In fact, the cell is not divided into so many grades, in the electric vehicle cell factory, the cell is only divided into qualified products and unqualified products. However, because the requirements of electric cells used in automobiles are very high, these unqualified products can still be well used in the field of energy storage. Including some cells already in cars, used and unused. In order to better sell and differentiate prices, there are grade B, grade C, grade D, etc, here we uniformly call it grade B cell.

Appearance

To ensure traceability, each cell has a unique QR code as proof of identity. If the cell is judged as grade B, the manufacturer will scratch off the QR code to distinguish. If you find that the QR code of the cell you receive is scratched off, most of it is the B cell. However, many B cells will be covered with a new piece of insulation, and if you notice that there is no visible QR code on the outside, you will have to tear off the insulation and check again.

Capacity

The capacity of each cell can be determined by the charge and discharge test. As you know that different temperature and discharge rate will affect the capacity of the cell.The capacity test is usually performed at 25°C with a charge/discharge rate of 1C. Record the actual test capacity values and compare the results with the specifications. Of course some manufacturers will send you a sample with a slightly higher capacity than claimed if your test results are slightly higher than the data sheet.

Internal Resistance

The internal resistance of the cell is divided into two kinds, one is DC internal resistance, one is AC internal resistance, generally speaking, DC internal resistance is more reliable. Follow the test conditions on the data sheet or confirm the test conditions with the Vnice Power. This is the temperature and SOC state. In general, manufacturers test AC internal resistance at 1KHZ. If your test results match the data sheet, it will be grade A cell.

Self­Discharging Rate

Calculate the self­discharge rate of the cell according to the voltage drop. The self­discharge rate will be different in different SOC states. At 100%SOC, the voltage will drop faster than at 50%SOC, so check the data sheet first to make sure you test the state of the SOC.

Test method: Store at room temperature 25°C for 28 days to test the rate of voltage drop. If the rate of decline is 0.107% per day, 0.107*30=3.21% for a month. If the data you tested matches the data sheet, it will be grade A cell.

Capacity Recovery

Perform a 100%DOD charge­discharge cycle on the battery cell to check whether the capacity recovery rate meets the requirements in the data table.

For example. 3.2V100Ah core, after 100%DOD charging and discharging, will have a capacity recovery rate of 95% when capacity exceeds 95Ah. If this data matches the data sheet, it will be grade A cell.

So, the question is, in order to ensure the quality of your products, will you choose grade A cell  3.2V 100Ah Prismatic Cell