DC fridge versus AC/DC fridge

M1010 Mike

Senior Member
Joined
Apr 17, 2011
Messages
174
Location
San Diego, CA
So I am looking to change my Norcold 3 way fridge for a compressor style unit. I need something that will run on DC with low current use, unlike the Norcold. Been looking at Nova Cool and Engel models (and a few others) and they are offered in a DC only and AC/DC models. Seems to be about a $150-$250 difference in price between them.

Since almost 100% of my camping will be remote, the only time I would even use AC power would be at home while getting things loaded up. It was suggested that a DC only would be fine as when at home, the AC would run through the converter while the battery is being charged, hence powering the DC fridge.

Opinions of if the added cost for the AC/DC model would be worth having given my needs? Has anyone just gone with a DC unit and have regrets?

Thanks!
smile.gif
 
Opinions of if the added cost for the AC/DC model would be worth having given my needs? Has anyone just gone with a DC unit and have regrets?

Thanks!
smile.gif




No regrets, I have a Coleman Stirling type that has a little converter so I can run on AC if I want but with solar and batteries I never bother. If I could find another one I'd probably buy it, one for cool, one for frozen.
 
Just like Barko, I bought my Coleman DC cooler and have no complaints. I like them so much that I bought another one! They are hard to find, but I think you cannot go wrong if you went with the Engel. Here is a link for the company that makes the stirling cooler, global cooling. This company made them for Coleman at one time.
 
I went with a Waeco/Dometic CR65. I could not be happier. It is quiet. Uses very little energy. Makes ice no problem.
With a 125 watt solar panel and dual batteries, I can boondock forever. All of my lights are led also.

Jeff
 
Short answer.

I think 12 VDC would be fine, without the AC option.
Especially, as you say, boondocking.

-------------------------------------

Long answer.

For me the thing to know is... from being off (at a nominal temp) to getting to the initial desired temp (34-35 degrees for a fridge, or just below 30 degrees for a freezer), how many amps are required and how long does it take to get there?

Then how many amps does it take to keep it at that temp for a total time of 24 hours?

- - - - - - - - - - -

My case study...

I've got 2, built-in, top loading, 1.5 cu ft, 12 VDC only units by Indel-Isotherm (marine industry).
These use the very common Danfoss BD35F, air cooled compressor, very quiet operation.
One as a fridge, the other as freezer.

Starting at an "off temp" of around 75 degrees cooling down to 33 degrees, measured with a VWR digital thermometer using a liquid filled bottle probe, takes about 4 amps and 40 minutes or so (OK, let's say 1 hour), loaded with already cold food.

A worst case scenario is to load it with food that is not already cooled and it should draw more amps and take a longer time to reach the desired temp. This could be a way to need AC power.

Then to hold that temp it's under 1 amp per hour.

So, in the first 24 hours it takes 4 amps (hour #1) + 23 amps (hours #2 thru #24) = 27 total amps (for me, for each unit).

That's what the sales info basically said for my units and that's what I've experienced in the couple of months of operation, so far.

As I've got two of the above units, they will use approximately 54 amps per 24 hour day.

I've got a solar panel that both of my cooling units will operate off of during daylight hours, with no drain on my battery. So, if I figure a 12 hour sunlight period (it's often more), then I can cut the amps per day back down to half... 27 amps for both units for overnight only operation.

I personally don't like to take a battery much below 50% of it's rated amperage, and I've got an AGM, 100 amp/hour battery, so that is plenty for overnight operation. I could probably be OK with a 60 amp/hour battery. And, the solar panel is large enough to recharge the battery and run the cooling units at the same time when the sun is up.

I personally prefer to not have any electrical connection to my truck. Just my choice.

- - - - - - - - - - - - -

So, see if you can find out the details of the initial amp draw to get to the desired temp, and then what is the average amps per hour to hold that temp.

Sometimes the power consumption will not be listed in amps, but in "watts per 24 hours". That's OK as Amps = Watts/Volts. So, watts per day of 270 / 12 VDC = 22.5 amps per day. That's usually an average, so add in another 20% or so, for the startup amps to get from nominal temp to 33-35 degree for a fridge, a little more for a freezer. So, for a fridge... 22.5 amps average + 4.5 amps (20%) = 27 amps.

Incidental usage of adding in "new, not cold" food items will add some amp draw to this equation.

If you have a front opening door that will let some cold air out every time the door is open, instead of a top loader that keeps the cold air mostly in the box, then add in some more amps to take care of opening the front door every now and then.

Once you calculate your 24 hour amperage draw, ask yourself... is your battery up to that?

And, ask... how will the battery get recharged so it can keep up the next 24 hours at the continuation amp draw rate?

Calculate your output, and then calculate your input, to get to a balance or surplus.

- - - - - - - - - - - - -

I believe that all of the units mentioned above by others are roughly like mine (amp/hour draw rate), however, you should confirm it.

My units are going to live permanently in my ATC Bobcat (built-ins), but I know that the portable units mentioned above are very good and very popular.
 
I have the Engle front load DC model and really see no need for the AC version. Your post mentioned your have the converter already, so when ever you plug in it will charge the batteries and power the fridge at the same time. As for performance of the Engle, I couldn't be happier. It's getting into the 90's in Vegas now. I have left the fridge running with a door full of beer, and a gallon jug of water in it to see how it does. At setting 3 (of 5) it keeps the temp at 36 degrees. It seems to cycle about once every 10 minutes for about 2 minute per cycle. Current draw varies a bit...not sure why, it's either about 1.8 or 2.2 amps. When I check the battery volts in the morning before the solar panel has had a chance to work much, the battery volts are still 12.9 or 13 volts from the day before. I guess I should mention I have 330 amp/hours capacity and a smaller battery bank will show a lower overnight voltage than what I see. Get the DC model and save a few bucks!
John
 
The only rational I see for the AC/DC version is if you intended to take the thing in/out of the camper and possibly use it in places with only AC power. However you can get a cheap AC to DC converter for much less than that upgrade cost so I'd still go the DC route if it was me.
 
Great info everyone. I'll add this info. Our trips are done where we are never in the same spot the next night. The only time we have ever spent more than one night in one spot was at Overland Expo in 2010. Since the next day is spent driving to our next location, the battery will be charged during the day. This is before I even get to putting solar on.

Current battery is a Optima blue top but I will be changing things down the road to a high capacity setup mounted to the truck and setup to be a "jump battery" should the need ever arise.

Sounds like going with the DC only will work fine. I originally thought about doing a Engel/ARB top load portable but don't want to give up the room. A front load to replace the current one just makes things simpler.

Thanks. Sounds like a DC only should work out well.
 
I know the in thing is to hate your 3 way fridge. But the one way ac fridge in our kitchen at home just decided to take a vacation. Guess where all the important items are getting cooled and who isn't drinking warm beer.
 
I love my 3 way! I have never had a problem with it and I like being able to cool it down the night before a trip with the AC at the house. Or, when my 15 year old daughter has half the neighborhood over for home made pizza, I have a place to go with cold beer in a fridge after I feed the hoards. I'm not trading my 3 way any time soon!

Good Camping!

Paul
 
Yeah, tonight definitely confirmed my decision to switch to a compressor style fridge. So I have the rig parked in the driveway, which is off course on an angle. Guess what??? I can't get the fridge to run in any mode, to cool down before loading food in the morning.

My new fridge is in the living room and will be promptly installed after this trip. For those who a 3-way fridge works for, great and glad it works for ya but for me and my needs, it's not for me.

Will post up a new install thread when I start the project. Going out for our first shakedown trip this weekend.
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I know the in thing is to hate your 3 way fridge. But the one way ac fridge in our kitchen at home just decided to take a vacation. Guess where all the important items are getting cooled and who isn't drinking warm beer.


My FWC has a 3 way and with the relighter mod I put on it I like it fine enough since it came with the used camper I bought. However on the new rig starting from scratch I'd rather a DC compressor fridge/freezer.
 
For me it was a no brainer. For they way I camp, the way a DC refrigerator works is perfect. They are larger inside due to the coil layout, work in non level conditions and will actually make and keep ice. I love mine, but yes it not a cheap mod and may not be for everyone.

Jeff
 

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