This paper proposes a method of compensation for the SOC estimation error of the current integration method using the power-off time of the vehicle system. The current integration method can derive accurate results in real time with simple algorithm application and low cost. However, a challenge arises when errors in the battery’s initial values and noise from current measurements accumulate, increasing SOC estimation errors. To solve this problem, the time from the vehicle’s ignition off to ignition on is regarded as the battery rest time. After a specific rest time, the accumulated error is corrected by measuring the open voltage of the battery and correcting the SOC value of the existing current integration method. To verify the proposed method a Battery Monitoring System (BMS) that can measure the amount of current change in real time is configured and the accuracy of the estimation method is verified by performing battery charging and discharging experiments.
