Charging is started with charge voltage set to a first voltage value (lower than a normal charge voltage) by a charge voltage change means, the first voltage value being predetermined to ensure that secondary batteries constituting a parallel-arrangement battery pack are charged up to and maintained at a predetermined SOC lower than full charge (between 80 and 90% of full charge). When a charge current detection means detects that charge current has decreased to a predetermined value A1, the charge voltage is set to a second voltage value (normal charge voltage) higher than the first voltage value by the charge voltage change means, the second voltage value being predetermined to enable the secondary batteries to be charged up to full charge. When a battery SOC detection means detects that at least one of the secondary batteries has reached full charge, charging is terminated.