Quote Originally Posted by Mechanic688 View Post
I run an 1100 watt and it'll run a hour or two cutting up scrap before I have to start my vehicle. I let it run about 15-20 min.s and it's good for quite a while longer.
If you're gonna go that route, it's best to have a deep cycle battery. Optima is the first brand that comes to mind but there are others.

Otherwise, I would leave the car running so you don't shorten the lifespan of your battery.