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Old 11-08-2019, 02:14 AM
williammandella williammandella is offline
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Is converting a freezer to a fridge to keep drinks cold more efficient than just buying a mini fridge? If you don't need to freeze anything, the small fridge will keep two cases of soft drinks or bottled water cold, and once the drinks are down to the desired temp, they help to keep the inside of the fridge cold. Since there's no freezer section, the compressor doesn't run very much after the desired temp is reached, and it doesn't draw much current , which means that you can use a smaller inverter.
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Old 11-08-2019, 05:40 PM
fordtrucksforever fordtrucksforever is offline
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Freezer conversions have become popular because they are supposed to be better insulated than the same size fridge. So should not run as much. Just have to swap out the thermostat to operate above 32 degrees.
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Old 11-08-2019, 05:49 PM
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Quote:
Originally Posted by Grizzly Guy View Post
Mountain I would go with a propane fridge if I had one, but I hate to spend money acquiring one when I already have a freezer. I'll need solar in the future so I might as well start now.
In my area it is common to find somewhat modern 3 way fridges from totaled campers on Craigslist for around $50.

I don't know how efficient they are or how cold they get, but you can run them on solar and use propane as a back up and the generator as a back up to your back up.


I just set up a solar system to power my cabin but also to keep my freezer cold in case of an extended power outage I have 1.5 usable kwh's of battery storage before my power inverter warning kicks on that the battery is too low and a 325 watt panel. Both of them are just right to keep the freezer running as long as the sun is out all day. As soon as their is a cloud in the sky the freezer won't be able to run all night. I for sure need more battery but should have double the panel as well. The freezer draws 1.3 kwh hours per day in the basement in cool fall weather.

Go with an MPPT charge controller. With an mppt your panel will still be able to slowly charge the battery even when it is cloudy or in shade. A PMW controller would be unable to put that power into a battery unless it is in full sun.

I went with Makeskyblue for my charge controller. I have only had a for a month or so so I can't say how good it is long term but so far I am impressed by it. I got the 30 amp and intend to order a 60 amp to be able to connect my other two panels. I stuck with 12 volt because it is very easy to find 12 volt items to run of the batteries(anything designed to run in a car will work on my batteries)
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Old 11-08-2019, 05:51 PM
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Originally Posted by fordtrucksforever View Post
Freezer conversions have become popular because they are supposed to be better insulated than the same size fridge. So should not run as much. Just have to swap out the thermostat to operate above 32 degrees.
A freezer with a top opening also doesn't spill out all the cold air when it is opened like a fridge does.
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Old 11-08-2019, 06:29 PM
jdemaris jdemaris is offline
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I bought a new Igloo 3.5 cubic foot chest freezer at Walmart a few years ago and have been using it as a refrigerator ever since. It needed NO conversion parts. I simply went into the actual thermostat and turned the adjuster screw a little to make it run warmer. I am on my 3rd year now and it has worked flawlessly. I paid $119 for it. Note I have a very high priced Sundanzer DC refrigerator that is made for solar and I do not like it as much (kind of noisy for one thing). That thing cost me over $1000. Back to this little Igloo with no mods other then turning a screw a little. At a 70 degree F air temp, it runs on 129 watt-hours a day. When I first did tests on it - I hooked it up to a single Walmart type 29 deep-cycle battery and a cheap modified wave inverter that cost me $99 at Harbor Freight. I left it hooked up for 36 hours and the battery was still at 70% charge at 12.3 volts. If I wanted to run it with the least amount of solar possible - obviously, it would take a panel capable of averaging 5.5 watts per hour for a 24 hour day. Since a solar-panel only makes good power for 4-6 hours a day (depending where you are) - a 50 watt panel, in theory, should work. Again, much depends on the sun you are getting. I have had it hooked to a single 120 watt panel and it worked fine. It is now in my cabin and I have a 1000 watts of panels and a 880 amp-hour battery bank so I no longer monitor just the use of the refrigerator. I will note that it absolutely runs on less when hooked to a good sine-wave inverter instead of a modified-wave inverter. Here are my first test results. I was very surprised how well this thing worked out considering how much money I wasted on that DC powered Sundanzer. I will note thjat the reason why these things work so well is because of the chest design instead of being a stand-up type chest that is much more inefficient. Igloo chest freezer converter to refrigerator
Ran it 141 hours and used .76 KWH
So 760 watt hours for 141 hours = 5.39 watts per hour on AC
129 watt-hours per day

Tested with inverter and type 29 DC Walmart battery - no-load voltages
12.9 volts - 12.05PM
12.65 volts - 2:45 PM
12.59 volts - 10:30 PM
12.51 volts - 7:30 AM .13 KWH - 19.32 hours
12.42 PM - 3:30 PM .17 KWH - 27.24 hours
12:40 volts - 6:30 PM .18 KWH - 30.23 hours
12.36 volts - 10:15 PM .2 KWH - 34.07 hours (70% charge)
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Old 11-08-2019, 07:33 PM
Grizzly Guy Grizzly Guy is offline
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jdemaris, I just wanted to say thanks. I thought it was doable. In the thread I was told it wouldn't work, and I was told by a few that it would. A few people said a 100 or 200 watt panel would work all the way to 600 watts of solar might not be enough. Some said it would be more efficient as a fridge, one person kept saying more efficient as a freezer. I finally just decided to try it as cheap as I can. 100 watt panel and a cheap deep cycle battery, I can always charge it. If it won't work I might just scrap the whole plan and try the ice maker on solar.
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Old 11-08-2019, 09:41 PM
JL1 JL1 is offline
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I will tell you this just for info. The size and quality of the inverter will affect fridge and/or freezer operation. I figured that much out before. Had 2 higher wattage inverters, one 2500 watt and one 3500 watt. Both cheap ebay units. Neither would start the 18 cu.ft fridge or small upright chest freezer I have in my shop. I ended up installing a hard start capacitor on both so they would start and run. Start up is always the hardest part for the compressor.
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Old 11-08-2019, 11:40 PM
notyoung notyoung is offline
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Kenmore made a very efficient counter height fridge, the 4.4 cu ft model 99783, which uses 27.5AH in 24 hours (5.09 amps for 5.4 hours) running on a 90% efficient pure sine wave inverter (PLUS the inverter's idle power) in a 78F environment. Many of the smaller "dorm fridge size" fridges use much more power (had one before getting the Kenmore). The Kenmore is the basement fridge and is usually filled with heirloom seeds and maybe a soda or two.
Last time I checked, these were discontinued but you might find one in a store somewhere.

I use Reliable Power inverters (search for reliablepower on Ebay). Not pretty, but they work and the power is cleaner that what our local electric co-op delivers. The 2000 watt pure sine wave inverter starts and runs the 28 cu ft fridge/freezer, the 13 cu ft freezer and the blower on the gas-fired central heat with no problems.

You'll find my estimates/designs are pessimistic because I plan for multiple days with limited or no sun, the capacity to recharge X days of use in one day of sun (that is how real weather happens) and for maximum battery life. If you run the inverter until it complains about the battery voltage, you are killing your batteries early. While the "Discharge to XX amp hours" test may take a battery to 10.5 volts or less under load, lead acid batteries have a VERY limited cycle life at 100% discharge - fewer than 100 charge/discharge cycles for some of them.
To get the rated power from a 100AH battery, the correct load would be 5 amps for 20 hours (most lead-acid batteries are rated at the 20 hour rate, although some are rated at the 10 hour rate and forklift batteries are often rated at the 8 hour rate - typical work day for a forklift). An AGM battery is typically fully discharged when it reads 12.1 or 12.2 volts at rest (24 hours with no charge or discharge). When I test batteries for capacity, they are tested at the specified load and to an under-load voltage of 11.1 volts (telecom full discharge voltage and maybe 85% of the 20 hour AH rating).
If you want maximum battery life, you must know the manufacturer's specs for charging and discharging your specific batteries (often specifed to a hundredth of a volt). The AGM batteries I replaced earlier this year were a few months shy of 9 years old - and I had bought them used (2 of the 6 batteries still have 80% of their original capacity). Being picky about battery care does pay off in the long term.
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Old 11-09-2019, 01:31 AM
williammandella williammandella is offline
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Quote:
Originally Posted by fordtrucksforever View Post
Freezer conversions have become popular because they are supposed to be better insulated than the same size fridge. So should not run as much. Just have to swap out the thermostat to operate above 32 degrees.
One reason I like the small fridge is that I can power it from the 12 volts in my SUV through the inverter. Flip the back seat down, put the fridge behind the passenger seat with the door facing the driver, and I can reach back for a cold drink or sandwich while driving. Now I can't go fishing, hunting or camping without the fridge. In hot weather, I keep my bait in the fridge. NO MORE CARRYING HEAVY COOLERS! NO MORE BUYING ICE! NO MORE SOGGY BACON. Yahoo!
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Old 11-09-2019, 01:40 AM
williammandella williammandella is offline
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If anyone likes fun projects, buy a Harbor Freight 212cc horiz shaft motor and a one-wire capable automotive alternator like a CS130D or AD244. Use a spider coupling to couple the motor to the generator, and use the set to charge your batteries. The motor even spins the alternator in the correct direction. Make sure the alignment is very good or the coupling will wear out. It also works great as an automotive battery charger, because that's what the alternators were designed to do.
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Old 11-09-2019, 07:09 AM
KLF KLF is offline
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I'm just gonna drop this here and run away
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Old 11-09-2019, 11:32 AM
fordtrucksforever fordtrucksforever is offline
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Quote:
Originally Posted by JL1 View Post
I will tell you this just for info. The size and quality of the inverter will affect fridge and/or freezer operation. I figured that much out before. Had 2 higher wattage inverters, one 2500 watt and one 3500 watt. Both cheap ebay units. Neither would start the 18 cu.ft fridge or small upright chest freezer I have in my shop. I ended up installing a hard start capacitor on both so they would start and run. Start up is always the hardest part for the compressor.
What setup are you using to pull 2500/3500 watt inverters?
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Old 11-09-2019, 01:45 PM
JL1 JL1 is offline
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What setup are you using to pull 2500/3500 watt inverters?
I had 4 150 watt solar panels, 4 6v 215aH batteries wired in series for 12v and a cheap 60A charge controller. It was more of an experiment of sorts. I could power up some of my saws with it, fridge and chest freezer. The fluorescent lights did not like it. Like I stated, inverters were cheap. Kind of thinking they were nowhere near the stated ratings. 1 good lightning strike took most of it out. Wasn't even a direct hit, just a near miss. Killed both inverters. Fried the diodes in 2 panels and all 4 of my florescent lights. Luckily I was able to replace the junction boxes on the two panels. Still haven't replaced the inverters and need to upgrade to a better charge controller. I did install a good ground system for the panels, batteries and charge controller.
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Old 11-09-2019, 05:25 PM
fordtrucksforever fordtrucksforever is offline
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Quote:
Originally Posted by JL1 View Post
I had 4 150 watt solar panels, 4 6v 215aH batteries wired in series for 12v and a cheap 60A charge controller. It was more of an experiment of sorts. I could power up some of my saws with it, fridge and chest freezer. The fluorescent lights did not like it. Like I stated, inverters were cheap. Kind of thinking they were nowhere near the stated ratings. 1 good lightning strike took most of it out. Wasn't even a direct hit, just a near miss. Killed both inverters. Fried the diodes in 2 panels and all 4 of my florescent lights. Luckily I was able to replace the junction boxes on the two panels. Still haven't replaced the inverters and need to upgrade to a better charge controller. I did install a good ground system for the panels, batteries and charge controller.
You dont have enough battery to pull anything more than 2000 watts, only if the batteries are in series to produce 24 volts.

The wire size for a 12 volt system to pull a 2500 watt inverter needs to be 2/0 or bigger. You would be pulling over 200 amps from the battery bank. I can see why there was problems.
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Old 11-09-2019, 06:17 PM
JL1 JL1 is offline
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Quote:
Originally Posted by fordtrucksforever View Post
You dont have enough battery to pull anything more than 2000 watts, only if the batteries are in series to produce 24 volts.

The wire size for a 12 volt system to pull a 2500 watt inverter needs to be 2/0 or bigger. You would be pulling over 200 amps from the battery bank. I can see why there was problems.
OK how do I rate what I use or need? The cable for the 3500 watt inverter was 4/0 to the batteries. I do realize I need more batteries. This was just a start.
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Old 11-09-2019, 07:38 PM
fordtrucksforever fordtrucksforever is offline
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OK how do I rate what I use or need? The cable for the 3500 watt inverter was 4/0 to the batteries. I do realize I need more batteries. This was just a start.
You need to get away from 12 volts pulling that much load. I cant believe 2500/3500 watt inverters are even available for 12 volt battery. You wont have any luck using solar panels with one. The draw on that 3500 is almost 300 amps.

This is a safe range for inverters.

12v-1000 watts
24v-2000 watts
36v-3000 watts
48v-4000 watts

Then add enough panels that your battery bank can be recharged in a day.
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Old 11-10-2019, 01:29 PM
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If you like building things there are all sorts of educational papers that show how to make batch ice makers powered by the sun they are based on the design of ammonia heat absorption fridges but use charcoal and methonal,gasoline,ethonal,paint remover or any other fast evaporating liquid. They can be built as simply as two propane tanks and a connecting pipe. One tank is filled with charcoal soaked with as much methonal as it can hold, the other is empty, draw a slight vacuum and seal it off.
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Old 11-11-2019, 10:36 AM
JRR JRR is offline
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I've been off grid for over a year. When I first started the planning stages I thought this way, too. Why buy an expensive dc fridge when I already have a perfectly good minifridge? All I need is a cheap inverter and I'll be good to go, right? Not even close. My small minifridge uses 1.3 amps. That's 13 amps at 12 volts. It has at least a 30% duty cycle, maybe as much as 50%, depending on various factors, such as outside temps, how much food is in it, temperature setting, the frequency it is opened, etc. So, 103 amp hours. At 12 volts, that's over 1200 watt-hours. You need to put that back every day. With 4 hours of peak sun - and you may get less depending on location and time of year - you'd need over 400 watts of solar before losses. That's before allowing for cloudy days, etc. So, figure 500 watts, minimum. That's $500 worth of panels or more. Now, compare that to my Engle fridge. It draws about 2.5 amps, cycles about every 15 minutes for less than 2 minutes, so 8 minutes an hour, more in the summer. Let's call that 10 minutes. That's 4 hours out of 24. 10 amp hours. In reality, it draws more than that, let's call it 30. That's still WAY less than the 103 the minifridge will use. My Engle will require a 100 watt panel to run, that's a $300 savings right there. That's my longwinded redneck math way of saying a dc fridge will take 1/4 the solar array of an ac fridge. 1/4 the price without factoring in the price of a larger charge controller, inverter, and wire.
All this is assuming you're using it as a refrigerator. As a freezer either fridge will take a ton more power to run.
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Old 11-11-2019, 12:02 PM
KLF KLF is offline
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I bought today 12V compressor fridge for my van. It's small but same principle stays: it is much more energy efficient than those that use absorption technique. Should be around 1amp/hour.
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Old 11-11-2019, 05:25 PM
Grizzly Guy Grizzly Guy is offline
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I have decided to go with a 100 watt panel with a cheap controller, using my 1000 watt inverter to run a small icemaker. Charliemeyer posted a video of in I think post 33. If it won't work I'll expand the system or run my generator for a few hours to make ice. I will, make my ice when the sun shines, if its a cloudy day it won't be so hot and I can do without.
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