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 > Anyone with 12v Air Conditioning Experience?

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wanderingaimlessly

Buggs Island lake

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Posted: 08/16/21 09:56am Link  |  Quote  |  Print  |  Notify Moderator

Not an AC expert, but have watched the threads in here and other places and dont really understand why more folks dont try or use mini splits, some small units are as high as 18 SEER to help with energy usage, and have seen some 8000-9000 btuh units with 650-800 watt energy consumption when operating. If operating consumption is that low, it seems a solar package of 1000 watts or more with a battery bank in the 500 AHr range should give a small camper at least several hours a day of usage.

S Davis

Western WA

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Posted: 08/16/21 11:17am Link  |  Quote  |  Print  |  Notify Moderator

wanderingaimlessly wrote:

Not an AC expert, but have watched the threads in here and other places and dont really understand why more folks dont try or use mini splits, some small units are as high as 18 SEER to help with energy usage, and have seen some 8000-9000 btuh units with 650-800 watt energy consumption when operating. If operating consumption is that low, it seems a solar package of 1000 watts or more with a battery bank in the 500 AHr range should give a small camper at least several hours a day of usage.


There are inverter driven window shakers that could work without the copper line set to leak. Mini splits can run at pressures above 500 psi so I would have concerns about the flair connections.

CA Traveler

The Western States

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Posted: 08/16/21 11:20am Link  |  Quote  |  Print  |  Notify Moderator

Hard to beat a single unit on the roof for unit cost and installation. Plus most RVs travel pedestal to pedestal so A/C efficiency is not a concern.


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Bob


3 tons

NV.

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Posted: 08/16/21 12:17pm Link  |  Quote  |  Print  |  Notify Moderator

S Davis wrote:

wanderingaimlessly wrote:

Not an AC expert, but have watched the threads in here and other places and dont really understand why more folks dont try or use mini splits, some small units are as high as 18 SEER to help with energy usage, and have seen some 8000-9000 btuh units with 650-800 watt energy consumption when operating. If operating consumption is that low, it seems a solar package of 1000 watts or more with a battery bank in the 500 AHr range should give a small camper at least several hours a day of usage.


There are inverter driven window shakers that could work without the copper line set to leak. Mini splits can run at pressures above 500 psi so I would have concerns about the flair connections.


Be advised that this boat has already left the dock, mini-splits are likely on thousands of OTR vehicles and trailers…

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valhalla360

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Posted: 08/16/21 01:08pm Link  |  Quote  |  Print  |  Notify Moderator

adamis wrote:

valhalla360 wrote:

500amp-hr at 12v battery bank is about 6kwh. Probably 5kwh usable with lithium.

The air/con you listed is just shy of 1500w when running. Your 5kwh of usable power gives you 3.3hr of run time.

500w of solar will only recharge about 2kwh per day, so 1.3hr unless you run the generator to recharge the batteries.

Not really any better than a stock 15k btu 120v air/con but only 12k btu so it will have to run longer consuming more power.


I don't think these calculations are representative of normal use, at least for the West Coast where I live. Here we tend to get cool nights in the 60s and hot days in the mid to high 90s. The Bigfoot camper is insulated pretty well so it tends to stay pretty cool inside until around noon at which point it has reached the 80s. I am also not intending to run the AC all day, just when I need it which generally would be for meals and possibly to cool things down prior to bed time when the camper walls are still heat soaked and so tend to keep interior warmer than outside.

The second part is that your back of the envelope calculations assume the compressor will be running at max current draw the entire time but that doesn't happen. In my experience it is about a 50% duty cycle and the draw when the compressor isn't running is just a few hundred watts for the fan. You also used the worst case scenario of 120A for the Max Cooling but the website states:

Eco Mode should be the default operation type on a Nomadic Cooling air conditioner. Powerful mode should only be used for short periods of time for maximum cooling, as powerful mode has increased consumption of energy.

Eco Mode consumes 35A to 55A according to the manufacturer. So using the 55A just for simplicity, that is 660 watts of draw and with a 5kwh of usable power, that is 7.57 hours of run time. That assumes the compressor is running 100% of the time but it doesn't because the compressor won't be running the entire time in eco mode. This doesn't even take into account 400w to 600w of solar that could be reducing the battery consumption even further.

For West Coast environment, these numbers would be more than sufficient. Maybe not for the South where AC runs essentially non-stop but then I don't think I would visit the South in the middle of the Summer if I didn't have to.


I never brought up duty cycle. If you really only need 2-3hr of air/con per day, sure it can be done but you don't see or hear of a lot of people doing that and you can do that with a standard air/con with an inverter without the need for an oddball 12v unit.

If you run on the low output mode, it will run proportionately longer, so there is no net savings in kwh consumed. The only advantage to that is if full power only takes 10-15min to cool the interior, it may not remove much humidity. Drying out the air is a big part of making it more comfortable. Of course, if you are just trying to stop for lunch to cool it down, if it takes an hour or two, you are already back on the road before the temps are comfortable.


Tammy & Mike
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Grit dog

Black Diamond, WA

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Posted: 08/16/21 01:14pm Link  |  Quote  |  Print  |  Notify Moderator

adamis wrote:

valhalla360 wrote:

500amp-hr at 12v battery bank is about 6kwh. Probably 5kwh usable with lithium.

The air/con you listed is just shy of 1500w when running. Your 5kwh of usable power gives you 3.3hr of run time.

500w of solar will only recharge about 2kwh per day, so 1.3hr unless you run the generator to recharge the batteries.

Not really any better than a stock 15k btu 120v air/con but only 12k btu so it will have to run longer consuming more power.


I don't think these calculations are representative of normal use, at least for the West Coast where I live. Here we tend to get cool nights in the 60s and hot days in the mid to high 90s. The Bigfoot camper is insulated pretty well so it tends to stay pretty cool inside until around noon at which point it has reached the 80s. I am also not intending to run the AC all day, just when I need it which generally would be for meals and possibly to cool things down prior to bed time when the camper walls are still heat soaked and so tend to keep interior warmer than outside.

The second part is that your back of the envelope calculations assume the compressor will be running at max current draw the entire time but that doesn't happen. In my experience it is about a 50% duty cycle and the draw when the compressor isn't running is just a few hundred watts for the fan. You also used the worst case scenario of 120A for the Max Cooling but the website states:

Eco Mode should be the default operation type on a Nomadic Cooling air conditioner. Powerful mode should only be used for short periods of time for maximum cooling, as powerful mode has increased consumption of energy.

Eco Mode consumes 35A to 55A according to the manufacturer. So using the 55A just for simplicity, that is 660 watts of draw and with a 5kwh of usable power, that is 7.57 hours of run time. That assumes the compressor is running 100% of the time but it doesn't because the compressor won't be running the entire time in eco mode. This doesn't even take into account 400w to 600w of solar that could be reducing the battery consumption even further.

For West Coast environment, these numbers would be more than sufficient. Maybe not for the South where AC runs essentially non-stop but then I don't think I would visit the South in the middle of the Summer if I didn't have to.


This all sounds like a very expensive, complicated solution to fix what is essentially not a problem. Find places to camp that wont kick you out for running a generator...
He!!, I'd quit camping before I'd drop $9k (+ more $ solar + a bunch of extra work) to "upgrade" a camper that has a perfectly good AC and power source already.


2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
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adamis

Northern California

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Posted: 08/16/21 01:39pm Link  |  Quote  |  Print  |  Notify Moderator

Just to be clear, my heart isn't set on a DC only unit. Having an AC unit on an inverter is fine as well. I was just questioning if someone had experience with a DC only unit and what their thoughts of it are.


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Kayteg1

California > Nevada

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Posted: 08/16/21 01:45pm Link  |  Quote  |  Print  |  Notify Moderator

Most of TC come with roof AC from the factory, so I don't see too many owners going for low-voltage system.
But if you lurk into Sprinter forums, some people there have 1200W of solar, 5 grands sink into batteries and bigger electric panels than average house.
Obviously with so much solar, the split AC compressor goes under the floor.





HMS Beagle

Napa, California

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Posted: 08/16/21 02:38pm Link  |  Quote  |  Print  |  Notify Moderator

Why not the Dometic RTX 2000? It is one large less than the Nomadic. Less current draw, less cooling too but probably enough for N. Ca. at 7K BTU.

As far as the cost goes, if you don't already have a large capacity inverter (and it has to have enough surge capacity to start an AC compressor) then that gets added to the cost of the install. I've seen mini splits on RVs, but I've yet to see one that didn't look like the guy forgot and left his Walmart shopping on the bumper. The mini split market is homes, they take no pains to make it compact.


Bigfoot 10.4E, 2015 F350 6.7L DRW 2WD, Autoflex Ultra Air Ride rear suspension, Hellwig Bigwig sway bars front and rear

wanderingaimlessly

Buggs Island lake

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Posted: 08/16/21 02:52pm Link  |  Quote  |  Print  |  Notify Moderator

S Davis wrote:

wanderingaimlessly wrote:

Not an AC expert, but have watched the threads in here and other places and dont really understand why more folks dont try or use mini splits, some small units are as high as 18 SEER to help with energy usage, and have seen some 8000-9000 btuh units with 650-800 watt energy consumption when operating. If operating consumption is that low, it seems a solar package of 1000 watts or more with a battery bank in the 500 AHr range should give a small camper at least several hours a day of usage.


There are inverter driven window shakers that could work without the copper line set to leak. Mini splits can run at pressures above 500 psi so I would have concerns about the flair connections.

understandable, but window units I thought were low efficiency and prone to a lot of heat/cooling loss due to design. And mini splits are available in a wide variety of sizes and SEER ratings.

And the question here was to dry, no hook up camping, NOT pedistal to pedistal.

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