Comparison and evaluation of charge equalization technique for series connected batteries

Charging and discharging of series connected batteries as a whole is associated with charge imbalance problems, which will result in damage to battery cells and reduction of battery life. Various circuits for charge/discharge equalization have been proposed. But so far there is no criterion for comparison and evaluation. In this paper, all the circuits are divided into four groups according to the structure, and each of them is qualitative analyzed and marked with 5-degree marking system. The results are helpful for people to select suitable charge/discharge equalization method. Furthermore, based on experimental results a novel evaluation method with two parameters is proposed, which is very convenient for estimating the equalization effects in static and dynamic equalization. All the results can be used for further study on charging equalization technique.