Fridge on 12 volts

**pmhellings** · 07-01-2017, 11:30 AM

I chose to start a new thread on this as the last one was 3 months old. In discussions of how to power your fridge while towing, there seem to be a few different schools of thought:
Cool down prior to leaving on shore power then
(a) switch to 12v and then close the camper
(b) unplug from shore power and expect the fridge to stay cold from its contents
(c) switch to propane with the fan on.

Jason Yuhas ( Sopper ) posted
"The way I do is to pack the camper the night before and leave the fridge set to 12V. I leave the camper plugged in to shore power and it overrides the 12V setting"

Is that how it works? I would like to close my camper up the evening before, with the fridge on 12v while on shore power. My thoughts were that the converter would power the fridge on 12v so that I would not run the batteries down. Is Jason correct that the shore power connection would "override" the 12v and that when shore power was disconnected the fridge would automatically change over to 12v?

I have 200 watts of solar and hoped that between the trickle from the TV and the solar panels that the fridge would stay cold without discharging the batteries.

I would prefer not to use propane while towing, even though many people do without incident.

Thoughts?

Paul

**Lesherp** · 07-01-2017, 01:22 PM

I have gone to switching to 12V and closing down the night before with TM plugged in. I am not sure how effective this is as I have never checked the battery to see if this keeps them at full charge. I think I will try this the day before I close down and check. If anyone knows if charging system keeps the battery charged while fridge is on 12V please post.

I was disappointed to discover my 150V solar and TV (with tow package) cannot keep up with the drain on the batteries when traveling using the fridge on 12V and the fan. The batteries are always discharges to some degree. My batteries are in the back so it is a long ways from my TV and that may be a factor. I think I will test to see what the deficit is when I have the fridge running with the fan and only solar as it would be easy to do while setting up.

I have seen discussion about running on propane but am not sure people are doing it. I am one to weigh risk against consequences. The risk may be low but I don’t want to look in the rear view mirror to see the TM on fire.

I have considered running 10ga wire as some have done but am reluctant to rewire the truck. Anyone know how much improvement there might be by just doing it to the TM?

Logman · 07-01-2017, 02:04 PM

I have 200w solar , flat on the roof that charges the batts as long as there is light. I run fridge on propane the day before leaving , then in the am close the camper & switch to 12V and fan as I prepare to leave. I have 2 12V parallel bats and always have working freezer and plenty of batts after an 8-10 hr drive. I ditched my microwave, haven't used AC and haven't started my genny since the solar install. I switch back to propane fridge soon after setup each nite. I almost never have hookups when camping.

**pmhellings** · 07-01-2017, 07:43 PM

Good to hear. I have 200 watts of solar as well and two 12v batteries in parallel like you.

Too late to do it for my upcoming trip, but I think I'll go heavier gauge wire for the next time around.

Paul

**Bill** · 07-01-2017, 09:15 PM

Quote:

Originally Posted by Lesherp

I have considered running 10ga wire as some have done but am reluctant to rewire the truck. Anyone know how much improvement there might be by just doing it to the TM?

Roger -

The TM is already wired with 10 gauge wire. In the case of my Ford Explorers, it was the tow vehicle that was inadequate. I got a copy of the Explorer wiring book on eBay, and found that there were half a dozen connectors between the alternator and the Bargman connector. Each one introduces resistance, of course. Worse yet, some of the runs between the connectors were wired with #12 (and one with #14!) wire.

As soon as I ran a parallel pair of #10 wires through the truck, the problem went away.

Bill

tentcamper · 07-01-2017, 09:27 PM

We do the run on 120V until we are ready to leave. Switch to 12V and close the camper. Some times we just turn it off if cool outside or short trip. I have made some wiring changes so I can switch off the battery and power the fridge only from the TV if headed out for dry camping.

Jason is that the way it works ""The way I do is to pack the camper the night before and leave the fridge set to 12V. I leave the camper plugged in to shore power and it overrides the 12V setting"

Not sure if the norcold is this way, but I think it is. I do know the dometic fridig I had with another camper. The 120V heating element went. Both the 120V and the 12V heating elements had labels on the wires with there watt rating. The 12V heating element was rated for about 1/2 the watts of the 120V element. Which with these fridges this means about about 1/2 the cooling. I think the norcold has about a 200 watt 120v heating element and the 12V element is around 90-100 watts. I think it uses about 9-10 amps on 12V.

Propane, we did try running the fridge on propane when traveling for for 10-15 trips maybe 5k miles. It worked well, but the burner ended up getting very sooted up. This leads me to believe that being closed with the fan. The ventilation where the burner is might be very good and it did not have the right propane/O2 mixture.

tentcamper · 07-01-2017, 09:39 PM

Quote:

Originally Posted by Lesherp

I have gone to switching to 12V and closing down the night before with TM plugged in. I am not sure how effective this is as I have never checked the battery to see if this keeps them at full charge. I think I will try this the day before I close down and check. If anyone knows if charging system keeps the battery charged while fridge is on 12V please post.

I was disappointed to discover my 150V solar and TV (with tow package) cannot keep up with the drain on the batteries when traveling using the fridge on 12V and the fan. The batteries are always discharges to some degree. My batteries are in the back so it is a long ways from my TV and that may be a factor. I think I will test to see what the deficit is when I have the fridge running with the fan and only solar as it would be easy to do while setting up.

I have seen discussion about running on propane but am not sure people are doing it. I am one to weigh risk against consequences. The risk may be low but I don’t want to look in the rear view mirror to see the TM on fire.

I have considered running 10ga wire as some have done but am reluctant to rewire the truck. Anyone know how much improvement there might be by just doing it to the TM?

I'm not sure it's the fridge that is draining the battery. The fridge adds to it. I think it has to do with the TV auto charging system. I did a test many years ago. I had the camper battery charged to 13.xV and headed out. Nothing was on in the camper. Arrived at the CS three hours later with the camper battery at about 12.7V. My TV charging system does not try to charge a battery to 13.xV, but about 12.7, this ended up with the battery in the camper discharging to feed the battery of the TV.

**Bailey'sMom** · 07-02-2017, 11:22 AM

Timely topic and one I haven't really figured out what is best.

a few days before trip I turn fridg on shore power to cool. Then 2 nights before trip, I fill fridg with food. Then the night before I switch to 12v and turn on fan and close up camper, hitch up everything except the lights, and back it all into garage.

Next morning I get up pack any last minute stuff, unlplug shore power and plug into TV and take off. I have 80 watt factory solar panel and hope I will have sun during trip.

From the time I unplug shore power to the time I arrive and set up and switch to propane, it is probably five hours. When I check my batteries they are pretty low.

My batteries are old and not the greatest, but it gets me by so I haven't bought new ones yet. So is that why they are so run down? Or does it just pull that much power in five hours?

So I kind of ask myself.....should I just not put fridg on battery for travel? How warm will my food get? Don't want stuff spoiling early.... But even so, I would still need the fan on because I close up camper night before....and would still have to be on shore power over night.

As for new batteries that is a whole new discussion......I'm not strong enough to pull them out of the compartment, and don't want to mess up the wiring and not get it put back correctly....

**rickst29** · 07-02-2017, 11:47 AM

Quote:

Originally Posted by Bill

In the case of my Ford Explorers, it was the tow vehicle that was inadequate.... Worse yet, some of the runs between the connectors were wired with #12 (and one with #14!) wire.
As soon as I ran a parallel pair of #10 wires through the truck, the problem went away.

The same problem exists in Toyota Trucks and SUVs of my vintage: The "Battery Charge Wire' is fused at 30A, but the wire size was much smaller than #10 (IIRC, it was #14

). Like you, I put in a bigger conductor: A single #10, but I'm usually using it at double the Voltage and half the Amps as compared to "normal".

**rickst29** · 07-02-2017, 12:02 PM

Quote:

Originally Posted by pmhellings

In discussions of how to power your fridge while towing, there seem to be a few different schools of thought:
Cool down prior to leaving on shore power then
(a) switch to 12v and then close the camper
(b) unplug from shore power and expect the fridge to stay cold from its contents
(c) switch to propane with the fan on.

Jason Yuhas ( Sopper ) posted
"The way I do is to pack the camper the night before and leave the fridge set to 12V. I leave the camper plugged in to shore power and it overrides the 12V setting"

Is that how it works? I would like to close my camper up the evening before, with the fridge on 12v while on shore power. My thoughts were that the converter would power the fridge on 12v so that I would not run the batteries down. Is Jason correct that the shore power connection would "override" the 12v and that when shore power was disconnected the fridge would automatically change over to 12v?

Jason posted wrongly: When the Fridge is set to "12V" and connected to shore power, there is no "override" within the Fridge: power is drawn from the 12V "distribution center", and power is supplied into that junction from the Converter. In comparison to running the Fridge on 120V, three things are different: #1, the Converter is only about 65% efficient - 35% heats up the interior of the TM, and runs a fan to help dissipate that heat through the interior. #2, you are using the 12V heater coil (which might be a good thing - if your 12V heater has been "blown up", you'll see a problem while you're still at home. On 120V, you use a different heater coil within the fridge. But such coil failures are extremely uncommon.)

But #3 is the most important for most people: There is ZERO chance that you will forget to switch from "120V mode" over to "12V mode" on the Fridge control dial before you lower the shells and leave - it's already in the right place for towing.