How to power a 3-way frig while driving?

[Stereo]

I'm new to using a 3-way frig. I'm told it will run down a 12v battery pretty quickly so when we're driving hours on the highway, we've been trying to run the frig off propane. Two problems with this. It's dangerous and the pilot keeps blowing out.

I don't want to invest in a heavy-duty wiring system to charge my house battery while driving, since we rarely need to recharge our battery once we're parked and can safely run the frig off propane. I also don't want to permanently attach a solar panel on the roof to charge the house battery while driving because I'm looking to use portable solar instead.

Is it feasible to power just the frig off the truck battery while driving using lighter gauge wiring? If so, will it continue to work without running down the battery once we slow to a crawl on tough back roads? If there is a way to do this, I would appreciate detailed instructions on how to do it. I'm handy but now well versed in 12v wiring, alternators, etc. My truck does not have a 120v outlet in the cab. The camper, however, does have a pigtail on the outside though of course, that would run to the house battery.

Thank you for your help.

 

[shellbackcva59]

If your truck has the trailer package with a 7 pin plug, you can pick up power from it. Should be enough to power your fridge while on the road, while not depleting your camper battery.

 

[GoinBoardin]

My truck has 10ga wire run to the factory 7 pin trailer of for charging a trailer battery. This wire is only hot when the truck is running, and is fused for 30A. This is part of a decent tow package in my 96 F150. I wired in a trailer plug on my camper using just the + & - terminals of the 7 pin so the battery gets charge from the alternator when the truck is running. My 2 way Dometic fridge states it draws something like 5A. So if starting with a charged battery, the truck charging system should easily keep up with 12v fridge operation.

I used 10ga marine wire, a marine pass through for getting the wire into the camper, a 7 pin trailer plug, 30A circuit breaker, various appropriately sized ring terminals and heat shrink tube. Truck charges the battery when driving now.

 

[Pntyrmvr]

My freezer needs 10 amps so no problem running it off a trailer harness battery feed like you ask.

Running the propane burner on the road is illegal around here.


"Talk is cheap. Whiskey costs money."

 

[Stereo]

Truck lacks a wiring harness

I thought since I didn't include anything about a wiring harness in the truck, it would be understood that it does not have one, but I was wrong. Sorry. I don't have the towing package or even just a wiring harness (though I do have the pigtail on the camper). Thank you, though, for all your answers as they did include important info. Just not the details I need. I need to know how to wire my truck to pass power to camper, or even just the frig directly. Can the connection be just battery to battery or does it involve the alternator? Do I need to include switches? How big of considering I'm only powering the frig?

 

[shellbackcva59]

You can wire direct from your battery, but do use a fuse or circuit breaker at the battery. Here's a good connector to use between the camper and the truck. https://www.amazon.com/Anderson-2-1...r=8-14&keywords=anderson+power+pole+connector
If you do connect straight from the battery, keep in mind that it could draw down your truck battery if not disconnected after parking the rig.

 

[Stereo]

Wire gauge?

You can wire direct from your battery, but do use a fuse or circuit breaker at the battery. Here's a good connector to use between the camper and the truck. https://www.amazon.com/Anderson-2-1...r=8-14&keywords=anderson+power+pole+connector
If you do connect straight from the battery, keep in mind that it could draw down your truck battery if not disconnected after parking the rig.

Thank you for the suggestions. What wire size? Is 12 OK? Or should I go with 10? From past readings, people have suggested 8 but I wonder if that's overkill for this use.

 

[mkish]

If you want to run on propane, you can find instructions for building a wind shield for the flame on most popup trailer sites, along with baffle plans and whatnot for getting the most from your fridge. They seem to have the same problems.

 

[shellbackcva59]

Thank you for the suggestions. What wire size? Is 12 OK? Or should I go with 10? From past readings, people have suggested 8 but I wonder if that's overkill for this use.

12 is okay to run the fridge. If you happen to deplete your camper battery and wanted to fast charge it off the truck, maybe 10 would be better.

 

[dwh]

Is it feasible to power just the frig off the truck battery while driving using lighter gauge wiring?

Sure. If the engine is running it'll just be running off the alternator anyway.

That BTW, is as designed. Three-ways aren't intended to actually run off batteries. The 12v is for driving with the propane turned off. (You do close the main valve on the propane tank before driving right? The way the law requires just about everywhere? )

If so, will it continue to work without running down the battery once we slow to a crawl on tough back roads?

Alternator output is based on RPM, not speed. Crawling in low gear usually keeps the RPMs up. But even at idle, it's unlikely the voltage will drop lpw enough to drain the battery at all.

If there is a way to do this, I would appreciate detailed instructions on how to do it. I'm handy but now well versed in 12v wiring, alternators, etc. My truck does not have a 120v outlet in the cab. The camper, however, does have a pigtail on the outside though of course, that would run to the house battery.

Thank you for your help.

You should just do it right.

http://forum.expeditionportal.com/t...ke-a-cheap-isolated-dual-battery-setup-for-50



HOWEVER...

You could use exactly the same setup to automatically turn on/off the power to the fridge when the engine is running. Just use smaller wire.

But if you are going to do that anyway, it would make sense to just use larger wire and again...do it right.

 

[dwh]

And BTW, unless I missed it, you still haven't told us which fridge you have.

 

[Stereo]

You're right. I shouldn't cut corners. The frig is a stock Dometic RM2193 which pulls 9.6 amps on 12v, 1.03 amps on 112v. Thank you for the link. That looks familiar. I remember looking at that a few years back when I first had my Skamper with no frig. I decided then I didn't need it due to our low power needs. Now we've got a frig and a fan in the vent that need to be fed.

 

[dwh]

"IMPORTANT: To prevent the refrigerator from being left on and draining the battery when the vehicle's engine is not running and charging the battery, it is recommended that an automatic cutout relay be installed between the battery and the refrigerator toggle switch so that the refrigerator will not draw current when the vehicle ignition is switched off."

http://bryantrv.com/docs2/docs/rm2193.pdf


Well. If you've got a house battery in the camper, you probably should do the evldave $50 split-charge relay just on GP.

But if you do, and run the fridge from the house battery, you'll still have to remember to switch off the 12v on the fridge manually when you fire up the propane. On the plus side, it would be the house battery, not the truck battery, that would get drained if you forgot.


Rigging an auto-disconnect just for the fridge as they recommend doesn't add much complexity, but it would add some. I doubt you really need it. Of course, if you were wiring the fridge to the engine battery instead of the house battery (w/isolator), I'd say you certainly should auto-disconnect the fridge when the engine is off.

 

[craig333]

Or if driving with propane doesn' t bother you theres always http://www.wanderthewest.com/forum/...-propane-refrigerators/?hl=+fridge +relighter

 

[Stereo]

Or if driving with propane doesn' t bother you theres always http://www.wanderthewest.com/forum/...-propane-refrigerators/?hl=+fridge +relighter

Thanks for the link. I'm glad to read that the gas valve is shut off as it cools. I was wondering, though I assumed there had to be a safety valve. The recommended device seems like a good idea even just in case of wind blow-out while parked.

There's also some additional information in the thread about the need to get the frig level. Last year, I asked Northstar how level the frig needed to be, and they suggested half a bubble. It can be tough to achieve that in the backcountry, but it also makes for a more comfortable night in bed.