Answer First
A tubular gel battery supplier earns the award on one document, not on a presentation: the manufacturer datasheet, complete, with values that can be checked against an independent source. Before you accept any tubular gel battery supplier’s quotation, require six published items, each carrying a source label and a reference temperature. Float charge voltage of 2.23 V per cell at 25 °C. Equalise charge voltage of 2.35 V per cell at 25 °C. Temperature compensation of −3 mV/°C/cell. A design float life of 20+ years @ 20 °C. Capacity stated at several discharge rates rather than one headline figure. And a certification trail naming IEC 60896-21/22, IEC 61427 and the rest.
If a tubular gel battery supplier cannot produce those six items within one working day, the reason is not a translation problem or a database problem. It is a process problem, and you will meet that process again during the warranty claim.
Key Takeaways
- Qualify on documentation, not on the factory presentation. A datasheet with reference temperatures, discharge rates and source labels is the only artefact that survives an audit.
- The four charge parameters travel together. Float at 2.23 V per cell at 25 °C, equalise at 2.35 V per cell at 25 °C, compensation at −3 mV/°C/cell and a float life of 20+ years @ 20 °C are one specification, and a supplier who changes one without changing the others is quoting a different cell.
- Capacity must be quoted with its rate. A single amp-hour number is a catalogue label; a long-time discharge table is a product.
- Certification is a chain, not a list. IEC 60896-21/22 covers the cell, IEC 61427 covers the cycling test, and the certificate numbers must be producible on request.
- Judge the warranty by its exclusions. Exclusions for operation outside the published charge voltage window, and for cells run without temperature compensation, are standard and are exactly the cases a site will hit.
§1 — Quick Specifications Table
The table below is the published rating for the reference 2 V 500 Ah tubular gel cell in the OPzV range. Every figure is taken from the manufacturer datasheet, and every figure in this article is either copied from that document or derived from it by arithmetic.
| Parameter | Value | Source |
|---|
| Model | OPzV2-500, 2 V tubular gel | Datasheet |
| Nominal voltage | 2 V | Datasheet |
| Nominal capacity | 500 Ah at C10 to 1.80 V per cell | Datasheet |
| Dimensions | 166 x 206 x 506 mm | Datasheet |
| Weight | 36.3 kg (80.0 lbs) | Datasheet |
| Float charge voltage | 2.23 V @ 25 °C | Datasheet |
| Equalise charge voltage | 2.35 V @ 25 °C | Datasheet |
| Design float life | 20+ years @ 20 °C | Datasheet |
| Temperature compensation | −3 mV/°C/cell | Datasheet |
| Internal resistance | approx. 0.56 mΩ at 25 °C | Datasheet |
| Max. charge current | 100 A | Datasheet |
| Max. discharge current, 5 s | 2,000 A | Datasheet |
| Short circuit current | 2,600 A | Datasheet |
| Self-discharge | approx. 2 % per month at 20 °C | Datasheet |
| Discharge temperature range | −40 to 65 °C | Datasheet |
| Charge temperature range | −30 to 65 °C | Datasheet |
| Storage temperature range | −25 to 45 °C | Datasheet |
| Terminal | Female copper insert M8, 10 to 12 N·m | Datasheet |
| Standards | IEC 60896-21/22, DIN 40472, IEC 61427, YD/T 1360, BS 6290 part 4, UL 1989, Eurobat | Datasheet |
| 24-cell string weight at 48 V | 24 x 36.3 kg = 871.2 kg | Arithmetic |
| 24-cell string internal resistance | 24 x 0.56 mΩ = 13.44 mΩ | Arithmetic |
| 24-cell string charge capacity | 24 x 100 A = 2,400 A | Arithmetic |
A qualification checklist for a tubular gel battery supplier can be built directly from that table. Each line below is something you ask for, the reason it matters, and what a refusal tells you.
| Check | What to ask for | Why it matters | Source |
|---|
| Charge voltage | Float 2.23 V and equalise 2.35 V per cell at 25 °C | Sets the controller limits and the plate life | Datasheet |
| Compensation | −3 mV/°C/cell with its reference temperature | Determines behaviour across a 45 °C site swing | Datasheet |
| Float life | 20+ years @ 20 °C, with the curve at 30 °C | Fixes the replacement date in the business case | Datasheet |
| Capacity | Table at C10, C24, C48, C72, C100, C120 and C240 | Selects the cell on the duty cycle | Datasheet |
| Cycle life | Curves against depth of discharge | Sizes the cell where the site cycles daily | Datasheet |
| Internal resistance | Value per model with its reference temperature | Sets busbar section and fuse rating | Datasheet |
| Construction | Container material, terminal type and torque | Determines handling and maintenance method | Datasheet |
| Standards | Certificate numbers, not names | Underpins the warranty | Datasheet |
The range itself is graded by capacity, and each grade publishes its own values. That is the first place to look for a supplier who is careful.
| Model | Voltage | Capacity | Dimensions (mm) | Weight | Internal resistance | Max. charge current | Source |
|---|
| OPzV2-500 | 2 V | 500 Ah | 166 x 206 x 506 | 36.3 kg | 0.56 mΩ at 25 °C | 100 A | Datasheet |
| OPzV2-700 | 2 V | 700 Ah | 254 x 210 x 506 | 51.0 kg | 0.55 mΩ at 25 °C | 140 A | Datasheet |
| OPzV2-1000 | 2 V | 1,000 Ah | 233 x 210 x 681 | 73.2 kg | 0.5 mΩ at 25 °C | 200 A | Datasheet |
| OPzV2-1500 | 2 V | 1,500 Ah | 275 x 210 x 831 | 102 kg | 0.45 mΩ at 25 °C | 300 A | Datasheet |
| OPzV2-2500 | 2 V | 2,500 Ah | 487 x 212 x 807 | 181 kg | 0.3 mΩ at 25 °C | 500 A | Datasheet |
The OPzV2-500 tubular gel model page carries the same published figures, which gives you a free cross-check: if a supplier’s datasheet and product page disagree, you have found the quality problem before you have placed the order.
§2 — The Pain
Buyers in telecom, solar and industrial power rarely report that a battery failed because the supplier was dishonest. The failures are almost always administrative, and they are always the same three.
The quotation that arrives before the specification. A request for 2 V gel cells for a 48 V DC bus in Nairobi or Lima produces three responses in a day, and none of them contains a float voltage. The buyer now has three prices and no way to compare them, because a price per unit is meaningless without the charge regime, the capacity rate and the certification status of the cell behind it. The practical consequence is a negotiation conducted on price alone, which is precisely the negotiation a factory that cuts corners will want.
The specification that is produced to order. In the second case the datasheet does arrive, and it has been assembled rather than published. The float voltage reads 2.23 V but the equalise voltage is stated as a range, the compensation coefficient appears without a reference temperature, and the capacity appears as a single number with no rate. Nothing here is a lie. Everything here is unusable, because the buyer must now decide what the supplier actually means, and the only person who can decide is the supplier.
The certificate that cannot be produced. IEC 60896-21/22, DIN 40472, IEC 61427, YD/T 1360, BS 6290 part 4 and UL 1989 are named on the quotation. Ask for the test reports behind them and the answer becomes vague. The IEC 61427 cycling test is the document that turns a cycle life figure into a measured number, and a supplier unwilling to produce it is asking you to accept an unmeasured claim on a ten year asset.
Underneath those three sits a fourth issue that only appears once the first shipment has been installed: consistency between grades. A supplier will quote 500 Ah and 2,500 Ah cells, and both datasheets will be complete and internally consistent, and yet the two will use different conventions. One will state internal resistance at 20 °C and the other at 25 °C, one will publish capacity at C10 and the other at C20, one will state a float life at 20 °C and the other will state a design life in years with no reference temperature at all. A buyer who has only ever seen one grade cannot see the inconsistency, and a buyer comparing two grades can see nothing else.
The fifth issue is commercial and structural. A tubular gel cell is a mature product with a published price band, so the spread between quotations comes from somewhere: from the cell, from the documentation, from the certification, from the warranty, or from the factory. When the quotation is thin on documentation, the spread is usually being taken out of the cell. The buyer who understands this can price the risk instead of accepting it.
§3 — The Choice
The first choice a buyer makes is not between manufacturers. It is between two constructions, because the construction decides the site handling, the freight terms and the operating temperature window, and those three things decide which suppliers can serve the site at all.
| Attribute | Tubular gel, OPzV2-500 | Tubular flooded, OPzS2-500 | Source |
|---|
| Nominal voltage | 2 V | 2 V | Datasheet |
| Nominal capacity | 500 Ah at C10 | 500 Ah at C10 | Datasheet |
| Dimensions | 166 x 206 x 506 mm | 104 x 206 x 399 mm | Datasheet |
| Weight without electrolyte | 36.3 kg (80.0 lbs) | 13.0 kg dry mass | Datasheet |
| Weight as shipped | 36.3 kg (80.0 lbs) | 17.5 kg with 4.5 kg acid | Datasheet |
| Electrolyte | Gelled, no free liquid | 4.5 kg diluted sulphuric acid | Datasheet |
| Internal resistance | 0.56 mΩ at 25 °C | 0.95 mΩ at 20 °C | Datasheet |
| Max. charge current | 100 A | 100 A | Datasheet |
| Self-discharge at 20 °C | approx. 2 % per month | approx. 4 % per month | Datasheet |
| Discharge temperature range | −40 to 65 °C | −25 to 65 °C | Datasheet |
| Storage temperature range | −25 to 45 °C | −15 to 40 °C | Datasheet |
| Site maintenance | None | Periodic watering and inspection | Datasheet |
The comparison is more useful to a buyer than any single number in it. A tubular gel cell is a heavier, larger object than a flooded cell of the same nominal capacity, and the reason is the construction: the gelled electrolyte and the separator assembly occupy volume that a free liquid electrolyte does not. In exchange the buyer gets no watering, roughly half the self-discharge, a wider discharge range and a storage range that tolerates a shipping delay in a hot port.
This is why the choice of tubular gel battery supplier is also a choice of freight and handling method. A flooded cell arrives with acid and is subject to dangerous goods rules for the sea leg, while a gel cell is not. That difference frequently moves the total landed cost more than the unit price does, and it is worth asking a tubular gel battery supplier to state the shipping classification on the quotation so that the freight forwarder and the customs broker are working from the same document.
The second choice is the capacity grade, and the published values make it straightforward. The internal resistance falls as the capacity rises, which reduces the busbar section and the voltage collapse during a high current discharge, while the cell mass and height rise sharply.
| Model | Capacity | Dimensions (mm) | Weight | 24-cell string weight | Internal resistance | Source |
|---|
| OPzV2-500 | 500 Ah | 166 x 206 x 506 | 36.3 kg | 24 x 36.3 kg = 871.2 kg | 0.56 mΩ at 25 °C | Datasheet |
| OPzV2-700 | 700 Ah | 254 x 210 x 506 | 51.0 kg | 24 x 51.0 kg = 1,224.0 kg | 0.55 mΩ at 25 °C | Datasheet |
| OPzV2-1000 | 1,000 Ah | 233 x 210 x 681 | 73.2 kg | 24 x 73.2 kg = 1,756.8 kg | 0.5 mΩ at 25 °C | Datasheet |
| OPzV2-1500 | 1,500 Ah | 275 x 210 x 831 | 102 kg | 24 x 102 kg = 2,448.0 kg | 0.45 mΩ at 25 °C | Datasheet |
| OPzV2-2500 | 2,500 Ah | 487 x 212 x 807 | 181 kg | 24 x 181 kg = 4,344.0 kg | 0.3 mΩ at 25 °C | Datasheet |
The third choice is the discharge rate, and this one is settled by published curves rather than by opinion. The final voltage that applies to each rate is fixed, and the capacity follows from it.
| Discharge current | Final voltage per cell | Source |
|---|
| Below 0.05 C | 1.90 V | Datasheet |
| 0.05 C to 0.08 C | 1.85 V | Datasheet |
| 0.08 C to 0.2 C | 1.80 V | Datasheet |
| 0.2 C to 0.6 C | 1.75 V | Datasheet |
| 0.6 C to 1.0 C | 1.70 V | Datasheet |
| 1 C to 2 C | 1.60 V | Datasheet |
A DC plant at a site in Chennai or Port Said typically runs its backup discharge between 0.2 C and 0.6 C, so the 1.75 V cutoff applies and the usable capacity sits below the C10 headline. A solar installation in Johannesburg running a shallow daily cycle reads the C100 figure instead. Any tubular gel battery supplier that quotes one capacity number without a rate has not engineered the duty cycle at all.
Cycle life is the published curve that separates a gel cell from a flooded cell over a decade, because the gel construction tolerates deep cycling without the same loss of plate capacity.
| Model | Depth of discharge | Published cycle life | Source |
|---|
| OPzV2-500 | 20 % | approx. 5,500 cycles | Datasheet |
| OPzV2-500 | 40 % | approx. 3,500 cycles | Datasheet |
| OPzV2-500 | 60 % | approx. 2,500 cycles | Datasheet |
| OPzV2-500 | 80 % | approx. 1,800 cycles | Datasheet |
| OPzV2-500 | 100 % | approx. 1,400 cycles | Datasheet |
| OPzV2-1000 | 20 % | approx. 5,500 cycles | Datasheet |
| OPzV2-1000 | 40 % | approx. 3,100 cycles | Datasheet |
| OPzV2-1500 | 20 % | approx. 5,700 cycles | Datasheet |
| OPzV2-1500 | 40 % | approx. 3,100 cycles | Datasheet |
| OPzV2-2500 | 20 % | approx. 5,500 cycles | Datasheet |
| OPzV2-2500 | 50 % | approx. 3,000 cycles | Datasheet |
§4 — The Framework
Seven steps settle a tubular gel battery supplier evaluation, and each step has an artefact that proves it.
1. Obtain the manufacturer datasheet. Not a catalogue page, not a photograph of a label. The datasheet carries the ratings table on page one and the long-time discharge, cycle life and solar application tables on page two. If it is not available, the evaluation stops there.
2. Check the four charge parameters as one block. Float 2.23 V per cell at 25 °C, equalise 2.35 V per cell at 25 °C, compensation −3 mV/°C/cell, float life 20+ years @ 20 °C. These four belong together, and the solar parameter set belongs with them: float 2.27 ± 0.005 V, regulation 2.40 ± 0.01 V, over-voltage disconnect 2.47 ± 0.01 V, array reconnection 2.23 ± 0.005 V, low voltage alarm 1.95 ± 0.005 V, low voltage disconnect 1.90 ± 0.005 V, load reconnect 2.09 ± 0.01 V, compensation −3 to −5 mV per cell per degree Celsius.
3. Confirm the capacity table and the final voltage table. A datasheet that publishes one but not the other is incomplete. You need both, because the final voltage sets the usable capacity at the rate your site runs.
4. Verify the certification chain. IEC 60896-21/22 for the stationary valve regulated cell, IEC 61427 for the cycling test, DIN 40472, BS 6290 part 4, UL 1989, YD/T 1360 for Chinese telecom deployments and Eurobat for the long life classification. Ask for the reports, not for the names.
5. Establish the construction. Container material, terminal format with its torque, whether the cell ships with electrolyte, the electrolyte specific gravity for flooded cells at 1.240 g/cm3, and the discharge, charge and storage ranges.
6. Do the string arithmetic yourself. For a 48 V bus of 500 Ah tubular gel cells: 24 x 36.3 kg = 871.2 kg, 24 x 0.56 mΩ = 13.44 mΩ and 24 x 100 A = 2,400 A. A supplier who will not let you check the arithmetic has not done it either.
7. Read the warranty exclusions against your site. Exclusions for operation outside the published charge voltage window, for cells operated without temperature compensation and for physical damage are standard. If your site does not run compensation, the warranty does not cover the failure that compensation prevents.
§5 — The Trust
Three failure patterns show up repeatedly when buyers qualify a tubular gel battery supplier, and all three are visible in the first exchange if you know what to look at.
The datasheet that is nearly right. This is the most common pattern and the most expensive one. The float voltage is correct, the capacity is correct, and the equalise voltage is stated as a range rather than a single figure, or the compensation coefficient is given without a reference temperature, or the float life is expressed in years with no temperature attached. Each of these omissions changes what you would configure. Ask for the reference temperature on every electrical parameter, and if it is missing, treat the value as unverified.
The certificate list with nothing behind it. IEC 60896-21/22, DIN 40472 and UL 1989 on the letterhead are easy. The IEC 61427 cycling report, which is the document behind the cycle life number, is the one that costs the factory real test time. Ask for it by name and by date.
The warranty written around the specification. Exclusions are normal, but a warranty that excludes operation outside the published charge voltage window is effectively a statement that the cell will only perform as specified. That is correct and fair, and it is also a reason to confirm that the controller settings match the datasheet before the shipment lands, because the enforcement of that exclusion will happen on your site rather than in the factory.
One test is worth running on every supplier you are serious about. Ask them to commit in writing to a guaranteed capacity at a stated discharge rate, a stated final voltage and a stated temperature, and to write that figure into the warranty. A supplier who accepts is telling you that its own production control is consistent enough to stand behind. A supplier who declines is telling you the number on the catalogue page is all it will support, and you can price that into the selection.
For a mid-range comparison, the 1,500 Ah tubular gel cell in the same range publishes 0.45 mΩ at 25 °C, 300 A of maximum charge current, 3,000 A at five seconds and 6,200 A of short circuit current, documented to the same standard as the 500 Ah cell. A supplier whose documentation holds across the range is a supplier with a controlled factory.
§6 — FAQ
Q1. How do I tell a qualified tubular gel battery supplier from a trading company? Ask for the manufacturer datasheet with the test reports behind the IEC 61427 cycling figures and the IEC 60896-21/22 certification. A factory produces those documents and knows the test dates and the specimen ratings. A trading company forwards a brochure and cannot.
Q2. What are the six things a quotation should contain before I award supply? Float charge voltage of 2.23 V per cell at 25 °C, equalise charge voltage of 2.35 V per cell at 25 °C, temperature compensation of −3 mV/°C/cell, a design float life of 20+ years @ 20 °C, capacity at several discharge rates with the matching final voltage, and the certification references.
Q3. Should I insist on the same reference temperature across all quoted parameters? Yes. Internal resistance for a gel cell is referenced to 25 °C and for a flooded cell to 20 °C, and comparing a quoted value against a different reference temperature produces an error of roughly five percent per ten degrees. Ask for the reference temperature on every parameter.
Q4. What does the 20+ years @ 20 °C float life mean for a site in a hot climate? It is the calendar life at the reference temperature on the datasheet. The published float life curve shows approximately 10 years at 30 °C, so a site with an annual average near 30 °C should plan on the curve rather than on the headline.
Q5. Is a gel cell worth the price difference over a flooded cell of the same capacity? That depends on the site. The gel cell needs no watering, loses about 2 % of capacity per month against 4 %, operates on discharge from −40 to 65 °C against −25 to 65 °C, and is not subject to dangerous goods restrictions on the sea leg. Against that it is larger and heavier, and for a site with scheduled maintenance and mild conditions the flooded cell is often the lower cost answer.
Q6. Why does the supplier’s certification list contain so many standards? Because the cell is sold into several markets with different rules. IEC 60896-21/22 covers the stationary valve regulated cell and its test methods, DIN 40472 is the German requirement, BS 6290 part 4 the British one, UL 1989 the North American listing, YD/T 1360 the Chinese telecom standard and Eurobat the long life classification. A single certificate is not sufficient for a global programme.
Q7. What documentation should travel with the shipment? Test certificates, the capacity curve at the specified rates, the charge-voltage recipe, the warranty terms and the failure-analysis route. Record the cell count and model designation against the packing list and confirm it at the point of unloading.
Q8. How long should qualification take? One working day for the documentation, and two to three weeks for the commercial and technical exchange. If a supplier cannot assemble six published parameters in a day, the delay will not be in the documentation but in the cell.
Expert Summary
Qualifying a tubular gel battery supplier is a documentary exercise, and the discipline is to demand one artefact rather than many impressions. The artefact is the manufacturer datasheet, and it has to carry six things. Float charge voltage of 2.23 V per cell at 25 °C. Equalise charge voltage of 2.35 V per cell at 25 °C. Temperature compensation of −3 mV/°C/cell, with its reference temperature stated. Design float life of 20+ years @ 20 °C, with the curve at 30 °C alongside it. Capacity published at several discharge rates, each with the final voltage that applies at that rate, running from 1.90 V per cell below 0.05 C down to 1.60 V per cell between 1 C and 2 C. And a certification chain naming IEC 60896-21/22, DIN 40472, IEC 61427, YD/T 1360, BS 6290 part 4, UL 1989 and Eurobat, with the cycling report behind the cycle life figure available on request. Behind those six items sit the values that decide the installation: internal resistance published per grade from 0.56 mΩ at 25 °C on the 500 Ah cell down to 0.3 mΩ on the 2,500 Ah cell, maximum charge current from 100 A to 500 A, short circuit current from 2,600 A to 6,200 A, self-discharge of about 2 % per month at 20 °C for a gel cell against about 4 % for a flooded cell, and string arithmetic the buyer can check without a datasheet, such as 24 x 36.3 kg = 871.2 kg for a 48 V bus of 500 Ah tubular gel cells. Add the construction decision, because a gel cell at 166 x 206 x 506 mm and 36.3 kg is a different object from a flooded cell at 104 x 206 x 399 mm with 13.0 kg of dry mass and 4.5 kg of acid, and it carries a different freight classification and a different maintenance regime. A supplier who publishes all of this on one document, from one factory, and who will commit a guaranteed capacity at a stated rate into the warranty, is a supplier whose warranty will mean something in year seven.
Contact CHISEN — 24-Hour Response
Send us the duty cycle, the bus voltage, the string configuration, the ambient temperature at the site and the discharge profile, and you will receive a sizing sheet with the cell grade, the string arithmetic and the charge settings calculated for your installation, within 24 hours.
- Sales: sales@chisen.cn
- General enquiries: jack@chisen.cn
- WhatsApp: +86 131 6622 6999
- Product reference: OPzV2-500 tubular gel, 2 V 500 Ah
Related reading: the OPzV tubular gel battery range.
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