Patent ID: 8531157

Claim:
A charging apparatus for charging a cell group, in which a plurality of secondary cells are connected in series, by supplying a charging current to the cell group, comprising: an overcharge protection circuit that includes a plurality of discharge route circuits each of which is provided respectively to each of the secondary cells, said overcharge protection circuit being adapted to detect cell voltages of the secondary cells, to compare the detected cell voltages with a predetermined overcharge protection voltage, and to cause the secondary cells being charged to discharge through the respective discharge route circuits by connecting the secondary cells to the respective discharge route circuits when the cell voltage of any one of the secondary cells exceeds the predetermined overcharge protection voltage or to stop discharging by cutting off the secondary cells from the discharge route circuits; and a charging controller that detects a discharge of any one of the secondary cells to the discharge route circuit thereof, performs a process of reducing the charging current until the discharge of the secondary cell being discharged to the discharge route circuit is stopped and fixing the charging current at a current value reached when the discharge of the secondary cell is stopped, and repeats the process until the charging current reaches a predetermined lower limit charging current value.