Ok, I'm I hope I can get this question answered here. I have a truck with a 7-pin trailer wiring setup. I tow a horse trailer has lights in the sleeping and tack area. How can I install a battery so I don't run the truck batteries down while camping? I would eventually like to make it so the truck will charge the battery while I'm driving. But for now, I just need the install. Any info will help. TIA!
Maybe I can help: I have a 18' cargo/work trailer which I added three (3) interior lights within when it arrived, then did the ceiling. I put a deep-cycle marine battery up front, behind the tool boxes. The interior lights are powered from this battery, via a switch. You state you have the 7-pin trailer wiring. As far a as I know, with all 7-pin wiring, one wire is HOT (12 V) coming from your vehicle at all times. I use this HOT 12 V wire to charge both my marine battery and my trailer brake emergency break-away battery. IF your unit has electric brakes and built since 2000 (I think), then your break-away battery should be wired so as to be charged from the 7-pin hook-up. SO--do a check on all 7 pins of the vehicle (different brands use different colors) to find the constant HOT wire. Then, find the corresponding connection on your trailer connector, trace this wire (whatever color) and you have the HOT wiring. I use my 12 V system to power my 18 V battery charger going to the jobs, and to power my radio at the job. No radio-no worky. You can install separate switches for each area if needed.I do not use a battery isolator between the truck and trailer, but do between the two truck batteries. I do not leave the unit hooked up overnight-IF I can remember to unplug it, just me. I hope this helps, David