Abstract: A starter circuit for a motor vehicle includes a circuit breaker responsive to a crash senor for disconnecting the starter circuit. A bypass switch is provided, which responds to a control circuit to provide power to the starter circuit following activation of the breaker, if the starter circuit is free of short circuits.

Abstract: The subject invention relates to a dual-battery system, that includes a generator (1), a starter (3), a starter battery (2), a starter battery switch, a vehicle electrical system battery (5), and a control device (7), in which the starter battery (2), along with the starter battery switch that is connected in series, is connected in parallel with the generator (1), starter (3), and vehicle electrical system battery (5), and the starter battery switch can be activated by the control device (7), the starter battery switch being configured as a power MOSFET (6) whose gate is connected to the control device (7).

Abstract: This invention provides a dual-battery system (1) and a method for activating it, which comprises a starter battery (2), a generator (3), primary load (4), a vehicle electrical system battery (6), a starter (8), and a power switch (10), arranged between the starter battery (2) and vehicle electrical system battery (6), by way of which the starter battery (2) and vehicle electrical system battery (6) can be connected together in parallel during the starting operation, and further includes a controllable electronic switch (13) connected in parallel to a power switch (10).

Abstract: In a process for determining the state of charge and the peak current loadability of batteries in the currentless pauses before and after a loading phase the no-load voltages U.sub.01 and U.sub.02 are measured. From them, with allowance for battery-specific parameters, especially the time curve of the no-load voltage, the true battery rest voltages U.sub.001 and U.sub.002 are computed. During the loading phase the converted current quantity q is measured and from the relationship U.sub.002 -U.sub.001 =C.sub.1 .multidot.q/Q.sub.0 the acid capacity Q.sub.0 of the battery is found. The relative state of charge SOC.sub.1 is determined from a curve of the rest voltage U.sub.00 linearized by the formula SOC.sub.1 =U.sub.002 /C.sub.1 -C.sub.2 as a function of the state of charge of the battery from which the absolute state of charge is calculated as SOC.sub.1 .multidot.Q.sub.0.From the internal resistance R.sub.