Whats the best way to charge your trailer battery after a day of draining it with fans running. With just a short drive it doesn't charge much from the truck. Normally I just plug in a battery charger @ night, but I am looking for a better solution. Weekends traveling to test, there isn't always a place to plug in at night to recharge. Has anyone ever installed a solar powered battery charger in a trailer/boat? Solar panel would need to be durable enough to be mounted on trailer and hauled down the road going to test/trials.