Due to the compact size and the high power to weight ratio of a Wankel engine, it has been proposed for electric vehicles as range extenders to provide supplementary power when electric battery levels are low. There have been a number of concept cars incorporating a series hybrid powertrain arrangement. A Wankel engine used only as a generator has packaging, noise, vibration and weight distribution advantages when used in a vehicle, maximizing interior passenger and luggage space. The engine/generator may be at one end of the vehicle with the electric driving motors at the other, connected only by thin cables. Mitsueo Hitomi the global powertrain head of Mazda stated, "a rotary engine is ideal as a range extender because it is compact and powerful, while generating low-vibration".