An electrical energy management system includes a first battery having a nominal operating voltage, a second battery having a charging voltage sufficiently close to the nominal operating voltage of the first battery such that the first battery can charge the second battery when the first battery and the second battery are electrically connected in parallel, a generator that is controllable to provide a variable output voltage, a starter motor, an electrical load, a plurality of switches each controllable to be in an open state or a closed state, and a controller that is configured to control the output voltage of the generator and to control the open or closed state of each of the plurality of switches.