Power source apparatus for vehicles

摘要

A power source apparatus for vehicles comprises first and second switch means respectively for controlling charging currents flowing from a rectifier of a generator to first and second batteries having equal open terminal voltages, and third switch means for controlling a current flowing through a field winding of the generator. The third switch means is controlled to be turned on/off in response to whichever of the voltages generated respectively by the first and second batteries is lower. The first and second switch means are controlled to be turned on/off on the basis of a duty factor set based on a voltage difference between the first and second batteries. When the voltage of the first battery becomes equal to or less than a predetermined voltage, that voltage being the lowest voltage that a starter motor needs to satisfactorily start an engine, the duty factor of the first switch means is made larger to charge the first battery with priority irrespective of whether the voltage of the first battery is larger than the voltage of the second battery or not.