To make my $24,000 solar ready super conductors worth something (see the PROBLEMS section), and to give the solar panel I bought something to talk to I added a solar charge controller. At work we use these Genasun controllers all over the planet. Literally. They are a pretty good product. This one was about $75. It's worth it. It can easily handle the 50 watt panel I bought. There's no frills to get fuzzy. There's just a simple LED indicator to tell you what's going on with the battery.
Since the connector on the outside of the trailer was on the wall of the forward port storage area I decided to put the controller in there. I mounted it on an oversized piece of ash that I had with some standoffs under it to allow the air to circulate between it and the board. The board is tall enough to get the controller up off the floor a bit so I can see it more easily. The board is Velcro'd to the front wall of the trailer. The section where the controller is located was covered by a long skinny piece of wood that was as long as the width of the trailer. I cut it so that just the part over the controller could be lifted up so I could take a quick peek at the LED after hooking up the solar panel.
To complete the job I ran fresh 12ga. red/black wire from the controller to the battery and added another little breaker/switch on top of the battery to disconnect the charge controller from the battery. When no solar panel is connected, or it's night, controllers can suck up a little bit of power and eventually drain the battery. Some cheaper controllers can burn up to tens of milliamps or more. These Genasun's are down in the microamps. I still added the breaker. These breakers are stuck to the battery with small squares of tar-like adhesive pads, so they can be removed if the battery needs replacing. It will probably get stolen first, and the breakers with it.