Your all cleverer than me by a mile so.....

[Upatdawn]

If an electrically powered car had an onboard super efficient genny to supply the batteries (in addition to regenerative charging and solar roof panels) would the fuel used be liable to road fuel duty even though it didnt mechanically connect directly to the road wheels.....


like the Ampera for instance

[Amateurish]

Fuel attracts duty if it is used as fuel in a road vehicle. So it doesn't matter how that fuel is converted into energy.

[Lowtimer]

Yes, of course it would attract duty. And does. The setup you suggest is already used in a number of vehicles (BMW i3 range extender being an obvious and well known one)