Rewired the Refrigerator Circuit
 

As most of you know, when traveling and running the refrigerator on 12 volts, when you stop for a time you either have to turn the refrigerator off or deal with it running down the camper battery. I rewired mine so when I turn off the truck it also cuts power to the refrigerator, but it will also charge the camper battery on the road. I used a single pole double throw center off 12 volt 30 amp switch and a 30 amp 5 pin relay (really only needed a 4 pin) Not charging the camper battery would eliminate the relay. To wire I needed to cut the 12 volt wiring going to the refrigerator and add a wire to the black wire on the pigtail from the vehicle and run it into the refrigerator compartment. After cutting the refrigerator wire I added female connectors to all 3 ends. The one from the refrigerator goes on the middle of the switch and the other 2 go on the ends. The relay gets wired with solenoid positive wire going to the wire coming from the pigtail (that I added and is energized only when the key is on) and naturally the negative goes to ground. The other 2 wires from the relay go on either end of the switch with the other wires. Now while going down the road I throw the switch to travel mode and the camper battery charges and the refrigerator works. I turn the vehicle key off and it cuts power to the refrigerator and the relay so it doesn't keep the refrigerator running draining the camper battery. When I get to the campground I open the cover for the refrigerator and set the switch to camping mode and it works normally.

Refrigerator rewire
 

Thanks for taking the time to post a description and the posting of pictures.

Neat idea! Looks like you put that switch behind the fridge? I'm guessing you have an easy way to get to it. (I'd have to take off an outside panel to get to one mounted behind mine.)

- Jack

On one of my previous tow vehicles I added a battery relay to the charging line it would automatically switch the power off when the engine was not running. It served the same purpose, without having to remember anything.

Wrong, because as soon as you turned off the key, the battery in the camper was drawn down by the refrigerator. I'm sorry Norton Rider I was not talking about the vehicle battery, I'm talking about the camper battery. I edited my post so people know which battery I was talking about.

Yes I have to take off the outside panel, takes less than a minute but worth it to me to keep the camper battery full while traveling especially on long trips, say from Pa to Outer Banks NC

Jack, you got me thinking I could do the same thing with 2-5 terminal relays with a simple on off switch mounted in the camper. I just may do that :D

I should think you'd be able to mount your current switch just about anywhere with longer wires to it. Am I missing something?

- Jack

The only problem with doing that is more voltage drop thru the wires, especially since your looking at adding at least another 10' or more of wire where as using another relay no extra voltage drop at all.

There isn't any additional voltage drop because I did not add any more wire than I already had for the power (charging) circuit that goes to the trailer connector on the truck. In other words, the voltage drop would have been the same, relay or no relay. I towed in this manner for 10 years and always had fully charged batteries and cold food when I got to my destination.

Norton, that statement was not meant for you. I agree you wouldn't add any more wire using a relay in the tow vehicle. Been there done that. I would have to if I wanted to move the switch from the refrigerator compartment into the kitchen area. I have a question for you thou. Say you stop for 3-4 hours on a trip, how do you keep your camper battery from discharging during that time. Do you turn the refrigerator off or just let it run. Leaving it run will use up over 24 amps in 3 hours or 32 amps in 4 hours out of the camper battery. Using a normal group 24 battery with approx 80 amp hours total and being able to use only 40 amp hours (don't draw battery below 50%) that doesn't leave much juice for camping, unless you have an electric site or drive for who knows how many hours to recharge the camper battery even thou you will still be using 8 amps for the refrigerator so what kind of a charge would be going back into the camper battery. BTW I know the amp draw on a 12 volt refrigerator because I just checked it. Looks like we will have to agree to disagree. :)

Maybe I'm not explaining myself well.

The way I wired the tow vehicle with a relay resulted in power going to the batteries only when the TV engine (and alternator) was running. At a stop the refrigerator would continue running from the battery and the batteries would not be charged. Once I got going again the batteries started getting charged again. Regardless of the calculations, I never had a problem in 10 years of camping with two group 24 batteries. I never paid attention to the % draw-down on the batteries either. I just checked them periodically for electrolyte specific gravity; I periodically load tested them as well. I think I got 3-4 years or so from each set. This was all with 90% dry camping, no power, water, etc.

I think that you should also look at your load assumptions. A refrigerator will not run constantly; so the draw should not be multiplied by the amount of time that one is stopped. Moreover, I always pre-cool the refrigerator on 110V overnight, prior to leaving on a trip. I also load it with food and drinks that are already cold. This minimizes the amount of time the refrigerator needs to run on 12V.

When you stop for a while either shut off the DC mode, things will stay cold for a while, or if are going to be away for a while to tour a cave or something run the top up and light the gas mode. We have done this many times.

True I did not take into account the possibility of the thermostat being met as far as temp, but even at 50% draw that's losing a lot of amps. The only difference between your way and my way is I took the camper batteries out of the loop when stopped.

MY 2209 also has 2 batteries and if I am going to stop longer than a half hour, I raise the top which you are supposed to do anyway and I just switch to the gas mod. With 3 batteries connected, I have never had a problem.