US Patent 8035247 Power supply device for vehicle

A power supply device for a vehicle includes a battery, a power line (power supply line and ground line, a connection unit, a charger that is an electric power supply unit, an accessory load, a voltage sensor and a control device. When the accessory load is operating, the control device sends signals to the connection unit to turn off all of three system main relays. Thereby, battery is electrically disconnected from charger. The control device further produces a power command based on a predetermined target voltage and a voltage detected by the voltage sensor such that the detected voltage attains the target voltage.