The device (10) has a position determining unit (16) to detect changes in position of vehicle. An ultrasonic transceiver (18) transmits and receives ultrasonic waves to determine run time changes of ultrasonic waves. A control unit (22) evaluates the signa...

The method involves measuring battery voltage (UB) by voltage measurement unit and decreasing battery current (Ic) for a time period (t1) by a load. The time period (t1) is more predeterminable by control unit. The battery voltage measured during the curre...