Implementations described and claimed herein provide systems and methods for supplying voltage to a load and battery. In one implementation, an unregulated DC-to-DC converter is electrically connected to a first energy source to down convert a first voltage supplied by the first energy source. A load is electrically connected to the unregulated DC-to-DC converter to receive the down converted first voltage. A regulated DC-to-DC converter is electrically connected to the unregulated DC-to-DC converter to regulate the down converted first voltage to a second voltage. A second power source is electrically connected to the regulated DC-to-DC converter to charge the second power source using the second voltage, and the second power source is switchably connectable to the load.