In case of the present invention, a microcomputer (271) controls a charging mode changeover switch (275) and connects the switch to a terminal (275d) to change the terminal (275d) to an initial charging mode power source (278). In this case, the microcomputer (271) requests the information on the charging capacity stored in a microcomputer (252) as charging information, the charging voltage measured by a voltage detector (258) and a standard charging capacity and obtains the information through a communication circuits (254) and (272). The microcomputer (271) obtains an actual charging capacity in accordance with a received measured charging voltage, compares the actual charging capacity with a stored charging capacity, and updates the actual charging capacity to zero when the comparison result is equal to or larger than a threshold value and the charging voltage is equal to or less than another threshold value. According to the present invention, a charging capacity is correctly corrected.