Battery Variable Current-discharge Resistance Characteristics and State of Charge Estimation of Electric Vehicle

Abstract

Through studying and characterizing variable current-discharge test data, dynamic modeling of battery used for electric vehicle or hybrid electric vehicle (EV/HEV) with the equivalent electromotive potential and resistance as essential parameters has been carried out. The resistance characteristics are analyzed and the stable condition of the equivalent resistance is discovered when the discharge current is high. A method based on this condition for battery's state of charge (SOC) estimation is detailed. Along with traditional methods, open circuit voltage method and ampere-hour integral method, the estimation of SOC is realized; its convenience and effectiveness for on-line real-time application are also proven by analyses and pilot tests