A battery pack assembly comprises at least one light emitting device, a switch for operating the light emitting devices, a case, and a battery pack. The battery pack assembly includes a support portion, an elastic connection portion, a button and an observation portion. The support portion is fixed to an inside of the case. The elastic connection portion is extended from one side of the support portion. The button is formed at an end portion of the elastic connection portion. The observation portion is fixed between the support portion and the case, and is configured to allow light emitted from the light emitting devices to pass therethrough. In the battery pack assembly, the button is exposed through the button hole, and light passing through the observation portion is exposed through the observation holes.