VARIABLE CURRENT DISCHARGE CHARACTERISTICS AND SOC ESTIMATION OF EV/HEV BATTERY

Through studying and characterizing variable current-discharge test data, along with dynamic modeling of battery used for EV/HEV with the equivalent electromotive potential and resistance as essential parameters, it is discovered that the equivalent resistance of the battery tends to be stabilized when the discharge current is greater than a certain point. Based on this important fact, a method relies on the equivalent electromotive potential for battery’s state-of-charge (SOC) estimation is detailed, which allows estimating the SOC simply by discharge current and terminal voltage of the battery. Its convenience and effectiveness for on-line real-time application are also proven by analyses and pilot tests.