I would far sooner see a hybrid run with Super Capacitors and no batteries . The capacitors are easily charged up from regenerative breaking , and the Gen-Set , they cost less than batteries , are good for over a million cycles , are not subject to cold extremes like batteries .
A short burst of power would get the vehicle up to highway cruising speed and the Gen-Set would maintain that speed while also charging the capacitors for passing or long hills .
Slowing down also instantly captures the regenerative energy for the next start from stop .
Design the cars the right way , use Super Capacitors not batteries in Hybrid vehicles .
Put the batteries in Pure Electric Vehicles .