Electric vehicles meet the development needs of modern society and have gradually replaced traditional fuel vehicles in the position of automobiles. However, the manufacturing technology of electric vehicle is still defective, and the urgent problem to be solved is the safety of battery pack. The battery pack is composed of batteries connected in series and in parallel, and connected-series battery string is easy to produce charge imbalance, which leads to short circuit and circuit breaking of battery pack and causes spontaneous combustion of battery pack. Therefore, it is necessary to eliminate the inconsistency of charge between batteries through effective equalization technology. Through research and analysis, it is found that there are various inconsistent states of battery charge, and the existing equalization technology only aims at one of the states. When other unbalanced states occur, the equalization efficiency is low. Therefore, based on the existing equalization technology, a novel equalization technology is proposed. According to unbalanced state of battery charge, the structure of the equalization circuit is adjusted by switching elements, so as to quickly eliminate the charge inconsistency. In order to verify the validity and feasibility of the method, a series battery string composed of 8 batteries were used for simulation and the results were analyzed. KEY WORDS： unbalanced states，series battery string，equalization technology，equalization circuit

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