Abstract: An alternator circuit comprises an alternator having an armature winding, a field winding, a voltage regulator, a fault detecting circuit, a lamp drive circuit having its input connected to the output of the fault detecting circuit, and a warning lamp driven by the drive circuit. The drive circuit includes a capacitor connected across its input, an input transistor, an output transistor, a current measuring resistor connected in series with the output transistor, and a transistor sensitive to both the voltage drop across the warning lamp and the voltage drop in the current measuring resistor. In the event of excessive current flow through the output transistor, the voltage sensitive transistor rapidly charges the capacitor thereby turning off the output transistor. The capacitor then discharges slowly and the cycle is repeated.

Abstract: A road vehicle battery charging system for a dual voltage electrical supply includes a conventional alternator/rectifier assembly for charging the main battery and a d.c. to d.c. converter connected to charge an auxiliary battery in series with the main battery. The converter includes an autotransformer with primary windings in series with respective transistors across the main battery and further windings connecting the transistor collectors in series with diodes to the auxiliary battery. The transistors form part of an oscillator which produces an a.c. waveform with a peak-to-peak voltage slightly less than twice the main battery voltage--the deficiency being made up by virtue of the further windings.

Abstract: A road vehicle battery charging system for a dual voltage electrical supply includes a conventional alternator/rectifier assembly for charging a main battery and a d.c. to d.c. converter for charging an auxiliary battery in series with the main battery. The converter includes two transistors connected with a feedback transformer to form an oscillator to drive an output transformer. The oscillator includes two diodes which need to be connected to one terminal of the main battery to allow the oscillator to run and a switching transistor is interposed in such connection and has its conduction controlled in accordance with the alternator output so as to inhibit the d.c. to d.c. converter when the alternator output is below a predetermined level.