Complex sentence: Due to the compact size and the high power to weight ratio of a Wankel engine, a number have been proposed for electric vehicles as range extenders to supplement when electric battery levels are low, with a number of concept cars incorporating a series hybrid powertrain arrangement.
Split into simpler sentences: 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.