An electric battery powered automobile has a wind driven rotor device driving a generator to furnish supplementary power to batteries of the electrical power system of the automobile. The rotor device includes a power rotor having a pair of curved blades forming an overlapping, S configuration, and an outer series of turbine blades which pivot to provide minimum resistance when moving into the wind and provide maximum power when moving with the wind. The rotor device is mounted between two discs one of which serves as the armature of an electrical power generator. The generator has a plurality of parallel windings which at low speeds are connected in series to the batteries and, at high speeds, are connected in parallel to the batteries. The armature can be mounted separately and caused to couple with the rotor assembly through a clutch when the rotor has reached a desired speed. A further embodiment includes a rotor having tapered S-shaped blades, and/or a plurality of wind velocity responsive shutters for speed control.