Abstract: A direct current power source for powering an electric vehicle. The power source has a rechargeable battery and a battery charger control unit for providing a charge to the battery with an amount of electrical energy which corresponds to the amount of electrical energy discharged since the previous charge plus a selected additional amount of charge to slightly overcharge the battery during a full restoration. The battery charger control unit includes a charge monitor for determining the flow of electrical energy into and out of the battery and a charge controller for controlling a battery charger. In one embodiment, the battery and the battery charger control unit are integrated. In the preferred embodiment, the charge controller includes means for controlling the battery charger in accordance with the amount of electrical energy charged to and discharged from the battery as measured by the charge monitor.