An apparatus for defining an AC power source having a predetermined amperage rating and for use with a pallet truck or fork lift lifting device. The apparatus includes a pair of terminal banks, a battery, a converter adapted to change DC to AC power, a relay, a controller, and a base adapted for engagement by the lifting device for transport of the apparatus. The apparatus is shaped so that it can be transported by the lifting device through a doorway. A pair of terminal banks, battery, converter, relay and controller are coupled to one another and configured for selective operation in a standalone configuration or a stacked configuration.