I think you guys are talking about two different things...
Marcus, you're talking about the breakaway battery, correct? You should ahve that battery wired into the charging system of your truck. That way while you're under way the breakaway box is being charged. If your truck is not wired for it, then put your breakaway on a battery tender occasionally to make sure it stays up to snuff. Out in the middle of Kansas at 2:00 AM is not where you'll want to test the breakway battery voltage; you'll never find your trailer until the next morning...
Joeg, you're talking about voltage to the trailer brakes, correct? Since most electrical trailer brakes are actuated by varying voltage, it is important to have good connections from the truck to the brakes, and back to ground. In fact, I know of some folks that rely on the hitch to provide ground back to the truck; bad move. Run a ground through your wiring harness back to the tow vehicle. Problems with bad connections on trailer brake wiring will manifest itself as inconsistent braking levels and possibly occasional lack of trailer brakes.
Capiche?