Patent ID: 7573238

Claim:
A voltage detection device for detecting voltage across one of a plurality of series-connected battery blocks, each including one or more rechargeable batteries, the voltage detection device comprising: a first switch group, including a plurality of switches connected to the plurality of battery blocks, for obtaining the voltage across the one of the battery blocks; a charge-discharge unit including two or more capacitors charged with the voltage across the one of the battery block that is supplied via two of the plurality of switches or charged with a predetermined internal reference voltage, wherein a connection state of the two or more capacitors is switchable between series connection and parallel connection; and a voltage detector for receiving a discharge voltage of the two or more capacitors and detecting the discharge voltage; wherein in a first period, the two or more capacitors are connected in series and charged with the voltage across the one of the battery blocks; in a second period, the two or more capacitors that have been charged in the first period are connected in series and discharged, with the voltage detector detecting a discharge voltage of the capacitors; in a third period, the two or more capacitors are connected in parallel and each capacitor is charged with the internal reference voltage; and in a fourth period, the two or more capacitors that have been charged in the third period are connected in series and discharged, with a detection error of the voltage detector being corrected using a discharge voltage of the capacitors as a reference.