What are the test methods for self-discharge of lithium batteries?

Self-discharge test methods: 1. Measure the capacity loss of the battery after being left for a period of time: The original purpose of the self-discharge research is to study the capacity loss of the battery after being left. However, it is difficult to implement the test capacity loss due to the following reasons: A. The irreversibility during the charging process is too large, even if the discharge is performed immediately after charging, the discharge capacity/charge capacity value is difficult to guarantee within 100% ± 0.5%. Such a large error requires that the shelving time between tests must be very long. And this obviously does not meet the needs of daily processing. B. A large amount of electricity and manpower and material resources are required to test the capacity, the process is complicated and the cost is increased. Based on the above two considerations, it is generally not the self-discharge standard of the battery to measure the discharge capacity after shelving and compare the loss of the previous charge capacity. 2. Measure the K value within a period of time: A very important indicator K value to measure the degree of self-discharge u003d △OCV/△t. The common unit of K value is mV/d. Of course, this is related to the factory's own standards (or the personal preference of the factory boss), the performance of the battery itself, and the measurement conditions. The method of calculating the K value by measuring the voltage twice is simpler and the error is smaller, so the K value is a conventional method to measure the self-discharge of the battery. The following text may mix K value and self-discharge, please pay attention. This circuit is mainly composed of lithium battery protection special integrated circuit DW01, charge and discharge control MOSFET1 (including two N-channel MOSFETs) and other parts. The single lithium battery is connected between B+ and B-, and the battery pack is from P+ and P -The output voltage. When charging, the charger output voltage is connected between P+ and P-, and the current flows from P+ to B+ and B- of the single battery, and then to P- through the charging control MOSFET. During the charging process, when the voltage of the single battery exceeds 4.35V, the OC pin of the dedicated integrated circuit DW01 outputs a signal to turn off the charging control MOSFET, and the lithium battery immediately stops charging, thereby preventing the lithium battery from being damaged due to overcharging. During the discharging process, when the voltage of the single battery drops to 2.30V, the OD pin of DW01 outputs a signal to turn off the discharge control MOSFET, and the lithium battery immediately stops discharging to prevent damage to the lithium battery due to overdischarge. The CS pin of DW01 is When the output of the current detection pin is short-circuited, the turn-on voltage drop of the charge and discharge control MOSFET increases sharply, the voltage of the CS pin rises rapidly, and the DW01 output signal makes the charge and discharge control MOSFET turn off quickly, thereby realizing over-current or short-circuit protection. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: What is the reason for the capacity degradation of lithium batteries?