Abstract: A portable power supply device comprises a stackable battery housing locating a plurality of batteries therein and an inverter housing locating an inverter therein which is arranged to convert the direct current from the batteries to an alternating current. The inverter housing is readily separable from the battery housing such that one or more battery housings can be readily interchangeable to provide a constant supply of power and to allow a variety of charging configurations of the batteries. First electrical connectors on the battery housing and second electrical connectors on the inverter housing automatically connect the inverter to the batteries upon stacking of the inverter housing on the battery housing. Furthermore charging terminals are mounted externally on the inverter housing for ready access to connect to a charging device in a convenient manner without requiring the housings to be opened or separated form one another.