Patent ID: 8314587

Claim:
Apparatus, comprising: a primary battery unit; a secondary battery unit that has no more than 20% the total discharge capacity of the primary battery unit and is removable from the primary unit; a switching circuit configured to permit at least the choice of charging the primary battery unit without charging the secondary battery unit and the choice of charging the secondary battery unit without charging the primary battery unit, and further configured to permit selective discharging of one or the other of said battery units at a given time; a battery management system (BMS); and a controller configured to receive battery charge state information from the BMS, and to control the charging and discharging of the battery units, wherein: the controller is configured to respond to local and remote commands for charging the battery units; the controller is configured to respond to at least local commands for discharging the primary battery unit; and for discharging the secondary battery unit, the controller is configured to respond to remote commands from a remote entity, subject to authentication of the remote entity and subject to local permission to discharge the secondary battery unit.