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How to make homemade 12v air conditioner?

14K views 67 replies 19 participants last post by  AstroWill 
#1 ·
Van is full insulated , has a roof vent to let heat escape , Windows are covered with insulation to keep suns heat from coming in , has a windshield shade .
How can i make a homemade 12v air conditioner to use for camping?
I was wondering if I could build something from taking the complete air conditioning
System out of a vehicle at pick n pull and then building it into a case and then turn the compressor with a small gasoline motor.
I already have a honda 2000 generator and window unit but it uses to much gas.
 
#2 ·
You can't/won't, the best bet for true air conditioning is what you have right now, or to plug into shore power :)

The best you can get for efficiency is going to be a ductless mini-split system, but they are more expensive.
 
#3 ·
My window Air conditioner is 6000 btu and kept the back cold, does that mean a 6000 btu mini split would work ?
Would the mini split be able to be powered from a smaller Honda 1000?
It would be nice to only carry around a Honda 1000 instead of a Honda 2000.
Or is the minisplit efficient enough to run off of Inverter and a few batteries?
Thanks
 
#4 ·
You will have to check the specifications of whatever unit you are thinking of using. The 1000s can run some of the 5,000btu window units, again depends on particular unit. Some of those units are using only about 500watts. I don't think they make that small of a mini-split, 8-9k btu is the smallest I have seen. With enough solar and batteries you can run anything, but it gets expensive and heavy very quickly.

There is a video on youtube showing how quite they are, he has it installed in his camper/trailer.

 
#5 ·
I'm thinking of taking a regular window unit and reconfiguring it, possibly with either a 12v motor or running it off an inverter. Just so happens I have a spare one laying around begging for me to rip it apart and tinker. I want it to be less box like and not stick out a foot from the van. Might be a while before I get to that project though.
 
#6 ·
For the price you can't beat the window shakers, but they are ugly as sin, and tend to be quite a bit louder.

If it could fit behind the spare tire so it would be hidden...
 
#7 ·
So, I ripped apart a "window shaker" to get a good look inside. Immediately I noticed two things. This unit is a sealed system with no service valve and it's using the new eco-friendly R410A refrigerant. My hope is to be able to take a cheap wall unit like this and reconfigure it so that the condensor and evaporator coils are in separate parts of the van, something like the split units mentioned earlier but way more compact and about $1,000 cheaper.

These units are painfully simple in design and the sections can be spaced out by splicing and brazing in new longer lines. The biggest obstacle is the pressure within those lines. R410A is under nearly 500psi of pressure. That is scary stuff for the inexperienced tinkerer. Add to that the lack of a service valve and things could get interesting. A bullet valve would be needed to bolt onto the line and puncture it for pressure relief into either a suitable recovery tank...or...well, the air we breathe. Supposedly R410A is not ozone depleting.

My original idea was to take this unit and convert it so it could run on R134A like the stock AC in the van and be powered using an inverter and house batteries and/or solar. After a little research and a consult with Leeann and her hubby I found that this is not as straight forward as I had hoped. The compressor for R410A is not compatible with R134A. So I began looking into swapping out the compressor for one that is designed to pump R134A. This seems possible as the rest of the system is just tubing and should work fine no matter the refrigerant used. The only problem is that for whatever reason new electronic R134A compressors tend to be priced in the $200 range! That kinda defeats the cheap aspect of this mod.

It is possible to open the existing system, braze in longer piping and refill with R410A and not have to swap out or replace any of the existing parts. This refrigerant is available for purchase without a license on the internet. I'm not entirely sure yet how much refrigerant would be needed (if any provided you are able to collect the original in a recovery tank) but it costs about $100 for 25lb tank. The filling process is the same as any other AC system, requiring pre-vaccumed lines, a set of gauges and manifold. A weight scale may be needed as well since these systems are best refilled by monitoring the weight of refrigerant added. Add another $200 for those tools. Now we're looking at a $400-$500 system and that doesn't include the extension lines and whatever materials you require to create an enclosure and mounting system. This is getting expensive, but still weighing in about about 100lbs less than a pre-made split system and a hell of a lot more compact.

Anyway, here are some pix of the 6,000btu unit I surveyed:



There are two separate rooms in this unit. The front part that is made out of a styrofoam enclosure has a fan blade inside that sucks air through the evaporator coil and out through the top vents. The rear portion consists of a fan blade inside a shroud that sucks ambient outside air in from vents in the side of the outer housing (removed for pix) and pushes it through the condensor coils back to the outside world. One motor with dual shafts is used to power both fans. The compressor is the black canister.













Inside the electrical panel:





Even though it will cost me some coin I am half tempted to continue exploring this project. I already have a vacuum pump so the tools and materials would cost me an additional $300 to $400. For me that is way worth it compared to some gigantic and heavy split system made for a house that weighs 150lbs and costs over $1200. It is however way less practical than just mounting the unit through the side of the van or out the back window. I don't have dutch doors so that cool little opening below the hatch isn't a possibility for me. I would have maybe done a permanent install in the drivers side rear door but my tire carrier is in the way. There are probably 100 other ways to mount an un-modded unit but I have a preference for an integrated assembly.

Ideally I would want the evaporator coil mounted inside the van someplace and the condensor coil underneath the van. Clearly I will need to add some sort of electric fan onto each coil, the exact same type as used for an e-fan conversion on the radiator. Piping needs to be extended and pass through the floor.

Take all this with a grain of salt. I am by no means knowledgeable on AC systems. My only experience is a clean piece by piece install of the R134A system in my van which was surprisingly easy. I have zero experience with R410A based systems. Anyone knowledgeable please feel free to add your suggestions and possible techniques for expanding the piping on this type of system.
 
#9 ·
twstone83 said:
I could be off, but wouldn't it be easier and cheaper to find parts for the aux rear ac units these vans came with and perhaps rig a separate R134a compressor to it?
Maybe and I did consider that. It would require rigging an electric motor to the compressor. So you have another $200 compressor to buy and a powerful motor, say $100 for that. I'm also not so sure the stock rear AC is gonna be good enough to cool the entire van for boondocking. I like to be frozen. I also like the plethora of controls already made with the wall unit. Otherwise I need a PID controller, thermostat....

It is plan B or C though.
 
#11 ·
The smallest mini-splits I have seen are 9000 btu units, can be had shipped for ~$600, the inverter style are ~$100 more and all of the ones I have seen come pre-charged, just have to vac once installed then open the valve. Other reasons that I have considered the splits are that you also get heat out of the unit, they are variable speed, and super quiet. So maybe you would save some weight/cost by not having to have another source of heat. http://www.amazon.com/dp/B00D9ZQFIO says that shipping weight for that unit is 110lbs, probably wouldn't need all 16ft of the lines either.

You will also need an extra fan motor as those are combined in the window units, service ports are readily available. I would love to see this done though, I had thought about this once with the interior part between the rear door and wheel well. I also know that you will do it right and document it well :)
 
#12 ·
AstroWill said:
The smallest mini-splits I have seen are 9000 btu units, can be had shipped for ~$600...
I see them starting at more like $700 plus tax so more like $800 and they still need to be vacuumed out so you have either a tech or compressor to add to that cost. Not too crazy BUT have you looked at the dimensions and weight?

For the Pioneer Ductless Mini Split INVERTER Air Conditioner, Heat Pump, 9000 BTU (3/4 Ton), 15 SEER, Cooling, Heating, Dehumidification, Ventilation. Including 16 Foot Installation Kit. 110~120 VAC unit the spec's are as follows:

Indoor unit: 26.77" Wide X 7.01" Deep X 10.04" High Weighing in at 15.43lbs. Maybe doable.

Outdoor unit: 25.98" Wide X 10.43" Deep X 21.26" High Weighing in at 63.93lbs. That's like a spare tire to find a home for with at least twice the weight.

By comparison a mini window shaker is roughly 13.4 inches x 15.5 inches x 18.5 inches and 45lbs for the entire unit. Granted there will be some extra weight with plumbing and housing materials but the housings can be made of the lightest material you can find. I think this system could be half the weight and half the footprint albeit with some major expense and work.

I think the pre-made split looks super easy to install and the heat is definitely a plus along with zero inrush inverter technology....I just can't imagine where I would install the outdoor unit. The driver side rear is taken with the spare tire and the passenger side isn't doable without flex hoses and some door mods. If I had airless military tires I could loose the spare :think:

I suppose the outdoor part could be reworked with the coil and fan separated from the compressor and placed in different locations but then you're back to HVAC tech work lengthening pipes which eliminates the convenience of the unit.

I know the split has been done on many vehicles I'm just trying to picture how that big box would fit (and look) on my van.

I have also looked at tractor truck cab units and they too are heavy and outrageously expensive.

I dunno if this will ever be anything more than a geistesprodukt for me...I still need to shell out $1200 for a Blue Sea electrical panel!

The window shaker could be installed intact with minimal protrusion outside the van with a little rework of the venting on the top and sides of the unit. Just have to cut a big hole someplace and cover it with some louvers. I'm still considering that as well. My useless rear wheel wells would be a great spot but I think it would look retarded. :blah:
 
#13 ·
I don't know where you would mount it on your rig, though I do like the idea of airless or run-flat inserts. On my Tiger I don't have rear doors, just the front two and a side(rv) door. On a stock Astro with dutch doors you could easily mount it on the drivers side bumper while being able to open the rear top and passenger side doors.

The non inverter model was right at $600 the last time I looked, now it's $639, so def makes the inverter version the hands down winner. I forgot that Amazon charges tax for certain states, they have charged me tax on gifts delivered to other states before. End of the season will probably be cheaper :)

They also offer window units that have heat as well, but they tend to be heavier as well, the 8,000 btu unit with heat/ac I was looking at was around 90lbs shipping weight so when I did my comparisons to that it wasn't much of a difference.

However I do wish that they made smaller units, they do have smaller head units but then they require two of them per outside unit. I also like the flush ceiling mount but they are more expensive, but if the height of the indoor unit was an issue, it would be an option.

I wonder how much could be done with reworking the outdoor unit, I have never seen one taken apart so it would be interesting to see what could be done with the coil/fan/compressor/electronics. I wonder if the coil/fan could be moved to a horizontal or diagonal configuration(sealed motor shaft?) or height reduced?

I have an issue with the window units hanging out of the side/back, but I only have a problem with the aesthetics of it. It is certainly the easiest/cheapest way to go if you have the room and don't mind the look.

The other other other option would be a portable unit, only requiring a 4inch outlet that could be hidden in the wheel well or pretty much anywhere but they take up so freaking much inside space. But easy to remove when you don't need it and just cap the 4inch vent outlet. Because of the design I'm sure they use quite a bit more energy as well.
 
#14 ·
I looked at portable units and most reviews said they just didn't get cold enough or remove enough moisture from the air. Also RV guys recommended a dual intake unit for better operation but those tend to be pricey, heavy and large too.

I'm not so sure about the orientation of the coils. I suspect they may need to be somewhat upright since there is a phase change from liquid to gas or vice versa there. Gravity may play a big part in keeping the liquid portion in the lower half...I'd have to research that.
 
#15 ·
97cargocrawler said:
So, I ripped apart a "window shaker" to get a good look inside. Immediately I noticed two things. This unit is a sealed system with no service valve and it's using the new eco-friendly R410A refrigerant. My hope is to be able to take a cheap wall unit like this and reconfigure it so that the condensor and evaporator coils are in separate parts of the van, something like the split units mentioned earlier but way more compact and about $1,000 cheaper.

These units are painfully simple in design and the sections can be spaced out by splicing and brazing in new longer lines. The biggest obstacle is the pressure within those lines. R410A is under nearly 500psi of pressure. That is scary stuff for the inexperienced tinkerer. Add to that the lack of a service valve and things could get interesting. A bullet valve would be needed to bolt onto the line and puncture it for pressure relief into either a suitable recovery tank...or...well, the air we breathe. Supposedly R410A is not ozone depleting.
I only use "supco" Bullet valves, I've used them for years and was working on a system with one on it, hit 550psi and no leaks. Two Supco bullet valves, a recovery machine and tank & nitrogen, will get you an empty system thats ready to cut/weld. Please don't let your freon into the atmosphere.
My original idea was to take this unit and convert it so it could run on R134A like the stock AC in the van and be powered using an inverter and house batteries and/or solar. After a little research and a consult with Leeann and her hubby I found that this is not as straight forward as I had hoped. The compressor for R410A is not compatible with R134A. So I began looking into swapping out the compressor for one that is designed to pump R134A. This seems possible as the rest of the system is just tubing and should work fine no matter the refrigerant used. The only problem is that for whatever reason new electronic R134A compressors tend to be priced in the $200 range! That kinda defeats the cheap aspect of this mod.
Yes, keep the R410a and its matching compressor oil, the expansion device in your window shaker is designed for the characteristics of R410a.
It is possible to open the existing system, braze in longer piping and refill with R410A and not have to swap out or replace any of the existing parts. This refrigerant is available for purchase without a license on the internet. I'm not entirely sure yet how much refrigerant would be needed (if any provided you are able to collect the original in a recovery tank) but it costs about $100 for 25lb tank. The filling process is the same as any other AC system, requiring pre-vaccumed lines, a set of gauges and manifold. A weight scale may be needed as well since these systems are best refilled by monitoring the weight of refrigerant added. Add another $200 for those tools. Now we're looking at a $400-$500 system and that doesn't include the extension lines and whatever materials you require to create an enclosure and mounting system. This is getting expensive, but still weighing in about about 100lbs less than a pre-made split system and a hell of a lot more compact.
I would at a minimum add a small liquid line filter drier and weld in two schrader/service ports. Refrigerant weigh in is the accurate way to do it. Too much freon will flood the compressor, bad, not enough freon compressor overheats, really bad. If you like to freeze, maybe look at an 8500 or 10,000 btu window shaker to help with satisfying your cooling load.
Anyway, here are some pix of the 6,000btu unit I surveyed:



There are two separate rooms in this unit. The front part that is made out of a styrofoam enclosure has a fan blade inside that sucks air through the evaporator coil and out through the top vents. The rear portion consists of a fan blade inside a shroud that sucks ambient outside air in from vents in the side of the outer housing (removed for pix) and pushes it through the condensor coils back to the outside world. One motor with dual shafts is used to power both fans. The compressor is the black canister.













Inside the electrical panel:





Even though it will cost me some coin I am half tempted to continue exploring this project. I already have a vacuum pump so the tools and materials would cost me an additional $300 to $400. For me that is way worth it compared to some gigantic and heavy split system made for a house that weighs 150lbs and costs over $1200. It is however way less practical than just mounting the unit through the side of the van or out the back window. I don't have dutch doors so that cool little opening below the hatch isn't a possibility for me. I would have maybe done a permanent install in the drivers side rear door but my tire carrier is in the way. There are probably 100 other ways to mount an un-modded unit but I have a preference for an integrated assembly.
The controls are really simple for an a/c, unlimited possibilities!
Ideally I would want the evaporator coil mounted inside the van someplace and the condensor coil underneath the van. Clearly I will need to add some sort of electric fan onto each coil, the exact same type as used for an e-fan conversion on the radiator. Piping needs to be extended and pass through the floor.
This will work just need to match the cfm of the fan to the original design or add a head pressure controller they're kinda expensive though. At this point its all about airflow, the proper amount though.
Take all this with a grain of salt. I am by no means knowledgeable on AC systems. My only experience is a clean piece by piece install of the R134A system in my van which was surprisingly easy. I have zero experience with R410A based systems. Anyone knowledgeable please feel free to add your suggestions and possible techniques for expanding the piping on this type of system.
Extending the lines is no problem, Nitrogen brazing with 15% silfos rod, stay away from mechanical connections! I've been hvac for 10 plus years now, I've done some pretty inventive stuff. Noting that I usually get to put my equipment in under stairways, closets, attics,crawl spaces, rarely do we get the room we want. It helps with this kind of project though.
 
#18 ·
My dual ac astro cools very well. If I had a roof vent....it would cool even better. The downside is that the compressors seem to be well taxed running both ends. Boy...are they noisy on mine. Mechanic days they are piston type. Noisy buggers.

I would go to a junk yard and get a roof top and a genny.
 
#19 ·
I can't imagine any kind of camping situation where you could run continuous A/C on batteries alone. Our RV starts the generator when you turn on the A/C if you're not plugged into shore.

Our fire dept has trucks that look sort of like ambulances that are for overheated firefighters. Wearing 100 lbs of gear and canvas clothing in 110 degree heat battling a building on fire tends to heat humans. They take a break, sit in the box and sip water and cool off via the rooftop A/C units.

Lump
 
#20 ·
Lumpy said:
I can't imagine any kind of camping situation where you could run continuous A/C on batteries alone.
Lump
I seen some folks on the innernet using solar power to run their AC. I can generate up to 1000W (in a perfect world) so powering a small unit in the hottest brightest part of the day might be possible. Maybe I should try it before spending the next year modding some junk. :think:
 
#21 ·
http://www.popupexplorer.com/forum/inde ... ic=79485.0
Check out this link , somebody mounts the window unit inside and vents the heat out.
Temporary solution until I find a way to make a more efficient AC that will run off batteries.
I'm thinking of doing this with small 5000 btu 4.9 amp draw power from Honda 1000
I already have the 5000btu
I think the most efficient window unit thats available on the market is 400 watts
 
#22 ·
Personally I wouldn't even consider a generator as an option. The weight of the unit plus the fuel, the footprint and the noise are all bad in my opinion. I think that weight and space is better filled with batteries and solar panels. Then you have a renewable energy supply and can run that AC all night long next to other campers.

I tested my wall AC a few weeks ago with battery power and a 2,000W inverter. I ran it for about 45minutes on a 90*+F day and cooled the van down to about 70* and I have zero insulation. The walls of the van were still hot to the touch from inside.







I wanted to make sure I could power the AC before I tore it apart and built it into the van. I have 300lbs of battery power hanging above the rear axle. I'm still not sure about running it all day long in conjunction with solar. This test was my worse case power scenario and it passed so I'm going forth with my plans to mod the window shaker. If I didn't have a rear tire carrier I think I would just make a huge hole in the rear drivers side door and pop it through when needed.

Cool link but I cannot imagine losing all that living space inside the van. I'm hoping to only have 1/3 of the wall unit taking up interior space.
 
#23 ·
If it helps the perspective -

My GF's RV/Horse trailer (called a "living quarters trailer" - LQ) has A/C. It has huge a huge solar array, three dedicated batteries, monster inverter. The solar supplies 17A @ 17v any time the sun barely shines. All obviously designed, engineered and installed to work together.

Still you cannot run the A/C without shore power. The current draw is just way too monsterous. And this is for an A/C unit that's designed for low draw, RV use.

Lump
 
#25 ·
97cargocrawler said:
Personally I wouldn't even consider a generator as an option. The weight of the unit plus the fuel, the footprint and the noise are all bad in my opinion. I think that weight and space is better filled with batteries and solar panels. Then you have a renewable energy supply and can run that AC all night long next to other campers.

I tested my wall AC a few weeks ago with battery power and a 2,000W inverter. I ran it for about 45minutes on a 90*+F day and cooled the van down to about 70* and I have zero insulation. The walls of the van were still hot to the touch from inside.







I wanted to make sure I could power the AC before I tore it apart and built it into the van. I have 300lbs of battery power hanging above the rear axle. I'm still not sure about running it all day long in conjunction with solar. This test was my worse case power scenario and it passed so I'm going forth with my plans to mod the window shaker. If I didn't have a rear tire carrier I think I would just make a huge hole in the rear drivers side door and pop it through when needed.

Cool link but I cannot imagine losing all that living space inside the van. I'm hoping to only have 1/3 of the wall unit taking up interior space.
That roof rack could probably be used to shade the van somehow and then make some kind of insulated shields that would lay flat on the roof rack and then flip down on each side insulating the side of the van and creating a barrier to the sun , wouldn't need as much air conditioning then.
Or you could chop the entire rear box off the back of the Astro , keep the cab , turn it into a flatbed chasis truck and then you have a foundation to build a nice big box out of extremely light weight strong materials such as foam insulation.
I don't know if you know what sip panels are but if you dont you should google search em .
I would make custom homemade sip panels out of glueing aluminum channel to the ends of rigid foam , you could connect all of the panels together by screwing the aluminum channel of one sip panel to the aluminum channel of the next panel.
Only problem is when you're done building the box you would need some kind of coating to make the box weather proof and preferably the coating would be a radiant barrier protecting from the sun .
I was thinking maybe you could coat it with that rubberized rv roof paint stuff that's supposed to keep the heat out.
The box wouldn't be strong enough to support the roof rack but you could have four posts one in each corner to hold the roof rack up , , Just some ideas to throw around.

I have a Honda 2000 gen right now and the only thing that bothers me about it is the fuel cost , I think the electricity from the generator costs around 80% more then to get electricity from the grid.
 
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