Install a foot crank on your car (or make a new vehicle) and it doubles as an engine.
It doesn’t need wheels.
I made this a long ago, but I remember you need like:
Foot crank, Controls, Alternator, Seedle (or something else to sit on, though i’m not sure if it is mandatory) and battery to recharge.
Press ‘^’, “accelerate” and just ride your standing-bike-charger, pressing the 5 on numerical pad. You will get tired and out of breath, but the battery will recharge a little 
Edit: Also you can remove/install bateries once the vehicle is running. Some days ago I made the mistake to leave the lights on and went to sleep, only to find my vehicle with a dead battery. Later on I found a barely dead battery on another car, installed that on my own car, started it, and put the original back, all while it running. It worked flawless.