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Open Roads Forum  >  Truck Campers

 > Anyone with 12v Air Conditioning Experience?

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adamis

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Posted: 08/15/21 06:42pm Link  |  Quote  |  Print  |  Notify Moderator

Having spent the better part of a week in a hot, dry and smokey campground that doesn't allow generators to run (I posted previously about this issue in another thread) it got me to thinking about some possible options... From what I can figure, the only real need for a genset is to run the Microwave and the AC unit. My problem with this however is that the generator isn't allowed in many places, is loud and sucks propane. That got me to thinking about eliminating the genset entirely and just using the space to house more LiFePo4 batteries. I think I could probably get 4 100AH batteries in the same space, coupled with the current 100AH battery that would get me 500AH of batteries to play with.

From a previous post and article discussing different air conditioning options, it seems that the van life community has created some interesting options for us that were not available even a few years ago. One potential contender is the Nomadic Cooling 3000 12v. Now it is pricey, nearly $4290! I guess these digital nomadic van life millennials have cash to burn.

Anyway, for the princely sum of ~$9k, one could have a 12v DC air conditioning that will run for hours on battery. Throw on 400w to 600w of solar and now you can stay cool in just about any situation. If money wasn't an option, I would probably do this in a heartbeat but sadly it is so it is hypothetical for now. One thing I could do is to space out purchasing of batteries and add to the capacity a little each year. Even with 200AH to start with, that should be enough for 30 minutes to an 1 hour of cooling, good enough for a quick lunch on the road side. The best thing about this is that unlike propane which requires refueling at a station, I can charge that battery bank through solar or DC to DC from the truck.

I know some of you have already done similar setups, being able to run AC off of batteries. I am however not aware of anyone who has ditched their genset entirely and gone with a 12v AC unit. Has anyone taken this extra step or contemplating it?


1999 F350 Dually with 7.3 Diesel
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CA Traveler

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Posted: 08/15/21 07:45pm Link  |  Quote  |  Print  |  Notify Moderator

A/Cs take a lot of power and doubtful you'll get much cooling in a hot TC for lunch. Perhaps grab what you need and eat in the truck with the cab air?

Max cool at 120Ax12V = 1440W so you'll need a LOT more solar than you posted and/or likely a much larger alternator on the truck.


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theoldwizard1

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Posted: 08/15/21 07:48pm Link  |  Quote  |  Print  |  Notify Moderator

Do not mix battery chemistry's ! Stay all lead acid or go LiFePO4.

Stick with an A/C unit that runs off a 120VAC. That way if your camp site has it, you are good to go. You absolutely need a Micro-Air EasyStart

Some of the Chinese brands of inverter are actually pretty good. Check out the YouTube channel DIY Solar Power with Will Prowse. He has actually done several battery/inverter/air conditioner builds. Some have run for weeks before he disassembled them.

Not a well know brand, but good reviews Ampere Time 12V 200Ah|2560W LiFePO4 battery 4000~8000 Cycles. Will Prowse has also done sever DIY LiFePO4 battery from individual Chinese cell. These are a fraction of the cost of per built batteries.

Use a 24V battery bank and inverter. Gut feel is you will need 200Ah @ 24V (400Ah @ 12V) higher voltage allows smaller wire.

* This post was edited 08/15/21 07:58pm by theoldwizard1 *

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jefferson,ga

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Posted: 08/16/21 03:29am Link  |  Quote  |  Print  |  Notify Moderator

Coachman has a class B, the beyond, that is all 12v. You may gleem some insight on what they feel is needed. Look under options.


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valhalla360

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Posted: 08/16/21 04:40am Link  |  Quote  |  Print  |  Notify Moderator

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.


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jaycocreek

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Posted: 08/16/21 08:07am Link  |  Quote  |  Print  |  Notify Moderator

I realize this isn't for everyone and that all truck camper windows will are not big enough for a window AC,but I haven't seen any RV AC come even close to these energy numbers with the AC compressor engaged and cooling...And very/very quiet...

Perfect Aire (Ace Hardware) 5K window AC on low cool with compressor running..

[image]

High cool with compressor running...

[image]

High fan only,no compressor..

[image]

Doing the math it will run on high cool with compressor running the whole time for 3 hours off the little jackery power station,more cycling....

Did I mention how quiet it is and how it purs on eco mode with my little honda..[emoticon]

Kayteg1

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Posted: 08/16/21 09:01am Link  |  Quote  |  Print  |  Notify Moderator

Ditto on AC taking much less than rated amps.
The ratings takes starting surge into count I guess, but I did measure my AC over the years and from my memory
15k BTU ac run at 8.3 amp
13k BTU runs on 6.3 amp.
When I have never seen real test on inverter efficiency, common knowledge says that it is over 90%, meaning you are not loosing much of battery capacity by using inverter with 120V AC v/s 12V AC
So why spend more money on limited use 12V unit, when you can have 120V unit for less and with much more potential use?
The only issue with using inverter at high load is giving it good cooling.





cewillis

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Posted: 08/16/21 09:18am Link  |  Quote  |  Print  |  Notify Moderator

One of several other 12v or 24v possibilities.
No experience, and not a recommendation.


Cal


adamis

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Posted: 08/16/21 09:23am Link  |  Quote  |  Print  |  Notify Moderator

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.

Kayteg1

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Posted: 08/16/21 09:28am Link  |  Quote  |  Print  |  Notify Moderator

In 2017 we visited Florida and were coming back mid-September via Texas to Las Vegas.
Don't recall a night we could sleep without AC.

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