One embodiment includes a method that includes monitoring a battery state of charge circuit that is coupled to a vehicle battery, calculating an averaged value of the state of charge over a time period, charging the vehicle battery by powering a generator with a fuel burning engine that powered on and powered off according to one of a first operational mode and a second operational mode, wherein in the first operational mode the engine is powered on when the battery state of charge drops below a first state of charge and continues until the averaged value of the state of charge increases to a first preprogrammed value.