Abschaltspannungssteuerung in the vehicle

A vehicle power system includes a control that reduces a voltage value of an alternator by a predetermined amount as a response to a size of electric charge that is provided by the alternator during a predetermined period exceeds a first threshold value and that a rate of change of the power output from the alternator exceeds a second threshold value during the period. The controller also regulates an output voltage of the alternator on the basis of the desired value.