ktmrfs
Portland, Oregon
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StirCrazy wrote:when it comes to power usage, a 12V is not near as energy efficient (battery power wise) as an adsorbition fridge. you will need much more battery capacity and solar or a generator if you switch to 12V compressor.
In terms of BTU or KWH needed to cool, compressor driven fridges are much more efficient than a absorption fridge. Generally you can get about 3x the input BTU used in cooling BTU from a compressor driven fridge. No it doesn't violate any laws of physics, it's the energy needed to move heat from one place to another.
By contrast an absoprtion fridge is much less efficient COP is on the order of 0.7 or less vs 3 or more for compressor fridges.
But in terms of how the energy is stored to use the fridge, propane in BTU/gallon or BTU/weight or BTU/volume FAR FAR FAR exceeds any battery for the same volume or weight.
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Vintage465
Prunedale CA.
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Fisherguy wrote:Vintage465 wrote:
... The day will come when everything will be 12v compressor and we will all need to adjust and by that time the solar and batteries will surely be up to the task.
And on that note I'm looking for advice. I have a chance to buy a trailer with 600 watts of solar panels, 3 - 100 Ah Lithiums and a 12 volt Norcold fridge.
I'll be installing a small inverter to power the TV and sat dish but no coffee makers or toasters etc for us.
If we only boondock do you think this setup will work for us? Maybe if I add another 200 watt panel and another 100Ah of Lithium?
We only very rarely need to run the genny to charge batteries with our current rig in my signature.
Thx
I think you have a good start there, but I'm certainly not any kind of expert on 12v longevity from a power stand point. But based on what you have and are willing to add to it you should be able hold out. You may encounter some issues if you winter camp using that kind of energy.
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StirCrazy
Kamloops, BC, Canada
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ktmrfs wrote:StirCrazy wrote:when it comes to power usage, a 12V is not near as energy efficient (battery power wise) as an adsorbition fridge. you will need much more battery capacity and solar or a generator if you switch to 12V compressor.
In terms of BTU or KWH needed to cool, compressor driven fridges are much more efficient than a absorption fridge. Generally you can get about 3x the input BTU used in cooling BTU from a compressor driven fridge. No it doesn't violate any laws of physics, it's the energy needed to move heat from one place to another.
By contrast an absoprtion fridge is much less efficient COP is on the order of 0.7 or less vs 3 or more for compressor fridges.
But in terms of how the energy is stored to use the fridge, propane in BTU/gallon or BTU/weight or BTU/volume FAR FAR FAR exceeds any battery for the same volume or weight.
if you looked I did preamble this in terms of power usage as in how much power is required of the batteries.. I understand the other side already but thats not the issue here. the issue is how much more it would cost in batteries solar panels or generator to boon dock with a 12V compressor fridge.
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goducks10
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There's no way a 12V fridge costs less than an absorption fridge to run or to install. Between the solar panels, larger/or more batteries and controller you can get an absorption fridge for much less and only need propane to run it on for weeks.
You have to have the best weather conditions and be in open view of the sky for the solar to work best. If not you need to buy and generator to compensate. Then buy gas.
Regardless of which one use less power, it's which power has the best upside.
Propane doesn't care if it's 90* and sunny or raining. It's going to run the fridge 24/7. Solar only runs the fridge in daylight. Batteries at night.
Batteries need recharged, rinse repeat until it rains or it's cloudy or you're in the trees. Then it's time to drag out the gen.
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Grit dog
Black Diamond, WA
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9 pages later, ^ here’s a good dose of common sense and truth.
Being more “efficient” in one way doesn’t necessarily mean less costly.
Sure both have different advantages and disadvantages but apples to apples, especially if considering replacing a perfectly good absorption fridge, it’s not even close.
* This post was
edited 01/03/23 08:11am by an administrator/moderator *
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Fisherguy
Vancouver BC
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Vintage465 wrote:Fisherguy wrote:Vintage465 wrote:
... The day will come when everything will be 12v compressor and we will all need to adjust and by that time the solar and batteries will surely be up to the task.
And on that note I'm looking for advice. I have a chance to buy a trailer with 600 watts of solar panels, 3 - 100 Ah Lithiums and a 12 volt Norcold fridge.
I'll be installing a small inverter to power the TV and sat dish but no coffee makers or toasters etc for us.
If we only boondock do you think this setup will work for us? Maybe if I add another 200 watt panel and another 100Ah of Lithium?
We only very rarely need to run the genny to charge batteries with our current rig in my signature.
Thx
I think you have a good start there, but I'm certainly not any kind of expert on 12v longevity from a power stand point. But based on what you have and are willing to add to it you should be able hold out. You may encounter some issues if you winter camp using that kind of energy.
Thanks.
It will be interesting. I've been doing a lotta research, apparently Lithium batteries charge a lot quicker than lead/acid as well which is good, the less genny time the better.
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theoldwizard1
SE MI
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Reisender wrote:Yah I hear you. Hence our back up plan with our little propane generator. ![[emoticon]](https://forums.goodsamclub.com/sharedcontent/cfb/images/smile.gif "smile") .
![[image]](https://live.staticflickr.com/65535/52387204385_ee9895e00a_c.jpg)
Curious. How many hours do you get on that generator on that small propane bottle ?
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Reisender
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Hmm. Is a bit of a guess but I’ll say 8 or 10 hours maybe. We used it 6 or 7 times for trailer battery charging on our cross country Canada trip, maybe 45 minutes to an hour every time and the tank still had some in it when we got home. We have to pack our front box of the trailer light because I’m trying to keep my hitch weight under 350 pounds. Hindsight says I had enough room for a 10 pounder but at the time the 5 pounder seemed like a better choice. One thing about small combos, you gotta watch everything you pack. .
![[image]](https://live.staticflickr.com/65535/52387203690_56dcf7ca64_c.jpg)
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Vintage465
Prunedale CA.
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ktmrfs wrote:StirCrazy wrote:when it comes to power usage, a 12V is not near as energy efficient (battery power wise) as an adsorbition fridge. you will need much more battery capacity and solar or a generator if you switch to 12V compressor.
In terms of BTU or KWH needed to cool, compressor driven fridges are much more efficient than a absorption fridge. Generally you can get about 3x the input BTU used in cooling BTU from a compressor driven fridge. No it doesn't violate any laws of physics, it's the energy needed to move heat from one place to another.
By contrast an absoprtion fridge is much less efficient COP is on the order of 0.7 or less vs 3 or more for compressor fridges.
But in terms of how the energy is stored to use the fridge, propane in BTU/gallon or BTU/weight or BTU/volume FAR FAR FAR exceeds any battery for the same volume or weight.
And ultimately this is my point, and why I still use an Absorption unit: "But in terms of how the energy is stored to use the fridge, propane in BTU/gallon or BTU/weight or BTU/volume FAR FAR FAR exceeds any battery for the same volume or weight."
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valhalla360
No paticular place.
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Grit dog wrote:9 pages later, ^ here’s a good dose of common sense and truth.
Being more “efficient” in one way doesn’t necessarily mean less costly.
Sure both have different advantages and disadvantages but apples to apples, especially if considering replacing a perfectly good absorption fridge, it’s not even close.
Truth depends heavily on the assumptions.
Tearing out a relatively new perfectly functional appliance rarely makes sense, no matter how bad the existing technology is. Are you going to rip out the perfectly functional 5 speed transmission in your truck and retrofit one of the new 10 speed units because it's better...of course not. It's a silly comparison.
If you are boondocking a lot with a single 12v starting battery and no solar, yeah, absorption is by far the better option but that's not a typical use pattern.
Vast majority of RVs rarely operate away from shore power. For these rigs, 12v compressor fridges are better both in terms of efficiency but also in terms of better operation (faster cooldown, able to hold colder temps, larger interior volume, etc....). I'm betting this represents 80-90% of new RV buyers, so this is where the manufacturers are focused.
For those who do a lot of boondocking, most will be installing a larger battery bank and solar anyway. Up sizing it to accommodate the relatively modest requirements of the 12v fridge is easy and doesn't incur a major cost. The cost difference between installing a couple of 200w panels and a couple of 300w panels, is pretty minimal. A few seasons of reduced propane use will cover the cost. Manufacturers are still on the learning curve but they are starting to outfit RVs with solar options. Not just for the fridge but for other convienences.
To find a place where your "truth" holds, you need to start looking at specialty cases that split the difference. Maybe someone who camps 60 nights per year with 15 of them boondocking and other than the fridge they are used to being very rustic (ie: using almost no 12v power when not on shore power). It's enough use where relying on shore power is problematic but they wouldn't otherwise need a solar system.
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