Patent ID: 8076797

Claim:
A method for transferring energy to and from a load using an energy transfer circuit comprising a first capacitor, a second capacitor, an inductor, a first switch between the inductor and the first capacitor, a second switch between the inductor and the second capacitor, and a control unit, the method comprising: connecting the load in parallel with the first capacitor of the energy transfer circuit; connecting a primary energy source having a first voltage in parallel with the first capacitor of the energy transfer circuit; connecting a secondary energy source having a second voltage in parallel with the second capacitor of the energy transfer circuit; communicating status information from the primary energy source to the control unit; communicating status information from the secondary energy source to the control unit; communicating energy requests from the load to the control unit; controlling the opening and closing of the first switch and the second switch using the control unit; responding to charging currents from the load; responding to power demands from the load; responding to energy requests for the primary energy source and the secondary energy source; and keeping the first switch and the second switch open unless responding to the charging currents, power demands or energy requests from the load, the primary energy source or the secondary energy source; wherein responding to charging currents from the load comprises: determining whether either of the primary energy source or the secondary energy source has a charge priority; charging the primary energy source when the primary energy source has the highest charge priority; charging the secondary energy source when the secondary energy source has the highest charge priority; running a trickle charge routine when neither of the primary energy source or the secondary energy source has the charge priority; discontinuing the response to the charging current from the load when the charging current ceases; and discontinuing the response to the charging current from the load after a limited time.