What’s the difference between A grade and B grade or recycling lifepo4 battery cells?
It is common knowledge that A grade cells are much more costly than B grade cells. As a result, if you want to compare two products, you must ensure that they are of the same caliber.
The best way to determine if a cell is A grade and B grade or recycling lifepo4 battery cells is to see if it meets the manufacturer's specifications. Today, we'll talk about some key parameters listed in the datasheet. By comparing the data to the specification, we can distinguish between Grade A and Grade B cells. Let's have a look.
Different grade Cells Dimension & Weight
The dimension and weight of different grade cells that it is important to confirm the SOC state with the supplier before measuring the cell. Once you have confirmed the SOC state, you can measure the cell's dimensions and weight. Then, you can compare your measurements to the values listed in the datasheet. If the measurements match the datasheet, then the cell is likely to be of good quality. a battery cell will vary slightly depending on its state of charge (SOC). However, if the measurements do not match the datasheet, then the cell may be defective or a Grade B cell.
Different grade Cells Appearance
Each battery cell is stamped with a unique QR code that serves as its identification. This makes it easier for manufacturers to identify the cell when providing after-sales service. Grade B cells are considered substandard and do not usually come with a warranty. To distinguish them from A grade cells appearance, manufacturers often scratch off the QR code. If you find a battery cell with a concealed QR code, it is likely a Grade B cell. However, all Grade B cells are also covered with a new insulating sheet. Therefore, if you do not see any obvious signs of a QR code on the outside of the cell, you will need to remove the insulating sheet.
Different grade Cells Capacity
The capacity of different grade lithium battery cells is usually tested at a temperature of 25 degrees Celsius, with a charging and discharging rate of 1C. The real tested capacity value should be recorded and compared to the specifications.
Tip: The capacity of a LiFePO4 cell can be affected by temperature. Therefore, some manufacturers may send cells with a capacity that is slightly higher than the claimed capacity. If your test results are slightly higher than the datasheet, that is not a problem.
Different grade Cells Internal Resistance
The internal resistance of a lithium battery cell can be measured at different frequencies. Most manufacturers test the AC internal resistance. However, some manufacturers may test the DC internal resistance. The DC internal resistance is generally considered to be more reliable.
First, check the testing conditions on the datasheet, or confirm that with suppliers. This includes the temperature and SOC state. Once you know the testing conditions, you can measure the cell's internal resistance. If your test results meet the datasheet, then the cell is likely to be a Grade A cell.
Different grade Cells Self-Discharging Rate
The self-discharge rate of different grade cell is calculated by measuring the voltage decrease over time. The self-discharge rate can vary depending on the state of charge (SOC) of the cell. The voltage will decrease more quickly at a 100% SOC state than at a 50% SOC state.
To determine the self-discharge rate, you can follow these steps:
Well know the determination of the self-discharge rate you can follow these steps that are :
- Check the datasheet to make sure you know the testing SOC state.
- Stock the cells in the specified testing conditions.
- Check and write down the voltage decrease of the cell each day.
- Calculate the self-discharge rate per day by dividing the total voltage decrease by the number of days.
- Calculate the monthly or weekly self-discharge rate by averaging the daily self-discharge rates.
Here are two possible testing methods:
There are 2 possible testing methods for you:
* Solution 1: Stock the cells at room temperature (25°C) for 28 days.
* Solution 2: Stock the cells at a higher temperature (45°C) for 7 days.
If the self-discharge rate is 3%:
If the self-discharge rate is 3% that maybe:
* For normal temperature, the self-discharge rate per day is 0.03/28 = 0.00107, which is about 0.107%.
* For high temperature, the self-discharge rate per day is 0.03/7 = 0.00428, which is about 0.43%.
Different grade Cells Capacity Recovery
The capacity recovery rate of different battery cell is the percentage of its capacity that is regained after a full discharge. To test the capacity recovery rate, you can do a 100% depth of discharge (DOD) charging and discharging cycle.
For example, for a 3.2V 100Ah battery cell with a capacity recovery rate of 95%, you would first measure the cell's capacity at the beginning of the test. If the capacity is 100Ah, then after a 100% DOD charging and discharging cycle, the cell's capacity should be more than 95Ah. If yes, then the battery capacity recovery rate meets the datasheet and the cell is a Grade A quality cell.
Conclusion
Well, the conclusion is here. The purpose of testing the capacity recovery rate is to compare the testing data with the specifications of the cells. This allows you to verify the accuracy of the datasheet and to trust the supplier. If all the data meet the specification or datasheet, then the cells are Grade A. If not, then the cells are Grade B.