According to an analysis, China shares 73% of global lithium cell manufacturing capacity. Therefore, knowing the Chinese battery market is a critical part for those who are enrolled in this industry. There are many factories producing LiFePO4 battery cells in China. And the quality standards are different. And every supplier claimed that they sell Grade A cells.
What exactly are Grade A and Grade B cells?
The best way to know a cell is Grade A or Grade B is to check if the cell meets the specifications. This article will introduce some important specifications on a datasheet. By comparing those specifications with the testing data. We’ll know the differences between Grade A and Grade B cells.
LiFePO4 Grade A cells should meet the manufacturer’s stated specifications for capacity, dimensions, weight, internal resistance, self-discharge, and capacity recovery under defined test conditions. Grade B LiFePO4 cells may show cosmetic defects, inconsistent test results, removed identification codes, lower usable capacity, or performance that falls outside the original specification.
1. Appearance
The first thing we can do to check a cell is to check its appearance. Each cell was produced with a unique QR code as proof of identity. Which also makes it more convenient for the manufacturers to offer after-sales services. And as we mentioned in the last post, Grade B cells are categorized as unqualified ones; they usually do not offer a warranty. That’s why they will scrape off this QR code. So if you find a battery cell with QR code concealed. Mostly it is Grade B battery cell. However, all Grade B cells will be covered with a new insulated sheet. So if there are no obvious signs of QR code outside, you’ll need to tear off the insulated sheet.
Tips: It does not mean that all battery cells with QR code are Grade A cells.
A clear QR code is useful for identification and traceability, but it cannot prove cell grade by itself. Buyers should combine appearance inspection with capacity testing, internal resistance measurement, dimensional checks, manufacturing records, and supplier documentation before classifying a cell.
2. Dimension&Weight
As dimension&weight will be slightly different at different SOC percentages, it would be necessary for you to confirm with the supplier of their testing SOC percentage. Then measure the size at the same SOC percentage level. And compare the measured value with the one they offered on the datasheet.
3. Capacity
Capacity is usually tested at the temperature of 25℃, charging and discharging rate of 1C. Record the real tested capacity. And compare these two data.
Note: Different temperatures will affect the capacity of lifepo4 battery cells. So some manufacturers will send you the cell with its capacity a little bit higher than it should be. If your testing capacity is a little bit higher than the datasheet. If only there weren’t too many differences. That will be alright.
Choosing Prismatic LiFePO4 Cells for Stationary Storage
When choosing prismatic LiFePO4 cells for a long-life stationary system, buyers should compare more than the initial capacity result. Cell consistency, internal resistance, manufacturing date, cycle-life data, self-discharge, capacity recovery, matching quality, and supplier traceability all affect long-term system performance.
Cells used in the same battery pack should be tested and matched under consistent temperature, SOC, charging, and discharging conditions.
4. Internal Resistance
Firstly, confirm the testing environment with suppliers. Including temperature and SOC conditions. AC internal resistance is usually tested at the frequency of 1000Hz. An AC internal resistance meter will help you with the testing. For other manufacturers, they will provide DC internal resistance. Then you may need a multimeter. Compare the real tested data with the one offered in the specifications.
5. Self-discharge Rate
The self-discharge rate differs at different SOC states. For example, the voltage decreases quickly at 100% SOC than at 50% SOC. So, before testing the self-discharge rate, check the battery specification about the testing SOC state first.
6. Capacity Recovery
To test the capacity recovery rate, you just do a 100% DOD charging and discharging cycle. And check if the capacity recovery rate meets the datasheet. For example, for a 3.2V 100Ah battery cell, if the recovery rate is 95%. We have tested the capacity at the beginning. It is 100ah. Then after all the tests, we do a 100% DOD charging and discharging. Then the capacity should be more than 95Ah. If yes, the battery capacity recovery rate meets the datasheet. It’s Grade A quality cell.
Conclusion
What we are doing is to compare the testing data with the specification of the cells. So we can trust the datasheet or the supplier. After all the tests and comparisons, if all the data meet the specification or datasheet, it is Grade A cells. If not, it is grade B cells. Ask your supplier for some samples. And test whether it is Grade A or Grade B cells? Any other questions, please contact us at: allen@seplos.com.
FAQs About LiFePO4 Grade A and Grade B Cells
LiFePO4 Grade A cells are cells that meet the manufacturer’s stated specifications for capacity, dimensions, internal resistance, appearance, self-discharge, and other quality requirements under defined testing conditions.
Grade B cells are cells that may not fully meet the original Grade A specifications. They may have cosmetic defects, inconsistent capacity, higher internal resistance, removed QR codes, or other performance differences.
No. A QR code can support identification and traceability, but buyers should also check capacity, internal resistance, dimensions, weight, self-discharge, production records, and supplier documentation.
Test the cell under controlled temperature, SOC, charge rate, discharge rate, and cutoff-voltage conditions. Compare the measured capacity with the manufacturer’s datasheet and confirm that the same test method is being used.
Internal resistance affects voltage drop, heat generation, efficiency, power performance, and cell consistency. Cells with significantly different internal resistance may perform unevenly when assembled into the same battery pack.
Cells with verified capacity, consistent internal resistance, low self-discharge, strong capacity recovery, traceable production records, and reliable matching are generally more suitable for long-life stationary storage.
