Most of those are wired with about an 18 ga wire. You can buy a battery trickle charger that's supposed to plug into one to charge the battery. How many amps can you stuff through 18 ga before it all melts down? Not all of those are live when they key's off.

“In a time of deceit telling the truth is a revolutionary act.”
― George Orwell

It's not over when you lose. It's over when you quit.