Hi Corey, what kind of barrel have you got? Is it metal? I'd be very careful with the jumper cables if you're using a car battery. It sounds rather dangerous to me.
I know that you can energize water in a larger container such as a stew pot just the same as with a small saucepan. Maybe it's the same for a metal barrel. I don't know, but it would be interesting to find out.
Let me know what technique you come up with. I'm always interested in finding new info. to add to the "hints & tips" page of the site. Pat.