1. Self discharge test

Generally, 24-hour self discharge is used to quickly test its charge holding capacity. The battery is discharged to 3.0V at 0.2C, charged to 4.2V at 1C with constant current and voltage, and the cut-off current is 10mA. After being put aside for 15 minutes, the battery is discharged to 3.0V at 1C to measure its discharge capacity C1. Then, the battery is charged to 4.2V at 1C with constant current and voltage, and the cut-off current is 100mA. After being put aside for 24 hours, the 1C capacities C2, C2/C1 are measured × 100% should be greater than 99%.

2. Internal resistance measurement

The internal resistance of the battery refers to the resistance caused by the current flowing through the battery when the battery is working, which is generally divided into AC internal resistance and DC internal resistance. Since the internal resistance of the rechargeable battery is very small, the electrode is easy to polarize when measuring the DC internal resistance, resulting in polarization internal resistance, so its true value cannot be measured; The measurement of its AC internal resistance can avoid the influence of polarization internal resistance and obtain the true internal value. The AC internal resistance test method is: using the battery's characteristics of being equivalent to an active resistance, give the battery a constant current of 1000HZ, 50mA, sample its voltage, rectify and filter it, and then measure its resistance accurately.

3. IEC standard cycle life test

The standard cycle life test of lithium battery specified by IEC is:

After the battery is discharged to 3.0V/piece at 0.2C, it will be charged to 4.2V at constant current and voltage at 1C, and the cut-off current will be 20MA. After it is put aside for 1 hour, it will be discharged to 3.0V at 0.2C (one cycle) for 500 cycles. The capacity should be above 60% of the initial capacity.