A switching control unit for the controlling the transfer of electrical power in a vehicle from at least one of a starter generator and a supercapacitor bank to/from at least one of a service battery and a plurality of electrical devices is provided. A switching device selectively connects/disconnects the at least one of the starter generator and the supercapacitor bank to/from the at least one of the service battery and the plurality of electrical devices. A switch controller is adapted to measure a voltage across the supercapacitor bank to generate a bank voltage signal, to measure a voltage across the service battery to generate a service voltage signal, and to control the switching device to connect/disconnect the at least one of the starter generator and the supercapacitor bank to/from the at least one of the service battery and the plurality of electrical devices in response to the voltage signals.