Wiring Vintage Lights Fixtures for 12v and 110v

Okay, a big decision has been made. I AM going to wire the trailer with almost everything running off 12 volts dc, everything except the four new receptacles I am installing. I am installing a power center with a built-in converter (Progressive Dynamics Mighty Mini) so that when I'm in camp with hookups and I can plug into shore power, everything will run off 110. Since I am not installing a fridge, I don't have any appliances, and I won't be running a toaster or anything like that when I'm boondocking.

Whew! That took a lot of brain damage to figure out, but I think I'm going to be happy. I'm going to install the power center under the street side dinette and camouflage it behind a vented screen to look like the original slider that was there. I'll post pics when I'm done.

Wish me luck!! Like I said before, I'm way more confident in my mechanical skills (carpentry, etc). Electrical makes me nervous!

One of the posters mentioned that 12 volt uses multi-strand (twisted) wire and 120 volt uses solid wire. I'm new to trailers and this surprised me. I had a boat for years and you were never supposed to use solid wire for 120 volt as it is considered dangerous due to vibration and the potential for the wire to break. On boats, you are supposed to use multis-trand for 120 volt. What is the case for trailers - solid wire or multi-strand for 120 volt?

Yep, you can simply use the existing 120v wiring (my original wire is multi-strand) for 12v power by running off a deep cycle 12v battery (often used in boats) that are designed to be discharged to a lower point than normal batteries and yet take many recharges. You can buy a good converter charger for under $100 that will take shore power (120v), send it to the converter (to 12v)/charger, then to the battery. Make sure you have EVERYTHING on fuses or circuit breakers (search for my post on "almost burned my camper!"). Then, simply replace your bulbs with 12v LEDs, either ones that fit traditional incandescent fixtures, or new and often compact  but bright new fixtures. Google a company named Superbriteled, or something like that. They sell corn cob style bulbs which give 360 degree lighting to mimic incandescent bulbs. Go for warm color bulbs. A 40 watt or 60 watt equivalent uses only about 3 watts. While you are doing all this, install a Fantastic Fan to replace the old roof vent. Again it uses only about 3 watts of power. With this setup, you can boondock for days. And when you are connected to shore power, you are charging the battery.

Yes, you can do this. First, DISCONNECT ALL SHORE AND BATTERY POWER. On my simple little camper I only had 4 different light fixtures. Everything was on one circuit and terminated in a fuse box. The shore power (120v) came into the fuse box, at which point two wires were connected. Those two wires connected with other "home run" wires that ran through the walls and ceiling to the four light fixtures.

I removed the fuse box leaving the two wires bare (positive and negative). Running from the shore power, I ran new wire to a new circuit breaker box; from there to a 120v outlet; from there to a charger/converter (which turned it to 12v); from there to a deep cycle battery; from there to a fuse block using new wire for the 12 volt circuits; and finally, from there to my two circuits (one as new wiring to a Fantastic Fan, and the other circuit back to the original two wires that came out of the original fuse box, which ran to the 4 lights).

However, BEFORE YOU HOOK UP TO THOSE WIRES, TEST FOR ELECTRICAL SHORTS in the existing wiring. You do this by using a continuity tester, which is an inexpensive tool with a short wire on one end, a probe on the other end, and a battery powered lightbulb and/or buzzer in the middle  You can attach a long single thin gauge wire to the wire end of the tester to reach anywhere in the camper from the original two wires that came from the original fuse box. I removed the four fixtures baring the wires and labeled them as I went with masking tape and letter codes. Then, one at a time, I wire-nutted my tester wire to the two original fuse box located wires and proceeded to touch the tester probe to each pair of bare wires at the fixture points. If each of those two wires are good and safe, you should get the light to turn on for only one wire at at time. The other wire should produce a light (continuity) when you switch the tester to the other fuse located wire. Do this systematically for each of the fixtures.

On my system, I found that when testing, BOTH wires lit up on one particular fixture. That meant I had a short. Turned out that the original wires had been mixed up when several wires from the lights were joined at the home run near the fuse box. Simply untwisting and connecting to the proper wire (one of two) fixed the problem.

Of course, I learned all this the hard way. I did not continuity test first. I did not use a fuse block between the battery and my 12 volt circuits. When I did hook my battery I created an un-resisted circuit sending 12v DC through my new 12v wire to the shorted wire and back to the battery.  Another name for that is FILAMENT. It took about 15 seconds to heat up the wires and melt the insulation. Fortunately for me, the short was right at the junction of the original termination wires and the heated wires were limited to those exposed ones I just installed.  Had the short been inside the walls or ceiling, I would have at best had to remove the aluminum skins to rewire. I could have burned down my camper.

I know that wiring can get much more complicated on some campers. Ours is quite simple with just those lights. But now, everything runs off the battery with very low wattage because we use LED lights.  The fridge runs off propane. We can easily boondock, probably for at least a week before needing any charging. My next camper will undoubtedly become more complicated, but I will always plan a system to do this.  And, when you ARE plugged in to 120v shore power, you are still running off 12v, but you are charging the battery at the same time, AND that 120v outlet or two you added on the way to the charger is giving you line voltage.  We like that in colder weather we can run a small space heater or charge our cell phones and tablets. I'm thinking I will add a 12v circuit to a cigar lighter so I can plug in a car charger for those devices.

BTW, I never figured out or got an explanation of why my lights worked before I converted to the 12 volt system. That short was always there.

Drake,

Yes, I am suffering from the heartbreaking Packer loss yesterday.

So, I have some pics for you. You should be able to see the layout as well as the model numbers of the battery and converter/charger. I did quite a bit of research on the Iota converter and ended up buying it from some boat supply place in Ohio. Works like a charm. Took the pics with lights on, running off battery that has not been plugged in to recharge all winter.

Note that the red device is a cheap Inverter from Harbor Freight that makes so much fan noise that I don't use it. I disconnected the wire from it to the blue outlet box because the noise makes it unbearable. I was hoping to use that box as a source of 120v so I could plug in our phone and tablet chargers. I intend to scrap the inverter and just run a 12v cigar lighter plug or something else to plug the device charger cords into.

Also note that the silver box is a 120v line that comes from shore power (through another electrical box wired for 120 volts), which then goes directly to the converter/charger, and from there to the battery. Note the small fuse block with auto tube fuses that is screwed to the floor. Also note that the battery is not bolted down, but rather just sits in a fairly shallow plywood box that is fastened to the floor. I wanted to be able to remove the battery easily if needed (I haven't so far). I figured if that heavy battery ever was forced out of that box, I'd have bigger things to worry about.

The last pic shows a voltage tester that I've yet to take out of the package.