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Olddawgsrule ![]() Senior Member ![]() Joined: 20 Sep 2017 Location: New Hampshire Online Status: Offline Posts: 1014 |
![]() ![]() ![]() ![]() Posted: 05 Jul 2021 at 5:56am |
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You still have some ghost draw to account for... Have you ever figured that out?
Spec's on your unit state: (.36DC@5/23C), (KWH/24hr) That works out to an 1.15ah average (using 13.1v). Are you testing while empty? That will skew the numbers higher. Assuming this is your unit: https://www.dometic.com/en-us/outdoor/food-and-beverage/refrigerators/rv-refrigerators/dometic-crx-110e-56279 |
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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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StephenH, I didn't see a sketch but if you place a shunt between each battery negative and a common negative connection point, then connect from there to your 12v system negative, that should work fine. Try to keep the total length of cable run the same to both batteries.
Re your fridge load, I think there is a bit of confusion still on your units. There is no unit of amps/hour. I think you mean that your fridge is using about 27 amp hours in 12 hours (around 54 amp hours per day). That's pretty good efficiency. But it's not really very hot weather right now in our area. I'll stick with my guesstimate that you'll be 75 amp hours per day or higher in hot weather, more if you are opening and closing the fridge much and/or putting warm things in there. Of course, you have additional load to provide energy for, as you say. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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Olddawgsrule ![]() Senior Member ![]() Joined: 20 Sep 2017 Location: New Hampshire Online Status: Offline Posts: 1014 |
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Curious what you base this on.. " I'll stick with my guesstimate that you'll be 75 amp hours per day or higher in hot weather,"
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StephenH ![]() podders Helping podders - pHp ![]() ![]() Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6417 |
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The figures would have included the ghost draws. I was testing while empty so the numbers are higher than just the refrigerator power draw. There was also a little LED light use included as well. In any case, while we are using it, there will be other items (lights, fans, etc.) using power as well. In any case, it is workable and I am considering adding another battery in parallel or just replacing the 100AH model with a 200AH model. I also looked into additional solar power. Since the kit I already have has a controller that would handle up to 200W, I could add another 100W suitcase without the controller except that I did not see that available on the Renogy site. I have an inquiry in about that. Since my solar is Renogy, I'm not sure if teaming another panel that is not the same type of cells would be okay. As I said, I don't really have a good way to isolate just the refrigerator draw. Also, when it is full, power use would likely be different also as it would have the mass of the contents to buffer temperature changes. The figures I provided are just a 12 hour test on battery power and are only a rough idea of what use would be like on an actual trip.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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Olddawgsrule ![]() Senior Member ![]() Joined: 20 Sep 2017 Location: New Hampshire Online Status: Offline Posts: 1014 |
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I talked to several folk that run 12v frig's and estimates of increase draw are all over the place.. Far too many factors involved. I tested mine empty when I first received it and it was barely 10% off empty/full. I've heard folks say they were up to 50% off... Mine being chest style and yours upright should really make no difference. Closed frig is just that. The company stated numbers on your unit are very close to what I see on mine. Mine is smaller, so numbers are as well, almost exactly by size. I would expect you would see better performance once loaded up. Didn't note if you had separate freeze/frig controls. Mine does not, so that again could be a reason for higher numbers.
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StephenH ![]() podders Helping podders - pHp ![]() ![]() Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6417 |
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Control is just one setting. No separate fridge/freezer controls. I was testing with it on the next to highest setting. I had it on highest and the refrigerator almost turned into a freezer.
I'm sure I can keep ice cream in the freezer easily.
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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My basis is test results for Danfoss vaccine fridges that I worked on and installed in Africa and Latin America. Danfoss has made pretty much the same compressor for going on 35 years now.
Also, you can base it on the COP numbers from the Danfoss spec sheets. Those are pretty accurate. You have to make assumptions about the fridge box insulation performance but that's not too difficult. Besides, in the real world ppl put warm things in their fridges to cool them down. That's just being human. That uses a lot of energy which the absorption fridges can't handle but the compressor fridges can (up to a point). I learned that the first time the chief in one of the African villages I installed a vaccine fridge in immediately commandeered it to cool down his beer bottles. All my energy calcs went right out the window. I would probably have needed a kw of solar to make him happy. ![]() |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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Olddawgsrule ![]() Senior Member ![]() Joined: 20 Sep 2017 Location: New Hampshire Online Status: Offline Posts: 1014 |
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OG: I have no idea how long ago this was, so then no idea of improvement since. Just sayin' 70+amps on a 24hr period is quite high even to work with the 32°C factor show n the site.
I looked, and posted the link, to the spec's... They are very close to what I see on mine.
Then again you haven't stated temps under which you saw this. Hard to justify... Stephen: Yours is much like mine as with a single control. I can keep things frozen if I stack accordingly and still not freeze what shouldn't be. That will take you time to work out. Ice is what lovely wishes and if done correctly... I can still have some for her 3 days later. That is a quest and involves some frozen foods and stacking. Reason I went with a chest unit. I'm sure you can work out a way in in upright. Have faith in ya! |
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offgrid ![]() Senior Member ![]() Joined: 23 Jul 2018 Online Status: Offline Posts: 5290 |
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Around 1990-ish but the bd35 compressors are essentially the same units, as are their COPs. In fact Danfoss markets and is proud that they have been around for over 35 years. Demonstrates their reliability.
The ASHRAE testing published by Danfoss was done with an ambient of 32C or 90F, which gives a COP of about 1.9 for an evaporator temp of -5C. Compressor only not including any fans. 90F is low, I used to test at 40C or 104F ambient, at which point the COP was around 1.5. The current Danfoss spec sheet is dated 2004 btw. |
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1994 Chinook Concourse
1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
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StephenH ![]() podders Helping podders - pHp ![]() ![]() Joined: 29 Nov 2015 Location: Wake Forest, NC Online Status: Offline Posts: 6417 |
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These are the performance specs from Dometic's web site:
Refrigerant, type R134a - Contains fluorinated greenhouse gases GWP 1430 Refrigerant amount 47 g CO2 equivalent 0,067 t Energy consumption (DC@5/25°C) 0.36 kWh/24h Climate class (EN 62552) T |
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StephenH
Happy is the man that findeth wisdom,... ouR escaPOD mods Former RPod 179 Current Cherokee Grey Wolf 24 JS |
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