Patent ID: 8305038

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: a discharge amount detection means for detecting an amount of power discharged from the cell group in a non-charging state; a charge amount detection means for detecting an amount of power charged into the cell group in a charging state; and a charging control means for, during a charging period, charging while reducing the charging current every time a charging voltage of any one of the secondary cells exceeds a specified overcharge protection voltage set lower than a full charge voltage until the charging current is reduced to a lower limit charging current value indicating that the respective secondary cells of the cell group are close to a fully charged state, then continuing charging with a current value equal to or smaller than the lower limit charging current value to increase the charging voltages of the respective secondary cells above the overcharge protection voltage, and stopping charging when the amount of power charged into the cell group by the charging becomes equal to the amount of power discharged from the cell group in the non-charging state.