Patent ID: 8692556

Claim:
A voltage detection device for an assembled battery including a plurality of unit batteries connected in series, the voltage detection device being configured to detect a voltage of each of the unit batteries of the assembled battery, the voltage detection device comprising: an operational amplifier having an input terminal biased at a predetermined reference voltage; first capacitors provided respectively to the unit batteries; first switch devices each provided between a high-voltage-side terminal of corresponding one of the unit batteries and one end of corresponding one of the first capacitors; second switch devices each provided between a low-voltage-side terminal of corresponding one of the unit batteries and the one end of corresponding one of the first capacitors; third switch devices each provided between an inverting input terminal of the operational amplifier and an other end of corresponding one of the first capacitors; a second capacitor and a fourth switch device provided in parallel between the inverting input terminal of the operational amplifier and an output terminal of the operational amplifier; and a control unit configured to detect the voltage by implementing the following first and second processes in order: the first process to: open both the second switch devices and the third switch devices corresponding to the unit batteries excluded from an object of voltage detection, close the fourth switch device, and close both one of the first switch devices and one of the third switch devices corresponding to one of the unit batteries being an object of voltage detection to charge corresponding one of the first capacitors; and the second process to: open the fourth switch device, and close one of the second switch devices corresponding to the one of the unit batteries being the object of voltage detection, instead of the one of the first switch devices.