Eric in North TX wrote:
You would probably be better off if you did kill them, dead folks don't
sue, but their families might. Consider those inexpensive game cameras
hunters use. They use motion sensors and digital cameras, catch them in
the act.
To answer your original question, a battery operated fence charger
should do the trick.

But make sure you use an old battery so you don't have to wait too long
for the battery to die before you can get back into your own car. ;-)