Study on passive balancing characteristics of serially connected lithium-ion battery string

Lithium-ion battery is widely used in large-scale energy storage and electric vehicle and other fields for its excellent performance, thus the development of new energy is of great significance. In this paper, the characteristics of passive balancing are obtained by the on-line passive balancing experiment of charge and discharge under different capacity, current ratio and equalizing threshold of lithium battery. The experimental results show that the balancing current ratio (ratio of the equalizing current to the main circuit current) can effectively enhance the effect of passive balancing. The passive balancing time ratio (ratio of balancing time to charging/discharging time of main circuit) and the balancing effect of the discharging state is larger than that of the charging state. The passive balancing of the discharging state is critical. The battery inconsistency can be effectively improved by appropriate reduction of the balancing threshold. In summary, the optimization of the passive balancing parameters of the battery pack plays an important role in improving the inconsistency of the battery pack.