Patent ID: 7696716

Claim:
A dual battery electrical system for a vehicle having an engine, the system comprising: a plurality of primary loads and a plurality of secondary loads and being switchable between an ON state in which the engine is running, an OFF state in which the engine is not running and a START state in which at least one of the primary loads requires power to start the engine; a first battery arranged to provide power to the primary loads; a second battery arranged to provide power to the secondary loads; switch means closeable to connect the first battery to the second battery, such that both batteries can provide power to both loads, control means arranged to open the switch means when the system is in the OFF state and to close the switch means when the system is in the ON state and the START state; and a connection system having a plurality of output terminals for connection to the plurality of primary and secondary loads and two input terminals for connection to the first and second batteries, respectively, wherein the plurality of primary loads are electrically disconnected from the plurality of secondary loads in the START state when the voltage charge of the second battery is less than the voltage charge of the first battery.