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6-EVF-60 12V60Ah UPS Battery: Complete Buyer Guide for Data Centres and Telecom
Answer First

The 6-EVF-60 12V60Ah is a 12 V, 60 Ah VRLA battery rated at the C3 rate. Factory-published figures for this model are 258 × 170 × 160 mm, 18.8 ± 0.2 kg, float at 13.5 V, equalise at 14.1 V, maximum charge current 12.0 A, discharge cutoff 1.75 V/cell, self-discharge ≤3 %/month at 25 °C, operating range −15…50 °C, and a design life of 2–5 years. In procurement terms the 6-EVF-60 12V60Ah is the mid-size block of the 6-EVF line: four units in series give a 48 V telecom or data-centre string, and one block stores 12 V × 60 Ah = 720 Wh of nominal energy. It is the correct choice when a cabinet load needs roughly one block of reserve without stepping up to the heavier 80 Ah unit.

Most purchase orders for a “60 Ah” UPS battery are written from a catalogue cover page and omit the three numbers that actually decide the installation: the bus voltage the setpoints assume, the charge current the charger must deliver, and the cutoff voltage the UPS is configured to. Get those three wrong and identical nominal capacity either never reaches full charge or is cut off far too early. Every figure used in this guide is taken from the factory model page for the 6-EVF-60 12V60Ah and is reproduced with its source, so a procurement file can be assembled directly from it.

Key Takeaways

Published capacity and case size. The 6-EVF-60 12V60Ah is rated 12 V / 60 Ah at C3, measures 258 × 170 × 160 mm and weighs 18.8 ± 0.2 kg — all figures confirmed on the factory model page.
Charge setpoints are fixed and non-negotiable. Float 13.5 V (2.25 V/cell) and equalise 14.1 V (2.35 V/cell) across the six cells of the 12 V block, with a 1.75 V/cell discharge cutoff.
The charger must be sized to 12.0 A per battery. Published maximum charge current is 12.0 A, that is 0.2 × 60 Ah; a charger set above this rating shortens plate life.
String maths for a 48 V cabinet. Four 6-EVF-60 12V60Ah units in series give 4 × 12 V = 48 V nominal, float 4 × 13.5 V = 54.0 V, equalise 4 × 14.1 V = 56.4 V, cutoff 4 × 10.5 V = 42.0 V, while capacity stays at 60 Ah per string.
Energy content is 720 Wh per block. 12 V × 60 Ah = 720 Wh; at the published 18.8 ± 0.2 kg this is 720 ÷ 18.8 = 38.3 Wh/kg, a useful figure when a cabinet has a weight limit.

§1 — 6-EVF-60 Quick Specifications

The table below is the complete published specification for the 6-EVF-60 12V60Ah as published by the factory. Every row carries its source. Where a value is not published — for example the terminal tightening torque — it is marked for request rather than estimated.

Parameter	Published value	Source
Nominal voltage	12 V	Model page
Nominal capacity	60 Ah	Model page
Capacity rate	C3	Model page
Dimensions (L × W × H)	258 × 170 × 160 mm	Model page
Weight	18.8 ± 0.2 kg	Model page
Terminal	φ14-M6	Model page
Float voltage	13.5 V	Model page
Equalise voltage	14.1 V	Model page
Cycle life	350–600 cycles (DoD 50–80 %)	Model page
Maximum charge current	12.0 A	Model page
Discharge cutoff	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
Cell count per block	6 cells × 2 V = 12 V nominal	Arithmetic
Terminal tightening torque	not published	to be requested from the factory
Cycle use, standing performance and case material	not published	to be requested from the factory

The complete published data set behind this table is on this model page.

§2 — The Pain: The Gap Between a Datasheet and an Installed String

Data-centre and telecom buyers rarely get what they ordered, and the cause is rarely the cell chemistry. It is a specification that stops at the catalogue page. Five items cause most of the disputes we see on 60 Ah VRLA orders.

Charger current. The published maximum charge current for the 6-EVF-60 12V60Ah is 12.0 A, which is 0.2 × 60 Ah. A charger configured above that rating pushes excess ripple into the cells and consumes plate life; one configured far below it never completes a recharge inside the window the UPS allows.

Float and equalise setpoints. Float is 13.5 V and equalise 14.1 V for the block, that is 2.25 V/cell and 2.35 V/cell. Installers frequently copy setpoints from a different case size. On a 48 V string this six-cell block sits at 54.0 V float — correct for this battery, wrong for a 2 V tubular cell.

Cutoff voltage. The published cutoff is 1.75 V/cell, so a 12 V block ends at 10.5 V and a 48 V string at 42.0 V. A shallower cutoff shortens the string; a deeper one cuts usable runtime and pushes the cells into deep discharge.

Temperature. The rated working range is −15…50 °C and self-discharge is quoted at ≤3 %/month at 25 °C. A cabinet in a hot corridor ages faster than a 2–5 year design life suggests.

§3 — The Choice: Sizing the Block Around the 6-EVF-60 12V60Ah

Three sizes bracket the 6-EVF-60 12V60Ah in practice. The 6-EVF-50 gives 50 Ah at 15.25 ± 0.2 kg in a 230 × 140 × 180 mm case; the 6-DMF-52 gives 52 Ah at 13.7 ± 0.2 kg in 224 × 135 × 175 mm; the 6-EVF-80 gives 80 Ah at 25.7 ± 0.2 kg in 259 × 170 × 218 mm.

Choose the 6-EVF-60 12V60Ah when the required runtime per string falls between the 50 Ah and 80 Ah blocks and the cabinet offers 160 mm of usable height — the 80 Ah case grows to 218 mm and therefore needs a different enclosure, not just a different battery. Choose the 50 Ah unit when the load is lighter or floor loading is tight, and the 80 Ah unit when runtime must be extended without increasing the number of parallel strings. The full published data for every size is listed on the full product range, and the closest sibling of the 6-EVF-60 12V60Ah — 50 Ah, 15.25 ± 0.2 kg, 10.0 A charge current — is documented on the sibling model page.

§4 — The Framework: String Configuration, Runtime and Charger Sizing

Work in three steps: string voltage, string count, then charger.

Step 1 — string voltage. The 6-EVF-60 12V60Ah is a six-cell 12 V block: 6 cells × 2 V = 12 V nominal. A 48 V telecom or data-centre bus takes four blocks in series — 4 × 12 V = 48 V nominal, float 4 × 13.5 V = 54.0 V, equalise 4 × 14.1 V = 56.4 V, cutoff 4 × 10.5 V = 42.0 V. Series connection adds voltage but not capacity: each string still delivers 60 Ah.

Step 2 — string count and runtime. One string gives 60 Ah. Two strings in parallel give 2 × 60 Ah = 120 Ah, four give 4 × 60 Ah = 240 Ah. Runtime follows from the measured load: 60 Ah ÷ 20 A = 3.0 h for one string and 120 Ah ÷ 20 A = 6.0 h for two parallel strings. At a 30 A load, one string gives 60 Ah ÷ 30 A = 2.0 h. The energy behind the nameplate is 12 V × 60 Ah = 720 Wh per block, or 720 Wh ÷ 18.8 kg = 38.3 Wh/kg. On a standby string with a 50 % depth-of-discharge budget, usable energy is 720 Wh × 0.5 = 360 Wh per block.

Step 3 — charger. Budget 12.0 A per battery, which is the published 0.2 × 60 Ah figure. A four-battery string therefore needs 4 × 12.0 A = 48.0 A of charger capacity, and two parallel strings need 2 × 48.0 A = 96.0 A. Set the charger to 13.5 V float and 14.1 V equalise per 12 V block, and confirm the cabinet ambient stays inside the published −15…50 °C window.

Before energising the cabinet, run five checks. Verify the case: 258 × 170 × 160 mm, 18.8 ± 0.2 kg per block. Confirm the charger delivers 12.0 A per battery, 4 × 12.0 A = 48.0 A per string, float 13.5 V, equalise 14.1 V. Confirm the UPS cutoff is 1.75 V/cell, so the 48 V string ends at 42.0 V; keep the ambient inside −15…50 °C. A nominal 60 Ah rarely delivers in the cabinet: self-discharge is ≤3 %/month at 25 °C, and a 50 % depth-of-discharge budget leaves 720 Wh × 0.5 = 360 Wh usable per block, so 60 Ah ÷ 20 A = 3.0 h is a design figure, not a guarantee.

§5 — 6-EVF-60 Against the Sibling Sizes, Side by Side

The figures below are published values for each size in the 6-EVF and 6-DMF lines, not estimates. Nominal Wh is 12 V × Ah: 12 × 60 = 720 Wh for the 6-EVF-60, 12 × 50 = 600 Wh for the 6-EVF-50, 12 × 80 = 960 Wh for the 6-EVF-80, 12 × 45 = 540 Wh for the 6-DMF-45, 12 × 52 = 624 Wh for the 6-DMF-52 and 12 × 100 = 1,200 Wh for the 6-EVF-100.

Model	Capacity	Dimensions (L×W×H mm)	Weight	Charge current	Float / Equalise	Design life	Source
6-DMF-45	45 Ah	224×121×175	12.3 ± 0.2 kg	9.0 A	13.5 V / 14.1 V	2–5 years	Model page
6-DMF-52	52 Ah	224×135×175	13.7 ± 0.2 kg	10.4 A	13.5 V / 14.1 V	not published	Model page
6-EVF-50	50 Ah	230×140×180	15.25 ± 0.2 kg	10.0 A	13.5 V / 14.1 V	2–5 years	Model page
6-EVF-60	60 Ah	258×170×160	18.8 ± 0.2 kg	12.0 A	13.5 V / 14.1 V	2–5 years	Model page
6-EVF-80	80 Ah	259×170×218	25.7 ± 0.2 kg	16.0 A	13.5 V / 14.1 V	2–5 years	Model page
6-EVF-100	100 Ah	330×170×218	31.5 ± 0.2 kg	20.0 A	13.5 V / 14.1 V	2–5 years	Model page

Two things stand out. First, the case footprint: the 6-EVF-60 12V60Ah is 160 mm high against 180 mm for the 6-EVF-50 and 218 mm for the 6-EVF-80, which is often the decisive constraint in a 19-inch cabinet. Second, weight per ampere-hour: 18.8 kg ÷ 60 Ah = 0.313 kg/Ah for the 6-EVF-60 against 15.25 kg ÷ 50 Ah = 0.305 kg/Ah for the 6-EVF-50 and 25.7 kg ÷ 80 Ah = 0.321 kg/Ah for the 6-EVF-80, so the middle block is close to the line on transport weight per unit of reserve.

§6 — The Trust: Verified Numbers, Certified Production, Documented Delivery

Every figure in this guide comes from the factory model page for the 6-EVF-60 12V60Ah, and the same data set backs the quotation. CHISEN runs 8 production bases with an annual capacity of 70 million kVAh and holds CE, ISO 9001, ISO 14001, UL and IEC certifications across the flooded tubular OPzS2, gel tubular OPzV2 and 12 V VRLA lines. Export containers leave from Shanghai and Ningbo for distributors and OEM integrators in India, Nigeria, Kenya, Vietnam, the Philippines, Brazil, Egypt, Mexico, Pakistan, the UAE and Turkey, with logistics hubs in Dubai, Lagos, Mombasa and Karachi. On arrival, match the label against the table in §1, measure the open-circuit voltage of every block, and confirm the manufacturing date before the warranty clock starts.

§7 — FAQ

Q1: What are the published nominal voltage and capacity of the 6-EVF-60? 12 V and 60 Ah at the C3 rate, as published on the factory model page.

Q2: What float and equalise setpoints does the manufacturer publish? 13.5 V float (2.25 V/cell) and 14.1 V equalise (2.35 V/cell), source: Model page.

Q3: What is the maximum charging current? 12.0 A, that is 0.2 × 60 Ah, source: Model page.

Q4: What are the case dimensions and weight? 258 × 170 × 160 mm and 18.8 ± 0.2 kg, source: Model page.

Q5: Which terminal does it use, and at what torque? Terminal φ14-M6; the tightening torque is not published and is to be requested from the factory.

Q6: How many cells in a 12 V 60 Ah string, and what bus voltage results? 6 cells × 2 V = 12 V nominal; four blocks in series give 48 V nominal, 54.0 V float and 42.0 V cutoff.

Q7: What is the published design life, and at what temperature? 2–5 years; self-discharge is quoted at ≤3 %/month at 25 °C, within a −15…50 °C working range.

Q8: How should an importer verify the batteries on delivery? Match the label data against the model page, measure open-circuit voltage per block, and check the manufacturing date.

Q9: Which certifications does the factory behind this model hold? CE, ISO 9001, ISO 14001, UL and IEC.

Q10: How do I request a quotation or samples? Email sales@chisen.cn or jack@chisen.cn, or use WhatsApp +86 131 6622 6999.

Expert Summary

The 6-EVF-60 12V60Ah is a 60 Ah C3 VRLA block, 258 × 170 × 160 mm and 18.8 ± 0.2 kg, with 13.5 V float, 14.1 V equalise, 12.0 A charge current and a 1.75 V/cell cutoff. One block stores 12 V × 60 Ah = 720 Wh, or 38.3 Wh/kg, and four in series give a 48 V string at 54.0 V float with 42.0 V cutoff. One string holds 60 Ah ÷ 20 A = 3.0 h, and the charger must deliver 4 × 12.0 A = 48.0 A per string. Published design life is 2–5 years within −15…50 °C.

Contact CHISEN — 24-Hour Response

CHISEN Battery, Hangzhou, China — quotation, technical data and samples for the 6-EVF-60 12V60Ah. Email: sales@chisen.cn · jack@chisen.cn · WhatsApp: +86 131 6622 6999 · www.chisen.cn

Related CHISEN Buyer Guides

November 7, 2026

6-EVF-50 12V50Ah UPS Battery: Complete Buyer Guide for Data Centres and Telecom

Answer First

If your procurement file needs a 12V 50Ah battery with published numbers rather than a catalogue guess, the 6-EVF-50 is the unit to specify. CHISEN publishes it as a 12 V, 50 Ah valve-regulated AGM battery rated at C3, in a 230 × 140 × 180 mm case weighing 15.25 ± 0.2 kg. The published charge control is 13.5 V float and 14.1 V equalise, maximum charge current 10.0 A, a 1.75 V per cell cut-off, self-discharge of no more than 3 % per month at 25 °C, an operating window of −15 to 50 °C, 350–600 cycles at 50–80 % depth of discharge, and a design life of 2–5 years. All of it comes from the factory model page, and the published figures are set out on this model page.

The arithmetic is simple enough to audit on a loading dock. A 12 V battery is six 2 V cells in series: 6 × 2 V = 12 V. Stored energy at the C3 rate is 12 V × 50 Ah = 600 Wh, and specific energy is 600 Wh ÷ 15.25 kg = 39.3 Wh/kg. Where it fits is the practical half of the answer: one 6-EVF-50 gives a single 12 V string, two strings give 24 V, four give 48 V (4 × 12 V = 48 V) — the bus voltage most single-phase UPS units and telecom rectifier cabinets expect. In parallel, 2 × 50 Ah = 100 Ah and 4 × 50 Ah = 200 Ah, so a 48 V / 100 Ah bank is four strings of two units, eight batteries weighing 8 × 15.25 kg = 122 kg before racks and cables. That makes the 6-EVF-50 a cabinet-scale battery for small server rooms, edge sites, base stations and 3 kW-class UPS installations.

Key Takeaways

Published setpoints: float 13.5 V and equalise 14.1 V for a six-cell string, which is 2.25 V and 2.35 V per cell (13.5 ÷ 6 and 14.1 ÷ 6).
C3 rating, 50 Ah nominal: capacity is measured at the 3-hour rate, so a 3 kW load on a 48 V bank is the design point.
Maximum charge current 10.0 A, which is 10.0 A ÷ 50 Ah = 0.2 of rated capacity per hour; size the charger to match.
600 Wh per unit at 39.3 Wh/kg (12 V × 50 Ah = 600 Wh; 600 Wh ÷ 15.25 kg = 39.3 Wh/kg), useful where weight or shelf space is limited.
Cut-off at 1.75 V per cell, so a string should be withdrawn at 1.75 V × 6 cells = 10.5 V.
350–600 cycles at 50–80 % depth of discharge and a 2–5 year design life — the honest planning window for a cabinet on mains most of the day.

§1 — 6-EVF-50 Quick Specifications

Every row below comes from the CHISEN model page for the 6-EVF-50, except where the source column reads Arithmetic. If you are writing a tender for a 12V 50Ah battery, these are the lines that belong in it.

Parameter	Value	Source
Nominal voltage	12 V	Model page
Nominal capacity	50 Ah	Model page
Capacity rate	C3	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
Equalise voltage	14.1 V	Model page
Cycle life	350–600 cycles (DoD 50–80 %)	Model page
Maximum charge current	10.0 A	Model page
Discharge cut-off	1.75 V per cell	Model page
Self-discharge	≤ 3 %/month at 25 °C	Model page
Working temperature	−15 to 50 °C	Model page
Design life	2–5 years	Model page
Cell configuration	6 × 2 V cells in series (6 × 2 V = 12 V)	Arithmetic
Energy per unit	12 V × 50 Ah = 600 Wh	Arithmetic
Specific energy	600 Wh ÷ 15.25 kg = 39.3 Wh/kg	Arithmetic
String cut-off	1.75 V × 6 cells = 10.5 V	Arithmetic
Float per cell	13.5 V ÷ 6 cells = 2.25 V	Arithmetic
Equalise per cell	14.1 V ÷ 6 cells = 2.35 V	Arithmetic

Internal resistance, self-discharge at temperatures other than 25 °C, and the cycle curve at each depth of discharge are not published for this model — treat them as “not published”, or request them from the factory before freezing the design.

§2 — The Pain: Why 12V 50Ah Procurement Goes Wrong

Most disputes over a 12V 50Ah battery are not technical. They come from documents that contradict each other, or from numbers copied between models that differ in more than their label. Three patterns dominate.

Rating-rate confusion. A 50 Ah figure printed without a rate means little, because lead-acid capacity falls as the discharge rate lengthens. The 6-EVF-50 is published at C3, so 50 Ah is the three-hour rate capacity. A rival datasheet showing 50 Ah at the 10-hour rate describes a different discharge profile, and a rack designed against the softer number will not deliver the expected autonomy. Write “50 Ah at C3” into the specification and let a supplier who publishes at another rate disqualify itself.

Setpoint drift. Float voltage is the most consequential line in a UPS battery file, because 0.05 V of error per cell across six cells is 0.3 V on the string, and 0.1 V per cell is 0.6 V. On long float this shows up directly as lost capacity or over-charge. The published values here are 13.5 V float and 14.1 V equalise; a cabinet shipping with a default of 13.6 V or 13.8 V is not a documentation error, it is a shortened service life.

Mechanical assumptions carried over. The 230 × 140 × 180 mm case and 15.25 ± 0.2 kg weight set shelf loading, tray spacing and lifting method, and the φ11.8-M6 terminal sets the cable lug size. A purchase order specifying only “50 Ah 12 V” leaves all three open, and those three are what cause returns.

§3 — The Choice: Narrowing the Field Before You Specify

The 12 V VRLA shelf contains four mechanical footprints, and choosing between them is an exercise in removing options with published numbers rather than adjectives.

The 6-DZF series covers the small end. The 6-DZF-12 is 151 × 99 × 99 mm and 3.6 ± 0.2 kg for 12 Ah at C2; the 6-DZF-20 is 180 × 76 × 170 mm and 6.1 ± 0.2 kg for 20 Ah at C2. Both are lighter than a 12V 50Ah battery and both are correct for a small cabinet that genuinely needs 12 or 20 Ah. They are the wrong choice where a 3 kW UPS load has to ride through a generator start.

The 6-DMF series is the step up, with 38 Ah, 45 Ah and 52 Ah options in a 224 mm-long, 175 mm-tall case. The 6-DMF-45 publishes 12.3 ± 0.2 kg and the 6-DMF-52 publishes 13.7 ± 0.2 kg, both at C3, both at 13.5 V float and 14.1 V equalise with a 1.75 V per cell cut-off. Their gravimetric performance is strong: 12 V × 45 Ah = 540 Wh, and 540 Wh ÷ 12.3 kg = 43.9 Wh/kg for the 6-DMF-45; 12 V × 52 Ah = 624 Wh, and 624 Wh ÷ 13.7 kg = 45.5 Wh/kg for the 6-DMF-52.

The 6-EVF series is the heavy-duty line, and the choice is genuinely open here. The 6-EVF-50 at 50 Ah sits at 39.3 Wh/kg; the 6-EVF-60 at 60 Ah and 18.8 ± 0.2 kg works out to 12 V × 60 Ah = 720 Wh, and 720 Wh ÷ 18.8 kg = 38.3 Wh/kg; the 6-EVF-80 at 80 Ah and 25.7 ± 0.2 kg works out to 12 V × 80 Ah = 960 Wh, and 960 Wh ÷ 25.7 kg = 37.4 Wh/kg. Specific energy falls as the case grows because the plates scale sub-linearly against case mass, so the larger units buy runtime per string rather than runtime per kilogram.

Two questions settle it. Is the load runtime-driven or space-driven? If floor area is the constraint, the 6-EVF-50 delivers 600 Wh in a 230 × 140 × 180 mm footprint. If runtime is the constraint and floor space is free, a larger unit wins, and the sibling model page for the 6-EVF-60 documents the 258 × 170 × 160 mm case and 60 Ah rating that a 48 V string needs on wider shelves. What does the charger allow? Maximum charge current scales with the model — 4.0 A on the 6-DZF-20, 9.0 A on the 6-DMF-45, 10.0 A on the 6-EVF-50, 12.0 A on the 6-EVF-60 — and a rectifier sized for the smaller model will under-charge the larger one indefinitely.

For the balance of the 12 V VRLA options, the full product range for the 6-EVF series lists every model in that line with its published dimensions, so a tender for a 12V 50Ah battery can be written against the whole list rather than a shortlist.

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

Step 1 — Fix the bus voltage and string count. A 48 V UPS needs four 12 V strings: 48 V ÷ 12 V = 4 strings, and 4 × 12 V = 48 V. A 24 V system needs two. Record the count in the tender so every quotation answers on the same basis.

Step 2 — Fix the required Ah at the design rate. Take the load in watts, divide by bus voltage to get amperes, multiply by required autonomy hours, then read the result against the C3 discharge curve. Convert to parallel strings: required Ah ÷ 50 Ah = parallel strings per series group. A 48 V / 100 Ah bank is 100 Ah ÷ 50 Ah = 2 parallel strings, so 4 × 2 = 8 batteries in total.

Step 3 — Check the energy budget end to end. Eight 6-EVF-50 units hold 8 × 600 Wh = 4,800 Wh. At a 50 % depth-of-discharge planning limit that is 4,800 Wh ÷ 2 = 2,400 Wh usable, which against a 3 kW load gives 2,400 Wh ÷ 3,000 W = 0.8 hours of runtime.

Step 4 — Size the charger from the published maximum. The 6-EVF-50 accepts 10.0 A. In a four-string parallel bank, a rectifier charging each string at the model maximum must deliver 4 strings × 10.0 A = 40.0 A. Set float at 13.5 V and equalise at 14.1 V, and confirm the cabinet controller holds both.

Step 5 — Fix the mechanical and acceptance items. Record 230 × 140 × 180 mm, 15.25 ± 0.2 kg, φ11.8-M6 terminals, the −15 to 50 °C operating window and the 1.75 V per cell cut-off, then require the supplier to confirm every line in the delivery dossier.

§5 — Published Comparison: 6-EVF-50 Against Its Closest Siblings

The table below uses only values published on the CHISEN model pages. The 6-EVF-50 row is the unit this guide is about; the surrounding rows are the options a tender committee will normally place beside it.

Model	Capacity	Rate	L×W×H mm	Weight	Terminal	Float / Equalise	Max charge current	Cycle life
6-DMF-38	38 Ah	C3	224 × 106 × 175	10.45 ± 0.2 kg	φ9.8-M5	13.5 V / 14.1 V	7.6 A	350–600
6-DMF-45	45 Ah	C3	224 × 121 × 175	12.3 ± 0.2 kg	φ11.8-M5	13.5 V / 14.1 V	9.0 A	350–600
6-DMF-52	52 Ah	C3	224 × 135 × 175	13.7 ± 0.2 kg	φ11.8-M6	13.5 V / 14.1 V	10.4 A	350–600
6-EVF-50 (this model)	50 Ah	C3	230 × 140 × 180	15.25 ± 0.2 kg	φ11.8-M6	13.5 V / 14.1 V	10.0 A	350–600
6-EVF-60	60 Ah	C3	258 × 170 × 160	18.8 ± 0.2 kg	φ14-M6	13.5 V / 14.1 V	12.0 A	350–600
6-EVF-80	80 Ah	C3	259 × 170 × 218	25.7 ± 0.2 kg	φ16-M6	13.5 V / 14.1 V	16.0 A	350–600
6-EVF-120	120 Ah	C3	407 × 170 × 240	40 ± 0.2 kg	φ20-M8	13.5 V / 14.1 V	24.0 A	350–600

All rows share the same published float and equalise setpoints, the same 1.75 V per cell discharge cut-off, self-discharge of no more than 3 % per month at 25 °C, and a −15 to 50 °C operating window.

Model	Energy per unit	Specific energy
6-DMF-45	12 V × 45 Ah = 540 Wh	540 Wh ÷ 12.3 kg = 43.9 Wh/kg
6-DMF-52	12 V × 52 Ah = 624 Wh	624 Wh ÷ 13.7 kg = 45.5 Wh/kg
6-EVF-50	12 V × 50 Ah = 600 Wh	600 Wh ÷ 15.25 kg = 39.3 Wh/kg
6-EVF-60	12 V × 60 Ah = 720 Wh	720 Wh ÷ 18.8 kg = 38.3 Wh/kg
6-EVF-120	12 V × 120 Ah = 1,440 Wh	1,440 Wh ÷ 40 kg = 36.0 Wh/kg

Two practical notes follow. A 6-EVF-50 is heavier than a 6-DMF-52 by 15.25 kg − 13.7 kg = 1.55 kg per unit while giving 600 Wh instead of 624 Wh, so the 6-DMF-52 is the value choice only where the footprint allows it. And the 6-EVF-60 needs a 258 × 170 mm shelf against the 6-EVF-50’s 230 × 140 mm, so a cabinet built for one will not physically accept the other without a new tray.

§6 — The Trust: Factory Evidence, Delivery and After-Sales

Behind every figure in this guide is a manufacturer with published production scale. CHISEN operates eight production bases with an annual capacity of 70 million kVAh and holds CE, ISO 9001, ISO 14001, UL and IEC certifications. Its lines span flooded tubular OPzS2, gel tubular OPzV2 and the 12 V VRLA 6-DZF, 6-DMF and 6-EVF series. That breadth matters for a buyer, because one supplier can cover the small cabinet battery, the mid-size string and the large tubular bank without re-qualifying a second vendor.

For delivery, ask for four documents and check four numbers. The documents: model datasheet, shipment batch test report, certificate of conformity covering CE and the applicable UL or IEC mark, and a packing list showing batch and date codes. The numbers: nameplate 12 V, terminal type φ11.8-M6, mass against 15.25 ± 0.2 kg per unit, and open-circuit voltage on arrival. For a 12V 50Ah AGM battery resting after shipment, an open-circuit reading of 12.4 to 12.8 V per string is normal; below roughly 12.0 V, or a spread of more than about 0.15 V between units in the same batch, should trigger a hold rather than an installation.

CHISEN ships 12 V VRLA units through the export desks in Hangzhou, with container loading from Shanghai and Ningbo and onward routing to distributor and installer accounts. Regular markets for this class of battery include India, Nigeria, Kenya, Vietnam, the Philippines, Brazil, Egypt, Mexico, Indonesia and Pakistan, with volumes moving through Karachi, Mumbai, Lagos, Mombasa, Colombo, Dubai and Jebel Ali for African and Middle East destinations, and through Hamburg and Santos for European and South American programmes. Documented batches and a written warranty matter more on those routes than on a domestic one, because the after-sales path is longer and the importer carries the risk.

§7 — FAQ

Q1: What are the published nominal voltage and capacity of the 6-EVF-50? 12 V and 50 Ah at the C3 rate (Model page). Six 2 V cells in series give 6 × 2 V = 12 V, and stored energy is 12 V × 50 Ah = 600 Wh per unit.

Q2: What float and equalise setpoints does the manufacturer publish for the 6-EVF-50? Float 13.5 V and equalise 14.1 V across the six-cell string (Model page), which is 13.5 V ÷ 6 = 2.25 V and 14.1 V ÷ 6 = 2.35 V per cell.

Q3: What is the maximum charging current for the 6-EVF-50? 10.0 A (Model page), or 10.0 A ÷ 50 Ah = 0.2 of rated capacity per hour. A four-string bank at the model maximum needs 4 strings × 10.0 A = 40.0 A from the rectifier.

Q4: What are the case dimensions and weight of the 6-EVF-50? 230 × 140 × 180 mm and 15.25 ± 0.2 kg (Model page), giving 12 V × 50 Ah = 600 Wh and 600 Wh ÷ 15.25 kg = 39.3 Wh/kg.

Q5: What terminal type and torque does the 6-EVF-50 use? The published terminal is φ11.8-M6 (Model page). Tightening torque is not published and should be requested from the factory with the recommended cable lug size for your busbar.

Q6: How many cells does a 12V50Ah string contain and what bus voltage does it give? Six 2 V cells in series, so 6 × 2 V = 12 V. Two strings in series give 24 V and four give 48 V: 4 × 12 V = 48 V, the common single-phase UPS and telecom rectifier bus voltage.

Q7: What is the published design float life of the 6-EVF-50 and at what temperature? Design life 2–5 years with 350–600 cycles at 50–80 % depth of discharge (Model page). Self-discharge of no more than 3 % per month is stated at 25 °C, and the operating window is −15 to 50 °C (Model page).

Q8: How should an importer verify the 6-EVF-50 on delivery? Check nameplate 12 V, terminal φ11.8-M6, unit mass against 15.25 ± 0.2 kg, and open-circuit voltage per string, normally 12.4 to 12.8 V after shipment. Keep the batch test report, certificate of conformity and packing list with the batch codes for warranty claims.

Q9: Which certifications does the CHISEN factory behind the 6-EVF-50 hold? CE, ISO 9001, ISO 14001, UL and IEC, across eight production bases with 70 million kVAh of annual capacity. The marks are stated at company level; ask for the certificate covering your specific shipment.

Q10: How do I request a quotation or samples for the 6-EVF-50? Send the model, bus voltage, string count, load, autonomy and destination port to the export desk. Samples can be arranged with the dossier for the 12V 50Ah battery, and the response is normally given within 24 hours.

Expert Summary

The 6-EVF-50 is a 12 V, 50 Ah C3 valve-regulated AGM battery suited to cabinet and small-room work: 230 × 140 × 180 mm, 15.25 ± 0.2 kg, 600 Wh per unit at 39.3 Wh/kg, 13.5 V float, 14.1 V equalise, 10.0 A maximum charge current, a 1.75 V per cell cut-off that becomes 10.5 V across six cells, 350–600 cycles at 50–80 % depth of discharge, 2–5 years of design life, self-discharge of no more than 3 % per month at 25 °C, and an operating window of −15 to 50 °C. A 48 V bank is four strings; a 48 V / 100 Ah bank is four strings of two units; eight units hold 4,800 Wh gross and about 2,400 Wh at a 50 % planning limit, covering a 3 kW load for 0.8 hours. Buy it when floor area is the constraint; choose the 6-DMF-52 or 6-EVF-60 when runtime per kilogram or per string matters more than footprint. Specify rating rate, setpoints, cut-off, dimensions, terminal type and maximum charge current in the tender, and require answers against those figures rather than a watt-hour headline.

Contact CHISEN — 24-Hour Response

CHISEN Battery, Hangzhou, China. Export desk: sales@chisen.cn and jack@chisen.cn. WhatsApp: +86 131 6622 6999. Technical details: www.chisen.cn. Send the bus voltage, string count, load and destination port and you receive the 6-EVF-50 dossier, the published specification table and a quotation within 24 hours.

Related CHISEN Buyer Guides

November 7, 2026

6-DMF-52 12V52Ah UPS Battery: DC Bus String Sizing and Runtime Engineering

Answer First

The 6-DMF-52 is a 12 V, 52 Ah sealed VRLA module built for the 6-DMF series cabinets used in UPS and DC-backup installations. The published numbers are fixed and checkable: 224 × 135 × 175 mm, 13.7 ± 0.2 kg, float 13.5 V, equalise 14.1 V, maximum charge current 10.4 A, discharge cutoff 1.75 V/cell, self-discharge ≤3 %/month at 25 °C, working range −15…50 °C, cycle life 350–600 cycles at 50–80 % depth of discharge (Source: Model page). The product page for the 6-DMF-52 12V52Ah carries these values.

Capacity on this model is rate-qualified. A C3 rating means the 6-DMF-52 is designed to deliver its full 52 Ah over three hours, so the rated discharge current is 52 Ah ÷ 3 h = 17.3 A, down to a 1.75 V/cell cutoff. Any runtime claim that ignores the rate and the cutoff is arithmetic fiction.

Sizing therefore works like this: voltage comes from the number of units wired in series, ampere-hours come from the number of parallel strings. On a 48 V DC bus, four 6-DMF-52 units in series give 4 × 13.5 V = 54.0 V at float and 4 × 14.1 V = 56.4 V at equalise, and a single string carries 52 Ah. Two strings in parallel give 2 × 52 Ah = 104 Ah, so the bank is a 48 V / 104 Ah assembly built from eight modules. Section §4 spreads that arithmetic out line by line.

Key Takeaways

52 Ah is a C3 figure, not a continuous 52 A figure: rated discharge current is 52 Ah ÷ 3 h = 17.3 A per string to a 1.75 V/cell cutoff.
Series strings set the bus voltage: 6-DMF-52 holds 6 cells, so 6 × 2.25 V = 13.5 V float and 6 × 2.35 V = 14.1 V equalise per unit; four units in series give a 48 V nominal bus.
Parallel strings set the ampere-hours: 4S × 2P = 48 V / 104 Ah, total mass 8 × 13.7 kg = 109.6 kg.
Charge current is capped at 10.4 A per unit (52 Ah × 20 %), which sets the minimum charger size for a parallel bank.
The 6-DMF series is the direct substitute for other 12 V cabinets, and the full 6-DMF range shows where the 52 Ah slot sits against 12, 20, 38 and 45 Ah variants.
Runtime comes from energy, not from the Ah label: at 42 V end-of-discharge voltage a 104 Ah bank holds 42 V × 104 Ah = 4,368 Wh, and an 80 % planning derate keeps about 3,494 Wh of usable energy.

§1 — 6-DMF-52 Quick Specifications

Every line below is taken from the published model page for the 6-DMF-52. Where a value is derived, the calculation is shown; where the factory has not published a figure, the cell says so rather than estimating.

Parameter	Published value	Source
Nominal voltage	12 V	Model page
Nominal capacity	52 Ah (C3)	Model page
Capacity rate	C3	Model page
Rated discharge current	17.3 A (52 Ah ÷ 3 h)	Arithmetic
Dimensions (L × W × H)	224 × 135 × 175 mm	Model page
Weight	13.7 ± 0.2 kg	Model page
Terminal	φ11.8-M6	Model page
Terminal torque	not published	To be requested from the factory
Float voltage	13.5 V (2.25 V/cell)	Model page
Equalise voltage	14.1 V (2.35 V/cell)	Model page
Maximum charge current	10.4 A (52 Ah × 20 %)	Model page
Discharge cutoff	1.75 V/cell	Model page
Cycle life	350–600 cycles (DoD 50–80 %)	Model page
Self-discharge	≤3 %/month at 25 °C	Model page
Working temperature	−15…50 °C	Model page
Design life	not published	To be requested from the factory
Cell configuration	6 × 2 V cells per 12 V unit	Arithmetic
Specific energy	45.5 Wh/kg for a 4S × 2P bank	Arithmetic

§2 — The Pain: Why 52 Ah Strings Get Oversized, Undersized, or Mis-Sized

Most 12 V battery buying errors are not made at the model level. They are made between the model and the DC bus, and the 6-DMF-52 exposes three of them.

The Ah label is not the load. A 52 Ah nameplate read as “52 A available” overstates a single 6-DMF-52 string by a factor of three. The published rating is C3, so the string supports 17.3 A for three hours, not 52 A. A 48 V inverter drawing 22.6 A needs two parallel strings even though a single string carries 52 Ah on paper.

Float voltage is the real bus voltage. A 48 V DC bus in a UPS is not held at 48.0 V; it floats at 54.0 V with four 6-DMF-52 units in series, because float is 13.5 V per 12 V unit. Inverters are rated for the floating range, not the nominal label, and a battery bank matched to the nominal number instead of the float number will trip on over-voltage during the equalisation phase, when the same four units sit at 4 × 14.1 V = 56.4 V.

Temperature and age eat capacity in silence. The published 52 Ah holds at 25 °C with self-discharge ≤3 %/month. A bank left on float in a 40 °C room loses capacity faster than the datasheet curve suggests, and the same bank in −15…50 °C ambient will see the usable figure move across the year. Runtime quoted at 25 °C with no temperature note is a number that will disappoint in July.

Runtime is set by the weakest parallel string. One undercharged or high-resistance string in a parallel bank drags the whole bank down, because the strings share the same bus and the same current. That is why string count, string balance and interconnects matter more to runtime than a single extra ampere-hour of nameplate capacity.

§3 — The Choice: Which 12 V Module and Which String Architecture

The 6-DMF-52 is one slot in a documented 12 V range, and the correct choice depends on two decisions: which model fills the cabinet slot, and how many strings the DC bus needs.

On the model side, the 6-DMF series shares one footprint language, and the 6-DMF-38 12V38Ah is the same 224 mm length at 106 mm width and 10.45 kg, so a 38 Ah and a 52 Ah module can sit in adjacent slots of the same cabinet range. The 6-EVF series steps up in capacity but changes the envelope: 6-EVF-50 is 230 × 140 × 180 mm at 15.25 kg, so it is 6 mm longer, 5 mm wider and 5 mm taller than the 6-DMF-52 and will not drop into a 175 mm-high 6-DMF rail. Cabinets designed around the 6-DMF footprint should stay inside that footprint; mixing series only works where the installer has confirmed rail clearance.

On the architecture side, three configurations cover most DC-backup demand:

Single string (1P). One series string per bus, the low-cost option, but it has no redundancy: any single module failure takes the load down, and the whole bank carries the full load current.
Two strings in parallel (2P). Doubles ampere-hours to 104 Ah on a 48 V bus and provides the redundancy that single-string designs lack. This is the default recommendation for the 6-DMF-52 in cabinet-scale installations.
Parallel strings with a DC breaker per string. Adds the ability to isolate one string for maintenance, but the branch protection must be coordinated with the 10.4 A per-unit charge limit so that a charging fault in one string cannot over-charge the other.

A bank that needs more than 104 Ah is normally answered with more parallel strings of the same module rather than with a single much larger unit, because redundancy scales with string count while it does not scale with the size of one module.

§4 — The Framework: DC Bus String Sizing and Runtime Arithmetic

This section works one example end to end: a 48 V nominal DC bus, a 1,000 W inverter with 92 % conversion efficiency, and modules from the 6-DMF range. Every number below is either published or calculated on the spot.

Step 1 — Count the units in series for the bus voltage.

Bus voltage target: 48 V nominal. Units in series: 48 V ÷ 12 V = 4 units. Float voltage of the string: 4 × 13.5 V = 54.0 V. Equalise voltage of the string: 4 × 14.1 V = 56.4 V. Cells in the string: 4 units × 6 cells = 24 cells.

Step 2 — Count the parallel strings for the ampere-hours.

Required DC power at the bus: 1,000 W ÷ 0.92 efficiency = 1,087 W. Current drawn from the 48 V bus: 1,087 W ÷ 48 V = 22.6 A. One 6-DMF-52 string supplies 52 Ah, so one string cannot carry 22.6 A at the C3 rate of 17.3 A. Parallel strings required: 22.6 A ÷ 17.3 A = 1.31 → 2 strings. Bank ampere-hours: 2 × 52 Ah = 104 Ah. Total units: 4 units × 2 strings = 8 modules.

Step 3 — Compute the bank energy and the mass.

Nominal energy: 48 V × 104 Ah = 4,992 Wh. End-of-discharge energy at the 1.75 V/cell cutoff: 24 cells × 1.75 V = 42 V, so 42 V × 104 Ah = 4,368 Wh. Planning energy at 80 % usable: 4,368 Wh × 0.8 = 3,494 Wh. Bank mass: 8 modules × 13.7 kg = 109.6 kg. Specific energy of the bank: 4,992 Wh ÷ 109.6 kg = 45.5 Wh/kg.

Step 4 — Convert energy into runtime.

Runtime on full energy: 4,368 Wh ÷ 1,087 W = 4.0 hours. Runtime on planning energy: 3,494 Wh ÷ 1,087 W = 3.2 hours.

Step 5 — Size the charger.

Per-unit charge limit: 10.4 A (published). Charger requirement for two parallel strings: the total should not exceed 10.4 A × 8 modules = 83.2 A, and a charger set below that figure keeps every module inside its published limit. A 60 A charger is a typical starting point for this bank and stays comfortably inside the 83.2 A ceiling.

Step 6 — Fix the temperature and aging margin.

The 52 Ah rating and the 3.2-hour runtime both hold at 25 °C. For an ambient range of −15…50 °C, the planning figure has to be set from the worst month rather than from the datasheet headline. If the installation runs at 35 °C or above, the 80 % planning factor should be treated as the optimistic case, not the conservative one.

The same framework scales. Changing only the parallel string count from 2 to 3 gives 3 × 52 Ah = 156 Ah, an end-of-discharge energy of 42 V × 156 Ah = 6,552 Wh, a planning energy of 6,552 × 0.8 = 5,242 Wh, a runtime of 5,242 Wh ÷ 1,087 W = 4.8 hours, and a mass of 12 × 13.7 kg = 164.4 kg. Nothing else in the calculation moves.

§5 — Sibling Models in the 12 V Range

The table below lists the published values of the neighbouring modules an installer is likely to compare against the 6-DMF-52. All figures are taken from the model pages of the same 12 V VRLA range; design life is shown as “not published” where the factory has not stated it.

Model	Capacity	Rate	L × W × H (mm)	Weight	Terminal	Float	Equalise	Charge current	Cycle life	Design life
6-DMF-38	38 Ah	C3	224 × 106 × 175	10.45 ± 0.2 kg	φ9.8-M5	13.5 V	14.1 V	7.6 A	350–600	not published
6-DMF-45	45 Ah	C3	224 × 121 × 175	12.3 ± 0.2 kg	φ11.8-M5	13.5 V	14.1 V	9.0 A	350–600	2–5 years
6-DMF-52	52 Ah	C3	224 × 135 × 175	13.7 ± 0.2 kg	φ11.8-M6	13.5 V	14.1 V	10.4 A	350–600	not published
6-EVF-50	50 Ah	C3	230 × 140 × 180	15.25 ± 0.2 kg	φ11.8-M6	13.5 V	14.1 V	10.0 A	350–600	2–5 years

Three readings of this table decide the choice. First, capacity alone does not decide it: the 6-EVF-50 offers 50 Ah at a 10.0 A charge limit and 15.25 kg, while the 6-DMF-52 offers 52 Ah at 10.4 A and 13.7 kg in a narrower 175 mm height. Second, the charge current scales with capacity — 7.6 A for 38 Ah, 10.4 A for 52 Ah, 10.0 A for 50 Ah — so a charger specification always follows the model. Third, the footprint changes with the series, and the 224 × 135 × 175 mm envelope of the 6-DMF-52 is the one to design the cabinet around.

§6 — The Trust: Factory Basis for Every Number Above

Every specification used in this article comes from the CHISEN product documentation for the 12 V VRLA range, not from a distributor listing or a catalogue round-up. The 6-DMF-52 is produced by CHISEN Battery, Hangzhou, China, which operates 8 production bases with an annual capacity of 70 million kVAh and holds CE, ISO 9001, ISO 14001, UL and IEC certifications. The same line produces flooded tubular OPzS2, gel tubular OPzV2 and the 12 V VRLA 6-DZF, 6-DMF and 6-EVF series.

CHISEN’s export desk ships 12 V VRLA modules to distributors and OEM panel builders in India, Nigeria, Kenya, Vietnam, the Philippines, Brazil, Egypt, Mexico, Indonesia, Pakistan, the UAE, South Africa, Poland, Germany, Spain, Australia, Thailand, Malaysia, Singapore and Hong Kong. Containers normally leave through Ningbo, Shanghai and Shenzhen, with project shipments also loaded at Guangzhou; delivery is worked out as FOB or CIF against port references such as Mumbai, Chennai, Karachi, Lagos, Mombasa, Durban, Cairo, Hamburg, Rotterdam, Antwerp, Valencia, Santos, Callao, Dubai and Colombo.

The factory facts matter for one specific reason: runtime commitments and audit trails need documentation that survives a shipment. A published model page with a stated charge limit, cutoff voltage, self-discharge rate and temperature range can be checked on arrival against the delivered unit. Figures that no factory publishes — terminal torque and design life for the 6-DMF-52 — are marked as not published here and can be requested in writing for a specific project.

§7 — FAQ

Q1: What are the published nominal voltage and capacity of the 6-DMF-52? 12 V and 52 Ah, rated at the C3 rate, which means 52 Ah delivered over three hours down to a 1.75 V/cell cutoff. The rated discharge current is therefore 17.3 A per string (Source: Model page).

Q2: What float and equalise setpoints does the manufacturer publish for the 6-DMF-52? Float 13.5 V and equalise 14.1 V per 12 V unit, which is 2.25 V/cell and 2.35 V/cell across the six cells of each unit (Source: Model page).

Q3: What is the maximum charging current for the 6-DMF-52? 10.4 A, equal to 20 % of the 52 Ah rating (Source: Model page). In the 4S × 2P example of §4 this caps the charger at 83.2 A across eight modules.

Q4: What are the case dimensions and weight of the 6-DMF-52? 224 × 135 × 175 mm and 13.7 ± 0.2 kg (Source: Model page). The same 224 mm length and 175 mm height as the 6-DMF-45, with 14 mm more width.

Q5: What terminal type and torque does the 6-DMF-52 use? φ11.8-M6 terminals (Source: Model page). Terminal torque is not published and should be requested from the factory in writing before installation.

Q6: How many cells does a 12V52Ah string contain and what bus voltage does it give? Six 2 V cells per unit, so a 48 V bus needs four units in series: 24 cells, 4 × 13.5 V = 54.0 V at float and 4 × 14.1 V = 56.4 V at equalise (Source: Model page, Arithmetic).

Q7: What is the published design float life of the 6-DMF-52 and at what temperature? Design life is not published. The published figures are a cycle life of 350–600 cycles at 50–80 % depth of discharge, self-discharge ≤3 %/month at 25 °C and a working range of −15…50 °C (Source: Model page).

Q8: How should an importer verify the 6-DMF-52 on delivery? Check the label against the model page for capacity, terminal type and dimensions, measure open-circuit voltage per cell and confirm the setpoints at 13.5 V float and 14.1 V equalise, then log the weight of each unit against 13.7 ± 0.2 kg before the consignment leaves the port.

Q9: Which certifications does the CHISEN factory behind the 6-DMF-52 hold? CE, ISO 9001, ISO 14001, UL and IEC, produced across 8 bases with an annual capacity of 70 million kVAh in Hangzhou, China (Source: company profile).

Q10: How do I request a quotation or samples for the 6-DMF-52? Send the target string configuration, bus voltage, load and required runtime to the export desk; samples and a project quotation are prepared against the published specification.

Expert Summary

The 6-DMF-52 is a 12 V 52 Ah C3 VRLA module, 224 × 135 × 175 mm at 13.7 ± 0.2 kg, float 13.5 V, equalise 14.1 V, 10.4 A charge limit, 1.75 V/cell cutoff, ≤3 %/month self-discharge at 25 °C, −15…50 °C working range, 350–600 cycles at 50–80 % DoD, design life not published. Sizing separates cleanly into two decisions: series strings set the bus voltage (4 units give a 48 V bus at 54.0 V float), parallel strings set the ampere-hours (2 strings give 104 Ah, 4,992 Wh nominal, 109.6 kg, 45.5 Wh/kg). Against a 1,000 W load at 92 % efficiency, the bank draws 22.6 A, needs 2 strings because one 17.3 A C3 string cannot carry it, and delivers 4.0 hours on full energy or 3.2 hours after the 80 % planning derate. Charge current, cutoff voltage and temperature set the real limits, and every unpublished figure should be requested from the factory rather than estimated.

Contact CHISEN — 24-Hour Response

Sales: sales@chisen.cn | Export desk: jack@chisen.cn | WhatsApp: +86 131 6622 6999 | www.chisen.cn

Technical sizing questions are answered within 24 hours. Send the bus voltage, the load in watts or amps, the required runtime and the cabinet dimensions, and the string configuration will be returned with the supporting arithmetic.

Related CHISEN Buyer Guides

November 6, 2026

6-EVF-50 12V50Ah UPS Battery: DC Bus String Sizing and Runtime Engineering

Answer First

The CHISEN 6-EVF-50 is a 12 V, 50 Ah VRLA AGM battery rated at the C3 discharge rate, and its sizing arithmetic fits on one sheet of paper. One 12V50Ah string delivers 12 V × 50 Ah = 600 Wh nominal at a published 15.25 ± 0.2 kg, so a 12V 50Ah battery carries 600 Wh ÷ 15.25 kg = 39.3 Wh/kg. Four strings in series give a 48 V bus of 2,400 Wh.

Runtime decides the design, and it is set by load and depth of discharge, not by the label. Usable energy per string at the published 1.75 V/cell cutoff and 50 % DoD is 600 Wh × 0.50 = 300 Wh, so runtime (h) = (strings × 300 Wh) ÷ (bus voltage × load current) — 16 strings on a 48 V, 20 A load give 4,800 Wh ÷ 960 W = 5.0 hours.

The second constraint is recharge: the published 10.0 A charge current means 50 Ah ÷ 10.0 A = 5.0 hours minimum to restore one string, which often dictates the generator window. Every figure below comes from the published CHISEN model page, and every derived number shows its arithmetic. Current datasheet values are on the 6-EVF-50 12V50Ah product page.

Key Takeaways

One 12V 50Ah battery is 600 Wh nominal (12 V × 50 Ah) at 15.25 ± 0.2 kg, or 39.3 Wh/kg.
Runtime = (strings × 300 Wh) ÷ (bus voltage × load current) at 50 % DoD; the label alone does not set autonomy.
Recharge governs the site: 50 Ah ÷ 10.0 A = 5.0 hours minimum per string at the published maximum charge current.
Series sets voltage, parallel sets amp-hours: 4 strings = 48 V / 50 Ah; 16 strings = 48 V / 400 Ah and four times the runtime.
Setpoints are fixed and published: 13.5 V float (2.25 V/cell), 14.1 V equalise (2.35 V/cell), 1.75 V/cell cutoff.

§1 — 6-EVF-50 Quick Specifications

Values come verbatim from the published CHISEN model page; derived rows show the calculation. The full 12 V VRLA range is on the EVF series overview.

Parameter	Published value	Source
Nominal voltage	12 V	Model page
Nominal capacity	50 Ah	Model page
Capacity rate	C3	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
Equalise voltage	14.1 V	Model page
Cycle life	350–600	Model page
Maximum charge current	10.0 A	Model page
Discharge cutoff	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
Nominal energy	600 Wh	Arithmetic
Specific energy	39.3 Wh/kg	Arithmetic

Terminal torque and per-cell internal resistance are not published and are to be requested from the factory. The 6-EVF-60 12V60Ah adds 20 % capacity on the same 170 mm depth.

§2 — The Pain: Why Nameplate Amp-Hours Fail in the Field

The most expensive failure in a UPS battery project is not a bad cell — it is numbers that were right on a spreadsheet and wrong on site. The 6-EVF-50 is published at 50 Ah C3, meaning 50 Ah over a three-hour discharge, and that qualifier belongs in every runtime calculation you sign off.

Pain one: C3 is not C10. A bank of 6-EVF-50 strings that looks oversized on paper delivers less than the arithmetic suggests when the real discharge runs eight or ten hours, the normal case for a telecom cabinet or a solar-backed site. That is a specification error, not a manufacturing defect.

Pain two: usable energy is 50 % DoD, not 100 %. The published 350–600 cycle life applies at 50–80 % depth of discharge, so designing on 600 Wh per string leaves no margin for the 1.75 V/cell cutoff, for ageing, or for cold-temperature capacity loss.

Pain three: the recharge window is the hidden constraint. The published maximum charge current for the 12V 50Ah battery is 10.0 A, so a 50 Ah string needs 50 Ah ÷ 10.0 A = 5.0 hours of continuous charging to restore full capacity. If the site’s generator or rectifier window is two hours, the bank never reaches 100 % and every later outage starts partly discharged.

Pain four: cabinet geometry sets the layout. At 230 × 140 × 180 mm and 15.25 ± 0.2 kg per unit, a 48 V / 400 Ah bank of 16 strings weighs 16 × 15.25 = 244 kg — often the constraint that changes the design.

§3 — The Choice: Where a 12V 50Ah Battery Fits — and Where It Does Not

CHISEN builds four relevant lines: flooded tubular OPzS2, gel tubular OPzV2, 12 V VRLA AGM (6-DZF / 6-DMF / 6-EVF), and lithium storage systems. The 6-EVF-50 sits in the third group, and it fits when four conditions hold.

Short-to-medium runtime in a small footprint. AGM needs no watering, no gas venting and no special room; the 180 mm case height fits a standard 200 mm shelf.
A maintenance-free installation. Sealed construction means no topping-up on site and predictable logistics for distributors.
A load profile that matches a C3 rating. Motor starting, DC bus ride-through, inverter peak support and moderate telecom loads are what this block is designed for.
A controlled environment and a budget that makes lithium unjustifiable. The published range is −15…50 °C, but capacity still falls in cold conditions, so unsheltered sites need controlled enclosures; for one cabinet, a lithium system with BMS and enclosure does not pay back against VRLA.

Where it does not fit: sub-hour bridge requirements suit a different chemistry; autonomy above ten hours needs a tubular product or a larger VRLA block; and high daily cycling falls outside the 350–600 cycle envelope.

§4 — The Framework: A Five-Step DC Bus String Sizing Method

Step 1 — inventory the load in watts. Sum the continuous load and, separately, the peak the inverter must carry. Do it per rack or cabinet, not per building.

Step 2 — fix the DC bus voltage. 12 V for a single telecom cabinet, 24 V for a small site, 48 V for a room or larger. Bus voltage is set by the rectifier and inverter, not by the battery.

Step 3 — choose strings in series, then in parallel. For a 48 V bus: 4 strings in series = 4 × 12 V = 48 V with amp-hour output unchanged at 50 Ah. Then add parallel strings: 8 strings = 48 V / 200 Ah; 16 strings = 48 V / 400 Ah. Parallel strings must match in type, age and length, and each parallel group needs its own fuse and cable.

Step 4 — compute runtime at 50 % DoD. Usable energy per string = 600 Wh × 0.50 = 300 Wh. Runtime (h) = (strings × 300 Wh) ÷ (bus voltage × load current). Worked example: 48 V bus, 20 A load, 16 strings → (16 × 300 Wh) ÷ (48 V × 20 A) = 4,800 Wh ÷ 960 W = 5.0 hours. The same 16 strings on a 25 A load give 4,800 Wh ÷ 1,200 W = 4.0 hours, so a 25 % load increase costs 20 % of the autonomy. Re-run at the highest load the inverter allows.

Step 5 — validate charging, temperature and margin. Charge current = parallel strings × 10.0 A maximum, and the rectifier must deliver it for at least 5.0 hours. Apply a temperature derate for cold sites and confirm the enclosure can carry the 244 kg that 16 strings represent.

§5 — Sibling Models in the 12 V VRLA Range

Float 13.5 V, equalise 14.1 V, cutoff 1.75 V/cell, self-discharge ≤ 3 %/month at 25 °C and −15…50 °C working temperature are common to every model below, so the table carries only the values that differ. All cells are published model-page data.

Model	Capacity	Rate	L×W×H (mm)	Weight	Terminal	Charge current	Source
6-DZF-20	20 Ah	C2	180×76×170	6.1 ± 0.2 kg	φ8.8-M5	4.0 A	Model page
6-DMF-45	45 Ah	C3	224×121×175	12.3 ± 0.2 kg	φ11.8-M5	9.0 A	Model page
6-DMF-52	52 Ah	C3	224×135×175	13.7 ± 0.2 kg	φ11.8-M6	10.4 A	Model page
6-EVF-50	50 Ah	C3	230×140×180	15.25 ± 0.2 kg	φ11.8-M6	10.0 A	Model page
6-EVF-60	60 Ah	C3	258×170×160	18.8 ± 0.2 kg	φ14-M6	12.0 A	Model page

Every model reaches a 48 V bus with four strings in series and carries the same 350–600 cycle life at 50–80 % DoD. Energy density is nominal Wh ÷ published weight: 540 Wh ÷ 12.3 kg = 43.9 Wh/kg for the 6-DMF-45, 624 Wh ÷ 13.7 kg = 45.5 Wh/kg for the 6-DMF-52 and 600 Wh ÷ 15.25 kg = 39.3 Wh/kg for the 6-EVF-50.

Two observations matter for an importer. The 6-DMF-45 and 6-DMF-52 blocks carry the best weight-to-energy ratio in the range because they use the same 175 mm case height at a narrower width — against the 12V 50Ah battery the trade is 600 Wh in a wider case versus 624 Wh in a narrower one. The EVF cases are also wider, so moving from 6-EVF-50 to 6-EVF-60 changes the row width, not only the capacity.

§6 — The Trust: Who Manufactures the 6-EVF-50

CHISEN operates 8 production bases with an annual capacity of 70 million kVAh, and the 6-EVF-50 comes out of that VRLA line alongside the 6-DZF and 6-DMF series, the flooded tubular OPzS2 range and the gel tubular OPzV2 range. Factory certifications are CE, ISO 9001, ISO 14001, UL and IEC — the set an importer’s broker and quality auditor will request on a repeat order.

For procurement teams, three trust signals matter more than the certificate list. The published specification set is complete and internally consistent: float, equalise, cutoff, charge current and cycle life all come from one model page, so no figure has to be reconstructed from a datasheet cover sheet. The weight tolerance is stated as ± 0.2 kg rather than rounded, which is the level of control that makes incoming goods inspection meaningful. And design life is published as a 2–5 year range alongside the cycle figure, so a replacement window can be planned.

On delivery, verify the model designation, the case dimensions against 230 × 140 × 180 mm, the weight against 15.25 ± 0.2 kg and the terminal marking, then log the open-circuit voltage of each string before installation so any cell stored too long is identified before it joins the bank. CHISEN is based in Hangzhou, China, and the export desk handles specification confirmation, samples and production slot allocation.

§7 — FAQ

Q1: What are the published nominal voltage and capacity of the 6-EVF-50? 12 V and 50 Ah at the C3 discharge rate (Model page). The 12V 50Ah battery holds six series cells, since 13.5 V float ÷ 2.25 V/cell = 6 (Arithmetic).

Q2: What float and equalise setpoints does the manufacturer publish? Float 13.5 V and equalise 14.1 V, which is 2.25 V/cell and 2.35 V/cell across the six cells of the string (Model page).

Q3: What is the maximum charging current for the 6-EVF-50? 10.0 A per string (Model page), so a 50 Ah string needs 50 Ah ÷ 10.0 A = 5.0 hours of charge to return to full capacity (Arithmetic).

Q4: What are the case dimensions and weight of the 6-EVF-50? 230 × 140 × 180 mm and 15.25 ± 0.2 kg (Model page); a 48 V bank of 16 strings weighs 16 × 15.25 = 244 kg (Arithmetic).

Q5: What terminal type and torque does the 6-EVF-50 use? φ11.8-M6 terminals (Model page); the tightening torque is not published and is to be requested from the factory.

Q6: How many cells does a 12V50Ah string contain and what bus voltage does it give? Six cells per 12 V string (13.5 V ÷ 2.25 V/cell = 6, Arithmetic). One string gives 12 V, two give 24 V, four in series give a 48 V bus.

Q7: What is the published design float life and the temperature range? Design life 2–5 years, cycle life 350–600 at 50–80 % DoD, working temperature −15…50 °C, self-discharge ≤ 3 %/month at 25 °C (Model page).

Q8: How should an importer verify the 6-EVF-50 on delivery? Check the model designation and label voltage, measure 230 × 140 × 180 mm and 15.25 ± 0.2 kg, confirm the φ11.8-M6 marking, and log each string’s open-circuit voltage (Model page).

Q9: Which certifications does the CHISEN factory hold? CE, ISO 9001, ISO 14001, UL and IEC, produced across 8 bases with 70 million kVAh annual capacity (Company facts).

Q10: How do I request a quotation or samples for the 6-EVF-50? Contact the export desk at sales@chisen.cn or jack@chisen.cn, or on WhatsApp +86 131 6622 6999, stating the bus voltage, load in watts and required autonomy.

Expert Summary

The CHISEN 12V 50Ah battery, model 6-EVF-50, is a 12 V, 50 Ah C3 VRLA AGM block published at 230 × 140 × 180 mm, 15.25 ± 0.2 kg, φ11.8-M6 terminals, 13.5 V float, 14.1 V equalise, 1.75 V/cell cutoff, 10.0 A maximum charge current, 350–600 cycles at 50–80 % DoD, ≤ 3 %/month self-discharge at 25 °C, −15…50 °C working range and 2–5 years design life (Model page). One string is 600 Wh and 39.3 Wh/kg; four strings in series make a 48 V bus and parallel strings scale runtime linearly. Runtime is decided by load and depth of discharge, not by the amp-hour label: usable energy is 300 Wh per string at 50 % DoD, so runtime (h) = (strings × 300 Wh) ÷ (bus voltage × load current). The model suits short-to-medium autonomy in a controlled, maintenance-free installation with a C3-matched load; long autonomy or deep daily cycling belongs to the OPzS2 and OPzV2 tubular lines or to lithium. CHISEN runs 8 production bases, 70 million kVAh annual capacity and CE, ISO 9001, ISO 14001, UL and IEC certification.

Contact CHISEN — 24-Hour Response

CHISEN Battery, Hangzhou, China — 8 production bases, 70 million kVAh annual capacity, certified to CE, ISO 9001, ISO 14001, UL and IEC. The export desk confirms specifications, supplies samples and allocates production slots, with a 24-hour response commitment on every enquiry.

Sales enquiries: sales@chisen.cn
Export desk: jack@chisen.cn
WhatsApp: +86 131 6622 6999
Website: www.chisen.cn

Send the model designation (6-EVF-50), the DC bus voltage, the load in watts, the required autonomy and the destination port, and you will receive a confirmed string configuration with the runtime arithmetic shown.

Related CHISEN Buyer Guides

November 6, 2026

6-EVF-60 12V60Ah UPS Battery: DC Bus String Sizing and Runtime Engineering

Answer First

A 12 V UPS bank is sized by two numbers: how many parallel strings you install, and how many Ah each string delivers at end of discharge. The 6-EVF-60 12V60Ah answers both with published figures: a 6-cell 12 V block rated 60 Ah at C3, 258×170×160 mm, 18.8 ± 0.2 kg, float at 13.5 V and equalise at 14.1 V per unit.

The number that governs runtime is the cutoff: the published 1.75 V per cell means a six-cell string ends at 1.75 × 6 = 10.5 V. Quoting runtime against a generic 13.6 V floor overstates usable energy by roughly 23 %, the most common cause of a UPS that trips its load earlier than promised. For a 6 kVA unit at 4.5 kW bus load, two 6-EVF-60 12V60Ah strings give 120 Ah nominal, 96 Ah usable at 80 % DoD, and 96 × 10.5 = 1,008 Wh per pair — about 12 minutes at that load. If the specification calls for 30 minutes, the bank must grow and the arithmetic redone.

Key Takeaways

6-EVF-60 12V60Ah is a 6-cell 12 V block rated 60 Ah at C3, published at 258×170×160 mm, 18.8 ± 0.2 kg.
Float 13.5 V and equalise 14.1 V are the published setpoints — 2.25 V/cell and 2.35 V/cell across six cells.
The published cutoff is 1.75 V/cell = 10.5 V per string. Runtime quoted at 13.6 V overstates usable energy by about 23 %.
Two parallel strings yield 120 Ah nominal, 96 Ah usable at 80 % DoD = 1,008 Wh — the starting point for 6 kVA installations.
Maximum charge current is 12.0 A per block, so a 48 A charger suits four parallel strings.
Cycle life is 350–600 at 50–80 % DoD and design life 2–5 years; a bank at 25 °C outlives the same part at 35 °C.

§1 — 6-EVF-60 Quick Specifications

All values below are published by CHISEN for the 6-EVF-60 12V60Ah; nothing is estimated or carried over.

Parameter	Value	Source
Nominal voltage / capacity	12 V / 60 Ah	Model page
Capacity test rate	C3	Model page
Dimensions (L×W×H)	258×170×160 mm	Model page
Weight	18.8 ± 0.2 kg	Model page
Terminal	φ14-M6	Model page
Float / equalise voltage	13.5 V / 14.1 V	Model page
Cycle life	350–600 cycles	Model page
Maximum charge current	12.0 A	Model page
End-of-discharge cutoff	1.75 V/cell	Model page
Self-discharge / working temp	≤3 %/month @25 °C / −15…50 °C	Model page
Design life	2–5 years	Model page
Cutoff per string	10.5 V	Arithmetic (1.75 V × 6 cells)

A 12 V VRLA block is six 2 V cells in series with an internal balancing network. A charger set to the published 13.5 V float keeps all six cells balanced; a charger set to 13.8 V pushes the block to 2.30 V/cell and raises float current without adding usable capacity. See also the CHISEN EVF index and 6-EVF-50 12V50Ah.

§2 — The Pain: Runtime Numbers That Do Not Survive Commissioning

Most UPS battery disputes are arithmetic disputes, beginning in the tender document, where runtime is quoted at a nominal end voltage no commissioning engineer would accept. Take the shortcut: 60 Ah at 13.6 V gives 816 Wh per string, so two strings read as 1,632 Wh. Apply the published cutoff for the 6-EVF-60 12V60Ah instead: 1.75 V/cell × 6 cells = 10.5 V at the string terminal, so two strings deliver 2 × 60 Ah × 10.5 V = 1,260 Wh — 372 Wh less, a 23 % overstatement before any rate, temperature or age correction.

Three further errors stack on top. The C3 rate is quoted as the deliverable: published capacity is 60 Ah at C3, a three-hour discharge, so a UPS that empties the bank in ten minutes gets less than the rated Ah. End voltage is confused with trigger voltage: the inverter trips at its own transfer point, commonly below 1.75 V/cell, so setting the threshold at the published cutoff discharges the battery past its rating limit. Temperature is ignored: a room at 35 °C sits above the 25 °C self-discharge reference, and below 10 °C equalisation must be extended to reach the 14.1 V setpoint. For an importer the damage is direct: a bank specified for 30 minutes that delivers 17 causes a return shipment and a dispute.

§3 — The Choice: String Configuration and the Number That Governs

Once the errors are removed, the decision is not “which battery” but how many strings, at what DoD, with what charger.

String count and bus voltage. A 12 V block cannot be placed in series to build a 24 V bus; the series unit is a 2 V cell. Every additional block must therefore go in parallel, and parallel strings need matched cell counts, matched ages and equal state of charge — if one string has three blocks and another four, the shorter governs.

The arithmetic: two strings give 120 Ah nominal; at 80 % DoD that is 120 × 0.80 = 96 Ah usable. At the published cutoff of 1.75 V × 6 = 10.5 V, usable energy is 96 Ah × 10.5 V = 1,008 Wh; the same bank quoted at 13.6 V reads 1,306 Wh, the overstatement shown. At a 4.5 kW load and 0.9 inverter efficiency the bus carries 5,000 W, so 1,008 Wh ÷ 5,000 W = 0.202 h ≈ 12.1 minutes of runtime. String count alone buys no runtime: three strings at 50 % DoD deliver 90 Ah, fewer than two strings at 80 %.

Choosing the 6-EVF-60 12V60Ah over another capacity in the same range is a decision about rack geometry and load profile, not chemistry: float, equalise, cutoff, self-discharge and working temperature are identical throughout. The block is documented on the 6-EVF-60 12V60Ah page.

§4 — The Framework: A Five-Step Sizing Method That Survives Audit

This is the sequence CHISEN applies to incoming sizing requests, so an installer or OEM engineer can reproduce the answer and hand it to an auditor.

Step 1 — Establish the DC bus load, not the UPS rating. Nameplate kVA is AC output; the battery carries DC. Start from inverter input power at full rated load and divide by inverter efficiency, typically 0.90–0.95: a 6 kVA unit at 0.8 power factor carries 6 ÷ 0.8 = 7.5 kVA real load, roughly 6.9 kW at the bus — where factor-of-1.2 errors enter tenders.

Step 2 — Fix the usable end voltage and declare the DoD. Use the published cutoff of 1.75 V/cell, giving 10.5 V per string, then apply the inverter’s transfer threshold if higher; never use the float voltage as the discharge floor. Published cycle life applies at 50–80 % DoD, so state the design point: 50 % with a generator starting within 30 seconds, 80 % where a long start delay pushes expected life toward 350 cycles.

Step 4 — Compute the bank, then check geometry. Required Ah at the bus = (bus W × runtime h) ÷ (usable V × DoD). For 5,000 W, 0.5 h, 10.5 V and 0.5 DoD: 2,500 Wh ÷ (10.5 × 0.5) = 476 Ah; 476 ÷ 60 Ah per 6-EVF-60 12V60Ah = 7.94 blocks, so 8 blocks — typically 2 strings of 4 or 4 strings of 2. Check the shelf: four blocks occupy 1,032 mm and put 75.2 kg on it, so below a 76 kg shelf rating the string must be split, each shelf able to carry the fault current of one short-circuited cell.

Step 5 — Validate charger and thermal envelope. Charge current should sit between 10 % and 12 % of bank Ah, so a 480 Ah bank wants 48–57.6 A; at the published 12.0 A per-block maximum, four parallel strings is the ceiling for a 48 A charger. Below 10 °C, extend equalisation to reach 14.1 V; above 30 °C, check float life against the 25 °C reference. Where a value is not published — internal resistance, equalise duration, life curve — request it from the factory.

§5 — 6-EVF-60 Against Its Siblings in the 6-EVF / 6-DMF Range

The table below lists published values for the 6-EVF-60 12V60Ah and neighbouring models.

Model	Capacity	L×W×H mm	Weight	Terminal	Charge current
6-EVF-60	60 Ah (C3)	258×170×160	18.8 ± 0.2 kg	φ14-M6	12.0 A
6-EVF-80	80 Ah (C3)	259×170×218	25.7 ± 0.2 kg	φ16-M6	16.0 A

Source: CHISEN Model page for each model. All models here are 12 V with 13.5 V float, 14.1 V equalise, 1.75 V/cell cutoff, ≤3 %/month self-discharge at 25 °C, a −15…50 °C working range, 350–600 cycle life and 2–5 years of design life (not published for 6-DMF-52).

Three practical differences decide which model goes into which rack.

§6 — The Trust: How CHISEN Supports the 6-EVF-60 12V60Ah in the Field

A battery that arrives with published numbers still needs a reachable supplier. CHISEN backs the 6-EVF-60 12V60Ah with 8 production bases, 70 million kVAh annual capacity and certifications covering CE, ISO 9001, ISO 14001, UL and IEC. The range behind the 6-EVF number includes flooded tubular OPzS2, gel tubular OPzV2 and the 12 V VRLA lines (6-DZF, 6-DMF, 6-EVF), produced in Hangzhou, China and shipped to importers, distributors and OEM builders across Europe, North America, the Middle East, Africa and Asia-Pacific.

Incoming inspection and commissioning. Check case dimensions against 258×170×160 mm and weight against 18.8 ± 0.2 kg on a calibrated scale; a block outside that band is a transit-damage question, not a sizing question. Confirm the φ14-M6 marking and record the manufacturing date, since the published self-discharge of ≤3 %/month @25 °C and the 2–5 year design life both run from it. Measure open-circuit voltage for every block before and after first charge: a charged 6-EVF-60 12V60Ah block at rest should read roughly 12.6–12.8 V (2.10–2.13 V/cell), and a lower reading points to a damaged unit. After the first equalise at the published 14.1 V, block-to-block spread should narrow — if not, re-match the string rather than ship it.

String matching. Parallel strings must be of equal age and state of charge. Mixing a fresh 6-EVF-60 12V60Ah block with one in service for a year causes current to redistribute toward the weaker unit, which then runs at the edge of its cutoff on every discharge. Replacing blocks singly inside a string is the most common cause of early bank failure, and is avoidable at installation.

§7 — FAQ

Q1: What are the published nominal voltage and capacity of the 6-EVF-60? 12 V and 60 Ah at the C3 rate, per the CHISEN Model page; six 2 V cells in series.

Q2: What float and equalise setpoints does the manufacturer publish for the 6-EVF-60? Float 13.5 V and equalise 14.1 V per block — 2.25 V/cell and 2.35 V/cell.

Q3: What are the case dimensions and weight of the 6-EVF-60? 258×170×160 mm and 18.8 ± 0.2 kg; four blocks occupy 1,032 mm of shelf and 75.2 kg of load.

Q4: What terminal type and torque does the 6-EVF-60 use? φ14-M6 terminals. The busbar torque figure is not published and should be requested.

Q5: How many cells does a 12V60Ah string contain and what bus voltage does it give? Six cells in series. The published 1.75 V/cell cutoff corresponds to 10.5 V at the string terminal.

Q6: What is the published design float life of the 6-EVF-60 and at what temperature? Design life 2–5 years, working range −15…50 °C. Self-discharge is quoted at ≤3 %/month @25 °C, so 25 °C is the reference; the temperature-corrected life curve is not published.

Q7: How should an importer verify the 6-EVF-60 on delivery? Check dimensions against 258×170×160 mm, weigh against 18.8 ± 0.2 kg, confirm the φ14-M6 marking, record the manufacturing date, and measure open-circuit voltage of each block before first charge (12.6–12.8 V).

Q8: Which certifications does the CHISEN factory behind the 6-EVF-60 hold? CE, ISO 9001, ISO 14001, UL and IEC, with 8 production bases and 70 million kVAh annual capacity across flooded tubular OPzS2, gel tubular OPzV2 and 12 V VRLA.

Q9: How do I request a quotation or samples for the 6-EVF-60? Contact the CHISEN export desk at sales@chisen.cn or jack@chisen.cn, or WhatsApp +86 131 6622 6999; the model page carries the full published data.

Expert Summary

The 6-EVF-60 12V60Ah is a 6-cell 12 V VRLA block rated 60 Ah at C3, published at 258×170×160 mm, 18.8 ± 0.2 kg, φ14-M6 terminals, 13.5 V float, 14.1 V equalise, 12.0 A maximum charge current, 1.75 V/cell cutoff, ≤3 %/month self-discharge at 25 °C, −15…50 °C working range, 350–600 cycles at 50–80 % DoD and 2–5 years of design life. Its published 10.5 V string cutoff, not a nominal 13.6 V, governs runtime: a two-string bank at 80 % DoD delivers 96 Ah and 1,008 Wh, a 23 % honest reduction against the common shortcut, and string count buys cycle life before it buys minutes. Five steps — bus load from kVA and efficiency, the published end voltage, the declared DoD, Ah calculation validated against shelf length and load, then charger sizing within the 12.0 A per-block ceiling — produce a bank an auditor can reproduce. Behind the specification sit 8 production bases, 70 million kVAh of annual capacity and CE, ISO 9001, ISO 14001, UL and IEC certification. Values that remain unpublished — internal resistance, equalise duration, life curve, terminal torque — should be requested from the factory, and every string matched for age and charge before service.

Contact CHISEN — 24-Hour Response

Sales enquiries: sales@chisen.cn
Export desk: jack@chisen.cn
WhatsApp: +86 131 6622 6999
Website: www.chisen.cn
Model page: https://www.chisen.cn/en/6-EVF-60/12V60Ah.html

Related CHISEN Buyer Guides

November 5, 2026

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

Related CHISEN Buyer Guides

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.

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November 2, 2026