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DIY: How to make your own 12V Fridge
#31
(07-12-2016, 06:21 PM)Almost There Wrote: I don't have the data to back it up but having used a pair of Whynter 65 qt units, one as a fridge (at 40F) and the other as a freezer (0F), I can safely report that there is a huge difference in power usage between the 2 of them.


I guess I should go borrow the Kill-a-watt meter from the local library and actually do some testing.

There should be a large difference IMO, between fridge and freezer mode, in terms of power consumption.

One of the reasons I am doing this test is because very soon I have to make a decision, buy another Engel as a fridge
or use a dorm fridge. For me anyway, having a decent fridge and freezer is simply a must!

So by playing with a number of permutations of 120v and 12 v systems, I hope to find the optimal point for me.

Unfortunately waiting 9 days for each test, or 18 even lol, makes it a slow process.

Almost There, remember a kill-a watt is only for 120v, you need an RC type for low voltage, ie 12v.

What I am ultimately trying to figure out in part, is which mode is more efficient on a so called 12 v compressor fridge.
If they are a true 12 v system, and the 120 v that is fed into them is regulated down to final 12v for the compressor, then I would expect they should consume more power at 120v due to inherent losses in the down regulation. I still need to prove that out.
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#32
(07-12-2016, 06:54 PM)highdesertranger Wrote: on my Engel when I us one as a freezer.  I flash freeze everything in it by turning it down all the way.  this will freeze everything rock solid in 12-24 hours depending on ambient temps.  then I turn it up to about 3(the dial goes from 0-6,  6 being the coldest)  this keeps everything like a rock even in 100 degree weather.

Ok, no more tests! I don't want to try that! hahaha

(07-12-2016, 06:54 PM)highdesertranger Wrote: I don't have numbers to back this up but I can run my 2 Engels off of 160 watts of solar and 2 12v marine batteries no problem even with several days of cloud cover.  before I got the Engels I tried using a dorm fridge after the second night my batteries would be below 50%,  even one cloudy day and it wouldn't make it to the second day.   maybe the dorm fridge I had was a lemon.  but it worked fine of off 120v.  this turned me of to dorm fridges.  for me it was a waste of good money.  highdesertranger

I hear ya, and I aim to find out because the theory is that you are correct, the practice...well...I just can't confirm yet either way.
I figure another month and I will have final numbers, to ...well....we'll see I guess...
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#33
(07-12-2016, 09:47 PM)ahh_me2 Wrote: Almost There, remember a kill-a watt is only for 120v, you need an RC type for low voltage, ie 12v.

Well, at least I'll be able to test power consumption on 120 since the units are dual power.

That will at least give us some idea of the difference between using them as a fridge and as a freezer.

Maybe next winter I can borrow an RV type while in AZ and test it on 12V
Worry is a misuse of imagination!
 
Build link: http://www.cheaprvliving.com/forums/Thre...g-Arabella
Full-timer again as of November 24, 2015 - 14 glorious years on the road before that!



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#34
Plugged my kil-o-watt into my Kenmore 4.4 fridge (has a little freezer compartment too) and averaged 0.9 kW per day on 110v. Figure inverter loss, and that equates roughly to 20% of my daily budget of 5220 Wh (50% of total 10440 Wh).

Certainly doable, but fairly inefficient. I think you'd basically have to have 200W solar and 160 Ah battery bank to make it work with a little left over...

Ford E450 Box Truck RV Conversion
...but no pictures thanks to Photobucket...
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#35
A mini fridge built for price point will be inefficient. One built to be efficient will cost ya. That's why the smallest cube fridges can use as much power as a medium sized 2 door.

Somewhere along the line I have heard that the refrigerator is 20% of the energy bill. You pegged it. Smile
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#36
I was given a RCA 3 ft mini fridge with a even minier freezer rated at .8a @ 120v. So roughly 8 amp at 12v plus losses. I use a 235w panel to keep the system up, it gets 5 solid hours at 14-15a and some shoulder output mid winter.

At a 50% duty cycle the fridge uses 96a plus losses, the panel puts out 75a plus shoulder output. It was almost enough but it wouldn't have been close were the panel flat. It would chip away at a smaller bank and a cloudy day would really take a bite.

We gave the fridge to the mother in law. The one I want is a two door, has a bigger freezer and uses less power. Many are rated at 1.5a @120v, even cubes. At that power level or slightly higher there are 9 and 10 ft models.
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#37
I've been working through a "second round" of 'fridge shopping now that I know a bit more about my power budget and what the numbers actually mean. 

And honestly, I have to say that in some ways, ignorance was bliss. I assumed that if one paid $1300 for the 12v/24v flavor of a mini-fridge that the energy savings versus the $130 one at Home Depot would be amazing. Turns out that's not really true...the "amazing" part definitely not. I have actually found expensive RV fridges that use about the same as my old Kenmore...if it weren't for inverter inefficiency, the $130 would tie the $1300 one.

Here's a decent comparison I think: Vitrifrigo Sea Steel C115iXAC for $1100 uses 45 watts. My old Kenmore uses 71 watts. A Vitrifrigo Sea Classic DP2600iAC Refrigerator / Freezer for $1600 uses 65 watts.

And here is a $1100 Dometic CRX-1110 3.7 cu/ft that uses 72 watts... what the heck??

I feel like I must still be missing something, because it sure appears that huge price tags don't equate to much energy savings...?

Ford E450 Box Truck RV Conversion
...but no pictures thanks to Photobucket...
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#38
how much refrigerated space do we need. grocery stores Walmarts in every town. deep into western wilderness could be handled as it has been for centuries.
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#39
(07-17-2016, 06:37 AM)ccbreder Wrote: how much refrigerated space do we need. grocery stores Walmarts in every town. deep into western wilderness could be handled as it has been for centuries.

Well, aside from nearest Walmart being 100+ miles away, what I "need" is a way to keep 1.5 cases of assorted beverages cold, as well as leftovers from my once-a-week cooking that I eat through the week. Deep in the wilderness sounds wonderful...unfortunately I have to work a lot which leaves me without the time or willingness to focus on small things, such as keeping my daily supply 8-pack of water/gatorade/propel cold.

Ford E450 Box Truck RV Conversion
...but no pictures thanks to Photobucket...
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#40
Don't worry, my friend. WAWA is coming to Florida! Smile
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