Studies on Equalization Strategy of Battery Management System for Electric Vehicle

Battery management system is one of the key technologies strengthening practical utilization and industrialization of electric vehicles. As an integral part of the battery management system, equalization system played an important role in development of electric vehicles. Based on the analysis of the key technologies of electric vehicle and the development trend of battery management system, a systematic method for bi-directional equalization of lithium ion battery pack is presented in this paper. The basic principle utilizes a Flyback Converter with a multiwinding transformer. Equalization with voltage is employed to balance the cell voltage of battery pack. In order to ensure the accuracy requirements of the cell voltage, a voltage measurement scheme based on analog multiplexers using photoelectric relay was adopted in this unit to detect the voltage of battery one by one. Experimental results show that the proposed battery equalization scheme can not only enhance the uniformity of power battery pack, but also improve the life of the battery as a whole.