The ampere-hour integral method in industry to estimate the state of charge (SOC) of battery. However, it is impractical to use open circuit voltage (OCV) to calibrate the cumulative error of ampere-hour integral method for wind-solar energy storage systems. Because the OCV method requires the battery to be stationary for several hours. To address this problem, a new calibration method is proposed, which is similar to the OCV method, but its calibration conditions only require the current of battery constant or maintain 4 min fluctuation in a small range, which is more suitable for calibrating the error accumulation problem in wind-solar energy storage systems using the amperehour integral method. 4S6P soft pack lithium-ion batteries is used for experimental testings in 3.9 V, 3.6 V and 3.2 V about three different voltage platforms, the proposed strategy and the actual OCV error were less than 10 mV, and the conversion to SOC is less than 1%, which prove the feasibility of the proposed strategy.