A voltage and internal resistance of a battery are measured in advance as its
capacity
decreases. In a flash memory of a device powered by the battery, voltages necessary
to drive a motor, an EL display, and a bezel input unit are stored. By comparing
the voltage of the battery with a resistor connected as a dummy load and the voltage
read from the flash memory, it can be determined whether it is possible to drive
the motor, the EL display, or the bezel input unit.
