A 100kW generator would be huge and incredibly inefficient.... you'd get much better performance using the gas/diesel to drive the wheels directly.Here is the basic idea. It will be a series hybrid type. Small V6 gas or diesel engine (leaning toward gas for convenience) mated to a generator (alternator) right at the flywheel. Then a large electric motor to power the drive wheels. The generator would have to be large enough to charge the batteries and power the vehicle; so my rough math says around 75-100 kw minimum.
That said, I have a colleague who is working on an electric RV. They are using two 'small' Tesla motors (FWD) and a complete Tesla battery pack. They are also using the BMW i3 REx (~20kW) for emergency range extension. They estimate electric only range at more than 250 miles using the Tesla 100kWh battery and said they will rarely drive beyond the battery range in a single day... it will be interesting to see if the REx is ever installed