An ECU performs processing including obtaining a current in a battery assembly, calculating a current in each battery, calculating an SOC of each battery, calculating an OCV of each battery, calculating ΔOCV, calculating an average value Ave of ΔOCVs, carrying out current restriction control when the average value Ave exceeds a first range and exceeds a second range, providing a warning signal when the average value Ave does not exceed the second range, and carrying out normal current control when the average value Ave does not exceed the first range.