Patent ID: 7733059

Claim:
An abnormality diagnostic device for diagnosing an abnormality in a battery pack having a plurality of cells connected in series, the abnormality diagnostic device comprising: a plurality of cell voltage detecting circuits with each of the cell voltage detecting circuits being connected in parallel to a corresponding one of the cells of the battery pack to detect a voltage of the corresponding one of the cells; a plurality of discharging circuits with each of the discharging circuits being connected in parallel to a corresponding one of the cells to selectively discharge an electric power of the corresponding one of the cells, each of the discharging circuits including a switch and a resistor that are connected in series; a switch drive circuit connected to the switches of the discharging circuits to selectively turn on and off the switches; a plurality of diagnostic voltage detecting circuits with each of the diagnostic voltage detecting circuits being electrically connected to a corresponding one of the discharging circuits to detect a voltage across the corresponding one of the discharging circuits; and an abnormality diagnostic control section configured to control the switch drive circuit to perform a first diagnostic operation in which the switches corresponding to either alternate even numbered ones of the cells or odd numbered ones of the cells are turned on simultaneously and a second diagnostic operation in which all of the switches of the discharging circuits are turned on simultaneously, and to determine whether a break exists in an electrical connection between one of the cells and a corresponding one of the discharging circuits and whether an abnormality exists in one of the switches based on the voltages detected by the diagnostic voltage detecting circuits during the first diagnostic operation and the voltages detected by the diagnostic voltage detecting circuits during the second diagnostic operation.