Traveling with Fridge on 12V?

[Byron Kinnaman]

Originally Posted by ehoepner

I always travel with the Frig on 12v dc. It keeps the Frig cool and I have no problem with Trailer battery discharge.

The problem people have when the trailer battery is discharged is related to the size of the wiring on their tow vehicle. Their tow vehicle wiring is to small for the number of amps the Frig pulls. Because the wiring is to small the wiring restricts the flow of electricity. Therefore the trailer battery is discharged because it is making up the difference in what is supplied by the tow vehicle and the requirements of the Frig.

Wiring sizes should be 10 gage, 12 gage is very marginal. 14 gage drains the trailer battery.

WOW!! You mean the size of alternator has nothing to with it? My fridge draws about 9amps on battery. AWG 14 is rated for 15 amps, AWG 12 is rated for 20 amps, and AWG 10 is rated for 30 amps. So the wire size makes a difference when ??

[ehoepner]

You also have to take into consideration the length of the wire as well as the number of volts. Yes you can get 20 amps through a 12 gage wire at 100 feet using 120v.

My Frig pulls 7 amps after it reaches set point, 9 amps during cool down.

[sokhapkin]

Originally Posted by Byron Kinnaman

WOW!! You mean the size of alternator has nothing to with it? My fridge draws about 9amps on battery. AWG 14 is rated for 15 amps, AWG 12 is rated for 20 amps, and AWG 10 is rated for 30 amps. So the wire size makes a difference when ??

Absolutely. The wire amperage rating means how much HEAT is acceptable by the wire due to the amperage. But to run a fridge on 12 v and charge the trailer battery another parameter comes to play - what is voltage drop on the wire size XXX at YYY amperes when the wire length is ZZZ ft? That's why AWG 10 (or even better) is a must.

Edit: Just an examle: I bult a 12V socket extender cable using 10' AWG12 wire (2 wires). I measured about 0.5V voltage drop at ~3A current when I connected 12V compressor fridge to it.

[Byron Kinnaman]

Originally Posted by sokhapkin

Absolutely. The wire amperage rating means how much HEAT is acceptable by the wire due to the amperage. But to run a fridge on 12 v and charge the trailer battery another parameter comes to play - what is voltage drop on the wire size XXX at YYY amperes when the wire length is ZZZ ft? That's why AWG 10 (or even better) is a must.

Edit: Just an examle: I bult a 12V socket extender cable using 10' AWG12 wire (2 wires). I measured about 0.5V voltage drop at ~3A current when I connected 12V compressor fridge to it.

Amps = amps no matter the size of the wire. As indicated above you with a smaller wire you may have larger voltage drop, that will always be the case even when comparing a 0000awg wire to 10awg wire, but amps is still amps. It don'[t change. Power might change not amps.


Besides all that the size the alternator has more to do with it. My truck at an idle requires north of 100amps with out AC running. I have a 150 amp alternator, I think I can keep up. But I don't see any reason to attempt to. I simply turn off the fridge when moving. Turn it back on when parked at home or in a campsite. FYI I keep my fridge running 24/7 when parked at home or in a campsite. At home on 120 at a campsite on propane.

[thrifty bill]

Originally Posted by ehoepner

I always travel with the Frig on 12v dc. It keeps the Frig cool and I have no problem with Trailer battery discharge.

The problem people have when the trailer battery is discharged is related to the size of the wiring on their tow vehicle. Their tow vehicle wiring is to small for the number of amps the Frig pulls. Because the wiring is to small the wiring restricts the flow of electricity. Therefore the trailer battery is discharged because it is making up the difference in what is supplied by the tow vehicle and the requirements of the Frig.

Wiring sizes should be 10 gage, 12 gage is very marginal. 14 gage drains the trailer battery.

All good recommendations here, but I highly doubt factory 7 pin wiring is 10 gauge. So it means rewiring that portion of the circuit. Not a huge job, but its still something you have to do.

As to the earlier comment on battery voltage, it you draw it down to 12.0 Volts, you are running a good chance of over-drawing the battery.

[Mollie]

You're camping ... food safe is nowhere to be found and the 5 second rule turns into a 30 minute rule.... I would use coolers with ice for transport.

[sokhapkin]

Originally Posted by Byron Kinnaman

Amps = amps no matter the size of the wire. As indicated above you with a smaller wire you may have larger voltage drop, that will always be the case even when comparing a 0000awg wire to 10awg wire, but amps is still amps. It don'[t change. Power might change not amps.

Correct. But keep in mind that fridge needs amps to stay cool, but the trailer battery needs VOLTAGE from the TV to be more than 12.6V to not discharge because of the fridge amperage draw.

[Mr Lynn]

Originally Posted by Byron Kinnaman

. . . FYI I keep my fridge running 24/7 when parked at home or in a campsite. At home on 120 at a campsite on propane.

Any reason to keep your trailer fridge running at home, unless of course you need extra fridge space? Our kitchen fridge is generally large enough, even when the kids and grandkids are here.

/Mr Lynn

[Sunrisetrucker]

When I read threads like this one which talk about 12vdc, 120vac, converters, inverters, amperage draw, 10 gauge wire, 12 gauge wire, 14 gauge wire, length of wire, replacing wire, voltage drop, depleting the battery, alternator output, twin 6 volt batteries and solar-panel supplementation, I get a headache.
It makes me so happy to run my fridge on propane. Simple, safe and no headaches!

[Mr Lynn]

So what do you all-electric folks (ParkLiner, Lil Snoozy, Egg Camper, etc.) do?

/Mr Lynn

[ehoepner]

This all comes down to a very simple mathematical formula.

The wiring you purchase in the store is rated at 120v AC. Amp flow is much lower when the working voltage is 12.6 volts.

[charlsara]

Originally Posted by Mr Lynn

So what do you all-electric folks (ParkLiner, Lil Snoozy, Egg Camper, etc.) do?



/Mr Lynn

We have a Truckfridge in our lil Snoozy. It is a very efficient compresser fridge. When we ran a Group 24 battery it had no problem running the fridge all day. With the present 2x6 volt batteries we have no problem going three days without a recharge. My wife has to keep insulin. A fridge we can run during travel is essential for us. The factory added a charge wire for us but the wire size (14) is to small to do much good.

[Civilguy]

I believe Cousin Lynn has the same Dometic RM2454 refrigerator as we have in our 2012. The manual notes:

"5.1 DC Heating Element

Remove the heater leads from the lower circuit board or relay and measure for proper resistance across the two leads. You should obtain the following readings ± 10%:

175 watts, 15.0 amps at 12 volts, .80 ohms.

NOTE: The DC mode is a holding mode not a full cooling mode. DC should be used once the unit is cooled down on gas or AC and driving (constant supply of DC) down the road. A continuity reading will indicate an open or complete circuit. Never over or under size the DC heater."

I don't recall the part about the refrigerator being in a "holding mode" on DC operation. Somehow, even when we come back to the same subjects, I think I keep picking up a little more each time. At least I hope so!

[Radar1]

All this talk about how many volts and amps the fridge needs on DC makes me wonder what's happening to the tow vehicle battery all this time. Is it being overcharged, or does the system automatically cut back the amps from the alternator so the tow vehicle battery is not overcharged, which then means the trailer is also then getting reduced amps?

[Snoopwagon]

Have 2002 17 ft SD 120 AH agm batt we run on 12 v traveling but turn fridge down to 2 after cooling at higher setting plugged in at house night before leaving 😊hope this helps!

[Radar1]

Originally Posted by Byron Kinnaman

WOW!! You mean the size of alternator has nothing to with it? My fridge draws about 9amps on battery. AWG 14 is rated for 15 amps, AWG 12 is rated for 20 amps, and AWG 10 is rated for 30 amps. So the wire size makes a difference when ??

I don't know, but our Dometic fridge manual seems to think wire size is important. Assuming 15 ft to 7 pin from alternator, and that the wiring to our fridge goes all the way around to the back of the camper and then back up the other side, we would be close to the 40' AWG 8 limit (others have even a lower length limit). We don't have a 12 volt fridge so not important in our case.

[Radar1]

Originally Posted by hwdornbush

We added an inverter so that we could convert 12vdc to 120vac and it worked fine. Our tow vehicle, Jeep Grand Cherokee, puts out enough current to keep the battery charged. I prefer to NOT have propane on while driving. This seems to be a comfort thing but I like the safety factor of not having one more inflammable thing while traveling.

Hadn't thought of that idea. Sounds good to me! Do you have a dedicated inverter that the fridge plugs into? If so, do you switch back to shore power on the fridge when you camp or just keep running it off the inverter while the shore power charges the battery?
I suspect an inverter that supplies at least 200 continuous watts is all you would need for the fridge on 110 volts, correct?

[Jann Todd]

Originally Posted by Gerry

I too use the propane while on the road but I thought I did read somewhere at some time that this was ill-eagle ???
Any knowledge of this?

It is not illegal to run your fridge on propane in any states that I know of or in Canada. The only place you can't have it on is in ferries and some tunnels.

[Jann Todd]

Originally Posted by Radar1

All this talk about how many volts and amps the fridge needs on DC makes me wonder what's happening to the tow vehicle battery all this time. Is it being overcharged, or does the system automatically cut back the amps from the alternator so the tow vehicle battery is not overcharged, which then means the trailer is also then getting reduced amps?

Your vehicle battery should be isolated from your trailer battery. This prevents draining of the vehicle battery. The way I was told it works is when the vehicle battery is charged fully then the trailer battery is charged also while driving. I would not have 2 batteries without an isolater. Isolaters can be very cheap or very expensive depending on what you put in. We had a cheap one in a camper van and one in our truck when we had a fifth wheel. The cheap ones are just little silver canister looking things with 3 places to hook wires. Last one was about $20.00 or so. It is also a safety so that if you get a short in your wiring it won't affect the trailer and tow vehicle. My isolater saved my truck wiring once when the camper on my truck shorted out.

[Jann Todd]

Originally Posted by Mr Lynn

I know this has been much discussed, but I'm still puzzled. *For short runs I usually just turn off the fridge, which stays cold for an hour or two. *Then in state parks without shore power, we run the fridge on propane.
*
We're heading on a two day trip Sunday. *I know some run their fridges on propane on the road, but I'm nervous about it, and would prefer to use 12V. *The issue seems to be whether the fridge will draw too much current and discharge the trailer battery, apparently because the tow vehicle can't keep up with the need. *Is this really likely? *And is there a cutoff in the fridge that will shut it off if the incoming voltage is too low?
*
We have a 2013 Ford Expedition with factory towing package, and a 2013 Casita SD 17.
*
/Mr Lynn*

We run our fridge on 12V when driving. It has not run the battery down as long as you are charging the battery while driving. Just don't leave it on 12V if you stop for a while doing something fun. We also have used a fridge on propane for over 35 years with no problems. I just don't think it is good to turn them off for very long and expect them to refreeze and get cold in a hurry. Just remember to turn off the fridge when fueling up if you run on propane because of the fumes from the gas. That's why we use 12V when towing. We also have a 17' Casita that is a 2007.