12 volt A/C

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12 volt A/C

July 29, 2022, 11:33:25 pm

I was wondering if anyone has installed a 12 volt A/C unit? Our rear A/C is original to our unit and I'm thinking about replacing it with a 12 volt unit in order to be able to run it directly off of the lithium battery bank that I'm going to install. Would like to hear opinions on this.

I want to be able to run the rear A/C while boondocking in hot weather and be able to sleep in comfort.

Kevin

Re: 12 volt A/C

Reply #1 – July 30, 2022, 12:17:23 am

It would be easier to move your rear air conditioner wires to the inverter breaker box and
run it through the inverter. It would be hard to run 12 volt cables up to a 12 volt air conditioner
if they even make them. You would need a really big battery bank to run an air conditioner all
night. It would be cheaper to the generator.

Re: 12 volt A/C

Reply #2 – July 30, 2022, 12:30:11 am

Search for the thread @Elliott did last year about this, he chronicles how he runs his front off solar and batteries. Lots of good info.

Re: 12 volt A/C

Reply #3 – July 30, 2022, 01:32:01 am

Kevin.
How much lithium do you have and the solar to support it. ?

Re: 12 volt A/C

Reply #4 – July 30, 2022, 04:07:28 am

Quote from: Bob & Sue – July 30, 2022, 01:32:01 am

Kevin.
How much lithium do you have and the solar to support it. ?

I am planning to install 2000 watts of solar and 1000 amp hours of lithium batteries to support this. If I run it off the inverter I'm going to have to probably install two of them in parallel to support it. That's why I was thinking of just running one directly off of the batteries. They make some incredibly efficient 12 volt air conditioners now. Off Grid Rooftop 12 Volt Air Conditioner - Mabru 12,000 BTU This one would work great for my rear unit which is currently a 9000 BTU unit. I am concerned about the wire size which is why I was asking if anybody else had done it.

I have found my generator to be largely unreliable and am tired of dealing with it. That, combined with the fact that most places we boondock are nice quiet little places where I don't even want to run a generator during the day, let alone all night.

Kevin

Re: 12 volt A/C

Reply #5 – July 30, 2022, 08:08:52 am

I didn't know Foretravel put in less than 13,500 btu

Re: 12 volt A/C

Reply #6 – July 30, 2022, 08:10:01 am

These 12 volt AC units are new to me (and I'm guessing a lot of other forum members too) but are a welcomed alternative to the standard RV stuff which is often inefficient and overpriced.
I'm somewhat skeptical of the efficiency claims but doing a little bit of research it's seems at least close to true. I think I would be inclined to try it. The low sound level and variable speed would be great over the sudden loud on/off of traditional units. The low roof profile is attractive to me too.

Depending the the wire run you will need either 6 or 4 gauge wire.
This seems to be a good guide to choosing: Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

The common wire feed through the frig roof vent would be a first consideration but I wouldn't be afraid of a new roof penetration if done right. I would protect the wire from the sun by placing it in some kind of conduit or even hose.

Re: 12 volt A/C

Reply #7 – July 30, 2022, 08:31:59 am

Looks like you need to cut a bigger hole in the roof. Hope no structure up there in the way.

Re: 12 volt A/C

Reply #8 – July 30, 2022, 09:22:40 am

Those 12v 9k BTU units are interesting but I'm not sure I'd be willing to sacrifice 30% cooling capacity. I would not want to be without my big AC units on days that it's 100+ degrees out. For the same money you could install a mini split in your rig instead.

Regarding a 2000w/1000ah system : there is only room on the roof for about 1500w of solar before you start running into issues with the other fixtures shading your panels. If you want more than that, you need to build racks for the panels that elevate them above everything on your roof. At that point, no sense stopping at 2000w since you can use the big cheap residential panels and already have the downsides that come with racks; might as well go all the way to 3000w. @Zach did exactly this and could give you some good insight. He often runs his AC off them during the day.

Based on my experience with 1500w/600ah/residential fridge, a 2000w/1000ah system probably isn't enough for extended use of traditional ACs. Your solar input won't come even close to breaking even with the output the AC demands and 1000ah is good for maybe 7 hours of runtime. That'd get you through the night but then you're dead in the water the next morning if the sun doesn't come out and you have an unreliable generator. If you have great sun all day the next day, I'd expect you to be topped off sometime in the afternoon. We are usually topped off between 11am and 1pm on those days. I think a 3000w system would take you from the fringe to never thinking twice about running your AC.

I personally think you need to get your generator running no matter what you do. It'll open up the options you have available to you and give you an important fallback. When it's cloudy out for multiple days in a row, we'll often turn ours on for a couple hours to top our batteries off, then we can coast off the batteries for another couple cloudy days. As someone who boondocks a lot, I've found it more important than I thought I would. It also comes in handy on the stupid hots days (or drives) that you need both AC units to keep the rig cool.

Attached is a rudimentary diagram of how my coach is wired to allow the front AC to run off batteries.

Re: 12 volt A/C

Reply #9 – July 30, 2022, 09:23:51 am

Very interesting topic for me...

We're "hooked" on the whole boondocking with no external power service or generator. It's impressive that we can stay anywhere for about two weeks "quietly" before we need water and dump. And we literally don't sacrifice anything but Air Conditioning...And that's a big issue sometimes! We never use our 10k whopper of a generator anymore, except to exercise monthly or cool down the unit quickly after a long hot drive.

I keep my eyes on innovations in the mobile AC and dehumidification technology, it's evolving slowly, however still very expensive products....

I think Europe has more choices with 120V, 50 hertz Air Conditioner that use inverters and more efficient compressor technology. Still, prices are high, availability here in the US for these units that have been modified to accept our 60 Hertz power.

The 12 Volt DC Rooftop units, great to see that there are more options out there. I'm really on the fence about these units in our rigs. l'm thinking it's going to be an expensive SO type copper cable to get power from our battery locations up on the roof... By the time you figure the total run length, and other calcs to minimize voltage drop. At 55 amp stated unit current draw, that's going to be a big set of cables. I don't see many 24v or 48v options out there either. That of course is another whole battery bank or boosting design that needs to be configured, more complexity...

At a minimum, I'd really like to have a small AC unit just to cool the bedroom at night for sleeping.

Option?
Mini-splits are just too invasive for me at this time.

There are some interesting compact 12V Marine units, in the 4000 BTU sizing. They can be plumbed so the inside unit is small, I thinking could be placed where the current flat screen TV is in the bedroom. We never watch TV isn the bedroom, that can go... However, these units are $4K last I looked. Expensive and they need an AC expert to install.

What about something like the truckers use? APU's, where there's a cooling unit. Haven't done my research.

Anyways, with 600ah of Llihium, I'd need at least 400ah more. Have 2,275 of Solor panels now up on the roof, (325 x 7 panels) have one more at homebase I can fit if needed, so good there. Just debating putting a Starlink base station up there, OR 5G. Jury still out on that stuff.

Hoping there's some good ideas that might come out of this thread. I'm all ears!

Thanks for the ideas folks.

Best. J & K

Re: 12 volt A/C

Reply #10 – July 30, 2022, 11:13:22 am

Another thought is to have a 12 volt pump down near the batteries, stack another condenser coil over
the the coach one and if possible to run the hoses up behind the drawers and have the evaporator
in the TV cabinet. You would need 3 hoses, one for a evaporator drain and the wiring.

Re: 12 volt A/C

Reply #11 – July 30, 2022, 12:17:39 pm

Quote from: kjsifer – July 29, 2022, 11:33:25 pm

I was wondering if anyone has installed a 12 volt A/C unit? Our rear A/C is original to our unit and I'm thinking about replacing it with a 12 volt unit in order to be able to run it directly off of the lithium battery bank that I'm going to install. Would like to hear opinions on this.

I want to be able to run the rear A/C while boondocking in hot weather and be able to sleep in comfort.

You would likely need #4 wires, which would certainly be doable as far as running them to the roof. It is hard to tell exactly what the power draw would be on the unit you linked to since it is variable speed and apparently rarely shuts down entirely, but assuming an average of 40A (based on a minimum of 22.5 and max of 54.4) a 1000AH battery bank would run it for about one full day. Obviously you could not do that for extended periods. What you need is an estimate of how much you really expect to run it. If only at night (which is what I would like a system for) then you could expect a max of 400AH overnight, so you would need enough solar to supply that plus any other draws you have. If you run it in the day also, your estimate would go up substantially. Another factor to consider is where you primarily camp. If you spend most of your time in the desert with nearly continuous sun your solar will go much farther than in places with inconsistent sun and lots of shade. Right now I am in the upper peninsula of Michigan in a site that is shaded part of the day, and the sun has been inconsistent. My 1800W of solar have only been averaging about 275AH of battery recharge per day. So be sure to consider everything as you size your system. I think what you are trying to do is workable as long as you understand the limits of your solar install. My advice is whatever your estimate for battery and solar capacity, add as much more to that estimate as you can afford and fit. I don't think you can ever have too much.

Re: 12 volt A/C

Reply #12 – July 30, 2022, 06:37:37 pm

Amazon.com: Universal 12V/24V RVs electric air conditioner ï¼Œ Rooftop air...
Comes with wires. Looks very well thought out .
Figure that 850 watts will require about twice that in solar if my system is model .

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Re: 12 volt A/C

Reply #13 – July 30, 2022, 06:54:42 pm

Quote from: Beeman – July 30, 2022, 09:23:51 am

There are some interesting compact 12V Marine units, in the 4000 BTU sizing. They can be plumbed so the inside unit is small, I thinking could be placed where the current flat screen TV is in the bedroom. We never watch TV isn the bedroom, that can go... However, these units are $4K last I looked. Expensive and they need an AC expert to install.

Many marine units use water cooled condensers.

Tim

Re: 12 volt A/C

Reply #14 – July 30, 2022, 07:08:57 pm

I have not found any Marine 12 volt AC. But , yes the units I have found use a sea water intercooler .

Re: 12 volt A/C

Reply #15 – July 30, 2022, 07:21:47 pm

If you can take both AC units off the roof, you would have room for at least two more panels. A mini split would fill that bill nicely. Having 1800 watts potential and only averaging 275 Ah just means the batteries are not getting that low and are up to voltage early in the day.

Pierce

Re: 12 volt A/C

Reply #16 – July 30, 2022, 07:42:41 pm

Quote from: Protech Racing – July 30, 2022, 06:37:37 pm

Amazon.com: Universal 12V/24V RVs electric air conditioner ï¼Œ Rooftop air...
Comes with wires. Looks very well thought out .
Figure that 850 watts will require about twice that in solar if my system is model .

1 watt/hr is equal to 3.41 Btu/hr.
2,200 watt cooling capacity is 7,502 btu
At a 850 watt load, to operate the unit, is a 71 amp load at 12V.
71 amps requires #2 wire at 25 feet. #1 wire at 30 feet.

Tim

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Re: 12 volt A/C

Reply #17 – July 30, 2022, 08:46:54 pm

Quote from: TGordon – July 30, 2022, 07:42:41 pm

1 watt/hr is equal to 3.41 Btu/hr.
2,200 watt cooling capacity is 7,502 btu
At a 850 watt load, to operate the unit, is a 71 amp load at 12V.
71 amps requires #2 wire at 25 feet. #1 wire at 30 feet.

Tim

that sounds about right. My mini runs at 4-7 amps. At 122 volt . 49-70 Amos of solar / battery . Thanks
The above ad shows wires with the unit but I did not look close enough at what sizes they are .

Re: 12 volt A/C

Reply #18 – July 30, 2022, 08:50:52 pm

The OE roof top unit uses about 14 amps running and may show a spike on start of 18-20 amps .
So any of the inverter style newer ac are about twice as efficient.

Re: 12 volt A/C

Reply #19 – July 31, 2022, 12:59:24 am

I would really like to put a mini split unit in and did a lot of research on it. I'm not seeing an easy way to do it right now on our rig. I keep hoping that someone will come out with a drop in unit for RVs.

There are some advantages to noisy roof units. They make great white noise generators if you are camped in a noisy spot like we are right now in Oshkosh. The helicopters at 7 in the morning no longer wake me up if I decide to sleep in!

I have a 3000 watt Victron inverter that I need to install. The other option would be to buy a second one, install it in parallel and just run the A/C off the inverter. I'm starting to think that's probably the cheaper and least invasive option although not the most efficient. I'm concerned about the amount of heat that will be generated from those inverters and there will have to be some sort of ventilation installed.

On another note, I brought our Starlink along and it is working fantastic despite the fact that there are probably 10,000 campers in the square mile surrounding us. I'm getting at least 40 Mb download when Verizon drops to less that 2. Actually surprised Verizon is even doing that well. Verizon is not good enough to stream a video without stuttering and only about half my texts with video attached are getting out. No issues on Starlink.

Kevin

Re: 12 volt A/C

Reply #20 – July 31, 2022, 08:16:18 am

Some interesting aspects about the US choices for DC air conditioning units.
Did You Know There Are 12V RV Air Conditioners? - TheRVgeeks.com

Also found this unit is back in stock @amazon It's a small capacity unit so would only cool perhaps a bedroom?
Amazon.com: CAMPELIFY Portable Air Conditioner Unit with Electric DC...

Best, Jeff

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Re: 12 volt A/C

Reply #21 – July 31, 2022, 11:05:02 am

I think the Ac only draws about 15amps on 120v? I added a 15k ac in the bedroom.. Dont worry the roof is overly solid so you would be able to add an ac just about anywhere on the roof.

I have ran my bedroom ac on the batteries and if I remember it took approx 5-600 amp hrs to run all night with the compressor kicking on and off.. I am low on solar but have some sitting to put on when I can.. with 1200w it can not recover if I am cloudy that day so I can get another night maybe. That would be no front ac .. I am thinking of upgrading the wires from the breakers to and from the inverter as the rest is already upgraded (batteries). A dedicated bedroom ac gets me through the night when we stay at a state park and no generator for the night but then I use the solar and generator to recharge next day during allowed noise times.

Next upgrade is going to be a victron 5000w inverter so I can run front and back ac and not overload the system when driving. I already put a 420amp alternator and working on tying it in to the system... My helper who was working on it has passed so kinda stuck right now until I find someone way smarter than me to help tie it in while I drive and not burn anything up.

1200w solar and 1200 ah lithium opens some doors but not all

Re: 12 volt A/C

Reply #22 – July 31, 2022, 09:13:07 pm

Quote from: NevadaBornRvR – July 31, 2022, 11:05:02 am

Next upgrade is going to be a victron 5000w inverter so I can run front and back ac and not overload the system when driving. I already put a 420amp alternator and working on tying it in to the system... My helper who was working on it has passed so kinda stuck right now until I find someone way smarter than me to help tie it in while I drive and not burn anything up.

1200w solar and 1200 ah lithium opens some doors but not all

Within your design schematic: I'd make sure I had a B2B charger device, (Sterling, Victron, etc) between that big alternator and that large 1200 ah battery bank. A depleted 1200ah battery bank will want to take every electron available from that alternator.

Re: 12 volt A/C

Reply #23 – August 01, 2022, 12:03:57 am

I have the sterling... But looking to get everything to the bank but not exactly sure yet.. Perfect Switch, LLC » Dual Rectifier 400 to 600 AMPS going to install that thing and see if I am able to accomplish what I think I want.. USe the sterling to feed the start batt.. Not exactly sure yet .. Not to derail this topic so I might start another when I get the energy to tackle it. Still recovering from surgery and need a couple more to finish becoming the bionic man.

Ok back on topic.. In reading up on the draw of the ac on 120v ... seems its about 150 amps approx so 70 amps would be an improvement ... I added an ac in the bedroom... Ran through the inverter so we can cool at night partially in quiet time... Maybe this 12v would be a little more effecient but the wiring would be problematic... Not sure how to get them where I need them in the bedroom.. Actually I could take it behind the drawers in the room between the drawers and the wash machine area then over to the ac.. Another thing to think about..

Re: 12 volt A/C

Reply #24 – August 01, 2022, 03:39:22 pm

Quote from: NevadaBornRvR – August 01, 2022, 12:03:57 am

I have the sterling... But looking to get everything to the bank but not exactly sure yet.. Perfect Switch, LLC » Dual Rectifier 400 to 600 AMPS going to install that thing and see if I am able to accomplish what I think I want.. USe the sterling to feed the start batt.. Not exactly sure yet .. Not to derail this topic so I might start another when I get the energy to tackle it. Still recovering from surgery and need a couple more to finish becoming the bionic man.

Ok back on topic.. In reading up on the draw of the ac on 120v ... seems its about 150 amps approx so 70 amps would be an improvement ... I added an ac in the bedroom... Ran through the inverter so we can cool at night partially in quiet time... Maybe this 12v would be a little more effecient but the wiring would be problematic... Not sure how to get them where I need them in the bedroom.. Actually I could take it behind the drawers in the room between the drawers and the wash machine area then over to the ac.. Another thing to think about..

Theres a couple of inches of air between the cap and the back of the cabinets. Possibly enough to run minisplit cables through.

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