I would first pull the battery and insure that it will hold a charge and that it does not have a weak and/or dead cell. I would then have the alternator and starter, including solenoid, checked to insure that neither has an internal short to ground. I would isolate all other components by pulling fuses to make sure that noting is grounded that's not supposed to be. It's then merely a matter of tracing the ignition/charging circuit looking for wires that could have chaffed and grounded.