I agree it should be possible from a car battery without the engine running. It's also easier to get someone to push you or even push start it yourself as long as the engine is in good running order and it just has a flat battery. Unless it has an automatic gearbox, like most scooters!
Okay. I'm going to go away and have another think about it. My electronics is fairly basic so I might be wrong.
However my point of, if a car battery will start it without the engine running, why risk running it; does stand.