Review of equalizing methods for battery pack

Batteries usually are connected in series to meet high voltage requirement, especially used in electric vehicles. Series connected batteries are suffering from imbalance problem, which would result in dramatic reduction in life and irreversible damage. Equalizing methods can be used to solve this problem. In this paper, non-dissipative equalizing methods were reviewed. Equalizing methods were classified into three big categories according to circuit topology, and then each big category was classified into several small categories according to their own characteristics. Equalizing methods were introduced in order of time and complexity in each category. Each method was described in these aspects: principle, improvement, advantages and disadvantages. Trend of equalizing method was explained based on the current technology and applications.