A primary cell and a secondary cell are distinguished from each other. A microcomputer of a digital camera determines a first cell (a primary cell) and a second cell (a secondary cell) as a built-in cell. When a dedicated charging device is connected to a digital camera, a microcomputer activates transistor switches to thus detect a terminal voltage of the second cell. When the terminal voltage shows a finite value, the second cell is determined to be incorporated. When the terminal voltage shows a value of essentially zero, the transistor switch is activated to thus apply a predetermined voltage. When a voltage drop attributable to a resistor has arisen, the second cell is determined to be overcharged. When both a terminal of the second cell and a terminal of the first cell show finite values, a short circuit is determined to have arisen.