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Old 05-20-2022, 11:40 AM   #1
Wavery
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Default Dorm fridge

If anyone has been thinking of installing a larger fridge in your TM, I have been doing a little experiment that some may be interested in.

The Norcold fridge in the TM is 2.7 cu ft. I may be replacing the Norcold with a 4.5 cu ft 110V dorm fridge/freezer. I bought a used Sanyo 4.5 cu ft mini fridge/freezer ($50) that will fit perfectly in the Norcold's place and have had the Sanyo mini fridge sitting on the floor in our TM running for a week now. It's running off of my batteries with an inverter. I have a 2000W pure sine wave inverter but it only needs a 400W (or smaller) pure sine wave inverter for the fridge.

I have been monitoring the electrical usage carefully in the system. The fridge is drawing <37W while running (it doesn't run full time). It draws about 150W at start-up for about 1-second. My best guess is that it draws about 50AH per day (max). My solar puts back about 80AH per (sunny) day (13A x 6hrs of full Sun) so I have a net gain of about 30AH per day that I can use for other devices.

I have a 200W solar array and the (225AH) batteries are fully charged by noon and stay that way until Sun down. When I check the voltage at 6:AM (after a full night of fridge running and a few lights on), it is still ~12.4V (under load).

We are going camping for 5-days in a couple weeks. I just turned off the fridge this morning and will turn it back on the night before we leave and report back the results.

We also run our microwave and electric coffee pot off of the inverter so I'm not removing the Norcold fridge until we are sure that it will all work out without having to purchase those expensive Lithium batteries.
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Old 05-21-2022, 04:38 PM   #2
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Please keep us posted. I’m also curious how it will work going down the road. I’ve kicked this idea around multiple times, and never gotten a clear answer. I’d rather do this than buy a $1000 AC/DC compressor fridge. I assume you’re running two 6V golf cart batteries?
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Old 05-21-2022, 07:57 PM   #3
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Quote:
Originally Posted by Shane826 View Post
Please keep us posted. I’m also curious how it will work going down the road. I’ve kicked this idea around multiple times, and never gotten a clear answer. I’d rather do this than buy a $1000 AC/DC compressor fridge. I assume you’re running two 6V golf cart batteries?
I'm currently using 2 (5-year-old), Trojan T125 6V batteries that I bought from another member.

As soon as these poop out, I'll probably go with 200W lithium's. They are coming down in price right now because so many sellers are struggling for market share.

The fridge sits forward of the axle a few feet so I'm hoping that the jarring while towing won't be too much for it. I put some styrofoam under the compressor to keep it from bouncing around too much.
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Old 05-22-2022, 04:27 AM   #4
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Ha! I didn’t even think about “going down the road” as in the jostling and bouncing of towing. I was referring to tow vehicle keeping the batteries alive while the fridge was running while towing. My Notcold doesn’t like 12VDC mode, it always seems to blow the 30A fuse at the battery.

Also did you do anything different at the vents on the side of the TM? Cover them up? Or just leave them be?

Now I need to go downstairs to the basement and see what size the inverter is that I have.
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Old 05-22-2022, 07:40 AM   #5
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Ha! I didn’t even think about “going down the road” as in the jostling and bouncing of towing. I was referring to tow vehicle keeping the batteries alive while the fridge was running while towing. My Notcold doesn’t like 12VDC mode, it always seems to blow the 30A fuse at the battery.

Also did you do anything different at the vents on the side of the TM? Cover them up? Or just leave them be?

Now I need to go downstairs to the basement and see what size the inverter is that I have.
The Norcold draws 300W (about 25A). I could see that blowing a 30A fuse if there is any surge for some reason. This mini-fridge draws 37W and runs off of the inverter with a 20A circuit through the converter. so I don't think that a blown fuse/breaker will be an issue. Besides, my solar should keep the batteries up during the day (if there is Sun).

At the moment, my Norcold is serving as dry storage in it's place in the TM. The mini-fridge is sitting next to it, on the floor until I am satisfied that all is well. However, I plan to leave the exterior vents in place. I'll put some sheets of carbon air filters on the inside of the exterior vents (to help keep rain out) and I will leave the current exhaust fan in place.

This fridge only requires a 500W (or less) pure sine wave inverter. The most wattage that I've seen at start-up was about 240W for about 1 second. Technically, a 150/300W inverter would do it but that's a bit iffy in my book. Don't even think about using a modified sine wave. The compressor won't like it. My bet is that the 12V/110V fridge that costs over $1K is simply a 110V fridge. I'll bet that they have a 12G, 12V input and an internal 250W (or so) inverter.

I built a 12V fridge/freezer on my yacht years ago. I put the compressor unit in the engine room and ran the refrigerant lines into the galley. I built the actual, heavily insulated fridge/freezer cabinets into the counters. I was even thinking about doing that in the TM because I could give my wife a 2 cu ft freezer and 4 cu ft fridge in the space between the galley sink counter and the place where the inner part of the slide out comes. I'm just getting too old for a massive project like that....... maybe....... nah...... well, maybe.


If you do need a new inverter, do a search for "Newpowa inverter". I would give you a link but the last time that I posted a link to them, they spammed this website. Their products are top notch but I'm a little disappointed in their marketing techniques. Their 500W pure sine wave inverter is only $65. I have their 2000w with remote control panel ($320).
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Old 05-22-2022, 12:18 PM   #6
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Wavery said “My bet is that the 12V/110V fridge that costs over $1K is simply a 110V fridge. I'll bet that they have a 12G, 12V input and an internal 250W (or so) inverter.”

My understanding is the compressor itself is built for 12VDC, and being brushless it is designed to ramp up to the needed pressure opposed to a conventional compressor which is simply either ON or OFF. Check out Danfoss compressors. Plus they were designed and built in Denmark, which is always a bonus to me.
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Old 05-22-2022, 12:32 PM   #7
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Quote:
Originally Posted by Shane826 View Post
Wavery said “My bet is that the 12V/110V fridge that costs over $1K is simply a 110V fridge. I'll bet that they have a 12G, 12V input and an internal 250W (or so) inverter.”

My understanding is the compressor itself is built for 12VDC, and being brushless it is designed to ramp up to the needed pressure opposed to a conventional compressor which is simply either ON or OFF. Check out Danfoss compressors. Plus they were designed and built in Denmark, which is always a bonus to me.
That's the 12V compressor that I had on my yacht. The compressor/evaporator kit alone cost about $1000 back in 1991 when I installed mine.

If they use a 12V 4-magnet motor in the compressor, think of how they would have to get it to run on 110V. I'm thinking the fridge must have a built-in converter (110V AC to 12V DC) in that case. That certainly wouldn't be very efficient.

Then again, I don't think that fridge is exactly built for efficiency. I thought that it is built for sleeper cabs in long haul semis. They leave their engines running 24/7 so I don't think that efficiency is a huge factor.
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Old 05-22-2022, 01:11 PM   #8
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But are we really worried about efficiency in 110VAC? That’s kinda like switching the running lights on your camper to LED because you think it’ll save your battery…

Anyway here’s an article that talks about the compressor. From everything I understand it’s a whole lot more efficient any which way opposed to absorption.

https://www.rvtravel.com/rv-electric...ng-compressor/

I’m not saying the dorm fridge isn’t feasible. Heck if you can make it work, I’m on board. I like saving money as much as the next guy.
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Old 05-22-2022, 02:20 PM   #9
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Quote:
Originally Posted by Shane826 View Post
But are we really worried about efficiency in 110VAC? That’s kinda like switching the running lights on your camper to LED because you think it’ll save your battery…

Anyway here’s an article that talks about the compressor. From everything I understand it’s a whole lot lore efficient any which way opposed to absorption.

https://www.rvtravel.com/rv-electric...ng-compressor/

I’m not saying the dorm fridge isn’t feasible. Heck if you can make it work, I’m on board. I like saving money as much as the next guy.
Shane........ we are talking about a 110V compressor driven fridges (not absorption fridge) running off of 12V batteries and solar.....

Anywho...... just for kicks, I went out and plugged the fridge in (with inverter running). The fridge is warm because it's been off for a few days. The wattage shows 59W @110v. It takes about 30 minutes to settle down to 35W + or minus. Of course, when the fridge cycles off, it drops to "0". I had it running for 2-weeks with 3-1/2G bottles of water in it and it seems to run about 8-hours a day. the 1/2G bottle in the freezer froze solid overnight. The other bottles did not freeze. It's been in the 70s and 80s here.

I have a "Digital Current Voltage Power Energy Meter" on order and should be here before my next trip. That will show all of the watts consumed and tally them up over time. I had a big electrical panel on my boat that displayed all of the electrical facts and acted like an electrical gas tank gauge. Back in the day, that thing was about $1K. Now I got this thing that does everything for under $20.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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Old 05-22-2022, 05:45 PM   #10
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This is the fridge that I bought.
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