What are the performance testing methods for lithium-ion batteries?
Method 1: Self-discharge test
The self-discharge test for nickel-cadmium and nickel-metal hydride batteries is as follows: Since the standard charge retention test time is too long, a 24-hour self-discharge test is generally used to quickly test their charge retention capacity. The battery is discharged at 0.2C to 1.0V, charged at 1C for 80 minutes, rested for 15 minutes, discharged at 1C to 10V, and its discharge capacity C1 is measured. The battery is then charged at 1C for 80 minutes, rested for 24 hours, and its 1C capacity C2 is measured. C2/C1×100% should be less than 15%.
The self-discharge test of lithium-ion batteries is as follows: Generally, a 24-hour self-discharge test is used to quickly test its charge retention capacity. The battery is discharged at 0.2C to 3.0V, charged at constant current and constant voltage at 1C to 4.2V, with a cutoff current of 10mA. After resting for 15 minutes, the battery is discharged at 1C to 3.0V to measure its discharge capacity C1. Then, the battery is charged at constant current and constant voltage at 1C to 4.2V, with a cutoff current of 100mA. After resting for 24 hours, the 1C capacity C2 is measured. C2/C1×100% should be greater than 99%.
Method 2: Internal Resistance Measurement
The internal resistance of a lithium-ion battery refers to the resistance encountered when current flows through the battery during operation. It is generally divided into AC internal resistance and DC internal resistance. Since the internal resistance of a rechargeable battery is very small, when measuring the DC internal resistance, the electrodes are prone to polarization, resulting in polarization internal resistance, so its true value cannot be measured. However, measuring the AC internal resistance can eliminate the influence of polarization internal resistance and obtain the true internal resistance value.
The AC internal resistance test method is as follows: taking advantage of the characteristic that a lithium-ion battery is equivalent to an active resistor, a constant current of 1000HZ and 50mA is applied to the battery, and its voltage is sampled, rectified and filtered, etc., to accurately measure its resistance value.
