Simulated 12V vehicle feed...
 

Hi All, I'd like to chase down a little potential problem.

I've been told that my 24'er has a history of letting the battery drop down to unusable levels during towing if the refridgerator is left on. My experience suggests this, at least, is possible. I'd like to chase the problem by simulating a vehicle hook-up without actually having the Tundra hooked and running for several hours.

So my plan is to get a suitable connector, and feed the trailer 12V just like a tow vehicle would. My question is - 12V at what amperage? I know it's weak, and probably weaker than a trickle charger?

Thanks for any help here. I may just find out that it's acting normally and I need a new battery and that it needs to start off well-charged. But verifying its operation before I put a lot of highways miles on it would be very nice.

I appreciate any thoughts/comments as always.

The problem with running fridges on 12v while traveling is the battery gets drained. This is a problem with all trailers, not just yours. The charging circuit from the tow vehicle to the 7 pin connector is not big enough. By that I mean the wiring. The factory wiring in not heavy enough to sustain the fridge. I would suggest running a new 8 gauge wire with fuse to the 7 pin connector. Some trucks, even with the tow package, do not have a relay and/or fuse in the fuse box under the hood for the 12v charging circuit. I know Ford includes them but places them in a plastic bag in the glove box. You will get more info on this if you use the search feature and type in refrigerators on 12v. There are quite a few posts listed on this subject. Hope this helps.

Bob

135 amp vehicle alternator with vehicle battery and other components already pulling amperage off it. long thin wire runs to trailer battery. Don't expect that 135 amps to make it to the trailer. A battery charger of 30 amps might simulate reality, or maybe lower. Don't try to run the fridge on DC power unless you have extensive solar, a running DC generator or hold stock in a battery company.
RV batteries are made to be run down, the starting battery that comes stock in these HILOs is not. One depletion will harm it, another will ruin it. Consider a dedicated battery bank just for the camper functions and leave the stock battery only for lifting.
Most people just keep the fridge on propane running down the highway. Yes, potential dangers. Deal with it.

Thanks for the input. I’ve been told a few wrong things about the trailer it seems, one of them is whether to expect the fridge to run off the 12V unmodified tow vehicle feed.

The fridge will run fine off the battery (provided you have a fridge that has an option to run off DC power), as long as the battery holds a charge, which will not be for long, and the trickle of DC power coming from the tow vehicle will not be enough at all to power anything. At best it will prolong the runtime for a few minutes. The tow vehicle is doing goo to just top off a slightly depleted battery. It needs hours to charge back.
You will kill the lift battery. You will have to manual lift the HILO. You will not have power to run the camper if battery is dead unless you plug in to shore line power and use converter.
A cold and loaded fridge will keep cold for hours. If a short 2-4 hr trip, just let the fridge be off.
Consider adding dedicated batteries.

Same problem with my 24' 2002. After several failed lifting experiences after towing the camper with the fridge on DC, I just don't use it on DC power anymore. We freeze some milk, ice tea and orange juice, put those in the fridge along with freezer packed with frozen food and use the fridge like an ice chest during the 6 hour trip to our favorite dry camping spot. It works fine for us. With a second battery and some conservation of electricity we are able to dry camp for more than 2 weeks at a time.

My HILO doesn't have a manual method to lift or lower the top.

I modified the battery box which is dropped down several inches so that it can be opened with the top down to allow emergency charging of the batteries. I cannot lift the top with jumper cables, so it's really a matter of waiting. Trying to use the 3-way frig with DC would not be a good idea.

Using the frig while moving can lead to coking around the heated tubing. The frig should be ideally level in use. I have found that the frig will stay cold enough during travel days as long as it was cold overnight. My freezer will get cold enough to ice a half gallon milk container, so that is used to help keep the frig cold. The fuller the refrigerator, the better as well.

I also have two batteries in my battery box with the crossover wire between the two under the wingnut posts so that I can separate the batteries in cases where I think that I may be without power for enough time to deplete a battery. That way, I always have power to close the top. Ideally you should never run the battery down past 12.1 volts or damage to the battery may result. There is a lot to read about batteries, so these are just the simpler aspects.

Even if you have suitable wiring from the truck to the trailer, you would likely still need an alternator upgrade. Solar is a great option, with panels easily topping 300w per panel. The frig probably uses 100-300 watts depending on what it's doing. It's not a simple matter of mounting a panel, however, as you''ll need a charge controller and some knowledge.

When we had our 1999 21T we tried to run the fridge on DC while in transit and always ended up with a dead battery at the next stop. Same thing happened when we got the 2005 27T. However, after changing the truck wiring to a heavier gauge we have not had any problems towing with the fridge pulling DC. Southern California to Alberta went without any problems and this past year Southern California to Massachusetts was done without any problems. And yes, we have dual batteries.:)

I appreciate the discussion and ideas here folks. Thanks as always.

Let me follow up with a second dumb question (it’s been a good day for these, earlier this afternoon the question was ‘how do I get the burned-out license plate lights out of the wagon?!?) ...

Under what conditions would one want to use the 12V supply for the fridge? Not while towing (without proper upgrades to wiring, additional battery etc), and not while plugged into shore power - why not just use the AC option?

What am I missing here?

r67, When hooked to shore power, of course switch to AC. I went to amazon an bought a 254 amp alt ($88) new, not rebuilt, for my Escalade. Added 10 gauge wire from the batt to a marine circuit breaker (very easy reset) mounted near the batt. From there to the 7 pin plug. That was the hard part. I separated the plug apart, pulled the existing pin and wire free of the plug. Spread the little wings apart, installed the heavier wire, soldered (snipped the old wire) and put it all back together. Worked from FL to Branson, MO and back, no problems. Well worth the bucks, if your gonna keep your Hi Lo. I know I could have purchased a new plug with the screws, but I've heard they leak pretty quick.

Thanks Tree - those are good details. Some of my struggles are sorting through what the previous owners told me and I’m find that they aren’t always accurate. I’ll add this mod to my list of things to do since I think the HiLo should get more and more use as the years roll on even though the start has been slow.

So in general, it seems like unless you do some upgrading to the system, you would almost never choose to have the fridge on DC except for a brief period of travel with a battery in decent shape. Of course, as many on the list mentioned, keeping some ice in it makes that uncessary.

Thanks again all

I don't understand your "why not AC option?". When plugged to shore use AC. When we travel, the frig is off. We have two Tupperware containers with solid ice in the box. Also, two ice cube trays in freezer. Temp rises from low 40s a couple of degrees during trip to next stop.

Sorry Jon - bad job on my part of saying what I had in mind. I just meant that when one is plugged into AC then obviously one should use the AC. And when not plugged in, keep cold stuff in like you suggested without using the DC between stopovers.

As far as using ice, dry ice is the way to go. It will keep for days and not “drip melt” like regular ice. Just don’t touch it with your bare hands.

Bob