An improved battery charging system for use on a non-motorized, ground-supported wheeled vehicle such as a horse-drawn buggy, including a generator incorporated into the hub assembly of at least one wheel, a voltage control unit for controlling the voltage output of the generator over the full range or vehicle speeds, and a battery. The synchronous generator features rare earth metal permanent magnets arranged in a three-phase, outside rotor disposed within a wheel brake housing of a buggy wheel hub. The stator is situated on an axle. Voltage regulation includes active switching whereby generator output voltage is rectified during low vehicle speed operation and an increasing portion directed away from the battery as vehicle speed and thus generator output voltage increases to a level which could damage the connected battery.