Abstract

A device for detecting a voltage of an individual unit cell included in a combination battery consisting of a number of unit cells connected in series. The unit cells are divided into several groups, and a voltage divider circuit having a cell-side resistor and a reference-side resistor is connected to each unit cell. A divided potential of each unit cell is supplied to a cell voltage detector from each voltage divider circuit. Also, a reference potential that is common to a cell group is supplied to the detector from a junction connecting two neighboring cell groups. The cell voltage detector determines the voltage of each unit cell, group by group, based on a difference between the divided potential and the reference potential. Since the reference potential is common to all the voltage divider circuits in one cell group, the voltage divider circuits can be simplified. To further simplify the circuits, the reference-side resistors for the first cell group are commonly used as the reference-side resistors for other cell groups.