The very broad plateau of LiFePO4 Li-ion batteries and serious polarization on both ends are not conducive to SOC estimation,but SOC value has definite major influence upon cell inconsistency and service life.Based on the existing SOC estimation methods of LiFePO4 Li-ion batteries and the analysis of voltammeter curve correspond-ing to electrochemical characteristics,a reliable and accurate method of △Q/△V under different charging rates and aging stages is presented in detail,and the SOC value is revised by peak △Q during the charging process.The online equaliza-tion of battery packs and control strategies of intelligent battery management system for electric vehicle are validated by the accuracy of SOC estimation.