Hey guys. I picked up a solar powered battery maintaner at wally world for 15 buck. It plusgs either into the cigarette light or can be wired directly to the battery. The maintainer will not charge a dead battery, but, it will keep a sitting battery from going dead. They have a 60 dollar model as well. That one will maintain the battery and will act as a trickle charger for dead batteries. It's a real good investment and I'd advice everyone to check it out.

walmart.com