Legal Question regarding diesel electric road vehicle

[richardland]

I believe that a battery powered electric vehicle does not need to be taxed nor does the electricity used to charge the batteries have to have duty paid upon it. This begs a question. If I use a red diesel or biodiesel fuelled generator to charge the batteries whilst the vehicle is on private ground, then drive on public roads, is duty payable? Moreover what happens if I then load the generator on to the vehicle and use it to charge the batteries whilst in motion on public roads. Does this change the duty payable requirements?