Abstract: An apparatus for monitoring and controlling electrical systems in a motor vehicle with electric or hybrid drive has a first and a second AC voltage source for an alternating voltage between a first or second terminal and a reference terminal. First and second voltmeters detect a first or second voltage between the first or second terminal and the reference terminal. A control unit controls the AC voltage sources, receives the voltages from the voltmeters and determines insulation resistance for subassemblies that are connected to the terminals. The insulation resistance is relative to a potential connected to the reference terminal. A precharge state of a capacitative load connected to the first terminal is determined. The load is precharged by a voltage supply unit connected to the second terminal. The switching state of at least one switch between two subassemblies is determined. The subassemblies are connected to the first or second terminal.

Abstract: An apparatus for monitoring and controlling electrical systems in a motor vehicle with electric or hybrid drive has a first and a second AC voltage source for an alternating voltage between a first or second terminal and a reference terminal. First and second voltmeters detect a first or second voltage between the first or second terminal and the reference terminal. A control unit controls the AC voltage sources, receives the voltages from the voltmeters and determines insulation resistance for subassemblies that are connected to the terminals. The insulation resistance is relative to a potential connected to the reference terminal. A precharge state of a capacitative load connected to the first terminal is determined. The load is precharged by a voltage supply unit connected to the second terminal. The switching state of at least one switch between two subassemblies is determined. The subassemblies are connected to the first or second terminal.

Abstract: A charging circuit for a lead-acid storage battery for a mobile radio transceiver which operates effectively with an input from a vehicular battery terminal that may vary over a range of 25 volts in output voltage has a control circuit for regulating the charging current connected between the charging current output and the same control input of the same pulse width modulator that is used for output voltage control. The pulse width modulator is part of an integrated circuit which includes also a d.c. to d.c. voltage converter and an output voltage regulator. A branch circuit includes a current sensing resistor (45) of less than 1 ohm. The voltage drop across said sensing resistor is too small to control a control transistor network (46, 52) and therefore a constant voltage is added thereto by a voltage adding resistor network (56, 57, 47, 48) coupled to said transistor network.