Battery charging systems for road vehicles

Claim 1

A battery charging system for a road vehicle, comprising in combination an alternator having a field winding, a full wave rectifier through which the alternator supplies power to first and second supply lines, a battery connected between said supply lines, a third supply line, diodes coupling the alternator to the third supply line so that when the alternator is producing an output the first and third supply lines are at substantially the same potential, a voltage regulator at least part of which is connected in circuit with said field winding between the first and second supply lines, a high impedance series circuit interconnecting the first and second supply lines, said series circuit including the vehicle ignition switch, the base-emitter of a transistor and a high value resistor, means coupling the junction of said high value resistor and said transistor to the third supply line, means operable by the collector current of said transistor for controlling a warning device, said warning device being rendered inoperative when the third and first supply lines are at substantially the same potential, and means for operating said warning device when the voltage of the battery exceeds a predetermined value.