Abstract: The adjacent cells comparing strategy has a low energy transfer efficiency, and the MAX/MIN value strategy has a slow equalization speed. Then, a new equalization strategy was proposed to overcome above disadvantages, and the uniform of the SOC of the battery strings was used as the equalization goal in this strategy. The strategy used the estimation of the average balanced SOC as a reference, and controlled the switch states and the energy transfer direction of each equalizer, according to the energy distribution of the entire battery strings. With this strategy the unnecessary energy loss during energy transfer was reduced and the equalization speed was speeded up. The simulation model was built with MATLAB, and simulation results were compared with the traditional adjacent cells comparing strategy and the MAX/MIN value strategy. The effectiveness of the proposed equalization strategy was verified.

Key words: battery equalization, equalization strategy, state of charge, cell to cell