DETACHABLE BATTERY DEVICE

PROBLEM TO BE SOLVED: To make it possible to attach a detachable battery device to electrically powered equipment in a dark place easily, securely or safely.SOLUTION: In a detachable battery device 21 which is attached to a motor driven two-wheeler in a detachable manner, assuming that a direction in which the detachable battery device 21 is inserted into the battery housing of the motor driven two-wheeler is an insertion direction A, a remaining amount display unit 38 is provided for an end portion facing the insertion direction A, which is specifically a downward-facing surface 33A on the bottom side of a case 32 of the detachable battery device 21. Light emitted from an LED lamp 39 of the remaining amount display unit 38 not only displays a battery remaining amount, but also functions as illumination light. When a user inserts the detachable battery device 21 into a battery housing of the motor driven two-wheeler, an insertion port of the battery housing can be illuminated by illumination light of the LED lamp 39, and the feet of the user can be illuminated by the illumination light of the LED lamp 39 when the user carries the detachable battery device 21 in a removed state.