To identify whether a low capacitor voltage is caused by an abnormality in a battery cell or that in a connection circuit when the voltage of a capacitor is low.
In a voltage measurement method of the battery cell, a series RC circuit is connected in parallel with a battery cell CL in a battery cell unit 2 via a connection circuit, a capacitor C in the series RC circuit is charged for prescribed charge time and then the voltage of the capacitor is measured. Then, it is determined whether the measured voltage of the capacitor C is smaller than a prescribed reference value. When the voltage of the capacitor C is smaller than the reference value, the value of resistance in the series RC circuit is changed to a small value. By performing charging and measurement processes after changing the value of resistance, the voltage of the capacitor C is measured again. When the difference between the voltage of the capacitor measured again and that of the capacitor measured previously is less than a prescribed threshold, it is determined that the battery cell CL is abnormal. When the difference in the voltage is not less than the threshold, it is determined that a first switch circuit 41 is abnormal.
Hiroshi Takeuchi
Takahisa Shimada
Yuji Takeuchi
Katsumi Imae
Atsushi Fujita
Kazunari Ninomiya
Tomoo Harada
Iseki Katsumori
Seki Kei
Yasuya Sugiura