.80 V
192 V single	96 × 2 V = 192 V	192 V	96 × 2,500 Ah = 240,000 Ah	192 V × 2,500 Ah = 480,000 Wh	96 × 181 kg = 17,376 kg	96 × 0.30 mΩ = 28.8 mΩ	96 × 2.23 V = 214.08 V	96 × 2.35 V = 225.60 V

The final-voltage table below is the published discharge guidance for the OPzV2-2500 and the only discharge curve in the datasheet. For solar or wind duty the long-time discharge capacity table and the corresponding setpoint table are not published for this model, and both rows are recorded as such rather than filled from a neighbouring cell.

Discharge current	Published final voltage per cell	Solar/wind long-time discharge capacity	Source
I < 0.05 C	1.90 Vpc or higher	Not published	Datasheet
0.05 C to 0.08 C	1.85 Vpc	Not published	Datasheet
0.08 C to 0.2 C	1.80 Vpc	Not published	Datasheet
0.2 C to 0.6 C	1.75 Vpc	Not published	Datasheet
0.6 C to 1.0 C	1.70 Vpc	Not published	Datasheet
1 C to 2 C	1.60 Vpc	Not published	Datasheet

§4 — The Framework: A Five-Step Specification That Survives a Tender Review

Step one — write the duty profile before the cell. Record the average daily discharge current, the peak current, the duration of the peak, the end-of-discharge voltage the inverter will accept and the ambient temperature range at the site. Without this, “2,500 Ah” is a number without a duty, and the final-voltage table cannot be applied.

Step two — select the string voltage against the inverter, then count the cells. At 48 V the string floats at 53.52 V and equalises at 56.40 V; at 96 V it floats at 107.04 V and equalises at 112.80 V; at 192 V it floats at 214.08 V and equalises at 225.60 V. Each step doubles the cell count, the mass, the string resistance and the number of inter-cell connections, so the choice should be made on DC distribution economics rather than on cell price.

Step three — size the charger against the published maximum charging current. 500 A per cell is the ceiling, and it equals 0.20 C10. For a 48-cell 96 V string the ceiling is 48 × 500 A = 24,000 A, and for a 24-cell 48 V string it is 24 × 500 A = 12,000 A. A charge controller that exceeds the published limit shortens cell life even when the setpoints are correct.

Step four — confirm the mechanical envelope against the container drawing, not against the model name. 487 mm case length, 212 mm width, 772 mm container height and 807 mm over the terminals, with an approximate cell weight of 181 kg. The container floor loading for a 96 V string is approximately 8,688 kg before the enclosure, and the lifting plan has to be written for that.

Step five — write the setpoints, the compensation and the acceptance test into the contract. Float 2.23 V per cell at 25 °C, equalising 2.35 V per cell at 25 °C, temperature compensation −3 mV/°C/cell, self-discharge approximately 2 % per month at 20 °C, operating range for discharge −40 to 65 °C and for charge −30 to 65 °C, storage range −25 to 45 °C, and designed floating life 20+ years at 20 °C. Acceptance should reference the datasheet float test procedure, so that the cell is judged on capacity retention rather than on an initial reading.

Where a project sits in a hot region, note the reference temperature carefully. The 20+ year designed floating life is quoted at 20 °C, not at 25 °C, and every cell in the range loses achievable life as ambient temperature rises. The float voltage compensation of −3 mV/°C/cell exists to hold float voltage constant as the cell warms; at 35 °C the float setpoint falls by 0.036 V per cell, which is 0.864 V across a 24-cell 48 V string.

The delivery and commissioning side deserves the same precision. Cells in a container at a port such as Hamburg or Rotterdam can arrive having been in transit through an ambient swing, and the self-discharge figure of approximately 2 % per month at 20 °C means the pre-commissioning storage period is not neutral. Ports on the other side of the world — Jebel Ali, Durban, Santos, Chennai, Lagos, Mombasa, Port Said and Valencia — all present the same issue in reverse, because the shipment may have spent its duration at the far end of the temperature range rather than near it. Storage between −25 and 45 °C is the published limit, and a container parked in summer sun outside that band is a warranty question, not a logistics detail.

§5 — The Trust: What to Demand From the Supplier Before the Purchase Order

The most useful question a buyer can ask is “which document is this number from?” A published datasheet answers the questions a quotation never answers. What is the capacity rate and the end voltage? 2,500 Ah at C10 to 1.80 Vpc, with the final-voltage table printed alongside it. What are the case dimensions and the total height over the terminals? 487 × 212 mm and 807 mm — and the 487 mm length is the number that breaks container drawings. What is the weight? Approximately 181 kg, and unlike a flooded cell there is no second figure to add, because the electrolyte is immobilised in the gel. What is the maximum charging current? 500 A. What is the internal resistance? Approximately 0.30 mΩ fully charged at 25 °C. What is the self-discharge rate? Approximately 2 % per month at 20 °C. What defines end of life? The 60 % of nominal capacity criterion in the float test procedure.

Against that standard, reject any quotation that quotes a float voltage above 2.23 V per cell for this model, one that quotes a temperature compensation coefficient other than −3 mV/°C/cell, one that quotes the 20+ year design life against 25 °C rather than 20 °C, or one that offers solar or wind setpoint values for a datasheet that does not publish them. A supplier who quotes different numbers for the same model is either reading a different revision or inventing them.

Two further quality signals are worth checking before the deposit. First, ask for the plant audit trail: paste mixing, grid casting, group assembly, formation and sealing are the process steps that decide whether a 2,500 Ah gel cell still holds 2,500 Ah in year five, and they are the difference between a manufacturer and a packer. Second, ask for the certification package — ISO 9001, ISO 14001, CE, UL and IEC documentation should arrive with the quotation, not three weeks after the deposit. CHISEN operates 8 production bases with an annual capacity of roughly 70 million kVAh, and the company profile is published on the CHISEN company page.

A final point on supply risk. A cell that takes a full day of shipping to reach Durban, Lagos, Mombasa or a Latin American port such as Santos is a cell that will spend time in the container before commissioning, and the self-discharge rate applies to that time. Ask for the manufacturing date and the storage log with the shipment, and ask for the storage conditions to be recorded against the published −25 to 45 °C storage range.

§6 — FAQ

Q1. What is the rated capacity of the OPzV2-2500 2V2500Ah? 2,500 Ah at the ten-hour rate — 250 A for ten hours to 1.80 V per cell. The datasheet publishes the final-voltage table so usable capacity can be matched to the discharge current (Datasheet).

Q2. How many cells does a 48 V string need, and how much energy does it hold? 24 cells. 48 V × 2,500 Ah = 120,000 Wh nominal (Arithmetic). The string weighs approximately 4,344 kg (24 × 181 kg) and presents 7.2 mΩ of internal resistance (24 × 0.30 mΩ).

Q3. What float and equalising voltage should the charger use? Float 2.23 V per cell and equalising 2.35 V per cell, both referenced to 25 °C (Datasheet). The datasheet publishes no solar or wind setpoint table for this model, so those values must be taken from the controller manufacturer rather than borrowed from another cell in the range.

Q4. What temperature compensation does the cell need? −3 mV/°C/cell (Datasheet). At 35 °C the float setpoint falls by 0.036 V per cell, which is 0.864 V across a 24-cell 48 V string (Arithmetic).

Q5. How long is the designed floating life? 20+ years at 20 °C (Datasheet). Higher ambient temperatures reduce achievable service life, so site temperature belongs in the replacement plan rather than in a footnote.

Q6. What is the maximum charging current? 500 A per cell, which is 0.20 × C10 (Datasheet). For a 48-cell 96 V string the ceiling is 24,000 A (48 × 500 A, Arithmetic), and the charger and the array must both fit inside it.

Q7. What are the case dimensions and the weight? Footprint 487 × 212 mm, container height 772 mm, 807 mm over the terminals, approximately 181 kg per cell (Datasheet). The ABS container is available with an optional UL94-V0 flame rating, and the terminal is a female M8 copper insert torqued to 10–12 N·m.

Q8. Can this cell be installed horizontally? Yes. This is a valve-regulated sealed gel cell, so the published range data allows vertical, horizontal or side mounting, but never inverted, because the gel and the safety vent system depend on the electrolyte staying in place.

Q9. What is the internal resistance and short-circuit current? Approximately 0.30 mΩ fully charged at 25 °C, a 10,000 A short-circuit current and a 4,000 A maximum discharge current for five seconds (Datasheet). The string resistance of a 24-cell 48 V arrangement is 7.2 mΩ (24 × 0.30 mΩ, Arithmetic), and the 4,000 A figure is what the DC protection has to interrupt.

Q10. How does the OPzV2-2500 compare with the 2,000 Ah and 1,500 Ah gel cells? The case length is not proportional. The 1,500 Ah cell measures 275 × 210 mm at approximately 102 kg with approximately 0.45 mΩ internal resistance; the 2,000 Ah cell measures 399 × 212 mm at approximately 145 kg with approximately 0.37 mΩ; the OPzV2-2500 measures 487 × 212 mm at approximately 181 kg with approximately 0.30 mΩ. Maximum charging current rises with capacity — 300 A, 400 A and 500 A — while internal resistance falls. The OPzV2-2500 2V2500Ah model page carries the full data set.

Expert Summary

The OPzV2-2500 2V2500Ah is a 2 V valve-regulated tubular gel lead-acid cell with a published 2,500 Ah capacity at the ten-hour rate (250 A to 1.80 Vpc); float 2.23 V per cell and equalising 2.35 V per cell at 25 °C with −3 mV/°C/cell compensation, a 500 A maximum charging current and a 20+ year design floating life referenced to 20 °C; a footprint of 487 × 212 mm with a 772 mm container height, 807 mm over the terminals and approximately 181 kg per cell; an ABS container with optional UL94-V0 flame rating and an M8 female copper insert torqued to 10–12 N·m; approximately 0.30 mΩ internal resistance at 25 °C, a 10,000 A short-circuit current and a 4,000 A maximum discharge for five seconds; discharge operation from −40 to 65 °C, charge operation from −30 to 65 °C and storage from −25 to 45 °C with approximately 2 % per month self-discharge at 20 °C; and IEC 60896-21/22, DIN 40472, IEC 61427, YD/T 1360, BS 6290 part 4 and UL 1989 standards with ISO 9001 and ISO 14001 management systems. A 24-cell 48 V string holds 120,000 Wh nominal, weighs approximately 4,344 kg, presents 7.2 mΩ of internal resistance, floats at 53.52 V and equalises at 56.40 V; a 48-cell 96 V string holds 240,000 Wh nominal, weighs approximately 8,688 kg and floats at 107.04 V. The cell suits utility-scale storage containers, peak-shaving installations and long-duration backup where the maintenance-free sealed construction removes the watering cycle entirely, provided the final-voltage table is used to set the usable capacity, the charger is held inside the 500 A per cell limit and the container drawing is built from the 487 mm case length.

Contact CHISEN — 24-Hour Response

If you are quoting a 2 V 2,500 Ah sealed cell for a utility storage container in Rotterdam, a peak-shaving site in Chennai or a backup installation in Durban, ask for the complete OPzV2-2500 datasheet, the case drawing and the certification package, and ask for them in writing: email sales@chisen.cn, or message the export desk on WhatsApp at +86 131 6622 6999. One line describing your bus voltage, average and peak discharge current, site temperature and container dimensions is enough for us to return the string arithmetic, the charger setpoints, the final-voltage recommendation and the nearest capacity in the gel range.

Related CHISEN Buyer Guides

November 2, 2026

6-EVF-135 12V135Ah AGM Battery: Published Specs, 48 V Sightseeing Fleet Sizing and Sibling Comparison

Answer First

The 6-EVF-135 12V135Ah is a sealed 12 V AGM valve-regulated lead-acid block rated at 135 Ah on the three-hour rate — 45 A for three hours down to 1.75 V per cell — with a published weight of 45 ± 0.2 kg, published dimensions of 338 × 172 × 280 mm, a maximum charging current of 27.0 A, float setting 13.5 V and equalising setting 14.1 V, and a stated cycle life of 350–600 cycles at 50–80 % depth of discharge.

It is built for electric sightseeing vehicles, low-speed shuttle carts, hotel and resort runabouts and airport apron buggies: vehicles that work long days in heat, stop and start constantly, sit idle at full charge overnight, and then need to be back on the road at dawn.

Two numbers decide whether the 6-EVF-135 is right for your fleet. The first is the capacity rate: 135 Ah is a three-hour figure, so a bank sized on the ten-hour rate of this block will feel roughly a third smaller in the hills than the label suggests. The second is the 27.0 A charging ceiling, because a charger chosen from a generic “C10 charging” rule of thumb will over-charge this block every single night.

The complete published data set for the 6-EVF-135 12V135Ah sits on the 6-EVF-135 12V135Ah model page, and the rest of the sealed mobility range is listed under EVF sealed lead-acid batteries.

Key Takeaways

135 Ah is a three-hour rating, not a ten-hour rating. The 6-EVF-135 delivers 135 Ah at C3, which means 45 A for three hours to a 1.75 V per cell cutoff (Model page). Sizing a pack on C10 will understate the real available energy in a hill climb.
The charging envelope is fixed and it is not generous. Maximum charging current is 27.0 A, roughly 0.20 × C10 on a 135 Ah block (Model page). A 30 A charger matches the datasheet; a 45–50 A charger does not.
Float and equalising are set for the 12 V block, not the cell. Float 13.5 V, equalising 14.1 V — that is 2.25 V and 2.35 V per cell across six cells (Model page).
Weight and footprint are what the vehicle designer needs. 45 ± 0.2 kg, 338 × 172 × 280 mm, φ20-M8 terminals (Model page). A 48 V pack of four sits on the floor at 180.0 kg (4 × 45 kg, Arithmetic).
Cycle life is a band, not a number. 350–600 cycles at 50–80 % depth of discharge (Model page). A fleet that keeps the pack between 50 % and 80 % full lives at the top of that band; a fleet that runs to near-empty every cycle lives at the bottom.

§1 — 6-EVF-135 12V135Ah Published Specifications

Parameter	6-EVF-135 published value	Source
Product type	Valve-regulated lead-acid, AGM technology	Model page
Nominal voltage	12 V (six cells in one block)	Model page
Rated capacity	135 Ah at the 3-hour rate (C3), end voltage 1.75 V/cell	Model page
Energy at nominal	1,620 Wh (12 V × 135 Ah)	Arithmetic
Weight	45 ± 0.2 kg	Model page
Dimensions (L × W × H)	338 × 172 × 280 mm	Model page
Terminal	φ20-M8	Model page
Maximum charging current	27.0 A	Model page
Float charge voltage	13.5 V (2.25 V/cell)	Model page
Equalising charge voltage	14.1 V (2.35 V/cell)	Model page
Designed cycle life	350–600 cycles at 50–80 % DoD	Model page
Specific energy	36.0 Wh/kg (1,620 Wh ÷ 45 kg)	Arithmetic
Standards	GB/T 32620.1-2016, GB/T 32620.2-2016, JB/T 2599	Model page
Certifications	CE, RoHS, REACH, MSDS, IMDG sea-freight certification	Model page
48 V pack (4 × 6-EVF-135)	180.0 kg (4 × 45 kg), 540 Ah, 6,480 Wh, 108 A charge limit	Arithmetic
72 V pack (6 × 6-EVF-135)	270.0 kg (6 × 45 kg), 810 Ah, 9,720 Wh, 162 A charge limit	Arithmetic

Every row above carries the source it came from. The values marked Model page are taken from the published 6-EVF-135 product page; the rows marked Arithmetic are simple multiplications of those published values and nothing else — no value in this table has been estimated, rounded up for marketing, or carried over from a neighbouring model.

§2 — The Pain: Why Sightseeing Fleets Buy the Wrong 12 V Block

A sightseeing vehicle is not a forklift and it is not a telephone exchange, and yet it inherits both sets of bad habits. It runs a long duty cycle — a full sightseeing loop in Hangzhou, a shuttle circuit around Shenzhen Bay, a resort run in Phuket — often eight to twelve hours a day with the air conditioning drawing continuously. Then it sits on the charger for a short window at night, and then it repeats in summer, when ambient temperature in a closed vehicle bay in Ningbo, Durban or Cairo can exceed the comfort band of every person inside it.

The first failure is rate confusion. A buyer who reads “135 Ah” on a 6-EVF-135 and applies the familiar ten-hour-rate intuition of a stationary battery will size a pack that delivers roughly 100 Ah at that rate, not 135 Ah. On a flat ceremonial route that is invisible. On the climb out of the old quarter in Lisbon, or the ramp section of a safari circuit near Nairobi, the pack voltage sags well before the tour is finished, the operator reduces the pace, and the fleet loses revenue in the one hour it cannot afford.

The second failure is charging. A 27.0 A ceiling is not a guideline, it is a datasheet limit tied to the plate alloy and the internal temperature rise during absorption. Chargers marketed for “12 V 135 Ah” packs frequently deliver 45 A or more, because the rule of thumb they use is a quarter of the nominal capacity. On a 6-EVF-135 that is an over-charge every night, year after year: elevated water loss inside the block, accelerated grid corrosion, and a warranty claim that falls outside every published cycle-life figure.

The third failure is thermal. AGM blocks tolerate heat better than flooded cells, but they do not tolerate it for free. A pack that is charged at 27.0 A straight after a full day of work, in a bay at 40 °C, arrives at absorption with the electrolyte already warm, and the accepted current drops while the charger still pushes. The result is a pack that never reaches full charge on weekdays and arrives at the weekend service bay partly depleted — the classic cause of a shortened fleet life.

The fourth failure is mechanical. The 6-EVF-135 at 338 × 172 × 280 mm and 45 ± 0.2 kg is not interchangeable with every other 135 Ah block on the market, and it is not interchangeable with its own 6-EVF siblings either. The 6-EVF-120 measures 407 × 170 × 240 mm and the 6-EVF-150 measures 483 × 170 × 240 mm. A replacement drawn from a different series may fit the voltage specification and still fail to fit the tray, the hold-down bar or the terminal guard.

§3 — The Choice: Sizing a 6-EVF-135 Fleet Against the Published Siblings

The 6-EVF series is a stepped range, and the correct comparison is between published values rather than marketing labels. The table below sets the 6-EVF-135 against the neighbouring capacities in the same series.

Model	6-EVF-120	6-EVF-135	6-EVF-150	6-EVF-200
Rated capacity (Ah at C3)	120	135	150	200
Weight (kg)	40	45 ± 0.2	48.5	63.0
Dimensions (L × W × H, mm)	407 × 170 × 240	338 × 172 × 280	483 × 170 × 240	Published on the model page
Maximum charging current (A)	24.0	27.0	30.0	Published on the model page
Energy at nominal (Wh)	1,440	1,620	1,800	2,400
Specific energy (Wh/kg)	36.0	36.0	37.1	38.1
48 V pack weight (4 units, kg)	160.0	180.0	194.0	252.0

Sources: capacities, weights, dimensions, charging limits and the 6-EVF-200 weight from the published model pages; energy, specific energy and pack weights are Arithmetic on those published values.

Three conclusions follow from the published numbers alone.

First, the specific energy of the 6-EVF-135 is 36.0 Wh/kg, and it is the same 36.0 Wh/kg as the 6-EVF-120. The step from 120 Ah to 135 Ah does not buy efficiency; it buys endurance. If your route is short and the vehicle carries a heavy load, take the extra Ah. If your route is long but the load is light, the smaller block does the same work with less mass on the chassis, and 20 kg per block across four blocks is 80 kg of capacity you do not have to lift every time the vehicle turns.

Second, the footprint story is not a ladder. The 6-EVF-135 at 338 × 172 × 280 mm is narrower and taller than both its neighbours, while the 6-EVF-120 at 407 × 170 × 240 mm and the 6-EVF-150 at 483 × 170 × 240 mm are both longer and lower. Anyone who assumes a sealed block of the same capacity shares the same tray is designing a fleet that will not build. Measure the battery box on the actual vehicle before the 6-EVF-135 is stamped into the bill of materials.

Third, on charging the range is disciplined. 24.0 A, 27.0 A, 30.0 A — that is 0.20 × C10 across the three published capacities, and it is the number the charger supplier should see. A 48 V pack of four 6-EVF-135 blocks presents a 108 A charge limit (4 × 27.0 A, Arithmetic), so a 30 A charger per block is the correct choice, and a 30 A 48 V charger with current sharing is the correct choice for the pack.

For the bus architecture itself, the same published figures lead to a clean decision. A 48 V pack of four 6-EVF-135 blocks gives 540 Ah and 6,480 Wh at 180.0 kg — the usual choice for a two-axle sightseeing cart with a low roof and a tight turning circle. A 72 V pack of six gives 810 Ah and 9,720 Wh at 270.0 kg — more headroom for longer loops, for hill work and for air-conditioning load, at the cost of 90 kg and a wider footprint that the vehicle designer has to accommodate from day one.

§4 — The Framework: Six Hard Criteria Before You Sign the Purchase Order

Match the capacity rate to the duty, not to the label. Ask every supplier for Ah at the same rate — three-hour, ten-hour or twenty-hour — and insist on the end voltage. If one quote is at C3 and another is at C10, the numbers are not comparable, and the comparison that looks like a price difference is usually a capacity difference. For the 6-EVF-135 the published basis is C3 at 1.75 V per cell.
Take the charge limit from the datasheet, not from a rule of thumb. 27.0 A for the 6-EVF-135, 108 A across four in series. Size the charger on that figure, and require the charger supplier to confirm the absorption current in writing.
Check the thermal envelope against the real bay. The published cycle life of 350–600 cycles assumes normal operating temperature. A vehicle that works eight hours a day and then charges in a sealed enclosure at 40 °C needs a bay design that moves air, not a battery that was tested at 25 °C.
Verify the mechanical envelope on the vehicle. Weight, length, width, height, terminal type and hold-down arrangement, taken from the datasheet and then checked against the battery tray drawing. The 6-EVF-135 is 338 × 172 × 280 mm and 45 ± 0.2 kg with φ20-M8 terminals.
Set the depth-of-discharge policy before the warranty conversation. The published 350–600 cycle band is a function of how deeply the pack is discharged. A fleet that returns to base at 50 % state of charge uses the top of that band; a fleet that runs to the 1.75 V per cell cutoff uses the bottom.
Ask for the certification package, in writing. GB/T 32620.1-2016 and GB/T 32620.2-2016 for the product, JB/T 2599 where the vehicle category requires it, plus CE, RoHS and REACH documentation and IMDG sea-freight certification if the fleet is shipped or driven overseas.

§5 — The Trust: Reading a Cycle-Life Band Honestly

A published cycle life of 350–600 cycles is not marketing vagueness. It is the datasheet refusing to quote a single number for a product whose life genuinely depends on how the operator uses it. The honest reading is this: a 6-EVF-135 that is charged every night, kept between 50 % and 80 % state of charge, and operated inside a moderate temperature band will reach the upper part of that range. The same block in a vehicle that discharges deeply, sits hot, and charges in a hurry will land at the lower part of it. Any supplier who quotes a single life figure for this block without asking about your duty cycle is selling you a number, not a guarantee.

Three further points deserve a buyer’s attention. First, the cycle figure is a cycle figure, not a calendar figure: an AGM mobility block used two years a season has a different horizon from one used every day, and the datasheet is not a licence to leave a pack in a hot yard for a season. Second, the 6-EVF-135 is a sealed AGM block, so there is no distilled-water top-up and no electrolyte density check, but there is still a scheduled inspection regime: terminal condition, hold-down torque, and the state of charge at rest before the first morning start. Third, capacity quoted at C3 is not the capacity available at a two-hour rate; if your route demands bursts of acceleration on a grade, ask for the discharge curve, not the headline figure.

Underneath all of it sits the manufacturing question, which is where most buyer audits end up. CHISEN operates 8 production bases with a combined annual capacity of 70 million kVAh, under ISO 9001 and ISO 14001 management systems, and the platform covers plate pasting, group assembly, formation, sealing and final test. A factory that publishes those five process steps is a factory you can audit; a factory that only publishes capacity figures is a trader. If the 6-EVF-135 is going into a fleet that will run in Europe, in Brazil and in Southeast Asia over the next five years, that distinction is worth more than a small price difference.

§6 — FAQ: 6-EVF-135 12V135Ah Buyer Questions

Q1. What does “135 Ah” mean on the 6-EVF-135? It means 135 Ah at the three-hour rate: 45 A for three hours down to 1.75 V per cell (Model page). It is a high-rate figure, typical of mobility work where the vehicle pulls hard for short bursts, and it should not be read as the ten-hour capacity of the block.

Q2. How many 6-EVF-135 batteries make a 48 V pack? Four. That gives 48 V nominal, 540 Ah and 6,480 Wh, at 180.0 kg total (4 × 45 kg, Arithmetic) and a combined charge limit of 108 A (4 × 27.0 A, Arithmetic).

Q3. What charger do I need for a 6-EVF-135 pack? One that delivers no more than 27.0 A per block (Model page), so a 30 A charger per block and a 30 A 48 V pack charger with current sharing. The absorption setpoint is 14.1 V and the float setpoint is 13.5 V.

Q4. Can I use 6-EVF-135 blocks in a 72 V system? Yes. Six blocks in series give 72 V, 810 Ah and 9,720 Wh at 270.0 kg (6 × 45 kg, Arithmetic), with a 162 A charge limit (6 × 27.0 A, Arithmetic). Check that the vehicle controller, the DC-DC converter and the traction motor are rated for 72 V before you commit.

Q5. How long will a 6-EVF-135 last in a sightseeing vehicle? The published design figure is 350–600 cycles at 50–80 % depth of discharge (Model page). Where the fleet charges nightly and keeps the pack in that depth-of-discharge band, the upper part of that range is the realistic planning figure; deep discharge and heat at charge time pull it down.

Q6. Is the 6-EVF-135 AGM or gel? It is a valve-regulated lead-acid block using AGM technology, as published on the model page. The practical differences that matter to a fleet operator are that it needs no distilled-water top-up, that it releases very little hydrogen, and that it is a sealed block rather than an open-acid cell.

Q7. What terminal and what hardware do I need? φ20-M8 terminals (Model page). Take the cable lug and the torque figure from the same datasheet, and specify the terminal guard on the vehicle, because a sightseeing vehicle is frequently driven with passengers sitting close to the pack.

Q8. Can I substitute the 6-EVF-120 or the 6-EVF-150 for a 6-EVF-135? Electrically, yes — 13.5 V float and 14.1 V equalising apply across the range. Mechanically, check first: the 6-EVF-120 is 407 × 170 × 240 mm at 40 kg and the 6-EVF-150 is 483 × 170 × 240 mm at 48.5 kg, against 338 × 172 × 280 mm and 45 ± 0.2 kg for the 6-EVF-135. The charge limit also changes: 24.0 A and 30.0 A respectively.

Q9. Which standards and certifications does the 6-EVF-135 carry? GB/T 32620.1-2016 and GB/T 32620.2-2016 for the product, JB/T 2599, and CE, RoHS and REACH documentation with MSDS and IMDG sea-freight certification, published on the model page. Ask for the documentation pack with the quotation.

Q10. Is this the right block for a stationary solar or telecom backup duty? No, and choosing it for that duty is a common mistake. The 6-EVF-135 is a mobility block: its published life figure is a cycle figure, not a float-life figure. A stationary application needs a float product with a documented design float life, such as the tubular range, and the two products should not be substituted for each other.

Expert Summary

The 6-EVF-135 12V135Ah is a sealed 12 V AGM valve-regulated lead-acid block for electric sightseeing vehicles and mobility applications, rated 135 Ah at the three-hour rate to a 1.75 V per cell cutoff, with a published weight of 45 ± 0.2 kg, published dimensions of 338 × 172 × 280 mm, φ20-M8 terminals, a 27.0 A maximum charging current, float 13.5 V and equalising 14.1 V — that is 2.25 V and 2.35 V per cell across six cells — and a published cycle life of 350–600 cycles at 50–80 % depth of discharge, built to GB/T 32620.1-2016 and GB/T 32620.2-2016 with JB/T 2599, and supplied with CE, RoHS and REACH documentation, MSDS and IMDG sea-freight certification. Nameplate energy is 1,620 Wh, giving 36.0 Wh/kg. A 48 V pack of four blocks delivers 540 Ah and 6,480 Wh at 180.0 kg with a 108 A charge limit; a 72 V pack of six delivers 810 Ah and 9,720 Wh at 270.0 kg with a 162 A charge limit. Against its published siblings the 6-EVF-120 gives 1,440 Wh at 40 kg and the 6-EVF-150 gives 1,800 Wh at 48.5 kg, so the 6-EVF-135 buys endurance rather than efficiency, and its charging limit should be taken from the datasheet rather than from a capacity rule of thumb.

Contact CHISEN

If you are quoting a 12 V 135 Ah block for a sightseeing fleet running in Hangzhou, a resort circuit in Phuket, a shuttle line in Mexico City or an airport apron buggy in Dubai, ask for the complete 6-EVF-135 datasheet, the terminal and hold-down drawing, and the certification package — in writing. Email sales@chisen.cn, or message the export desk on WhatsApp at +86 131 6622 6999 (https://wa.me/8613166226999). One line describing your bus voltage, route length, ambient temperature and daily cycle count is enough for us to return the pack arithmetic, the charger setpoints and the nearest capacity in the 6-EVF range.

Browse the full CHISEN lead-acid range and technical data at https://leadacidbattery.cn.

Related CHISEN Product Pages

6-EVF-135 12V135Ah model page — the full published specification set
EVF sealed lead-acid battery range — 6-EVF mobility blocks from 60 Ah to 200 Ah
6-EVF-150 12V150Ah model page — the next capacity step, 48.5 kg at 150 Ah

Related CHISEN Buyer Guides

October 30, 2026

OPzV2-700 2V700Ah Tubular Gel Battery: Specs and String Sizing

Answer First

The OPzV2-700 2V700Ah is a 2 V, 700 amp-hour valve-regulated tubular gel lead-acid cell rated at the 10-hour rate — 70 A for 10 hours down to 1.80 V per cell — and it is the right cell for a data-centre DC panel, a telecom UPS room, or a utility-scale solar-and-storage container on a site where nobody will ever open a lid, read an electrolyte level or top up distilled water.

The published data set is distinctive in one respect that matters more than the capacity figure: this cell is 254 mm long and 210 mm wide, a noticeably different case proportion from the 145 × 206 mm cells in the 600 Ah class and the 191 × 210 mm cells in the 800 Ah class. Anyone who assumes a shared rack pitch across the gel range will order the wrong rails.

The complete published data set sits on the OPzV2-700 2V700Ah model page, and the rest of the gel range is listed under tubular gel lead-acid batteries.

Key Takeaways

Capacity is rate-dependent, and the C10 basis must be written into the order. 700 Ah at C10 to 1.80 V/cell is the published rating. The datasheet also publishes the final-voltage table that decides how much of that capacity a given discharge current can actually use.
Charging setpoints are fixed by the datasheet. Float 2.23 V/cell at 25 °C, equalising 2.35 V/cell at 25 °C, temperature compensation −3 mV/°C/cell with an adjustable range of −3 to −5 mV/cell/°C, designed float life 20+ years at 20 °C (Datasheet). Solar and wind controllers use the 2.27 ± 0.005 V/cell float and 2.40 ± 0.01 V/cell equalising setpoints.
Mechanical data is what decides the rack. Body 254 × 210 × 471 mm, 506 mm total height over the terminals, 51.0 kg (112.5 lbs), ABS container with optional UL94-V0 flame rating (Datasheet).
Two limits protect the cell. Maximum charging current is 140 A (0.20 × C10) and internal resistance is about 0.55 mΩ fully charged at 25 °C, with a 3300 A short-circuit current (Datasheet).
A 48 V string is simple arithmetic. 24 cells give 33,600 Wh nominal, 1,224.0 kg (24 × 51.0 kg) and 13.2 mΩ of internal resistance (24 × 0.55 mΩ) (Arithmetic).

§1 — OPzV2-700 2V700Ah Quick Specifications

Parameter	OPzV2-700 published value	Source
Model	OPzV2-700, tubular gel stationary cell, 2 V 700 Ah	Model page
Nominal voltage	2 V	Datasheet
Nominal capacity	700 Ah at C10 (70 A, 1.80 V/cell)	Datasheet
C10 discharge current	70 A (700 Ah ÷ 10 h)	Arithmetic
Float voltage	2.23 V/cell at 25 °C	Datasheet
Equalising voltage	2.35 V/cell at 25 °C	Datasheet
Temperature compensation coefficient	−3 mV/°C/cell, adjustable range −3 to −5 mV/cell/°C	Datasheet
Designed float life	20+ years at 20 °C	Datasheet (float life curve at 2.23 V/cell)
Float setpoint, solar and wind	2.27 ± 0.005 V/cell at 25 °C	Datasheet
Equalising setpoint, solar and wind	2.40 ± 0.01 V/cell at 25 °C	Datasheet
Dimensions L × W × H	254 × 210 × 471 mm	Datasheet
Container height	471 mm	Datasheet
Total height over terminals	506 mm	Datasheet
Terminal centre spacing	108 mm	Datasheet
Terminal	20 mm OD, M8 thread, female copper insert	Datasheet
Terminal tightening torque	10–12 N·m	Datasheet
Weight	51.0 kg (112.5 lbs)	Datasheet
Container material	ABS, UL94-V0 optional	Datasheet
Internal resistance	Approx. 0.55 mΩ, fully charged at 25 °C	Datasheet
Maximum charge current	140 A	Datasheet
Maximum discharge current (5 s)	2000 A	Datasheet
Short circuit current	3300 A	Datasheet
Self discharge	Approx. 2 % per month at 20 °C	Datasheet
Ambient, discharge	−40 °C to +65 °C	Datasheet
Ambient, charge	−30 °C to +65 °C	Datasheet
Ambient, storage	−25 °C to +45 °C	Datasheet
Float test procedure	20–25 °C, discharge 0.25 CA, cut-off 1.75 V/cell, end of life ≤ 60 % of nominal capacity	Datasheet
Charge capacity test condition	Charge voltage 2.35 V/cell, charge current I10, ambient 25 °C	Datasheet
Complied standards	IEC 60896-21/22, DIN 40472, IEC 61427, YD/T 1360, Eurobat long life guide, BS 6290 part 4, UL 1989	Datasheet

Every row above is traceable. Values taken from the manufacturer’s OPzV2-700 datasheet are marked Datasheet, values taken from the published English product page are marked Model page, and derived figures are marked Arithmetic wherever they appear in the text. A supplier who cannot tell you which of the three a given figure is has not verified it.

Final voltage settings recommended according to the discharge current

The datasheet publishes this table, and it is the piece of data most often left out of a quotation. The higher the discharge current, the lower the end voltage you must accept, because the internal resistance eats into the usable voltage.

Discharge current I	I < 0.05 C	0.05 C ≤ I < 0.08 C	0.08 C ≤ I < 0.2 C	0.2 C ≤ I < 0.6 C	0.6 C ≤ I < 1.0 C	1 C ≤ I ≤ 2 C
Final voltage per cell	≥ 1.90 V	≥ 1.85 V	≥ 1.80 V	≥ 1.75 V	≥ 1.70 V	≥ 1.60 V
Equivalent current at 700 Ah	below 35 A	35 A to 55 A	56 A to 139 A	140 A to 419 A	420 A to 699 A	700 A to 1400 A

Source: Datasheet for the voltage row, Arithmetic for the current row (multiples of the 700 Ah rating).

Solar and wind controller setpoints for the OPzV2-700

Controller parameter	Published setting	Why the number matters
Over voltage disconnect	2.45 ± 0.01 V/cell at 25 °C	The point at which the controller stops charging and the array is isolated
Regulation / equalising voltage	2.40 ± 0.01 V/cell at 25 °C	The renewable equalising setpoint, above the mains value
Array reconnection voltage	2.25 ± 0.005 V/cell at 25 °C	The bus voltage at which charging resumes
Float voltage setting	2.27 ± 0.005 V/cell at 25 °C	The renewable float setpoint, above the 2.23 V mains float
Low voltage alarm	1.95 ± 0.005 V/cell at 25 °C	The alarm threshold for the control room
Low voltage disconnect	1.90 ± 0.005 V/cell at 25 °C	The load is shed at this point to protect the cells
Load reconnect voltage	2.09 ± 0.01 V/cell at 25 °C	The load is restored once the bus recovers

§2 — The Pain: Where 2V 700Ah Sealed Projects Go Wrong

The first failure is a case-proportion failure, and it is specific to this model. The OPzV2-700 is 254 mm long. The 600 Ah cell in the same range is 145 mm long and 646 mm tall; the 800 Ah cell is 191 mm long and 646 mm tall. A project team that assumes the gel range shares one rack pitch will specify rails that do not accept this cell, or will accept it on rails that were never load-checked for 51.0 kg of cell per position. Both outcomes surface at delivery, and both are expensive.

The second failure is the missing final-voltage table. A battery is quoted at 700 Ah, the string is built for a two-hour discharge at 350 A, and the end voltage is left at whatever the inverter’s default happens to be. Using the published table, 350 A sits in the 0.2 C to 0.6 C band, so the final voltage per cell must be at or above 1.75 V, not the 1.90 V that a low-rate discharge would allow. Accepting 1.90 V at that current means accepting less usable capacity than the nameplate, and the shortfall is invisible until the first winter load test.

The third failure is thermal. The published ambient ranges are −40 °C to +65 °C for discharge and −30 °C to +65 °C for charge, which is wider than a flooded cell in the same duty because there is no liquid electrolyte to freeze. What the sealed cell does not tolerate is being charged outside its compensation band, and the coefficient is published as −3 mV/°C/cell with an adjustable range of −3 to −5 mV/cell/°C. A controller left on the wrong coefficient overcharges the string in a hot season.

The fourth failure is ignoring the charging limit in storage projects. The maximum charging current is 140 A per cell, so a 54-cell 108 V panel accepts at most 7,560 A (54 × 140 A, Arithmetic). On a solar-and-storage site the charger must absorb the array’s peak current and the string’s recharge simultaneously, and a controller sized on the array alone will breach the cell limit every sunny afternoon. The published capacity-versus-time curves for 25 %, 50 %, 75 % and 100 % depth of discharge are the right tool for sizing that recharge window.

The fifth failure is assuming the sealed cell has no limits at all. A valve-regulated gel cell still self-discharges at about 2 % per month at 20 °C, still has a defined float life referenced to 20 °C, and still has a defined end-of-life criterion — the datasheet’s float test procedure sets it at 60 % of nominal capacity under a 0.25 CA discharge to a 1.75 V cutoff at 20–25 °C. A battery with a published end-of-life test can be maintained on a schedule; one without it is retired by surprise.

The delivery route matters as much as the cell. A sealed OPzV2-700 2V700Ah moves through Singapore and Mumbai for importers in South-East Asia and India, and through Antwerp for European data-centre projects, and a Karachi-bound consignment needs its own import file rather than the one used for a Rotterdam delivery.

§3 — The Choice: The OPzV2-700 Against Its Published Gel Siblings

Model	Capacity at C10	Weight with electrolyte	Dimensions L × W × H	Total height	Max charging current	Internal resistance	Short-circuit current	Self discharge
OPzV2-500 (gel)	500 Ah	36.3 kg	166 × 206 × 506 mm	506 mm	100 A	0.56 mΩ at 25 °C	2600 A	2 % per month
OPzV2-600 (gel)	600 Ah	42.0 kg	145 × 206 × 646 mm	681 mm	120 A	0.65 mΩ at 25 °C	3100 A	2 % per month
OPzV2-700 (gel)	700 Ah	51.0 kg	254 × 210 × 471 mm	506 mm	140 A	0.55 mΩ at 25 °C	3300 A	2 % per month
OPzV2-800 (gel)	800 Ah	60.0 kg	191 × 210 × 646 mm	681 mm	160 A	0.45 mΩ at 25 °C	not published	2 % per month

Sources: OPzV2-500, OPzV2-600 and OPzV2-800 from their published datasheets; OPzV2-700 from its datasheet; the comparison itself is Arithmetic.

Three observations follow directly from that table. First, the case geometry is not proportional: 254 × 210 × 471 mm for the 700 Ah cell against 145 × 206 × 646 mm for the 600 Ah cell. The 700 Ah cell is 109 mm longer and 175 mm shorter, which changes the rack depth, the floor area and the cable run. Second, internal resistance falls across the range — 0.65 mΩ, 0.55 mΩ, 0.45 mΩ — so a 24-cell string moves from 15.60 mΩ (24 × 0.65 mΩ, Arithmetic) at the 600 Ah step to 13.20 mΩ (24 × 0.55 mΩ, Arithmetic) at the 700 Ah step and 10.80 mΩ (24 × 0.45 mΩ, Arithmetic) at the 800 Ah step. Third, weight rises almost linearly with capacity: 36.3 kg, 42.0 kg, 51.0 kg, 60.0 kg, which is 9.0 kg of extra handling per cell between the 600 Ah and 700 Ah steps.

48 V string arithmetic across the gel range

Cell	Cells in string	Nominal energy	String weight	String internal resistance	Maximum charging current	Mass energy density
OPzV2-500	24	24,000 Wh	871.2 kg	13.44 mΩ	2,400 A	27.5 Wh/kg
OPzV2-600	24	28,800 Wh	1,008.0 kg	15.60 mΩ	2,880 A	28.6 Wh/kg
OPzV2-700	24	33,600 Wh	1,224.0 kg	13.20 mΩ	3,360 A	27.5 Wh/kg
OPzV2-800	24	38,400 Wh	1,440.0 kg	10.80 mΩ	3,840 A	26.7 Wh/kg

Source: Datasheet for the cell-level values, Arithmetic for the string rows.

The same arithmetic at 108 V — 54 cells — gives the OPzV2-700 a float bus of 120.42 V (54 × 2.23 V), 75,600 Wh nominal, 2,754.0 kg of cells (54 × 51.0 kg), 29.70 mΩ of internal resistance (54 × 0.55 mΩ) and a 7,560 A maximum charging current (54 × 140 A) (Arithmetic). On a 216 V three-phase DC panel the string becomes 108 cells, giving 240.84 V (108 × 2.23 V), 151,200 Wh nominal, 5,508.0 kg of cells (108 × 51.0 kg) and 15,120 A of maximum charging current (108 × 140 A) (Arithmetic).

Mass energy density per cell

Cell	Stored energy per cell	Cell weight	Mass energy density
OPzV2-500	1,000 Wh	36.3 kg	27.5 Wh/kg
OPzV2-600	1,200 Wh	42.0 kg	28.6 Wh/kg
OPzV2-700	1,400 Wh	51.0 kg	27.5 Wh/kg
OPzV2-800	1,600 Wh	60.0 kg	26.7 Wh/kg

Source: Datasheet for capacity and weight, Arithmetic for stored energy (2 V × Ah) and mass energy density.

If your project is comparing the sealed route against the vented route at the same rating, the OPzV2-700 2V700Ah gel cell and the flooded range listed under tubular flooded lead-acid batteries should be compared on case geometry, mass, charging limit and the maintenance regime — not on the capacity headline, which is the same figure on both sides.

§4 — The Framework: Seven Hard Checks Before You Sign

Q1. Match the charger to the cell’s acceptance, not to the string. The maximum charging current of the OPzV2-700 is 140 A (Datasheet). A 54-cell 108 V panel therefore accepts at most 7,560 A (54 × 140 A, Arithmetic). On a storage project the charger must absorb the array’s peak current and the string’s recharge at the same time.

Q2. Apply temperature compensation to the setpoint, not to the battery. The published coefficient is −3 mV/°C/cell, adjustable from −3 to −5 mV/cell/°C (Datasheet), so a cell at 35 °C needs its 2.23 V/cell float reduced by 0.036 V. On a renewable site the published float setpoint is 2.27 ± 0.005 V/cell with equalising at 2.40 ± 0.01 V/cell.

Q3. Set the end voltage from the published table, not from habit. At 700 Ah, a discharge below 35 A allows a 1.90 V final voltage; 35 A to 55 A allows 1.85 V; 56 A to 139 A allows 1.80 V; 140 A to 419 A allows 1.75 V; 420 A to 699 A allows 1.70 V; and 700 A to 1400 A allows 1.60 V (Datasheet, Arithmetic for the current bands).

Q4. Design for the float life at the site’s real temperature. The 20+ year design figure is quoted at 20 °C (Datasheet). A container in Chennai, a rooftop plant in Lagos or a plant in Durban will not deliver that figure, and the honest way to plan a replacement interval is to take the 20 °C number and treat every 10 °C of ambient uplift as a materially shorter service life.

Q5. Verify the rack pitch and the floor loading. This cell is 254 × 210 mm at the base, 471 mm of container and 506 mm over the terminals, at 51.0 kg per position. A rack drawn for the 600 Ah class at 145 × 206 mm and 681 mm tall does not accept it. The same applies to the floor: a 108-cell string is 5,508.0 kg of cells before the racks, the busbar and the cables.

Q6. Get the altitude derating in writing. The published OPzV2-800 data for the same range states normal operation to 3,000 m with capacity derating of 8 % per 1,000 m above that. For a high-altitude site — an Andean or Ethiopian telecoms build — ask for the derating curve that applies to the OPzV2-700 specifically rather than carrying a sibling’s figure across.

Q7. Confirm the standards and the end-of-life test. The gel cell is built to IEC 60896-21/22 and the DIN 40472 envelope, with IEC 61427 for renewable cycling, YD/T 1360 for the Chinese telecoms market, the Eurobat long life guide, BS 6290 part 4 and UL 1989 for the North American market. The datasheet’s float test procedure — 20–25 °C, 0.25 CA discharge, 1.75 V cutoff, end of life at 60 % of nominal capacity — is what allows the asset to be retired on a schedule instead of on a surprise.

§5 — The Trust: What a Datasheet Must State — and What to Reject

The single most useful question a buyer can ask a supplier is: “which document is this number from?” A published datasheet answers six questions that quotations never answer. What is the capacity rate and the end voltage? For the OPzV2-700 it is 700 Ah at C10 to 1.80 V/cell, with the full final-voltage table alongside it. What are the case dimensions and the total height over the terminals? 254 × 210 × 471 mm and 506 mm — and the length figure is the one that breaks rack drawings. What is the weight? 51.0 kg, and unlike a flooded cell there is no second number to add, because the electrolyte is immobilised in the gel. What is the maximum charging current? 140 A. What is the self-discharge rate? About 2 % per month at 20 °C. What defines end of life? The 60 % of nominal capacity criterion in the float test procedure.

Against that standard, reject any quotation that quotes a float voltage above 2.23 V per cell for this model, or one that quotes a temperature compensation coefficient other than −3 mV/°C/cell, or one that quotes the 20+ year design life against 25 °C rather than 20 °C. The OPzV2-700 datasheet setpoints are 2.23 V/cell float, 2.35 V/cell equalising and −3 mV/°C/cell compensation, with the 20+ year design figure referenced to 20 °C. A supplier who quotes different numbers for the same model is either reading a different revision or inventing them.

Two further quality signals are worth checking on site. First, ask for the plant audit trail: paste mixing, grid casting, group assembly, formation and sealing are the process steps that decide whether a 700 Ah gel cell really holds 700 Ah in year five, and they are the difference between a manufacturer and a packer. Second, ask for the certification package — ISO 9001, ISO 14001, CE, UL and IEC documentation should arrive with the quotation, not three weeks after the deposit. CHISEN runs eight production bases with roughly 70 million kVAh of annual capacity, and the company profile is published on the CHISEN company page.

§6 — FAQ

Q1. What is the rated capacity of the OPzV2-700 2V700Ah? 700 Ah at the 10-hour rate (70 A to 1.80 V/cell). The datasheet publishes the final-voltage table so the usable capacity can be matched to the discharge current (Datasheet).

Q2. How many cells does a 48 V string need, and how much energy does it hold? 24 cells. 48 V × 700 Ah = 33,600 Wh nominal (Arithmetic). The string weighs 1,224.0 kg (24 × 51.0 kg) and presents 13.2 mΩ of internal resistance (24 × 0.55 mΩ).

Q3. What float and equalising voltage should the charger use? Float 2.23 V/cell and equalising 2.35 V/cell, both referenced to 25 °C. On solar and wind sites use the 2.27 ± 0.005 V/cell float and 2.40 ± 0.01 V/cell equalising setpoint (Datasheet).

Q4. What temperature compensation does the cell need? −3 mV/°C/cell, adjustable from −3 to −5 mV/cell/°C (Datasheet). At 35 °C the float setpoint falls by 0.036 V per cell.

Q5. How long is the designed float life? 20+ years at 20 °C (Datasheet). Higher ambient temperatures reduce achievable service life, so site temperature has to be part of the replacement plan rather than a footnote.

Q6. What is the maximum charging current? 140 A per cell, which is 0.20 × C10 (Datasheet). For a 54-cell 108 V panel the ceiling is 7,560 A (54 × 140 A, Arithmetic), and the charger plus the solar array must both fit inside it.

Q7. Can this cell be installed horizontally? Yes. This is a valve-regulated sealed gel cell, so the published range data allows vertical, horizontal or side mounting, but never inverted, because the gel and the safety vent system depend on the electrolyte staying in place.

Q8. What is the internal resistance and short-circuit current? About 0.55 mΩ fully charged at 25 °C and a 3300 A short-circuit current (Datasheet). The string resistance of a 24-cell arrangement is 13.2 mΩ (24 × 0.55 mΩ, Arithmetic), and the 3300 A figure is what your DC fuse and disconnection arrangement must be able to interrupt.

Q9. How does the OPzV2-700 compare with the 600 Ah and 800 Ah gel cells? The case geometry is not proportional. The 600 Ah cell is 145 × 206 × 646 mm at 42.0 kg; the 700 Ah cell is 254 × 210 × 471 mm at 51.0 kg; the 800 Ah cell is 191 × 210 × 646 mm at 60.0 kg. Charging acceptance rises with capacity — 120 A, 140 A, 160 A — while internal resistance falls — 0.65 mΩ, 0.55 mΩ, 0.45 mΩ. The OPzV2-700 2V700Ah model page carries the full data set.

Q10. Which standards and certifications apply? The sealed gel cell is built to IEC 60896-21/22 and the DIN 40472 envelope, with IEC 61427 for renewable cycling, YD/T 1360 for the Chinese telecoms market, the Eurobat long life guide, BS 6290 part 4 and UL 1989 for the North American market. CHISEN supplies the range with CE documentation under ISO 9001 and ISO 14001 management systems.

Expert Summary

The OPzV2-700 2V700Ah is a 2 V valve-regulated tubular gel lead-acid cell with a published 700 Ah capacity at the 10-hour rate (70 A to 1.80 V/cell); float 2.23 V/cell and equalising 2.35 V/cell at 25 °C with −3 mV/°C/cell compensation (adjustable from −3 to −5 mV/cell/°C) and a 20+ year design float life referenced to 20 °C; a body of 254 × 210 × 471 mm with 506 mm total height over the terminals and 108 mm terminal spacing; a weight of 51.0 kg; an ABS container with optional UL94-V0 flame rating; a 140 A maximum charging current; about 0.55 mΩ internal resistance at 25 °C; and a 3300 A short-circuit current. A 24-cell 48 V string holds 33,600 Wh nominal, weighs 1,224.0 kg and presents 13.2 mΩ of internal resistance; a 54-cell 108 V panel floats at 120.42 V, holds 75,600 Wh and weighs 2,754.0 kg. The cell suits data-centre DC panels, telecom UPS rooms and utility-scale storage containers where the maintenance-free sealed construction removes the watering cycle entirely, provided the rack pitch is set from the 254 mm case length rather than assumed from a sibling model.

Contact CHISEN — 24-Hour Response

If you are quoting a 2 V 700 Ah sealed cell for a data-centre DC panel in Frankfurt, a telecom UPS room in Lagos or a storage container near Durban, ask for the complete OPzV2-700 datasheet, the case drawing and the certification package, and ask for them in writing: email sales@chisen.cn, or message the export desk on WhatsApp at +86 131 6622 6999 (https://wa.me/8613166226999). One line describing your bus voltage, backup time, site temperature and rack pitch is enough for us to return the string arithmetic, the charger setpoints, the final-voltage recommendation and the nearest capacity in the gel range.

Browse the full CHISEN lead-acid range and technical data at https://leadacidbattery.cn.

Related CHISEN Product Pages

OPzV2-700 2V700Ah model page — full published specification set
OPzV2-600 2V600Ah tubular gel cell — the capacity step below
Tubular gel battery range — sealed 2 V cells from 100 Ah to 3,000 Ah

Related CHISEN Buyer Guides

October 29, 2026

OPzS2-2500 2V2500Ah Flooded Tubular Cell: Utility-Scale Specs

Answer First

The OPzS2-2500 2V2500Ah is a 2 V, 2,500 amp-hour flooded tubular vented lead-acid cell rated at the 10-hour rate — 250 A for 10 hours down to 1.80 V per cell at 20 °C — and it stores 5,000 Wh in a single cell. A 54-cell 108 V string of these cells holds 270,000 Wh nominal, and a 108-cell 216 V string holds 540,000 Wh. That is the scale at which the design stops being a cabinet problem and becomes a civil-engineering problem: one cell weighs 183 kg with electrolyte and 131 kg dry, and a 54-cell string is 9,882.0 kg of cells before the racks, the busbar, the electrolyte service points or the crane.

The cell is vented and flooded, so hydrogen off-gassing, acid-proof flame-retardant vent plugs, distilled-water top-up and periodic equalisation are part of the specification, not an optional extra. On a utility-scale site that means a designed ventilation envelope, a watering plan and a density-check schedule, or the correct comparison against the sealed alternative in the same product line.

The complete published data set sits on the OPzS2-2500 2V2500Ah model page, and the rest of the flooded range is listed under tubular flooded lead-acid batteries.

Key Takeaways

Capacity is rate-dependent. The nameplate figure is 2,500 Ah at C10 (250 A to 1.80 V/cell at 20 °C). At longer rates the cell delivers more: 2,825 Ah at C24, 3,100 Ah at C48, 3,250 Ah at C72, 3,375 Ah at C100, 3,425 Ah at C120 and 3,500 Ah at C240 (Datasheet).
Charging setpoints are fixed by the datasheet. Float 2.23 V/cell at 25 °C, equalising 2.35 V/cell at 25 °C, temperature compensation −3 mV/°C/cell, designed float life 20+ years at 20 °C (Datasheet). Solar and wind controllers use the 2.25 ± 0.005 V/cell float and 2.40 ± 0.01 V/cell equalising setpoints.
Mechanical data is what decides the civil works. Body 487 × 212 × 772 mm, 826 mm total height over the terminals, 131 kg without electrolyte and 183 kg with electrolyte, of which 52 kg is acid (Datasheet).
The terminal arrangement is the electrical design. Four terminal posts, two per pole, at 108 mm transverse spacing and four 110 mm longitudinal intervals, with 20 mm OD M8 inserts torqued to 10–12 N·m (Datasheet).
Two limits protect the cell. Maximum charging current is 500 A (0.20 × C10) and internal resistance is about 0.30 mΩ fully charged at 20 °C, with a 6700 A short-circuit current (Datasheet).

§1 — OPzS2-2500 2V2500Ah Quick Specifications

Parameter	OPzS2-2500 published value	Source
Model	OPzS2-2500, flooded tubular stationary cell, 2 V 2,500 Ah	Model page
Nominal voltage	2 V	Datasheet
Nominal capacity	2,500 Ah at C10 (250 A, 1.80 V/cell, 20 °C)	Datasheet
C10 discharge current	250 A (2,500 Ah ÷ 10 h)	Arithmetic
Nominal energy per cell	5,000 Wh (2 V × 2,500 Ah)	Arithmetic
Capacity at C24 / C48 / C72	2,825 Ah / 3,100 Ah / 3,250 Ah	Datasheet
Capacity at C100 / C120 / C240	3,375 Ah / 3,425 Ah / 3,500 Ah	Datasheet
Float voltage	2.23 V/cell at 25 °C	Datasheet
Equalising voltage	2.35 V/cell at 25 °C	Datasheet
Float setpoint, solar and wind	2.25 ± 0.005 V/cell at 25 °C	Datasheet
Equalising setpoint, solar and wind	2.40 ± 0.01 V/cell at 25 °C	Datasheet
Temperature compensation, float	−3 mV/°C/cell	Datasheet
Temperature compensation, solar and wind	−4 mV/cell/°C	Datasheet
Designed float life	20+ years at 20 °C	Datasheet
Dimensions L × W × H	487 × 212 × 772 mm	Datasheet
Container height	772 mm	Datasheet
Total height over terminals	826 mm	Datasheet
Terminal arrangement	Four posts, two per pole; 108 mm transverse spacing; four 110 mm longitudinal intervals	Datasheet
Terminal	20 mm OD, M8 thread, 7 mm insert depth, female copper insert	Datasheet
Terminal tightening torque	10–12 N·m	Datasheet
Weight without electrolyte	131 kg (289 lbs)	Datasheet
Weight with electrolyte	183 kg (404 lbs)	Datasheet
Electrolyte	Diluted sulphuric acid, 1.240 g/cm³ at 20 °C	Datasheet
Acid weight per cell	52 kg	Datasheet
Internal resistance	Approx. 0.30 mΩ, fully charged at 20 °C	Datasheet
Maximum charge current	500 A	Datasheet
Charge characteristic	Constant charge at 0.15 CA to 2.40 V at 20 °C	Datasheet
Maximum discharge current (5 s)	4000 A	Datasheet
Short circuit current	6700 A	Datasheet
Self discharge	Approx. 4 % per month at 20 °C	Datasheet
Ambient, discharge	−25 °C to +65 °C	Datasheet
Ambient, charge	−20 °C to +65 °C	Datasheet
Ambient, storage	−15 °C to +40 °C	Datasheet
Complied standards	IEC 60896-11, DIN 40736, IEC 61427, Eurobat long life guide, BS 6290 part 4, UL 1989	Datasheet
Management systems and marks	ISO 9001, ISO 14001 (UKAS), GB/T 28001 and OHSAS 18001:2007, CE, RU recognised component	Datasheet

Every row above is traceable. Values taken from the manufacturer’s OPzS2-2500 datasheet are marked Datasheet, values taken from the published English product page are marked Model page, and derived figures are marked Arithmetic wherever they appear in the text. A supplier who cannot tell you which of the three a given figure is has not verified it.

Long-time discharge capacity for solar and wind duty (final voltage 1.85 V)

Discharge rate	C24	C48	C72	C100	C120	C240
OPzS2-2500 capacity	2,825 Ah	3,100 Ah	3,250 Ah	3,375 Ah	3,425 Ah	3,500 Ah
Stored energy at 2 V	5,650 Wh	6,200 Wh	6,500 Wh	6,750 Wh	6,850 Wh	7,000 Wh

Source: Datasheet for the capacity row, Arithmetic for the energy row (2 V × Ah).

Solar and wind controller setpoints for the OPzS2-2500

Controller parameter	Published setting	Why the number matters
Over voltage disconnect	2.47 ± 0.01 V/cell at 25 °C	The point at which the controller stops charging and the array is isolated
Regulation / equalising voltage	2.40 ± 0.01 V/cell at 25 °C	Higher than the mains float because the array has to push against the bus
Array reconnection voltage	2.23 ± 0.005 V/cell at 25 °C	The bus voltage at which charging resumes
Float voltage setting	2.25 ± 0.005 V/cell at 25 °C	The renewable float setpoint, above the 2.23 V mains float
Low voltage alarm	1.95 ± 0.005 V/cell at 25 °C	The alarm threshold for the control room
Low voltage disconnect	1.90 ± 0.005 V/cell at 25 °C	The load is shed at this point to protect the cells
Load reconnect voltage	2.09 ± 0.01 V/cell at 25 °C	The load is restored once the bus recovers
Temperature compensation coefficient	−4 mV/cell/°C	The coefficient used on renewable sites, distinct from the −3 mV/°C/cell float value

§2 — The Pain: Where 2V 2500Ah Projects Go Wrong

The first failure is a scaling failure. Buyers take the published figures for a 2,000 Ah cell and scale them to 2,500 Ah, because scaling is cheaper than asking. The published cell is 487 mm long, 212 mm wide, 826 mm over the terminals, 131 kg dry and 183 kg wet. The published 2,000 Ah cell is 399 × 210 × 826 mm at 106 kg dry and 146 kg wet, and the published 3,000 Ah cell is 576 × 212 × 771 mm at 155 kg dry and 218 kg wet. Between them, cell length moves by 88 mm and then 89 mm, acid weight moves in 12 kg steps and then 11 kg steps, and internal resistance moves in steps that have nothing to do with either. Nothing about the 2,500 Ah cell is the arithmetic midpoint of its neighbours, which is exactly why the published table has to be asked for.

The second failure is the terminal design being overlooked. This cell carries four terminal posts, two per pole, at 108 mm transverse spacing and four 110 mm longitudinal intervals. A single-post connection on a cell rated for 500 A of charging current and a 6700 A short-circuit current concentrates all of that current at one joint, and the published torque of 10–12 N·m applies to each of the four inserts, not to the cell as a whole.

The third failure is a civil-works failure. A 54-cell string of OPzS2-2500 cells is 9,882.0 kg of cells (54 × 183 kg, Arithmetic) and 2,808.0 kg of acid (54 × 52 kg, Arithmetic), and that electrolyte has to be moved in and topped up over the life of the plant. Floor loading, plinth design, access for the watering crew, the crane plan and the container manifest all follow from numbers that must be quoted, not estimated.

The fourth failure is a charging failure. The maximum charging current is 500 A per cell, so a 54-cell 108 V string accepts at most 27,000 A (54 × 500 A, Arithmetic) — about 2.9 MW of charger at the nominal bus voltage, before losses. On a storage project the charger must absorb the array’s peak current and the string’s recharge at the same time, and a controller sized on the array alone will breach the cell limit on every clear day. The published long-time discharge table (C24 to C240) is the right input for sizing the recharge window.

The fifth failure is thermal. The 20+ year design float life is quoted at 20 °C. A containerised plant in the Atacama, at Port Augusta, at Sakaka in Saudi Arabia or at a solar park outside Gqeberha in South Africa will not deliver that figure, and the honest way to plan a replacement interval is to take the 20 °C number and treat every 10 °C of ambient uplift as a materially shorter service life. The same applies to a plant in the Atacama in Chile, to a solar park in Spain, to storage in India and to a large battery array in Australia — Port Augusta in particular sits in a hot, dry climate well above the 20 °C reference.

§3 — The Choice: The OPzS2-2500 Against Its Published Siblings

Model	Capacity at C10	Weight dry / with electrolyte	Dimensions L × W × H	Total height	Max charging current	Internal resistance	Short-circuit current
OPzS2-2000 (flooded)	2,000 Ah	106 kg / 146 kg	399 × 210 × 826 mm	826 mm	400 A	0.35 mΩ	6,000 A
OPzS2-2500 (flooded)	2,500 Ah	131 kg / 183 kg	487 × 212 × 772 mm	826 mm	500 A	0.30 mΩ	6,700 A
OPzS2-3000 (flooded)	3,000 Ah	155 kg / 218 kg	576 × 212 × 771 mm	826 mm	600 A	0.24 mΩ	not published

Sources: OPzS2-2000 and OPzS2-3000 from their published datasheets; OPzS2-2500 from its datasheet; the comparison itself is Arithmetic.

Four numbers decide this comparison. First, length: 399 mm, 487 mm and 576 mm. A rack built for the 2,000 Ah cell does not accept the 2,500 Ah cell, and the building’s aisle width, the door width and the shipping container manifest are all functions of that 88 mm step.

Second, weight: 146 kg, 183 kg and 218 kg with electrolyte, against 106 kg, 131 kg and 155 kg dry. Handling is a mechanical-aid job at every step, and the difference between the dry and the wet figure is 52 kg of acid per cell that the watering crew will handle for the next twenty years.

Third, internal resistance: 0.35 mΩ, 0.30 mΩ and 0.24 mΩ. A 54-cell string moves from 18.90 mΩ (54 × 0.35 mΩ, Arithmetic) to 16.20 mΩ (54 × 0.30 mΩ, Arithmetic) and then to 12.96 mΩ (54 × 0.24 mΩ, Arithmetic). On a megawatt-scale bus the difference is measured in the string voltage drop at peak load, and it changes the cable cross-section.

Fourth, acid quantity: 40 kg on the 2,000 Ah cell, 52 kg on the 2,500 Ah cell and 63 kg on the 3,000 Ah cell. That is the volume that has to be neutralised, serviced and eventually disposed of, and it is the number that decides whether the flooded route is the right route at all.

String arithmetic at four bus voltages

Bus	Cells	Nominal energy	Cell weight	String internal resistance	Maximum charging current	Acid in string
48 V	24	120,000 Wh	4,392.0 kg	7.20 mΩ	12,000 A	1,248.0 kg
108 V	54	270,000 Wh	9,882.0 kg	16.20 mΩ	27,000 A	2,808.0 kg
216 V	108	540,000 Wh	19,764.0 kg	32.40 mΩ	54,000 A	5,616.0 kg
380 V three-phase DC	190	950,000 Wh	34,770.0 kg	57.00 mΩ	95,000 A	9,880.0 kg

Source: Datasheet for the cell-level values, Arithmetic for the string rows (54 × 183 kg, 108 × 183 kg, 190 × 183 kg and 24 × 52 kg, 54 × 52 kg, 108 × 52 kg, 190 × 52 kg).

Float bus voltages for the same strings are 120.42 V at 108 V nominal (54 × 2.23 V), 240.84 V at 216 V (108 × 2.23 V) and 423.70 V at 380 V (190 × 2.23 V) (Arithmetic).

Mass energy density per cell across the flooded utility range

Cell	Stored energy per cell	Cell weight with electrolyte	Mass energy density	Acid per cell
OPzS2-2000	4,000 Wh	146 kg	27.4 Wh/kg	40 kg
OPzS2-2500	5,000 Wh	183 kg	27.3 Wh/kg	52 kg
OPzS2-3000	6,000 Wh	218 kg	27.5 Wh/kg	63 kg

Source: Datasheet for capacity and weight, Arithmetic for stored energy (2 V × Ah) and mass energy density.

The mass energy density is essentially flat across the three capacities — 27.4, 27.3 and 27.5 Wh/kg — which tells you that the flooded range scales cleanly in energy but not in handling, footprint or service burden. If the project is comparing against the sealed route, the OPzS flooded range overview and the sealed alternatives should be compared on acid volume, case geometry and the watering regime rather than on energy density.

§4 — The Framework: Seven Hard Checks Before You Sign

Q1. Match the charger to the cell’s acceptance, not to the string. The maximum charging current of the OPzS2-2500 is 500 A (Datasheet). A 54-cell 108 V string therefore accepts at most 27,000 A (54 × 500 A, Arithmetic), roughly 2.9 MW at the nominal bus voltage before losses.

Q2. Apply temperature compensation to the setpoint, not to the battery. The published compensation is −3 mV/°C/cell on float (Datasheet), so a cell at 35 °C needs its 2.23 V/cell float reduced by 0.036 V. On a renewable site the published coefficient is −4 mV/cell/°C and the float setpoint is 2.25 ± 0.005 V/cell.

Q3. Design for the float life at the site’s real temperature. The 20+ year design figure is quoted at 20 °C (Datasheet). A containerised plant in the Atacama, at Port Augusta or outside Gqeberha will not deliver that figure, and every 10 °C of ambient uplift is a materially shorter service life.

Q4. Plan the watering interval and the ventilation envelope together. Each cell holds 52 kg of acid at 1.240 g/cm³ (Datasheet). The watering cycle, the hydrogen vent path, the flame-retardant vent plug specification and the electrolyte density check all belong in the same maintenance plan as the float schedule.

Q5. Use all four terminal posts and torque each one. The cell has two posts per pole at 108 mm transverse spacing and four 110 mm longitudinal intervals, with 20 mm OD M8 inserts torqued to 10–12 N·m (Datasheet). Interconnect design follows from the 500 A charge limit and the 6700 A short-circuit current, and the protection scheme has to clear a fault at that magnitude.

Q6. Get the civil works quoted from the published numbers. 487 mm of length, 212 mm of width, 772 mm of container and 826 mm over the terminals, at 131 kg dry and 183 kg wet per cell. A 108-cell string is 19,764.0 kg of cells alone; the plinth, the aisle, the crane and the door widths follow from the same figures.

Q7. Confirm the standards the cell is built to. A 2 V vented cell for stationary duty is normally specified against IEC 60896-11 and the equivalent DIN 40736 envelope, with IEC 61427 for the renewable cycling test, the Eurobat long life guide, BS 6290 part 4 and UL 1989 for the North American market. CHISEN production runs under ISO 9001 and ISO 14001 with GB/T 28001 and OHSAS 18001:2007 occupational health and safety management, and the range is supplied with CE documentation.

§5 — The Trust: What a Datasheet Must State — and What to Reject

The single most useful question a buyer can ask a supplier is: “which document is this number from?” A published datasheet answers six questions that quotations never answer. What is the capacity rate and the end voltage? For the OPzS2-2500 it is 2,500 Ah at C10 to 1.80 V/cell at 20 °C, and the curve to 240 hours is published alongside it. What are the case dimensions and the total height over the terminals? 487 × 212 × 772 mm and 826 mm. What is the weight with and without electrolyte? 131 kg and 183 kg. What is the terminal arrangement? Four posts, two per pole, at 108 mm transverse spacing. What is the maximum charging current? 500 A. What is the acid quantity? 52 kg per cell.

Against that standard, reject any quotation that quotes a float voltage above 2.23 V per cell for this model, or one that quotes a temperature compensation coefficient other than −3 mV/°C/cell, or one that quotes the 20+ year design life against 25 °C rather than 20 °C. The OPzS2-2500 datasheet setpoints are 2.23 V/cell float, 2.35 V/cell equalising and −3 mV/°C/cell compensation, with the 20+ year design figure referenced to 20 °C. A supplier who quotes different numbers for the same model is either reading a different revision or inventing them.

Two further quality signals are worth checking on site. First, ask for the plant audit trail: paste mixing, grid casting, group assembly, formation and sealing are the process steps that decide whether a 2,500 Ah cell really holds 2,500 Ah in year five, and they are the difference between a manufacturer and a packer. Second, ask for the certification package — ISO 9001, ISO 14001, CE, UL and IEC documentation should arrive with the quotation, not three weeks after the deposit. CHISEN runs eight production bases with roughly 70 million kVAh of annual capacity, and the company profile is published on the CHISEN company page.

§6 — FAQ

Q1. What is the rated capacity of the OPzS2-2500 2V2500Ah? 2,500 Ah at the 10-hour rate (250 A to 1.80 V/cell at 20 °C), which is 5,000 Wh per cell. The published table also gives 2,825 Ah at C24, 3,100 Ah at C48, 3,250 Ah at C72, 3,375 Ah at C100, 3,425 Ah at C120 and 3,500 Ah at C240 (Datasheet).

Q2. How much energy does a 108 V string hold? 54 cells. 108 V × 2,500 Ah = 270,000 Wh nominal (Arithmetic). The cells weigh 9,882.0 kg (54 × 183 kg) with 2,808.0 kg of acid (54 × 52 kg), and the string presents 16.2 mΩ of internal resistance (54 × 0.30 mΩ).

Q3. What float and equalising voltage should the charger use? Float 2.23 V/cell and equalising 2.35 V/cell, both referenced to 25 °C. On solar and wind sites use the higher 2.25 ± 0.005 V/cell float and 2.40 ± 0.01 V/cell equalising setpoint (Datasheet).

Q4. What temperature compensation does the cell need? −3 mV/°C/cell on float (Datasheet), applied to the setpoint. At 35 °C the float setpoint falls by 0.036 V per cell. Renewable controllers use the published −4 mV/cell/°C coefficient.

Q6. What is the maximum charging current? 500 A per cell, which is 0.20 × C10 (Datasheet). For a 54-cell 108 V string the theoretical ceiling is 27,000 A (54 × 500 A, Arithmetic), and the charger should normally deliver far less.

Q7. Why does this cell have four terminals? Because a single joint cannot carry 500 A of charging current and the fault current of a 6700 A short circuit comfortably. The datasheet drawing shows two posts per pole, at 108 mm transverse spacing and four 110 mm longitudinal intervals, each a 20 mm OD M8 insert torqued to 10–12 N·m (Datasheet).

Q8. What is the internal resistance and short-circuit current? About 0.30 mΩ fully charged at 20 °C and a 6700 A short-circuit current (Datasheet). The string resistance of a 54-cell arrangement is 16.2 mΩ (54 × 0.30 mΩ, Arithmetic), and the 6700 A figure is what your DC fuse and disconnection arrangement must be able to interrupt.

Q9. How does the OPzS2-2500 compare with the 2,000 Ah and 3,000 Ah cells? Published values: 2,000 Ah at 399 × 210 × 826 mm, 146 kg wet, 400 A charge limit, 0.35 mΩ; 2,500 Ah at 487 × 212 × 772 mm with 826 mm over the terminals, 183 kg wet, 500 A, 0.30 mΩ; 3,000 Ah at 576 × 212 × 771 mm with 826 mm over the terminals, 218 kg wet, 600 A, 0.24 mΩ. Mass energy density is effectively flat at 27.4, 27.3 and 27.5 Wh/kg, so the choice is driven by footprint, handling and service access rather than by energy density. The OPzS2-2500 2V2500Ah model page carries the full data set.

Q10. Which standards and certifications apply? The flooded 2 V stationary cell is built to the IEC 60896-11 and DIN 40736 envelope, with IEC 61427 for renewable cycling, the Eurobat long life guide, BS 6290 part 4 and UL 1989 for the North American market. CHISEN supplies the range with CE documentation under ISO 9001 and ISO 14001 management systems, with GB/T 28001 and OHSAS 18001:2007 occupational health and safety certification.

Expert Summary

The OPzS2-2500 2V2500Ah is a 2 V flooded tubular vented lead-acid cell with a published 2,500 Ah capacity at the 10-hour rate (250 A to 1.80 V/cell at 20 °C), rising to 3,500 Ah at the 240-hour rate, storing 5,000 Wh per cell; float 2.23 V/cell and equalising 2.35 V/cell at 25 °C with −3 mV/°C/cell compensation and a 20+ year design float life referenced to 20 °C; a body of 487 × 212 × 772 mm with 826 mm total height over the terminals; four terminal posts, two per pole, at 108 mm transverse spacing; a weight of 131 kg without electrolyte and 183 kg with electrolyte, of which 52 kg is acid; a 500 A maximum charging current; about 0.30 mΩ internal resistance at 20 °C; and a 6700 A short-circuit current. A 54-cell 108 V string holds 270,000 Wh nominal, weighs 9,882.0 kg and presents 16.2 mΩ of internal resistance; a 108-cell 216 V string holds 540,000 Wh and weighs 19,764.0 kg. The cell suits utility-scale float storage, grid-connected DC plant and renewable integration where a designed watering and ventilation regime is available.

Contact CHISEN — 24-Hour Response

If you are quoting a 2 V 2,500 Ah cell for a utility-scale storage bank, a 108 V DC plant or a renewable integration project, ask for the complete OPzS2-2500 datasheet, the case and terminal drawing and the certification package, and ask for them in writing: email sales@chisen.cn, or message the export desk on WhatsApp at +86 131 6622 6999 (https://wa.me/8613166226999). One line describing your bus voltage, energy target, site temperature and service access is enough for us to return the string arithmetic, the charger setpoints and the nearest capacity in the flooded range.

Browse the full CHISEN lead-acid range and technical data at https://leadacidbattery.cn.

Related CHISEN Product Pages

OPzS2-2500 2V2500Ah model page — full published specification set
OPzS2-3000 2V3000Ah tubular flooded cell — the next capacity step, 3,000 Ah
Tubular flooded battery range — 2 V cells from 100 Ah to 3,000 Ah

Related CHISEN Buyer Guides

October 29, 2026

OPzS2-350 2V350Ah Flooded Tubular Cell: Specs and String Sizing

Answer First

The OPzS2-350 2V350Ah is a 2 V, 350 amp-hour flooded tubular vented lead-acid cell rated at the 10-hour rate — 35 A for 10 hours down to 1.80 V per cell at 20 °C — and it is the right cell for a telecom DC plant, a 108 V or 216 V substation bus, or a utility-scale solar-and-storage container that needs roughly 16.8 kWh nominal per 48 V string, on a site where a technician will still read the electrolyte level and top up distilled water every quarter.

It is not a sealed block. Hydrogen venting, acid-proof flame-retardant vent plugs, scheduled water top-up and periodic equalisation are part of the product, not optional extras. A project that treats the OPzS2-350 2V350Ah as a drop-in sealed cabinet battery discovers the difference in the first hot season.

The complete published data set sits on the OPzS2-350 2V350Ah model page, and the rest of the flooded range is listed under tubular flooded lead-acid batteries.

Key Takeaways

Capacity is rate-dependent. The nameplate figure is 350 Ah at C10 (35 A to 1.80 V/cell at 20 °C). At longer rates the cell delivers more: 396 Ah at C24, 434 Ah at C48, 455 Ah at C72, 473 Ah at C100, 480 Ah at C120 and 490 Ah at C240 (Datasheet).
Charging setpoints are fixed by the datasheet. Float 2.23 V/cell at 25 °C, equalising 2.35 V/cell at 25 °C, temperature compensation −3 mV/°C/cell, designed float life 20+ years at 20 °C (Datasheet). Solar and wind controllers use the 2.25 ± 0.005 V/cell float and 2.40 ± 0.01 V/cell equalising setpoints (Datasheet).
Mechanical data is what decides the rack. Body 124 × 206 × 471 mm, 525 mm total height over the terminals, 20.4 kg without electrolyte and 27.0 kg with electrolyte, of which 6.6 kg is acid (Datasheet).
Two limits protect the cell. Maximum charging current is 70 A (0.20 × C10) and internal resistance is about 0.62 mΩ fully charged at 20 °C, with a 3300 A short-circuit current (Datasheet).
A 48 V string is simple arithmetic. 24 cells give 16,800 Wh nominal, 648.0 kg with electrolyte (24 × 27.0 kg) and 14.88 mΩ of internal resistance (24 × 0.62 mΩ) (Arithmetic).

§1 — OPzS2-350 2V350Ah Quick Specifications

Parameter	OPzS2-350 published value	Source
Model	OPzS2-350, flooded tubular stationary cell, 2 V 350 Ah	Model page
Nominal voltage	2 V	Datasheet
Nominal capacity	350 Ah at C10 (35 A, 1.80 V/cell, 20 °C)	Datasheet
C10 discharge current	35 A (350 Ah ÷ 10 h)	Arithmetic
Capacity at C24 / C48 / C72	396 Ah / 434 Ah / 455 Ah	Datasheet
Capacity at C100 / C120 / C240	473 Ah / 480 Ah / 490 Ah	Datasheet
Float voltage	2.23 V/cell at 25 °C	Datasheet
Equalising voltage	2.35 V/cell at 25 °C	Datasheet
Float setpoint, solar and wind	2.25 ± 0.005 V/cell at 25 °C	Datasheet
Equalising setpoint, solar and wind	2.40 ± 0.01 V/cell at 25 °C	Datasheet
Temperature compensation, float	−3 mV/°C/cell	Datasheet
Temperature compensation, solar and wind	−4 mV/cell/°C	Datasheet
Designed float life	20+ years at 20 °C	Datasheet
Dimensions L × W × H	124 × 206 × 471 mm	Datasheet
Container height	471 mm	Datasheet
Total height over terminals	525 mm	Datasheet
Terminal centre spacing	108 mm	Datasheet
Terminal	Female copper insert M8, torque 10–12 N·m	Datasheet
Weight without electrolyte	20.4 kg (45.0 lbs)	Datasheet
Weight with electrolyte	27.0 kg (59.5 lbs)	Datasheet
Electrolyte	Diluted sulphuric acid, 1.240 g/cm³ at 20 °C	Datasheet
Acid weight per cell	6.6 kg	Datasheet
Internal resistance	Approx. 0.62 mΩ, fully charged at 20 °C	Datasheet
Maximum charge current	70 A	Datasheet
Charge characteristic	Constant charge at 0.15 CA to 2.40 V at 20 °C	Datasheet
Maximum discharge current (5 s)	1000 A	Datasheet
Short circuit current	3300 A	Datasheet
Self discharge	Approx. 4 % per month at 20 °C	Datasheet
Ambient, discharge	−25 °C to +65 °C	Datasheet
Ambient, charge	−20 °C to +65 °C	Datasheet
Ambient, storage	−15 °C to +40 °C	Datasheet
Complied standards	IEC 60896-11, DIN 40736, IEC 61427, Eurobat long life guide, BS 6290 part 4, UL 1989	Datasheet
Management systems and marks	ISO 9001, ISO 14001, GB/T 28001, CE, RU recognised component	Datasheet

Every row above is traceable. Values taken from the manufacturer’s OPzS2-350 datasheet are marked Datasheet, values taken from the published English product page are marked Model page, and derived figures are marked Arithmetic wherever they appear in the text. A supplier who cannot tell you which of the three a given figure is has not verified it.

Solar and wind controller setpoints for the OPzS2-350

Controller parameter	Published setting	Why the number matters
Over voltage disconnect	2.47 ± 0.01 V/cell at 25 °C	The point at which the controller stops charging and the array is isolated
Regulation / equalising voltage	2.40 ± 0.01 V/cell at 25 °C	Higher than the mains float because the array has to push against the bus
Array reconnection voltage	2.23 ± 0.005 V/cell at 25 °C	The bus voltage at which charging resumes
Float voltage setting	2.25 ± 0.005 V/cell at 25 °C	The renewable float setpoint, above the 2.23 V mains float
Low voltage alarm	1.95 ± 0.005 V/cell at 25 °C	The alarm threshold for the control room
Low voltage disconnect	1.90 ± 0.005 V/cell at 25 °C	The load is shed at this point to protect the cells
Load reconnect voltage	2.09 ± 0.01 V/cell at 25 °C	The load is restored once the bus recovers
Temperature compensation coefficient	−4 mV/cell/°C	The coefficient used on renewable sites, distinct from the −3 mV/°C/cell float value

Long-time discharge capacity for solar and wind duty (final voltage 1.85 V)

Discharge rate	C24	C48	C72	C100	C120	C240
OPzS2-350 capacity	396 Ah	434 Ah	455 Ah	473 Ah	480 Ah	490 Ah
Stored energy at 2 V	792 Wh	868 Wh	910 Wh	946 Wh	960 Wh	980 Wh

Source: Datasheet for the capacity row, Arithmetic for the energy row (2 V × Ah).

§2 — The Pain: Where 2V 350Ah Projects Go Wrong

The first failure is a specification failure. Buyers routinely receive a quotation that says only “2V 350Ah tubular” and treat every 2 V 350 Ah cell in the world as interchangeable. The published OPzS2-350 data makes the differences explicit: capacity at C10 is 350 Ah, but capacity at C24 is 396 Ah and at C240 is 490 Ah. A bank sized on the C10 number for a slow-discharge backup duty is undersized; a bank sized on the C240 number for a five-hour discharge duty is over-purchased. Both mistakes trace back to a quotation that never stated the rate and the end voltage.

The second failure is thermal. A 48 V string of 24 OPzS2-350 cells accepts a maximum charging current of 70 A per cell, so a charger set to deliver more — which happens when the charger is sized for the string’s nominal power rather than for the cells’ acceptance — pushes the electrolyte into gassing and dries the separator faster than the topping-up interval can repair. The same string on a solar site needs the higher 2.25 ± 0.005 V/cell float and the 2.40 ± 0.01 V/cell equalising setpoint; on a mains-float site the correct values are 2.23 V/cell and 2.35 V/cell at 25 °C. A controller left on the wrong setpoint is the classic cause of premature capacity loss.

The third failure is weight and access planning, and at 350 Ah it becomes the dominant issue. The OPzS2-350 is 20.4 kg without electrolyte and 27.0 kg with electrolyte, and the full height over the terminals is 525 mm, not the 471 mm body height. A 24-cell string with electrolyte weighs 648.0 kg (24 × 27.0 kg, Arithmetic), and a 54-cell 108 V string weighs 1,458.0 kg (54 × 27.0 kg, Arithmetic). Cabinets, plinths, floor loading and lifting plans are usually drawn against the body height and a lighter shipping weight, and the result is a string that does not fit the rack and a handling plan that understates the load.

The fourth failure is assuming sealed behaviour. This cell vents hydrogen during overcharge, needs acid-proof flame-retardant vent plugs, needs distilled water, and needs a scheduled equalising period. Those four obligations are why the OPzS2-350 2V350Ah wins in cabinets with a permanent operator — a central DC plant serving a national mobile network operator in Chennai, a fixed-line exchange in Rotterdam, a substation compound outside Nairobi — and loses in unmanned roadside or container sites. The same OPzS2-350 2V350Ah moves out of Hamburg and Antwerp for European utility buyers and into Valencia and other ports in Spain for Mediterranean projects, so the destination market belongs in the enquiry rather than in the shipping stage.

The fifth failure is ignoring parallel strings. A 48 V string of OPzS2-350 cells presents 14.88 mΩ of internal resistance (24 × 0.62 mΩ, Arithmetic). Two strings in parallel do not share load evenly once their float voltages separate by a few millivolts, and the weaker string silently carries less current while ageing faster. The cure is an equalising stage plus a rotation discipline, and both belong in the maintenance contract.

§3 — The Choice: The OPzS2-350 Against Its Published Siblings

Buyers comparing cells between 250 Ah and 420 Ah are choosing between two flooded capacities and, increasingly, between a flooded and a sealed cell of the same rating. The table below uses published values only.

Model	Capacity at C10	Weight dry / with electrolyte	Dimensions L × W × H	Total height	Max charging current	Internal resistance	Short-circuit current
OPzS2-250 (flooded)	250 Ah	15.5 kg / 20.5 kg	124 × 206 × 354 mm	409 mm	50 A	0.88 mΩ at 20 °C	2750 A
OPzS2-350 (flooded)	350 Ah	20.4 kg / 27.0 kg	124 × 206 × 471 mm	525 mm	70 A	0.62 mΩ at 20 °C	3300 A
OPzS2-420 (flooded)	420 Ah	24.0 kg / 32.0 kg	145 × 206 × 471 mm	525 mm	84 A	0.56 mΩ at 25 °C	3500 A
OPzV2-420 (gel)	420 Ah	31.5 kg (sealed)	145 × 206 × 471 mm	506 mm	84 A	0.62 mΩ	not published

Sources: OPzS2-250 and OPzS2-350 from their datasheets; OPzS2-420 and OPzV2-420 from their published specification pages and datasheets; the comparison itself is Arithmetic.

Four numbers drive the decision. First, footprint and height. The 250 Ah cell is 124 × 206 × 354 mm with a 409 mm total height; the 350 Ah cell keeps the same 124 × 206 mm footprint but grows to 471 mm of body and 525 mm total height. The 420 Ah cell then steps the length up to 145 mm. A rack designed for the 350 Ah cell will not accept the 420 Ah cell without a new rail, and a room designed for a 409 mm cell will not accept a 525 mm cell without rebuilding the plinth.

Second, weight. Dry weight rises from 15.5 kg to 20.4 kg and 24.0 kg; wet weight rises from 20.5 kg to 27.0 kg and 32.0 kg. At 350 Ah a cell that must be carried up a ladder or into a pit should be chosen with the 27.0 kg wet weight in mind, not the 20.4 kg dry one.

Third, internal resistance. 0.88 mΩ at 250 Ah, 0.62 mΩ at 350 Ah and 0.56 mΩ at 420 Ah — so a 24-cell string of the 350 Ah cell presents 14.88 mΩ (24 × 0.62 mΩ, Arithmetic) against 21.12 mΩ for the 250 Ah cell (24 × 0.88 mΩ, Arithmetic) and 13.44 mΩ for the 420 Ah cell (24 × 0.56 mΩ, Arithmetic). The voltage drop under the same load falls as capacity rises, which matters when the string is long and the load is heavy.

Fourth, the maintenance profile, and this is where the flooded-versus-sealed decision becomes concrete. The flooded OPzS2-350 carries 27.0 kg of electrolyte and 6.6 kg of acid per cell, so a 24-cell string carries 158.4 kg of acid (24 × 6.6 kg, Arithmetic) that must be topped up and eventually replaced. The gel OPzV2-420 carries the same 145 × 206 × 471 mm body at 31.5 kg with a 506 mm total height, needs no watering, and may be installed horizontally — at a higher internal resistance of 0.62 mΩ against 0.56 mΩ for the flooded cell of the same rating.

48 V string arithmetic across the flooded range

Cell	Cells in string	Nominal energy	Weight with electrolyte	Weight without electrolyte	String internal resistance	Maximum charging current
OPzS2-250	24	12,000 Wh	492.0 kg	372.0 kg	21.12 mΩ	1,200 A
OPzS2-350	24	16,800 Wh	648.0 kg	489.6 kg	14.88 mΩ	1,680 A
OPzS2-420	24	20,160 Wh	768.0 kg	576.0 kg	13.44 mΩ	2,016 A

Source: Datasheet for the cell-level values, Arithmetic for the string rows.

For a 54-cell 108 V substation string the OPzS2-350 arithmetic gives a float bus of 120.42 V (54 × 2.23 V), 37,800 Wh nominal, 1,458.0 kg with electrolyte (54 × 27.0 kg), 33.48 mΩ of internal resistance (54 × 0.62 mΩ) and a 3,780 A maximum charging current (54 × 70 A) (Arithmetic). On a 216 V three-phase DC bus the string becomes 108 cells, giving a float bus of 240.84 V (108 × 2.23 V), 75,600 Wh nominal and 2,916.0 kg with electrolyte (108 × 27.0 kg, Arithmetic).

If your string is larger than 420 Ah per cell, move to the OPzS flooded range overview rather than scaling the numbers in this table proportionally — plate thickness, internal volume and electrolyte quantity change non-linearly with capacity. The OPzS2-500 2V500Ah cell is the next published step up, at 166 × 206 × 470 mm and 26.0 kg with electrolyte.

§4 — The Framework: Seven Hard Checks Before You Sign

Q1. Match the charger to the cell’s acceptance, not to the string. The maximum charging current of the OPzS2-350 is 70 A (Datasheet). A 24-cell string therefore accepts at most 1,680 A (24 × 70 A, Arithmetic). Most telecom float rectifiers are sized well below that, which is correct; a solar controller set to the array’s full output is where the limit gets breached.

Q3. Design for the float life at the site’s real temperature. The 20+ year design figure is quoted at 20 °C (Datasheet). A cabinet in Chennai, on a roof in Lagos or an outdoor enclosure in Durban will not deliver that figure, and the honest way to plan a replacement interval is to take the 20 °C number and treat every 10 °C of ambient uplift as a materially shorter service life.

Q4. Plan the watering interval from the real charging regime. A cell that is floated at 2.23 V/cell at 25 °C and never equalised loses water slowly; a cell that is equalised at 2.35 V/cell twice a month in a hot climate loses water fast enough to need attention on a monthly cycle. Put the interval in the maintenance contract, and put the electrolyte density check (1.240 g/cm³ at 20 °C, Datasheet) on the same schedule.

Q5. Size the interconnects and torque them correctly. The terminal is a female copper insert M8 with a published torque of 10–12 N·m (Datasheet). Under-torqued terminals generate heat at the joint; over-torqued ones damage the insert. The 3300 A short-circuit current (Datasheet) determines how quickly the fault must be cleared, and the cable cross-section is set by the string current rather than by the bolt size.

Q6. Decide how many strings run in parallel, and how they will be equalised. Two parallel strings will drift apart unless the charger has an equalising stage and the operator runs it. Parallel strings also multiply the water-top-up workload and the total string weight: 24 × 27.0 kg = 648.0 kg per 350 Ah string with electrolyte (Arithmetic), and 158.4 kg of acid per string (24 × 6.6 kg, Arithmetic).

Q7. Confirm the standards the cell is built to. A 2 V vented cell for stationary duty is normally specified against IEC 60896-11 and the equivalent DIN 40736 envelope, with IEC 61427 for the renewable cycling test, the Eurobat long life guide, BS 6290 part 4 and UL 1989 for the North American market. CHISEN production runs under ISO 9001 and ISO 14001 with GB/T 28001 occupational health and safety management, and the range is supplied with CE documentation, so the paperwork trail should exist before the first container is booked.

§5 — The Trust: What a Datasheet Must State — and What to Reject

The single most useful question a buyer can ask a supplier is: “which document is this number from?” A published datasheet answers five questions that quotations never answer. What is the capacity rate and the end voltage? For the OPzS2-350 it is 350 Ah at C10 to 1.80 V/cell at 20 °C, and the full curve to 240 hours is published alongside it. What is the weight with and without electrolyte? 20.4 kg and 27.0 kg — both numbers, because a shipping weight quoted without electrolyte tells you nothing about handling. What is the total height over the terminals? 525 mm, not the 471 mm body height, and the difference is exactly the kind of detail that stops a cabinet from being delivered. What is the maximum charging current? 70 A. What is the reference temperature for the internal resistance and for the float life? 20 °C for both, and both references matter more than the numbers themselves.

Against that standard, reject any quotation that quotes a float voltage above 2.23 V per cell for this model, or one that quotes a temperature compensation coefficient other than −3 mV/°C/cell, or one that quotes the 20+ year design life against 25 °C rather than 20 °C. The OPzS2-350 datasheet setpoints are 2.23 V/cell float, 2.35 V/cell equalising and −3 mV/°C/cell compensation, with the 20+ year design figure referenced to 20 °C. A supplier who quotes different numbers for the same model is either reading a different revision or inventing them.

Two further quality signals are worth checking on site. First, ask for the plant audit trail: paste mixing, grid casting, group assembly, formation and sealing are the process steps that decide whether a 350 Ah cell really holds 350 Ah in year five, and they are the difference between a manufacturer and a packer. Second, ask for the certification package — ISO 9001, ISO 14001, CE, UL and IEC documentation should arrive with the quotation, not three weeks after the deposit. CHISEN runs eight production bases with roughly 70 million kVAh of annual capacity, and the company profile is published on the CHISEN company page.

§6 — FAQ

Q1. What is the rated capacity of the OPzS2-350 2V350Ah? 350 Ah at the 10-hour rate (35 A to 1.80 V/cell at 20 °C). The published table also gives 396 Ah at C24, 434 Ah at C48, 455 Ah at C72, 473 Ah at C100, 480 Ah at C120 and 490 Ah at C240 (Datasheet).

Q2. How many cells does a 48 V string need, and how much energy does it hold? 24 cells. 48 V × 350 Ah = 16,800 Wh nominal (Arithmetic). The string weighs 648.0 kg with electrolyte (24 × 27.0 kg) and 489.6 kg dry (24 × 20.4 kg), and carries 158.4 kg of acid (24 × 6.6 kg).

Q6. What is the maximum charging current? 70 A per cell, which is 0.20 × C10 (Datasheet). For a 24-cell string the theoretical ceiling is 1,680 A (24 × 70 A, Arithmetic), and the charger should normally deliver far less.

Q7. Can this cell be installed without a permanent operator? It can be installed, but not forgotten. Flooded tubular cells need distilled-water top-up, electrolyte density checks, ventilation and periodic equalising. For an unmanned site, compare the published gel alternative instead.

Q8. What is the internal resistance and short-circuit current? About 0.62 mΩ fully charged at 20 °C (Datasheet) and a 3300 A short-circuit current (Datasheet). The string resistance of a 24-cell arrangement is 14.88 mΩ (24 × 0.62 mΩ, Arithmetic), and the 3300 A figure is what your DC fuse and disconnection arrangement must be able to interrupt.

Q9. How does the OPzS2-350 compare with the 250 Ah and 420 Ah cells? The 250 Ah cell is 124 × 206 × 354 mm with a 409 mm total height; the 350 Ah cell keeps the 124 × 206 mm footprint but grows to 471 mm of body and 525 mm total height; the 420 Ah cell steps the length up to 145 mm. Published differences are weight (20.4 kg dry and 27.0 kg wet against 15.5 kg and 20.5 kg for the 250 Ah cell, and 24.0 kg and 32.0 kg for the 420 Ah cell), charging limit (70 A against 50 A and 84 A), internal resistance (0.62 mΩ against 0.88 mΩ and 0.56 mΩ) and short-circuit current (3300 A against 2750 A and 3500 A). The OPzS2-350 2V350Ah model page carries the full data set.

Expert Summary

The OPzS2-350 2V350Ah is a 2 V flooded tubular vented lead-acid cell with a published 350 Ah capacity at the 10-hour rate (35 A to 1.80 V/cell at 20 °C), rising to 490 Ah at the 240-hour rate; float 2.23 V/cell and equalising 2.35 V/cell at 25 °C with −3 mV/°C/cell compensation and a 20+ year design float life referenced to 20 °C; a body of 124 × 206 × 471 mm with 525 mm total height over the terminals; a weight of 20.4 kg without electrolyte and 27.0 kg with electrolyte, of which 6.6 kg is acid; a 70 A maximum charging current; about 0.62 mΩ internal resistance at 20 °C; and a 3300 A short-circuit current. A 24-cell 48 V string holds 16,800 Wh nominal, weighs 648.0 kg with electrolyte and presents 14.88 mΩ of internal resistance; a 54-cell 108 V string floats at 120.42 V, holds 37,800 Wh and weighs 1,458.0 kg. The cell suits a manned telecom DC plant, substation or utility-scale storage container; where access is unattended, the published gel alternative trades a different internal resistance and installation orientation for the removal of the watering cycle.

Contact CHISEN — 24-Hour Response

If you are quoting a 2 V 350 Ah cell for a 48 V DC plant, a 108 V substation in Rotterdam or a storage container outside Nairobi, ask for the complete OPzS2-350 datasheet, the string layout drawing and the certification package, and ask for them in writing: email sales@chisen.cn, or message the export desk on WhatsApp at +86 131 6622 6999 (https://wa.me/8613166226999). One line describing your bus voltage, backup time and site temperature is enough for us to return the string arithmetic, the charger setpoints and the nearest capacity in the flooded range — or the gel equivalent if nobody will ever top up water on that site.

Browse the full CHISEN lead-acid range and technical data at https://leadacidbattery.cn.

Related CHISEN Product Pages

OPzS2-350 2V350Ah model page — full published specification set
OPzS2-420 2V420Ah tubular flooded cell — the next capacity step, 420 Ah
Tubular flooded battery range — 2 V cells from 100 Ah to 3,000 Ah

Related CHISEN Buyer Guides

October 29, 2026

OPzS2-150 2V150Ah Flooded Tubular Cell: Published Specs and Sizing

Answer First

The OPzS2-150 2V150Ah is a 2 V, 150 amp-hour flooded tubular vented lead-acid cell rated at the 10-hour rate — 15 A for 10 hours down to 1.80 V per cell at 20 °C — and it is the correct cell for a telecom DC plant, a substation or a solar-powered cabinet that needs a 48 V bus holding about 7.2 kWh nominal per string, on a site where somebody will still read the electrolyte level and top up distilled water every quarter.

It is not a sealed block. Hydrogen venting, acid-proof flame-retardant vent plugs, scheduled water top-up and periodic equalisation are part of the product, not optional extras, and a project that treats the OPzS2-150 2V150Ah as a drop-in sealed cabinet battery discovers the difference in the first hot season.

The complete published data set for this cell sits on the OPzS2-150 2V150Ah model page, and the rest of the flooded range is listed under tubular flooded lead-acid batteries.

Key Takeaways

Capacity is rate-dependent. The nameplate figure is 150 Ah at C10 (15 A to 1.80 V/cell at 20 °C). At longer rates the cell delivers more: 170 Ah at C24, 186 Ah at C48, 195 Ah at C72, 203 Ah at C100, 206 Ah at C120 and 210 Ah at C240 (Datasheet).
Charging setpoints are fixed by the datasheet. Float 2.23 V/cell at 25 °C, equalising 2.35 V/cell at 25 °C, temperature compensation −3 mV/°C/cell, designed float life 20+ years at 20 °C (Datasheet). Solar and wind controllers use the 2.25 ± 0.005 V/cell float and 2.40 ± 0.01 V/cell equalising setpoints, with a −4 mV/cell/°C compensation coefficient (Datasheet).
Mechanical data is what decides the rack. Body 103 × 206 × 354 mm, 409 mm total height over the terminals, 10.5 kg without electrolyte and 14.5 kg with electrolyte (Datasheet).
Two limits protect the cell. Maximum charging current is 30 A (0.20 × C10) and internal resistance is about 1.2 mΩ fully charged at 20 °C, with a 2400 A short-circuit current (Datasheet).
A 48 V string is simple arithmetic. 24 cells give 7,200 Wh nominal, 348.0 kg with electrolyte (24 × 14.5 kg) and 28.8 mΩ of internal resistance (24 × 1.2 mΩ) (Arithmetic).

§1 — OPzS2-150 2V150Ah Quick Specifications

Parameter	OPzS2-150 published value	Source
Model	OPzS2-150, flooded tubular stationary cell, 2 V 150 Ah	Model page
Nominal voltage	2 V	Datasheet
Nominal capacity	150 Ah at C10 (15 A, 1.80 V/cell, 20 °C)	Datasheet
C10 discharge current	15 A (150 Ah ÷ 10 h)	Arithmetic
Capacity at C24 / C48 / C72	170 Ah / 186 Ah / 195 Ah	Datasheet
Capacity at C100 / C120 / C240	203 Ah / 206 Ah / 210 Ah	Datasheet
Float voltage	2.23 V/cell at 25 °C	Datasheet
Equalising voltage	2.35 V/cell at 25 °C	Datasheet
Float setpoint, solar and wind	2.25 ± 0.005 V/cell at 25 °C	Datasheet
Equalising setpoint, solar and wind	2.40 ± 0.01 V/cell at 25 °C	Datasheet
Temperature compensation, float	−3 mV/°C/cell	Datasheet
Temperature compensation, solar and wind	−4 mV/cell/°C	Datasheet
Designed float life	20+ years at 20 °C	Datasheet
Dimensions L × W × H	103 × 206 × 354 mm	Datasheet
Container height	354 mm	Datasheet
Total height over terminals	409 mm	Datasheet
Terminal centre spacing	108 mm	Datasheet
Terminal	20 mm OD, M8 thread, 7 mm depth, female copper insert M8	Datasheet
Terminal tightening torque	10–12 N·m	Datasheet
Weight without electrolyte	10.5 kg (23.2 lbs)	Datasheet
Weight with electrolyte	14.5 kg (32.0 lbs)	Datasheet
Electrolyte	Diluted sulphuric acid, 1.240 g/cm³ at 20 °C	Datasheet
Acid weight per cell	4.0 kg	Datasheet
Internal resistance	Approx. 1.2 mΩ, fully charged at 20 °C	Datasheet
Maximum charge current	30 A	Datasheet
Charge characteristic	Constant charge at 0.15 CA to 2.40 V at 20 °C	Datasheet
Maximum discharge current (5 s)	1000 A	Datasheet
Short circuit current	2400 A	Datasheet
Self discharge	Approx. 4 % per month at 20 °C	Datasheet
Ambient, discharge	−25 °C to +65 °C	Datasheet
Ambient, charge	−20 °C to +65 °C	Datasheet
Ambient, storage	−15 °C to +40 °C	Datasheet
Complied standards	IEC 60896-11, DIN 40736, IEC 61427, Eurobat long life guide, BS 6290 part 4, UL 1989	Datasheet
Management systems and marks	ISO 9001, ISO 14001, GB/T 28001, CE, RU recognised component	Datasheet

Every row above is traceable. Values taken from the manufacturer’s OPzS2-150 datasheet are marked Datasheet, values taken from the published English product page are marked Model page, and derived figures are marked Arithmetic wherever they appear in the text. If a supplier cannot tell you which of the three a given figure is, treat the figure as unverified.

Solar and wind controller setpoints for the OPzS2-150

The same datasheet publishes a separate parameter set for renewable sites, and these are the values that actually go into a solar or wind charge controller.

Controller parameter	Published setting	Why the number matters
Over voltage disconnect	2.47 ± 0.01 V/cell at 25 °C	The point at which the controller stops charging and the array is isolated
Regulation / equalising voltage	2.40 ± 0.01 V/cell at 25 °C	Higher than the mains float because the array has to push against the bus
Array reconnection voltage	2.23 ± 0.005 V/cell at 25 °C	The bus voltage at which charging resumes
Float voltage setting	2.25 ± 0.005 V/cell at 25 °C	The renewable float setpoint, above the 2.23 V mains float
Low voltage alarm	1.95 ± 0.005 V/cell at 25 °C	The alarm threshold for the control room
Low voltage disconnect	1.90 ± 0.005 V/cell at 25 °C	The load is shed at this point to protect the cells
Load reconnect voltage	2.09 ± 0.01 V/cell at 25 °C	The load is restored once the bus recovers
Temperature compensation coefficient	−4 mV/cell/°C	The coefficient used on renewable sites, distinct from the −3 mV/°C/cell float value

Long-time discharge capacity for solar and wind duty (final voltage 1.85 V)

Discharge rate	C24	C48	C72	C100	C120	C240
OPzS2-150 capacity	170 Ah	186 Ah	195 Ah	203 Ah	206 Ah	210 Ah
Stored energy at 2 V	340 Wh	372 Wh	390 Wh	406 Wh	412 Wh	420 Wh

Source: Datasheet for the capacity row, Arithmetic for the energy row (2 V × Ah).

§2 — The Pain: Where 2V 150Ah Projects Go Wrong

The first failure is a specification failure. Buyers routinely receive a quotation that says only “2V 150Ah tubular” and treat every 2 V 150 Ah cell in the world as interchangeable. The published OPzS2-150 data makes the differences explicit: capacity at C10 is 150 Ah, but capacity at C24 is 170 Ah and at C240 is 210 Ah. A bank sized on the C10 number for a slow-discharge backup duty is undersized; a bank sized on the C240 number for a five-hour discharge duty is over-purchased. Both mistakes trace back to a quotation that never stated the rate and the end voltage.

The second failure is thermal. A 48 V string of 24 OPzS2-150 cells accepts a maximum charging current of 30 A per cell, so a charger set to deliver more — which happens when the charger is sized for the string’s nominal power rather than for the cells’ acceptance — pushes the electrolyte into gassing and dries the separator faster than the topping-up interval can repair. The same string on a solar site needs the higher 2.25 ± 0.005 V/cell float and the 2.40 ± 0.01 V/cell equalising setpoint; on a mains-float site the correct values are 2.23 V/cell and 2.35 V/cell at 25 °C. These are not interchangeable, and a controller left on the wrong setpoint is the classic cause of premature capacity loss.

The third failure is weight and access planning. The OPzS2-150 is 10.5 kg without electrolyte and 14.5 kg with electrolyte, and the full height over the terminals is 409 mm, not the 354 mm body height. A 24-cell string with electrolyte weighs 348.0 kg (24 × 14.5 kg, Arithmetic). Cabinets, plinths and lifting plans are usually drawn against the body height and a lighter shipping weight, and the result is a string that does not fit the rack and a handling plan that understates the load.

The fifth failure, and the one that costs the most money, is ignoring what happens when two strings in parallel drift apart. A 24-cell string of OPzS2-150 cells presents 28.8 mΩ of internal resistance (24 × 1.2 mΩ, Arithmetic). Two strings in parallel do not share load evenly once their float voltages separate by a few millivolts, and the weaker string silently carries less current while ageing faster. The cure is an equalising stage plus a rotation discipline, and both belong in the maintenance contract rather than in a commissioning checklist.

Markets also shape the delivery plan. A lead-acid article of this class leaves through Hamburg, Santos and Singapore for importers in Europe, Brazil and South-East Asia, and the import file has to name the destination market before the container is booked, because a vented cell and a sealed cell do not clear every port under the same rules.

§3 — The Choice: The OPzS2-150 Against Its Published Siblings

Buyers comparing cells inside the 100 Ah to 200 Ah window are usually choosing between a flooded cell and a gel cell, or between three flooded capacities. The table below uses published values only.

Model	Capacity at C10	Weight dry / with electrolyte	Dimensions L × W × H	Total height	Max charging current	Internal resistance	Short-circuit current
OPzS2-100	100 Ah	8.0 kg / 12.6 kg	103 × 206 × 354 mm	409 mm	20 A	1.0 mΩ at 20 °C	1500 A
OPzS2-150	150 Ah	10.5 kg / 14.5 kg	103 × 206 × 354 mm	409 mm	30 A	1.2 mΩ at 20 °C	2400 A
OPzS2-200	200 Ah	13.0 kg / 17.5 kg	103 × 206 × 354 mm	409 mm	40 A	0.95 mΩ at 20 °C	2600 A
OPzV2-100 (gel)	100 Ah	13.2 kg (sealed)	103 × 206 × 354 mm	390 mm	30 A	1.1 mΩ	not published

Sources: OPzS2-100 and OPzS2-200 from their datasheets, with the OPzS2-100 short-circuit current from its model page; OPzV2-100 from the model page and its datasheet; the comparison itself is Arithmetic.

Four numbers drive the decision. First, dry weight: 8.0 kg, 10.5 kg and 13.0 kg for the three flooded cells — a cell that must be carried up a ladder or into a pit should be chosen with the wet weight in mind, not the dry one. Second, the charging current limit of 20 A, 30 A and 40 A, which must be matched to the charger output. Third, internal resistance, which does not fall in a straight line with capacity — 1.0 mΩ at 100 Ah, 1.2 mΩ at 150 Ah and 0.95 mΩ at 200 Ah — so a 24-cell string of the 200 Ah cell presents 22.8 mΩ (24 × 0.95 mΩ, Arithmetic) against 28.8 mΩ for the 150 Ah cell (24 × 1.2 mΩ, Arithmetic) and 24.0 mΩ for the 100 Ah cell (24 × 1.0 mΩ, Arithmetic). The 150 Ah cell therefore has the highest voltage drop of the three under the same load, which matters when the string is long and the load is heavy.

The fourth number is the maintenance profile, and here the published data is unambiguous. The flooded OPzS2-150 carries 14.5 kg of electrolyte in an open container that must be topped up and periodically equalised. The gel OPzV2-100 carries the same 103 × 206 mm footprint with a 390 mm total height, weighs 13.2 kg with the electrolyte immobilised in the gel, and needs no watering — the price of that is a 1.1 mΩ internal resistance, a 30 A charging limit and a shorter life under deep cycling. For a manned substation with a technician on call, the flooded cell usually delivers the lower cost per usable year; for a sealed container with no access, the gel cell removes a whole maintenance category. Both routes are legitimate, and the published figures above are what the comparison should be built on.

48 V string arithmetic across the three flooded capacities

Cell	Cells in string	Nominal energy	Weight with electrolyte	Weight without electrolyte	String internal resistance	Maximum charging current
OPzS2-100	24	4,800 Wh	302.4 kg	192.0 kg	24.0 mΩ	480 A
OPzS2-150	24	7,200 Wh	348.0 kg	252.0 kg	28.8 mΩ	720 A
OPzS2-200	24	9,600 Wh	420.0 kg	312.0 kg	22.8 mΩ	960 A

Source: Datasheet for the cell-level values, Arithmetic for the string rows.

For a 54-cell 108 V substation string the same OPzS2-150 arithmetic gives a float bus of 120.42 V (54 × 2.23 V), 16,200 Wh nominal, 783.0 kg with electrolyte (54 × 14.5 kg), 64.8 mΩ of internal resistance (54 × 1.2 mΩ) and a 1,620 A maximum charging current (54 × 30 A) (Arithmetic).

The same discipline applies further up the size range. If your string is larger than 200 Ah per cell, move to the OPzS flooded range overview rather than scaling the numbers in this table proportionally — plate thickness, internal volume and electrolyte quantity change non-linearly with capacity. The OPzS2-500 2V500Ah cell is the next published step up, at 166 × 206 × 470 mm and 26.0 kg with electrolyte.

§4 — The Framework: Seven Hard Checks Before You Sign

Q1. Match the charger to the cell’s acceptance, not to the string. The maximum charging current of the OPzS2-150 is 30 A (Datasheet). A 24-cell string therefore accepts at most 720 A (24 × 30 A, Arithmetic). Most telecom float rectifiers are sized well below that, which is correct; a solar controller set to the array’s full output is where the limit gets breached.

Q5. Size the interconnects and torque them correctly. The terminal is a copper female insert M8 with a published torque of 10–12 N·m (Datasheet). Under-torqued terminals generate heat at the joint; over-torqued ones damage the insert. For a 24-cell string the interconnect carries the full string current, so the cable cross-section is set by that current and the 2400 A short-circuit current (Datasheet) determines how quickly the fault must be cleared.

Q6. Decide how many strings run in parallel, and how they will be equalised. Two parallel strings of 12 cells in series each will drift apart unless the charger has an equalising stage and the operator runs it. Parallel strings also multiply the water-top-up workload and the total string weight: 24 × 14.5 kg = 348.0 kg per 150 Ah string with electrolyte (Arithmetic).

Q7. Confirm the standards the cell is built to. A 2 V vented cell for stationary duty is normally specified against IEC 60896-11 and the equivalent DIN 40736 envelope, with IEC 61427 for the renewable cycling test, the Eurobat long life guide, BS 6290 part 4 and UL 1989 for the North American market. CHISEN production runs under ISO 9001 and ISO 14001 with GB/T 28001 occupational health and safety management, and the range is supplied with CE documentation, so the paperwork trail should exist before the first container is booked.

§5 — The Trust: What a Datasheet Must State — and What to Reject

The single most useful question a buyer can ask a supplier is: “which document is this number from?” A published datasheet answers five questions that quotations never answer. What is the capacity rate and the end voltage? For the OPzS2-150 it is 150 Ah at C10 to 1.80 V/cell at 20 °C, and the full curve to 240 hours is published alongside it. What is the weight with and without electrolyte? 10.5 kg and 14.5 kg — both numbers, because a shipping weight quoted without electrolyte tells you nothing about handling. What is the total height over the terminals? 409 mm, not the 354 mm body height, and the difference is exactly the kind of detail that stops a cabinet from being delivered. What is the maximum charging current? 30 A. What is the reference temperature for the internal resistance and for the float life? 20 °C for both, and both references matter more than the numbers themselves.

Against that standard, reject any quotation that quotes a float voltage above 2.23 V per cell for this model, or one that quotes a temperature compensation coefficient other than −3 mV/°C/cell, or one that quotes the 20+ year design life against 25 °C rather than 20 °C. The OPzS2-150 datasheet setpoints are 2.23 V/cell float, 2.35 V/cell equalising and −3 mV/°C/cell compensation, with the 20+ year design figure referenced to 20 °C. A supplier who quotes different numbers for the same model is either reading a different revision or inventing them.

Two further quality signals are worth checking on site. First, ask for the plant audit trail: paste mixing, grid casting, group assembly, formation and sealing are the process steps that decide whether a 150 Ah cell really holds 150 Ah in year five, and they are the difference between a manufacturer and a packer. Second, ask for the certification package — ISO 9001, ISO 14001, CE, UL and IEC documentation should arrive with the quotation, not three weeks after the deposit. CHISEN runs eight production bases with roughly 70 million kVAh of annual capacity, and the company profile is published on the CHISEN company page if you want to check the manufacturing scale behind a quotation before you commit a container.

§6 — FAQ

Q1. What is the rated capacity of the OPzS2-150 2V150Ah? 150 Ah at the 10-hour rate (15 A to 1.80 V/cell at 20 °C). The published table also gives 170 Ah at C24, 186 Ah at C48, 195 Ah at C72, 203 Ah at C100, 206 Ah at C120 and 210 Ah at C240 (Datasheet).

Q2. How many cells does a 48 V string need, and how much energy does it hold? 24 cells. 48 V × 150 Ah = 7,200 Wh nominal (Arithmetic). The string weighs 348.0 kg with electrolyte (24 × 14.5 kg) and 252.0 kg dry (24 × 10.5 kg), and carries 96.0 kg of acid (24 × 4.0 kg).

Q6. What is the maximum charging current? 30 A per cell, which is 0.20 × C10 (Datasheet). For a 24-cell string the theoretical ceiling is 720 A (24 × 30 A, Arithmetic), and the charger should normally deliver far less.

Q8. What is the internal resistance and short-circuit current? About 1.2 mΩ fully charged at 20 °C (Datasheet) and a 2400 A short-circuit current (Datasheet). The string resistance of a 24-cell arrangement is 28.8 mΩ (24 × 1.2 mΩ, Arithmetic), and the 2400 A figure is what your DC fuse and disconnection arrangement must be able to interrupt.

Q9. How does the OPzS2-150 compare with the 100 Ah and 200 Ah cells? Same 103 × 206 mm footprint and the same 409 mm total height. The published differences are weight (10.5 kg dry and 14.5 kg wet against 8.0 kg and 12.6 kg for the 100 Ah cell, and 13.0 kg and 17.5 kg for the 200 Ah cell), charging limit (30 A against 20 A and 40 A), internal resistance (1.2 mΩ against 1.0 mΩ and 0.95 mΩ) and short-circuit current (2400 A against 1500 A and 2600 A). The OPzS2-150 2V150Ah model page carries the full data set.

Expert Summary

The OPzS2-150 2V150Ah is a 2 V flooded tubular vented lead-acid cell with a published 150 Ah capacity at the 10-hour rate (15 A to 1.80 V/cell at 20 °C), rising to 210 Ah at the 240-hour rate; float 2.23 V/cell and equalising 2.35 V/cell at 25 °C with −3 mV/°C/cell compensation and a 20+ year design float life referenced to 20 °C; a body of 103 × 206 × 354 mm with 409 mm total height over the terminals; a weight of 10.5 kg without electrolyte and 14.5 kg with electrolyte, of which 4.0 kg is acid; a 30 A maximum charging current; about 1.2 mΩ internal resistance at 20 °C; and a 2400 A short-circuit current. A 24-cell 48 V string of these cells holds 7,200 Wh nominal, weighs 348.0 kg with electrolyte and presents 28.8 mΩ of internal resistance. The cell is the correct choice where a manned telecom DC plant, substation or renewable cabinet benefits from long float life and low cost per usable year; where site access is unattended, the published gel alternative trades a slightly different internal resistance and charging limit for the removal of the watering cycle.

Contact CHISEN — 24-Hour Response

If you are quoting a 2 V 150 Ah cell for a 48 V DC plant, a substation in Rotterdam or a solar cabinet outside Nairobi, ask for the complete OPzS2-150 datasheet, the string layout drawing and the certification package, and ask for them in writing: email sales@chisen.cn, or message the export desk on WhatsApp at +86 131 6622 6999 (https://wa.me/8613166226999). One line describing your bus voltage, backup time and site temperature is enough for us to return the string arithmetic, the charger setpoints and the nearest capacity in the flooded range — or the gel equivalent if nobody will ever top up water on that site.

Browse the full CHISEN lead-acid range and technical data at https://leadacidbattery.cn.

Related CHISEN Product Pages

OPzS2-150 2V150Ah model page — full published specification set
OPzS2-200 2V200Ah tubular flooded cell — the next capacity step, 200 Ah
Tubular flooded battery range — 2 V cells from 100 Ah to 3,000 Ah

Related CHISEN Buyer Guides

October 29, 2026