PURPOSE: To enable the indication of the quantity of precise residue of a battery even just before a battery pack is mounted again by providing a battery voltage detection part for detecting the voltage of the battery, a storage part for storing the quantity of the residue of the battery and a calculation part for calculating the quantity of the residue of the battery on the basis of information from the battery voltage detection part and the storage part.

CONSTITUTION: At the time of full charge a battery voltage detection part 5 monitors the voltage of a charge type battery 4 to transmit its information to a calculation part 7. Next, in the calculation part 7 the information from the battery detection part 5 is compared with the other information of battery capacity from a storage part 6 to find the quantity of the battery residue and its information is transmitted to a control part 8 of the inside of a device body 2. And in the case where a battery pack 3 is detached from the device 1, the calculation of the quantity of battery residue is always performed in the inside itself of the battery pack 3. Further, when the battery pack 3 is mounted on the device 1 again, the quantity of the correct battery residue from the calculation part 7 is output into the control part 8 to show on a display 9.