I have a 35AH Gel battery in a box in the back of my truck that is charged by the solar panel on the roof (see my other instructable). It's in a Plano Marine box which can be removed and taken into my tent when camping. I use it to charge my phone and bluetooth speaker or run the 12V fan in the back of the truck when not driving.
Step 1: Wiring
I've installed this charging socket along with a voltmeter and a small switch. I've drawn out how it is wired. It's easy to cut through the plastic toolbox, just carefully score over your line several times with a knife.
I build a tiny wooden platform that slips over the battery and the charge controller is screwed down onto.
Step 2: Finished
I've cut a small viewing hole through the top and just taped it with clear packing tape so I can view the lights on the charge controller, because I've had issues with the connection to the solar panel wiggling loose and then not charging the battery.
I haven't wired the Ammeter up because I don't have a shunt. Might do that in the future.