12v Refrigeration - What size do you use?

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12v Refrigeration - What size do you use?

Postby TimC » Sun Jul 28, 2019 11:56 am

I'm looking into upgrading my ice chests to one 12v refrigerator and one ice chest (I like having ice cubes for drinks). Ideally the frig will run primarily on battery/solar energy, but, have 110v capability. Currently I have a 50 watt panel and 72ah of battery capacity (actual usable is 36ah). I will approach the solar battery bank upgrades issue after determining the frig I purchase. I currently use less than 7ah/day without refrigeration. My concern is more on the frig sizing dilemma.

I'd like to know the size of frig folks are using for similar amounts of food and time as spelled out below. I'm considering sizes from 15 liter to 44 liter. I've read these small chest refrigerators do not circulate air well so I want to be able to pack fairly loosely. On the other hand I don't want an abundance of refrigerator space. Weight and its footprint will allow just enough space for my needs (it will live in my tow vehicle and on the ground under the TD).

Here's what I typically bring along that needs constant cold for a three night trip; 1/2 gal milk, 1/2 # cheese, 1/4 # cold cuts, four servings of yogurt, couple chicken breasts, couple hamb patties, stick of butter, 1/2 doz eggs, breakfast sausage, condiment packets. That's about it. My ice chest has a half gallon of iced tea, a couple beers, and as much ice as I can fit. It's an old Igloo with added 1 1/2" foam all around. Ice will typically last well into my fourth day.

I'm not really looking at models and price ranges yet. I see what's out there and will likely settle on a unit under $500 such as Costway or similar. Dometic and the others are a bit rich for my pocketbook. Tim
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Re: 12v Refrigeration - What size do you use?

Postby Cosmo » Sun Jul 28, 2019 6:03 pm

I wrestled with the quantity of food I could fit in a Dometic CFX-35 Internal volume is one cubic foot.
The cooler I was using was larger but according to Yeti the ratio of Ice to food should be 2/3 ice. That reduces the useable space for food a great deal.

My solution was to construct a box out of cardboard that matched the storage area of the fridge to see what I could fit.

I am running a 125 amp hour deep cycle AGM battery and I typically use two 100 watt solar panels which work great most of the time. In cloudy weather I use an third 100 watt panel which I store under my mattress.

I have videos on this topic.
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Re: 12v Refrigeration - What size do you use?

Postby absolutsnwbrdr » Mon Jul 29, 2019 7:09 am

We've got a Dometic CFX-50, and love it. It's expensive, but no more ruined food sitting in water, and no more worrying about running out for ice when we're far from civilization. To us, the convenience is well worth the upfront cost.

We have two 75ah Sealed-lead acid batteries with two 100w solar panels on the roof. They keep up well, but we also have a 2200w Briggs & Stratton inverter generator that we carry along just in case its super overcast or rains for couple days.
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Re: 12v Refrigeration - What size do you use?

Postby TimC » Mon Jul 29, 2019 12:06 pm

Thanks Zach and Cosmo. I've done some calculations and now need to build my solar capacity.

I decided the Alpicool CF35 would be good. I will usually take an additional cooler with ice for refreshments and the odd item that may not fit the frig. Like I said, I like ice in my refreshments, at least the non beer types.

I've ordered the Alpicool CF35, along with a 100w Renogy panel and four additional batteries. The new batteries along with existing batteries will equal 108ah. Sounds like a lot of batteries (6) to get 108ah, but, I started with one 18ah battery, upgraded to a second when I wanted to have enough reserve for my limited use of lights and fans and now I will be adding four more 18ah to my bank. Why 18ah? That's what I started with and I am afraid to hook up different rated batteries together. Also, those little suckers are very easy to stuff into unused spaces. I've measured enough extra space to put in up to ten of those little buggers; 180ah sounds like a comfortable number, eventually. Yeah, the price is a bit more than just buying a 100ah battery, but, that's where I started and I don't think the inefficiency of that many in a bank is going to kill alot of power.

I have a new Renogy 50 watt panel that I am going to experiment with a separate charge controller. I see that it can be done. Don't know what extra electronics might be needed, but, research will be done to make sure I don't burn anything up.

Cosmo, what do you call those plugs and receptacles on your trailer exterior wall? I'm thinking I'd like to hook up the frig to something like that for 12v use.

Tim

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Re: 12v Refrigeration - What size do you use?

Postby Cosmo » Mon Jul 29, 2019 1:10 pm

Those are SAE connectors.
Check polarity with a meter end to end, before opening the beer!

Max capacity on most of these is 10 amps. Some examples Affiliate links
https://amzn.to/2Qq4ul7
https://amzn.to/2Qq4ul7
https://www.amazon.com/s?k=sae+connector&ref=nb_sb_noss

These small fridges do not have a fan in them to circulate air.
That could work in your favor or not. I filled the fridge with small water containers. Then let it run for 24 hours on the 33 degree setting
The water at the bottom was 33 the water at the top was 40 degrees Sort of zone cooling. Then I gave up some space and added a fan. With the fan 24 hours later all water containers were the same temp. I have thought about but never tried to get the bottom layer to freeze while not freezing the rest. Mine is a one zone fridge. Affiliate link
https://amzn.to/36lUsGZ

For me - these are no the type of fridge I am going to quick cool a six pack in. These fridges work by adding cold slowly. I find its best to precool the fridge for 12 to 24 hours as well as any food going into the fridg. This spikes effectiveness and reduces run time saving battery life while you get the food to the desired temp. I did the same with my coolers. I sacrificed a bag of ice in advance to cool everything down for max ice life on the road.

I have used multi controllers for a third panel when I need more power on very cloudy days. Its an option. It works for me. Would not hurt to check with the controller makers. I am using Flexcharge controllers.

Like Zach I love my fridge!

Enjoy
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Last edited by Cosmo on Fri Jan 03, 2020 5:09 pm, edited 4 times in total.


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Re: 12v Refrigeration - What size do you use?

Postby TimC » Mon Jul 29, 2019 1:44 pm

That's the video I got the idea from to run two different ch controllers from different panels. Great idea. Any further fusing or blocking diodes needed before connecting to the battery?

Yup, one common suggestion from DC frig owners is to precool the frig and the contents on 110v before connecting to solar-battery bank. Makes a lot of sense...
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#3 My son's Benroy Foamie team build - Started July '20 - http://www.tnttt.com/viewtopic.php?f=50&t=72877

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Re: 12v Refrigeration - What size do you use?

Postby Cosmo » Mon Jul 29, 2019 6:10 pm

Fuses have saved me a number of times from my own mistakes Its cheap insurance.
The fridge seems to be a good price. The price of the Dometic doubled since I purchased.

I am looking forward to your field reports.

Enjoy
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Re: 12v Refrigeration - What size do you use?

Postby TimC » Mon Jul 29, 2019 8:19 pm

Looks like everything has shipped so I am preparing by adding a fused, but non-switched outlet (direct from battery) in my galley dedicated to the frig. I'm also upgrading all wiring to 12g from the charge controller downstream thru the battery bank and to my fuse panel. I have about seven or eight days before the gear arrives of plenty of time. It's called Patience I stead of Prime. :D

Where do you have fuses between the panels and the batteries when you run two charge controllers? I'm wondering if blocking diodes would help just before the battery on each hot line. I will spring for another 100w panel if there is any problem with using my 50w with my 100w.
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#3 My son's Benroy Foamie team build - Started July '20 - http://www.tnttt.com/viewtopic.php?f=50&t=72877

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Re: 12v Refrigeration - What size do you use?

Postby Cosmo » Mon Jul 29, 2019 9:31 pm

There are lots of experienced fridge users here so I hope you get more input than me.

I put fuses on both sides of the controllers In and out.
The solar panels I am using and the controllers have blocking diode's. I would be surprised if yours do not have diodes. It pays to check.

I think the majority of people would use a large controller and add panel's when needed. In my case
I had extra controllers and was at the limit of my main controller so parallel controllers made sense for me.

In the morning when the fridge has been running all night the batteries are at their lowest charge. At that point both controllers will dump all the power they can produce into the battery - aka "bulk charging". So there is no contention between the controllers they will be on and not off.

After bulk charging the controllers will toggle on and off depending on the charging algorithm of the controller (in my experience). By then the battery is mostly charged and the pulse charging will squeeze in the last bit of energy. One controller will probably dominate at that point. None of this is an issue - its just how it works.

My trailer is set up so the car charges the trailer battery when connected. That saves battery power if you are driving long distance. It can also be handy of the sun refuses to shine. I have not had to resort to that so far - but I like the concept.

In a test I set my fridge on the lowest setting and put a half gallon of tap water in it. 24 hours later the water was only partially frozen.

How about some input from other successful fridge users? What are you using? How is it working for you?

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Re: 12v Refrigeration - What size do you use?

Postby fishboat » Tue Jul 30, 2019 6:24 am

I have a new setup in a CTC that consists of 230AH (2 x 6V golf cart batts, 115AH useable capacity) and a Truckfridge TB51A (50 quarts). We've done one trip so far and the fridge worked perfectly. Since this is a new build, I hadn't yet finished installing/wiring in all the power draws. I had only the fridge and some overhead LED lights wired up..the lights were used for about 5 minutes over the 5 day trip. I have a Bayite power meter installed and wired with a DPDT switch to monitor both charge and discharge rate.

The trip started with 1 gallon of frozen water in the fridge(frozen by the fridge with 120V pre-trip cooldown) along with 3 pounds of frozen meat. The fridge was full of various foods when we left. All cold drinks were kept in a separate iced cooler. Outdoor daily temps were 75-85 degrees in a campsite that was about 80% shade. The fridge is installed in a drawer in cabinets built into the v-nose of the 6x12 trailer.

Some data(driveway depart to driveway return):

>Battery voltage when 120V support stopped(we left home): 12.83v
>Fridge setpoint: 34F set on "ECO" mode (2.5a draw when running)
>Hours fridge used: 4.9 days(118 hrs)
>Amp-Hrs consumed: 88.6
>Power consumed: 1107 watt-hrs
>Average amp/hr consumed over entire trip: 0.75a
>Theoretical run time on initial batt charge(based on 115ah limit) and use-rate: 6.4 days
>End voltage prior to recharge: 12.32v
>Time to recharge to 14,2v absorption stage(Iota DSL45 + IQ4 controller converter-charger): 1.25 hrs

The fridge was used/opened as needed during meal times. By the trip-end maybe a third of the food remained(condiments, some fruit, cheese..etc), the meat was gone and the (previously frozen) gallon jug of water was 80% water/20% ice.
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Re: 12v Refrigeration - What size do you use?

Postby working on it » Tue Jul 30, 2019 8:36 am

fishboat wrote: Outdoor daily temps were 75-85 degrees in a campsite that was about 80% shade. The fridge is installed in a drawer in cabinets built into the v-nose of the 6x12 trailer.


* Though you listed the estimated average high temperatures outside the trailer (but not the overall average of day/night), you also stated that the fridge is in the nose of your trailer. Is that inside-only, or accessible from the outside, too? If it's totally contained inside the trailer, what are the ambient temperatures there? Is the trailer insulated and/or with air conditioning being used. All those questions are to determine the overall climatic conditions that your fridge has to operate under. For my usage, here in N.Texas, I have to figure in the average upper 80's-100 daytime highs (with 70's at night), and storage under an un-insulated hatch or under a canopy in the open-air campsite. My tow vehicle is a single-cab truck, with no SUV-type enclosed storage area in the rear.

* I've been trying for years to determine how to incorporate a mini-fridge (dorm-style cube, compressor-driven, $100-150 or so) into my limited space in the galley (where my semi-effective Igloo Ice Cube-turned-Frankencooler http://www.tnttt.com/viewtopic.php?f=2&t=68543 resides), but it'd be a tight fit. I've hesitated, due to not camping much, and lacking the desire to install it only a few times a year into the trailer, while usually using it in my home office (computer browsing/dog-sitting room, since I'm retired). The price of a true outdoor fridge isn't justified, and there's no space large enough inside my 4x8 TTT to house it.

* I've also considered using a thermo-electric cooler inside my trailer (also un-insulated), where it would be in an air conditioned space (with A/C on, full-time, the ambient air temperature there would be in the 60's) where a thermo-electric unit could be effective in Texas heat. The fan noise wouldn't be noticed by me (I always have at least one running, anyway), and the negligible heat put out by the Peltier-effect cooler would be easily handled by the 5000 btu A/C inside the 88 cubic foot cabin interior. But, I really don't want more stuff crammed inside that small space, and I would rather not run the A/C unit 24/7 at camp (I camp to hear nature, not machinery running). So for now, ice is nice.
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Re: 12v Refrigeration - What size do you use?

Postby fishboat » Tue Jul 30, 2019 9:19 am

working on it wrote:
fishboat wrote: Outdoor daily temps were 75-85 degrees in a campsite that was about 80% shade. The fridge is installed in a drawer in cabinets built into the v-nose of the 6x12 trailer.


* Though you listed the estimated average high temperatures outside the trailer (but not the overall average of day/night), you also stated that the fridge is in the nose of your trailer. Is that inside-only, or accessible from the outside, too? If it's totally contained inside the trailer, what are the ambient temperatures there? Is the trailer insulated and/or with air conditioning being used...


I live in the north country..we were camping not far from the Wisconsin/UP Michigan border. No AC running..if it were, I wouldn't have needed to track 12V usage. Fridge is mounted in a drawer, inside the cabinet in the nose of the trailer(early in the build process pic is below). Access is only from inside the trailer. The trailer was parked in 90% shade with the top vent and side windows open..inside and outside temps were the same. We only had one day at 85/86. The rest of the 4ish days were 75-82 tops. Night temps were 60ish.

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Re: 12v Refrigeration - What size do you use?

Postby Pinstriper » Tue Jul 30, 2019 10:15 am

Seems to me in that build you could put a 3-way rv fridge and run propane for a lot less money than the batteries, charger and solar panels cost. Cool it down on 110v before the trip, run on dc in transit, and propane at destination. You would still need a battery system to support the electronic control board, but soooooo much less.


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Re: 12v Refrigeration - What size do you use?

Postby sagebrush » Tue Jul 30, 2019 10:46 am

We use a Truckfrige tf65, one group 29 marine/rv battery and a 100 watt solar panel mounted flat on the roof. Tow vehicle charges when in transit. This has worked since 2014. One summer we were stationary for 4 months and the battery stayed up with about 50% exposure during the day.
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Re: 12v Refrigeration - What size do you use?

Postby Cosmo » Tue Jul 30, 2019 11:09 am

Pinstriper wrote:Seems to me in that build you could put a 3-way rv fridge and run propane for a lot less money than the batteries, charger and solar panels cost. Cool it down on 110v before the trip, run on dc in transit, and propane at destination. You would still need a battery system to support the electronic control board, but soooooo much less.


Propane was not a good match for my needs but for others, I found this 3 way found on Amazon. I know nothing about it - such as venting etc. There are several models available on Amazon.
https://www.amazon.com/Smad-Electric-Ab ... way&sr=8-3

Reviews of this fridge https://www.amazon.com/Smad-Electric-Ab ... merReviews

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