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Truck Camper Battery

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We've owned our Palomino truck camper for about 8 years now and typically get 2-3 years use out of the deep cycle group 24 battery used to run the 3-way fridge, lights, CO2 and propane detector loads. Before our recent trip, I purchased a new battery from WalMart. All was good until about 10 days out when I noted the fridge had turned off. Camper lights barely glowed telling me it was the battery. WalMart did replace the battery and it got us (and food) home.


Right after we bought the camper, I had an outfit (no longer in business) install a battery isolator and heavy gage wires from the 7-way plug into the campers battery connection. In reading some threads on this subject, it sounds like getting sufficient voltage and current from the truck, to adequately recharge the camper battery while in route to destinations, can be challenging.


I'm going to check with my voltmeter today and see what readings I get both on the truck side and camper side with the engine off and running; also with the truck camper refer running and off. If anyone has suggestions on troubleshooting this issue, I'd appreciate the info.




Here's the voltmeter readings:


RV Battery disconnected with no load (12.4V)

+/- posts on Battery Isolator under truck hood with engine idling (15.1V)

Incoming on 7-way pin connector to camper with truck idling (15V)

Incoming +/- wires to RV Battery with truck idling (15V)

RV Battery with leads connected, truck idling and gas detector load (12.4V)

RV Battery with leads connected, truck off and both gas detector and refer on (12.2V)


This suggests that I'm getting ample incoming power from the truck to recharge while driving.

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I have only the most basic understanding of electrical stuff so please take that into consideration before doing anything that I've done.

I had the same problem back years ago when I had a hallmark pop-up slide in camper, and that was that I couldn't get enough amps from the truck to the camper to charge up the battery while I was driving, it would charge up a little but not enough to last me through the night.

So here's what worked for me. I bought a 20 foot jumper cable from Walmart, I think the wire was # 6 size, and I ran that jumper cable wire from the battery isolator [solenoid] in the truck to the camper where I put a large plug that would handle high amps in the wall of the camper. Then I ran the rest of the jumper cable to the camper battery.

So basically what I had was a # 6 cable running from the trucks battery solenoid to the camper battery with a way to disconnect it at the camper. You can use any large wire I just used Walmart jumper cable because it was dirt cheap compared to going out and buying big wire. Also you need a big plug that will pass all those amps I don't think the normal camper plug will do it.

After doing that, when my truck was idling and putting out 14.8 Volts to the truck battery, I was getting the same amount back at the camper battery.


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One of the on-line articles I came across discussed upsizing of the wire to allow more current to flow; so it seems you are onto something here. I think the wiring installed by the outfit who wired the truck isolation switch and connection inside the camper used #8. As noted, I am getting ~15V coming in from the truck's alternator, but maybe the existing wire size is still too restrictive.


I use the 7-way plug I had installed inside the bed of the truck (OEM plug is at the rear bumper) as it is a better arrangement for the outlet on the truck camper. I'm not certain what size the OEM 7-way plug wiring size is as it's all wrapped up -- though I'm guessing it not as large (probably #12?). These are intended to run trailer lights and brakes and may be a bit undersized for battery charging.


Did you just route the #6 wire from your isolation contactor posts, down under the frame, up into the truck camper, and directly to the battery posts?

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There is good reason for the modification made by theboondork to have worked. I have been an electrical tech my entire career so do have some knowledge of electrical work, repairs, and modifications. It is important to understand that wire size has the same effect upon current flow as does the diameter of your water hose on the amount of water that will flow through it. Just as a restrictive sized hose will cause the water pressure to drop in passing through it, the same is true for a small wire causing a loss of driving pressure for the electrical current and that driving pressure is called voltage. That small wire would eventually charge your battery but it might take several days or more with the restriction of current flow and the resulting loss of voltage through it.


When theboondork went to the jumper cables he increased the volume capability of the wire and so eliminated most of the voltage loss. Many of us in the RV world have used welding cables to provide enough capability to carry the amount of current needed.

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Makes sense. The more I'm researching the more I see this to be a shortcoming and issue. It would seem like the RV industry would (should) wire the trailers, campers in such a manner as to be effective. Our final leg of the trip was a solid 8 hours of freeway driving; yet the no load voltage on the battery after that charge time was only 12.4V. I did have the refer on (propane mode) and of course the gas detector is always on when the battery is hooked up... but wouldn't think those would draw that much?


With the current truck/camper wiring choke points, running a straight length of #6 wire from the +/- posts on the isolator sounds like the best option. The current wiring has a fuse in line with the positive line -- I'm thinking it would be smart to include one on the new configuration as well - thoughts?

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Running a straight length of wire should do the trick. Be sure to get flexible wire, like this from Amazon, and not the stiff wire from Home Depot or Lowes. That stiff wire is hard to run through tight spaces.


An easier fix would be to not run the fridge on battery, just run it on propane. The fridge on propane only pulls about 0.3 amps and your gas detector pulls less than 0.1amp.


There are some folks who NEVER run their RV fridge on propane while traveling, then there are lots of folks, like us, who just put the fridge on auto and let it default to propane anytime there isn't shore power.

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Count me among the offenders who run their reefer's while on the road. My Dometic has the auto function and it will use propane if available. I've done this for over 20 years (going back to other RV's) and never had an issue. Thanks for the replies/recommendations; I'll have a look at the flexible heavy gage wire.

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Count me among the offenders who run their reefer's while on the road. My Dometic has the auto function and it will use propane if available. I've done this for over 20 years (going back to other RV's) and never had an issue.

I too operate my refrigerator while traveling and have done so for years. But I have added the ARPrv device to mine just to be sure that things do not overheat.

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