An expeditious and simple scheme for measuring self-discharge rate of lithium batteries

摘要

The inconsistency of the self-discharge rate of each cell in series has an impact on the capacity of the battery pack, which is one of the best interpretations of the Cannikin Law. The cells with high self-discharge rate in series determine the pack capacity. In addition, the cells with high self-discharge rate usually means lower reliability and higher safety risk. Compared to traditional measurement methods, we previously proposed a method to calculate the self-discharge rate by "pre-parallel" equalization and then observing the current change of parallel branch. However, this method still has the problems of time-consuming and difficult in batch sorting. This paper replaces the previous "pre-parallel" operation with the initial voltage measurement of the cells. Combined with the established equivalent circuit model, the self-discharge rate of each cell is calculated. The method further shortens the measurement time, which is suitable for sorting the cells in batches. The results show that the method can identify the absolute self-discharge rate of each cell in a shorter time with relatively high accuracy.