Abstract: A multiple voltage alternator system for directing power in a vehicle between an alternator, a single battery and loads connected thereto which require power at a higher DC voltage and a lower DC voltage. In one embodiment, first and second bi-directional converters operate synchronously and are coupled together through a transformer having first and second windings. The alternator supplies power directly at one voltage and indirectly through the bi-directional converters at the other voltage when the vehicle engine is running. The battery operates at the opposite voltage from the alternator, preferably at the lower voltage, and directly supplies power at one voltage and indirectly at the other voltage when the alternator is not providing power. In an alternative embodiment the bi-directional converters are coupled through an autotransformer.