Dumping the 3 ways for a 12v Compressor w/solar, help with Choices

Discussion in 'Refrigerators and Coolers' started by mpking, Jan 27, 2018.

  1. bearman512

    bearman512 Well-Known Member

    Apr 17, 2010
    Albuquerque NM
    I agree for part of what you are saying except price for the OP particular situation. They have a functional 12v system and camp on the beach in full sun. The dorm fridge will run at least 30-40 minutes of every hour as the insulation is designed for an air conditioned room thus drawing large amps. Sure with a good inverter that pulls very little amps but the fridge will drain a group 24 past the 40 percent mark in less than 8 hours with solar it could be maintained barely during the afternoon but the 12 hours from 6-6 will drain a group 24 past the point of no return. Not to mention the longevity of the dorm fridge is questionable if it is knocked over or laid on its side it may not work again. Personal experience with this. With a Danfos type fridge/freezer it has almost twice the insulation virtually impossible to knock over and the biggest point it will not run more than 15 minutes every hour out of direct sunlight. So it will not drain a group 24 past 12.1 in any 12 hour period.
    There are many people like me that tried the dorm fridge route just to end up with a good Danfos 12/24/110/240v compressor fridge that will last for years. I have a 15 year old ARB and have had it plugged in to house current the whole time except when I throw it in the Jeep or truck. Never worry about ice or wet food or the worst case knocking it over as it will start up even after you roll your Jeep on the trail. And the contents will stay put because the lid securely latches.
    Last edited: Feb 2, 2018
  2. bearman512

    bearman512 Well-Known Member

    Apr 17, 2010
    Albuquerque NM
    https://shedheads.net/12v-refrigerator A friend of mine did the home chest freezer mod. It is doing very well an will operate using a inverter on a group 24 for up to 4 days.
    The following is from shedheads article:

    The ARB fridge is world class, and it’s certainly the easiest way to get a fridge set up in your RV. But if you’re reading shedheads, you’re likely the type of guy who likes to get things done himself. This project will allow you to make your own ARB style fridge for only 200 bucks. And the best part of all? You can get it done in an hour.

    Remember, what made the ARB fridge great was the fact that it was well insulted, the compressor required very little load, and it had a light duty cycle so the compressor was off most of the time. And of course, it was top loaded.

    An apartment freezer is very similar to the ARB 12V refrigerator. Since it’s designed to be kept below 0 degrees, the walls are generally very well insulated. Compressing coolant to the point of reaching subzero temperatures is very challenging. If you ran these compressors all the time, they’d very quickly burn out. To correct this, manufacturers run them on a 25% duty cycle. Every hour, it’s only supposed to work for 15 minutes.
    [​IMG]Check Current Price on Amazon >

    The first step was to find a freezer that used very little current. This wasn’t easy. Most manufacturers don’t publish the true power use, only their useless energy star ratings. After digging through a few that were drawing upwards of 3 amps (yikes!) we finally came across the Midea WHS-129C1. It was almost perfect. 3.5 cubic feet of space, a low foot print, and it only draws 1.1A while running! Plus, there is a two-year warranty on the compressor. These are the most common points of failure, and the fact that there was a warranty indicated to us that it was a reliable unit.

    After ordering it, we opened the package and checked it out. It was nice and spacious, very well insulated for the price, and the compressor was rated for at least twice the duty cycle. After plugging it in, we ran it on a kill-a-watt meter for a few days. 1.5 kilowatts per day, not too shabby!

    The next step is to turn it into a fridge. Basically, these freezers have little controllers in them. When the temperature is around -4, they shut off the compressor. It slowly warms up to 0, and the compressor kicks on again. Obviously, this won’t work for us. For a couple of bucks, we picked up the Inkbird Dual Stage Digital Temperature Controller.


    Check Current Price on Amazon >

    This handy little controller lets us control the temperature ourselves. You can buy dedicated fridge controllers, but these are usually sold at 10x the price. This is a more advanced device, and will let us do the exact same thing.

    The first step is to wire it up. We removed the end from an extension cord to reveal the three wires. You’ve got a hot (red wire), and neutral (black wire), and a ground (green wire). Follow the diagram above to wire it up.


    The first thing you’ll connect is your hot lead. Take the red wire and connect it to pin 1, and connect the black wire to pin 2. You are now going to take a small length of wire and shove that into the connector for pin 1 along with your hot lead, then connect the other side to pin 7. Your next jumper will connect from pin 2 to the neutral lead on your freezer. The next jumper goes from pin 8 to the hot lead on your fridge. Finally, you’ll want to connect the ground from the freezer to the ground on your extension cord.

    Power on the controller and press the S button. Next to the “cool” value select the number 4, and next to the heat select 0. Finally, turn the setting knob on the freezer to the highest value.

    This might seem complicated at first, but it’s very simple. The controller stands between your freezer and the power source. When the freezer is on, it wants to get as cold as possible as fast as possible. The temperature controller has a long cord with a thermometer inside of it. You drop that in the freezer and close the lid. If the temperature inside is four degrees or above, the power is turned on. Once the temperature hit’s 0, the 12V refrigerator is turned off. Now you’ve got a fridge.

    Remember, the duty cycle of the compressor was 15 minutes. But that was to freeze it. With our controller in line, it only runs for about 6 minutes per hour. At 12V DC, the compressor draws 10 amps. Since it only runs for 1/10th of an hour, we’re using 24 amp hours per day. Your 100 AH deep cycle battery can run this fridge for almost 4 days without a single recharge, comparable to the ARB.

    The last thing you’ll need is an inverter. Both the temperature controller and the fridge itself sit on the 120V side of the circuit. What an inverter does is convert your 12V DC electrical source into a 120V AC source. There is, however, one big catch with the inverter. If the fridge only draws 10 amps, then in theory you’ll only need a 120 watt inverter. But there is a very brief moment where the inverter pulls a very high amperage when the compressor first starts to turn over, for that reason, we recommend getting a 500 watt inverter minimum, or 1000 watt if you want to run other things on the circuit.

    Overall, this is a very affordable way to get a 12V refrigerator. But if you’re willing to spend a little extra, you can get a very professional finish that performs a little better than the DIY option.
    Last edited: Feb 2, 2018
  3. mpking

    mpking Active Member

    Jun 17, 2014
    Raynham, MA
    So a few updates. I ended up buying the Dometic CFX-65W from my12voltstore.com from @Popiworks suggestion. My wife and I talked it over, and we don't see the need for the space loss to have a freezer.
    For the money we ended up saving by getting from my12voltstore.com over amazon, we ended up getting the insulated cooler cover, made of reflextics. (It was like $25 dollars).

    The published rate for the CFX-65W is 0.85 Ah/h at 12V, 41F interior, 90F ambient.

    After I purchased the CFX-65W, I did run across the Nova Kool R2600 http://www.novakool.com/products/single_doors/r1900_2600.htm It's rated at 30watts. That works out to 2.5 AH, or about 1AH/h with a 30% duty cylce (run about 20 minutes an hour). I wanted to mention that, since it never made it into this thread.

    We went with the CFX primary since it was portable, we expect to use it for things other than camping. (Parties, extra fridge / freezer storage on holidays). That we could use it independent of the camper really drew us.

    I ended up with the Renogy 20A MPPT controller (Bought from Renogy's used devices section on Ebay) and the Renogy 100w solar suitcase without a controller (also used from Renogy's ebay store). I also picked up 20 feet of 10 gauge solar cord with the MC connectors. I'll grab some 10 gauge wire and ring terminals this weekend, and my solar kit will be complete.

    I still need to figure out the 12V connection on the side of the camper.
    I'm looking at this guy:

    What do you guys think? Wire directly to the battery, or run to the converter?

    Think I should put it on a switch?

    I did find this. I could mount it underneath the camper (Not really thrilled with this)

    Still working on upgrading from a group 24 to a group 27, or dual 27's. I have another thread with that saga, but I at least know now that it is possible to get a 27 on the tongue.
    bearman512 likes this.
  4. ArizonaJoe

    ArizonaJoe Member

    Oct 18, 2017
    You need to have a disconnect to kill power between your battery, the controller and the pannel. Always make sure the charge controller is connected to the battery bank via switch, disconnect or whatever you decide to use and that it is powered on before you send power from the solar panel. If you do things in reverse, you can fry your controller.
    I perfer to run a fuse pannel and any 12v accessories off of that. Makes it easy to keep safe and you can run a simple disconnect switch to it as well.

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