Solar Powered Fridge

Converting Cargo Trailers into TTTs

Re: Solar Powered Fridge

Postby John61CT » Thu Mar 14, 2019 8:06 am

bdosborn wrote:The most important item to have when living off grid, IMHO, is a battery meter that tracks amp-hrs (Trimetric and Victron are the big names).
Both excellent, Xantrex LinkPro also,

but for battery SoC only without the coulomb counting, Merlin SmartGauge is more accurate, much simpler less fiddly and more user-friendly.

The new hotness for those looking for the bleeding edge is Balmar SG200, integrates both technologies and claims to track State of Health as well.
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Re: Solar Powered Fridge

Postby bdosborn » Thu Mar 14, 2019 10:43 am

Thanks for the links, I haven't looked at battery SOC meters in several years. The Trimetric is supposed to use Peukert's law to calculate battery reserve rather than just a straight accounting of amps in and out so I'd be interested in seeing a comparison of various meters, if you have a link. I'd be careful which Balmer Smartgauge you buy, the SG200 has an amp meter but the older version does not, which would be a deal breaker for me. I use the amp meter on my Trimetric all the time; I can tell if I've left things on and I'm always experimenting with equipment combinations to try and get my amp-hr rate down.

The Trimetric has a really important feature IMHO, you can turn the display completely off at night. ;) :goodnight:

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Re: Solar Powered Fridge

Postby travist » Thu Mar 14, 2019 11:39 am

Lots of good advice here. I'm also going to do a 12V solar fridge. I bought this one: https://www.homedepot.ca/product/unique ... 1001188238

As you can see they list the Wh or Ah for 24 hour run time (once cold), so at 24 VDC it uses around 20 Ah, which really helped me think through how much battery power and solar power I think I would need.

It is spendy, but its nice to have upright, separate fridge and freezer, and the dc only takes care of the need for venting, as I am doing a rear galley kitchen in my cargo trailer, so I couldn't back the fridge against an exterior wall.
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Re: Solar Powered Fridge

Postby McDave » Thu Mar 14, 2019 11:25 pm

Hey jwh,
I was able to pick up a never used norcold 12v/120v about 2 cu ft from ebay for 170.00 shipped. It was taken out of a boat still had all the packing material. It has a small freezer and will make ice and keep frozen foods solid. If you just need to refrigerate to 38f it is very efficient. 2-2.5amps. runs about 1 min/10min., or 6min/hr. or 2.5hr/day. So lets call it 3 hrs. @ 2.5 amp or 7.5AH/day. That's summer in Montana, 60f to 100f+, 80f average ambient temp., 70f if 120v is available to run the A/C. The condenser coil is external mounted on the back of reefer and I was able to create a "chimney duct" that cools the condenser with outside air and keeps the condenser isolated from the cabin air. The duct runs from my vented storage compartment,( battery, LP tank, water pump, stinky slinky etc.) to an upper vent at the radius wall/roof. It's about 4in deep x 18 wide x 4ft tall and enters the top of the vented storage (2' x 2' x 3') and exits at roof. There is a constant draft and when the reefer cycles you can see a noticeable increase as the heat rises and draws cool air in. The duct is sealed to the rear wall of the reefer to keep that air out of the cabin. It is not as good as the chest type ARB's and such but I have it mounted at eye level over the sink and microwave so very handy. I just try to keep it full of bottled water and Jameson to limit the air space and keep the door shut. Works pretty good. Single 125 AH deep cycle, no solar.. yet, so I try to keep it topped off with the generator. I can run 3-4 days if need be without a charge but rarely go more than a day.

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Re: Solar Powered Fridge

Postby John61CT » Fri Mar 15, 2019 1:43 am

bdosborn wrote: The Trimetric is supposed to use Peukert's law to calculate battery reserve rather than just a straight accounting of amps in and out

That and Charge Efficiency Factor are a basic requirement of any true bank SoC gauge.

Otherwise just a crude coulomb counter, worth maybe $40-50 max including the shunt.
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Re: Solar Powered Fridge

Postby John61CT » Fri Mar 15, 2019 1:52 am

bdosborn wrote: I'd be careful which Balmer Smartgauge you buy, the SG200 has an amp meter but the older version does not, which would be a deal breaker for me
Balmar just rebadges Gibbo's SmartGauge, actually from Merlin in the UK.

Yes, no coulomb counting, but that's what makes it so easy and user friendly.

It also happens to be **the** most accurate SoC meter out there, at least for lead chemistries.

Many boaters use both, or SG + a $40 Ah-counter with Andersons to test specific loads or source circuits.

But the SG200 is Balmar's own in-house design, and possibly a real game-changer if it proves anywhere near as accurate as SmartGauge.

IMO too new to say yet though. I believe Bruce @ OceanPlanet is putting all the leading meters through a standardized suite of tests, but haven't heard much, other than some were way way off.

And for me a minor point, SG200 uses Ah counting, but only internally. When the BT module comes out you'll be able to track them on your phone, as Victron does now with their BMV.
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Re: Solar Powered Fridge

Postby jwh92020 » Fri Mar 15, 2019 7:42 am

I am searching for a 12v fridge as we speak. I figure buying a new fangled, untested unit is not the best thing for my restricted budget. I will jusst bite the bullet (hope it's a small caliber) and find a quality unit at the best price I can find.
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Re: Solar Powered Fridge

Postby John61CT » Fri Mar 15, 2019 10:41 am

If you want long lifespan, worth paying more for an Engel. Next IMO is ARB.

Regardless make sure to verify directly with the maker that the sales channel qualifies for the full warranty.
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Re: Solar Powered Fridge

Postby jwh92020 » Fri Mar 15, 2019 1:47 pm

McDave wrote:Hey jwh,
I was able to pick up a never used norcold 12v/120v about 2 cu ft from ebay for 170.00 shipped. It was taken out of a boat still had all the packing material. It has a small freezer and will make ice and keep frozen foods solid. If you just need to refrigerate to 38f it is very efficient. 2-2.5amps. runs about 1 min/10min., or 6min/hr. or 2.5hr/day. So lets call it 3 hrs. @ 2.5 amp or 7.5AH/day. That's summer in Montana, 60f to 100f+, 80f average ambient temp., 70f if 120v is available to run the A/C. The condenser coil is external mounted on the back of reefer and I was able to create a "chimney duct" that cools the condenser with outside air and keeps the condenser isolated from the cabin air. The duct runs from my vented storage compartment,( battery, LP tank, water pump, stinky slinky etc.) to an upper vent at the radius wall/roof. It's about 4in deep x 18 wide x 4ft tall and enters the top of the vented storage (2' x 2' x 3') and exits at roof. There is a constant draft and when the reefer cycles you can see a noticeable increase as the heat rises and draws cool air in. The duct is sealed to the rear wall of the reefer to keep that air out of the cabin. It is not as good as the chest type ARB's and such but I have it mounted at eye level over the sink and microwave so very handy. I just try to keep it full of bottled water and Jameson to limit the air space and keep the door shut. Works pretty good. Single 125 AH deep cycle, no solar.. yet, so I try to keep it topped off with the generator. I can run 3-4 days if need be without a charge but rarely go more than a day.

McDave

I was looking at these on Ebay. Do you know what kind of coolant they use? I'm guessing something like ammonia. There are some off brand 12v/110v fridges like the Norcold, but they draw a lot more power. A lot of people recommended thermoelectric coolers, but with a max cooling of 40 below the ambient temperature, I'd have to keep the trailer at 75 to keep the beverages frosty.
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Re: Solar Powered Fridge

Postby John61CT » Fri Mar 15, 2019 5:33 pm

jwh92020 wrote:I was looking at these on Ebay. Do you know what kind of coolant they use? I'm guessing something like ammonia. There are some off brand 12v/110v fridges like the Norcold, but they draw a lot more power. A lot of people recommended thermoelectric coolers, but with a max cooling of 40 below the ambient temperature, I'd have to keep the trailer at 75 to keep the beverages frosty.
Norcold is hardly an off brand.

Anyone recommending chip (Peltier effect) coolers for off grid living is off their rocker, very very high consumption besides being ineffective in hot ambient.

And why would you care about the refrigerant used?

Pretty inside-baseball for a regular consumer.

https://www.danfoss.com/en-us/about-dan ... nt-trends/
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Re: Solar Powered Fridge

Postby jwh92020 » Fri Mar 15, 2019 6:59 pm

Maybe I didn't word it properly. I wasn't calling a Norcold an off brand, but the ones that look like NCs but cost tons less. As for the cooling fluid, it was just a question. I read that some 12v/110v non-compressor fridges use a coolant that breaks down fairly quickly. I'm leaning towards one of the 12v compresor units.
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Re: Solar Powered Fridge

Postby John61CT » Sat Mar 16, 2019 2:15 am

They are the only way to go, unless you want to use propane-fired rather than electrickery when living off grid.

I believe all the Danfoss-type use 134a since R12 was banned.

Always follow the compressor manufacturer’s recommendations.

Richard Kollman over on cruisersforum.com is a great resource, maintains a good reference website too.
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Re: Solar Powered Fridge

Postby hankaye » Sat Mar 16, 2019 10:07 am

jwh92020, Howdy;

Here's a page that explains the how's and how to's with RV fridges.
https://www.arprv.com/how-dometic-norco ... -works.php

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Re: Solar Powered Fridge

Postby McDave » Sat Mar 16, 2019 11:59 am

Hey jwh,
You are getting some good info. on this one. John61 and Hank are always helpful resources. So, Yes my Norcold is a compressor driven 134a type. 134a and 410 are about all you see anymore. Absorption style reefers use ammonia and a heat source to boil/distill the liquid. They work OK on LP but suck the juice on 12v. Compressors are much more efficient and effective for 12vdc applications. Electricity is probably the worst way to make heat (except as a by-product) and the whole make heat to get cold seems cludgy at best. While compressors do produce heat, it is a by-product of the motor and the pressure. In theory, a 12v reefer/solar set up could be almost perpetual and maintenance free. Set it and forget it, that's the ticket.
I bought mine in an auction on ebay. Demand for these units dictates the cost and availability so dead of winter is a buyers market. I had my ebay set up to watch for these when they came up for auction, that helps a lot.
The external condenser coil is what allows me to eliminate the heat and pump it out of the cabin, instead of in circles. Otherwise you are dependant on the A/C to pump the heat out. At that point you might as well just run a full size 120vac side x side, ... just sayin'
Remember, chest type are better because heat rises and cold falls so you don't lose all the cold air every time you open the door... but you get what you play for. :thinking:

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Re: Solar Powered Fridge

Postby flboy » Sat Mar 16, 2019 12:18 pm

McDave wrote:Hey jwh,

The external condenser coil is what allows me to eliminate the heat and pump it out of the cabin, instead of in circles. Otherwise you are dependant on the A/C to pump the heat out. At that point you might as well just run a full size 120vac side x side, ... just sayin'
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That's getting a little deep there don't you think. :lol: :lol:
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