Ok....so with so many boondockers going the mini split route to run air conditioning off batteries but on those not nights when you pull off the road or into a rest area and you don't want to run the generator, what's the latest thinking on the abundance of low volt airs. I'm planning on 2000 watts of solar roughly and a separate lithium battery bank separate from my starting lead acid battery. Heck, I don't know know how I'm going to work at all the specifics but plopping a 12/24 volt air into a vent opening instead of a mini split sounds much easier. Just browsing Amazon, they show quite a number of low volt units? I just haven't heard much in regards to function?

physics is the limitation, Even if the efficiency is double a conventional rooftop which puts it in the ballpart of high efficiency home units, your still looking at near a 50A draw from 12V, 24V would be around 25A, more tolerable. If the efficiency is near that of todays RV AC units, double those numbersTypical RV AC unit at 12A draw is about 1500W=4500BTU AC output is 13K BTU so your running about 3:1, or an Engergy efficient ratio of about 10. (BTU out/wattsin) which actually is a meaningless number, the units don't match. It should be BTU out/bTU in, but then the number is 3x less. That aside the top AC units approach 20 for a EER, and that still puts you in the 50A range from 12V.A quick look at the amazon units claim decent efficiency, 750W for 13Kbtu vs the 1400W for a rooftop RV, but still that's around 25A at 24V and it requires 50+A for startup.

Kept in mind if you go with a lower btu unit, it will run more.So if a 15k btu runs 25% of the time a 5k btu will run 75% of the time...net result is the same number of Amp hours used.While it's possible, it gets expensive compared to just breaking out the generator. Those that jump thru the hoops usually live with limited use.

ktmrfs wrote:That aside the top AC units approach 20 for a EER, and that still puts you in the 50A range from 12V.A quick look at the amazon units claim decent efficiency, 750W for 13Kbtu vs the 1400W for a rooftop RV, but still that's around 25A at 24V and it requires 50+A for startup.Comparing a 12VDC A/C to a 12VDC compressor refrigerator (they are close cousins), all DC refrigerators that I know of actually take the DC voltage run it through an inverter and generate a 3 phase AC output (3 phase motors much more efficient than single phase).It can be done, but is it the best solution from a total energy consumption standpoint ?As pointed out, most mini-splits have a very high EER. There are a few "window shakers" that have similar EER.

theoldwizard1 wrote:ktmrfs wrote:That aside the top AC units approach 20 for a EER, and that still puts you in the 50A range from 12V.A quick look at the amazon units claim decent efficiency, 750W for 13Kbtu vs the 1400W for a rooftop RV, but still that's around 25A at 24V and it requires 50+A for startup.Comparing a 12VDC A/C to a 12VDC compressor refrigerator (they are close cousins), all dc refrigerators that I know of actually take the DC voltage run it through an inverter and generate a 3 phase AC output (3 phase motors much more efficient than single phase).It can be done, but is it the best solution from a total energy consumption standpoint ?As pointed out, most mini-splits have a very high EER. There are a few "window shakers" that have similar EER.even the best units today are around EER=20 or so, vs. about 10 for the typical 13.45K BTU RV AC unit. So 12V or 24V draw is till pretty high. would be nice if rooftop RV AC units were around 15 or so, with decently low LRA so they would easily start and run on a 2Kwatt inverter generator. Best rooftops I've seen are still around 10A vs. 13 or so. To add to the confusion SEER which is often a higher number than EER EER is the BTU out/watts in at outside temp of 95F. that's the important one if running off batteries. I've seen units with SEER of 25 but the EER is usually in the 18-19 range. SEER uses a range of temps from 65F to 95f and units are more efficient at lower outside temps. If you want to know what it takes to cool the RV when outside temps is high EER is the key and will give you a good idea of the input power needed. Figure a EER of 20 is pretty much best you will get, likely somewhat less.https://servicechampions.com/blog/difference-between-eer-and-seer/#:~:text=Where%20EER%20is%20calculated%20using,F%20to%20104%C2%B0F.

12 / 24 volt air conditioner | Good Sam Community

12 Replies

valhalla360
Navigator
Jul 04, 2023
Kept in mind if you go with a lower btu unit, it will run more.

So if a 15k btu runs 25% of the time a 5k btu will run 75% of the time...net result is the same number of Amp hours used.

While it's possible, it gets expensive compared to just breaking out the generator. Those that jump thru the hoops usually live with limited use.
ktmrfs
Explorer III
Jul 04, 2023
physics is the limitation, Even if the efficiency is double a conventional rooftop which puts it in the ballpart of high efficiency home units, your still looking at near a 50A draw from 12V, 24V would be around 25A, more tolerable.

If the efficiency is near that of todays RV AC units, double those numbers

Typical RV AC unit at 12A draw is about 1500W=4500BTU AC output is 13K BTU so your running about 3:1, or an Engergy efficient ratio of about 10. (BTU out/wattsin) which actually is a meaningless number, the units don't match. It should be BTU out/bTU in, but then the number is 3x less.

That aside the top AC units approach 20 for a EER, and that still puts you in the 50A range from 12V.

A quick look at the amazon units claim decent efficiency, 750W for 13Kbtu vs the 1400W for a rooftop RV, but still that's around 25A at 24V and it requires 50+A for startup.

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12 / 24 volt air conditioner

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