How to Distinguish LiFePO4 Grade A and Grade B Prismatic Cell

What exactly are Grade A and Grade B cells?

1. Appearance

Tips: It does not mean that all battery cells with QR code are Grade A cells.

2. Dimension&Weight

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.

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.