# Air conditioner idea... what are your suggestions



## Tesseract (Sep 27, 2008)

*IF* I remember this correctly, the typical vehicle (whatever that is) requires 18,000 to 24,000 btus (1.5-2 tons) of cooling capacity (mainly because cars aren't insulated worth a damn 

The window units around here that cost $100 are only 5000-6000 btus in capacity...

But why use a 12V inverter in an EV when you have a 100-250V battery pack at your disposal? Much better would be for someone -  - to design an inverter that converted the battery pack voltage to 120VAC/60Hz power for running just such things.

A possible hack - modern 12V inverters use an SMPS to step up the 12V from the battery to 165V then chop that with an H-bridge at 60Hz to create a 120Vrms/60Hz "quasi square wave" (basically a square wave with 120/165 duty cycle). It would be simple to rip out the SMPS from one of these inverters and just use the H-bridge if your battery pack was, say, 168V.


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## voltmatic automaton (Nov 2, 2008)

I have considered the smaller effecive coolong capacity, i'm not looking for refrigerator cold from the unit, but something to keep the oven temperature away when i'm making my commute. I have been wondering how long i can expect the thing to work in terms of amp hours from the battery if an inverter is used.


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## ga2500ev (Apr 20, 2008)

why not drive an AC compressor with a second motor?

Now you can control when the AC is on/off.

Also it will be more efficient than the house unit and the inverter.

Just a though.

ga2500ev


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## ga2500ev (Apr 20, 2008)

voltmatic automaton said:


> I don't really want to go with a swamp cooler as i don't have ready access to ice on my trip FROM work, and after a 10 hour shift in Texas the ice won't last.


Have you thought about dry-ice?

According to this site:

http://www.airgas.com/content/details.aspx?id=7000000000103

Dry ice can stay cold in an insulated container for days.

ga2500ev


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## Twilly (Jan 22, 2008)

Even a small window A/C unit will draw 2000 to 3000 watts while running, and maybe twice that when starting. You are going to need one big inverter.

The most efficiant way to get A/C is to hook your stock compressor to a rotating source.


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## TX_Dj (Jul 25, 2008)

I hate to sound like a meanie, but this has been discussed here before, and a quick search would probably turn up the threads.

I was considering using a compressor from a window unit as well, but the caveats I found in my research were things like, tubing diameter differences between a car AC and a window unit AC are significantly different, which would cause the compressor output to act like an orifice tube before the orifice tube, either freezing up the compressor or contributing heavily to efficiency loss, also stationary compressors are designed to be left stationary, and it's questionable as to how long they would last in a bumpy high-vibration environment like a moving vehicle, and also in getting the DC to AC, whether from 12v (not advisable) or from pack voltage, you would incur additional efficiency loss from the inverter.

The best methods I've seen are like such:

1) Retain the vehicle's stock compressor, and affix it to the tailshaft of the traction motor. Replace the electromagnetic compressor clutch at the compressor with an electromagnetic compressor clutch on the tailshaft, so that when the AC is off you don't experience efficiency loss due to belt and pulley drag. Main caveat- compressor only turns while the vehicle is in motion, leaving you in the heat at a stop light.

2) Better idea is to remove the compressor pulley altogether, and direct drive from a pack-voltage rated 2-ish HP motor via lovejoy coupler. Connect the compressor clutch signal line to a contactor that will switch on and off the motor instead. No drivetrain losses, simple construction, most efficient compromise, but difficult to find a motor at that power rating that matches your desired pack voltage without spending a small fortune.

3) Another idea was to build a "Swamp Cooler" inside the cab. Add ice, add water, use a pump to circulate the water thru a coil, blow fans over the coil and icewater and out into the cab. Probably not as effective as a real air conditioner, but does provide the most cooling for the least energy usage.


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## jlsawell (Apr 4, 2008)

Oh for crying out loud!

Man up and use a foil windscreen reflector when parked, then roll down the window when driving.

It worked for the last 100 years, until we all got weak and allowed marketing departments to tell us we "needed" these comforts.



OK, I'll admit I'm only half serious.


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## TX_Dj (Jul 25, 2008)

I'm entirely serious when I say I really don't want to be stuck in traffic in my nice work clothes in 110 F (43 C) with 80%+ relative humidity. 

Some places, AC is luxury. Other places, it's necessity lest we all stink like a hog.


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## voltmatic automaton (Nov 2, 2008)

Heh heh, nice to get so many lively responses  

searching the site did bring up a fairly lengthy thread though so thanks for the info on that.

I have to admit though that while the 70 360 air conditioner is good at some of the more mild times of year it really has to be seen as necessary for some parts of the country.
That is a tangent though, I am perfectly willing to try the 12/48 volt inverter idea on a window unit, and then see what physical modifications would be necessary and what kind of performance i could get.
As another aside, the window unit does have all the parts to make a custom ac unit yes? Compressor, fan, coils etc am I out of line in thinking that i can't make something useful with these?
As far as commuting time all i really need is about 30 minutes run time on the batteries. (i drive in the morning when its a lot cooler and so don't need the ac then)
one other point i would make is that i intended this thread as a way to drill for ideas , positive and constructive criticisms are invaluable.

so if possible, keep the ideas rolling and keep them cheap... my wife is already of the opinion that this is costing a lot.


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## Twilly (Jan 22, 2008)

One more issue is that your giant inverter will also need to supply a sine wave output. Most inverters produce AC by switching DC back and forth at 60hz, resulting in a square wave. And a square wave will not turn a motor.


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## HDS (Aug 11, 2008)

I agree that A/C is as important in the sunbelt as heat is in the snow belt. 

I think that it is important to keep in mind that most EV's have a run time of a couple of hours so the a/c only has to last for this duration. Another helpful option might be to be able to "chill" the vehicle prior to departing while still on utility power. That way the vehicle's a/c system is just maintaining the temp and not recovering from the vehicle sitting in the sun. Not so easy for the ride home unless you are fortunate enough to have a place to plug in while at work.

I think that the power consumed by the a/c compressor is going to be about the same whether it is a completely separate system or it is attached by pulley to the drive system as it is in the ICE car now. I also think that these things are pretty efficient from the standpoint of being sized and designed to service the vehicle now. And when OFF, it wastes little or no power. Certainly, I hope that experts out there correct me if I am wrong. 

If all that is true than it might be better to add the amp-hours of batteries being considered for the a/c system to the drive train and just pulley connect a standard a/c compressor.

Another thought is, if the vehicle is in "maintaining temp mode", to have a switch labelled "ECONO-MODE" (or something) that only engages the electric clutch for the compressor when the brake pedal is depressed. That way you are only using the vehicle's kinetic energy to compress the refrigerant and not battery power. I don't know if this has ever been tried before or if the amount of time that we actually depress the brake pedal will sufficiently compress enough refrigerant to do the job, but it is a thought.

Best of luck
HDS


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## Rook (Jun 5, 2008)

You could also consider modifying a dehumidifier. A dehumidifier is just an air conditioner with the coils back to back. I’m on my second one, so naturally I took the first one apart. Since the air flows through it, it is easier to modify than a window A/C unit. It wouldn’t provide the BTU’s of a regular A/C unit, but I don’t think it would use as much power either. When running in my studio mine uses three amps. 

Whether this or a window unit I would suggest using the coils from the original unit because they are sized for the compressor. Also you will have to shock mount the compressor and the freon lines.

*Larry*


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## voltmatic automaton (Nov 2, 2008)

sweet, keep the ideas coming 

with a dehumidifier i see different types some with the traditional compressor/refrigerant setup others with peltier systems...

which would be better able to do the job?
your opinions please?

these units are super smaller than the windoe units though which is neat, and just so some posters know, the idea is to cool the area direcly around the driver, so that as im sitting there im getting some relief. in texas a plain old fan will not work since you're likely to broil yourself 

but these ideas are just down my alley...


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## HDS (Aug 11, 2008)

I also thought about Peltier systems for the heat and the a/c. See the company below.

www.novelconceptsinc.com

I emailed them to get more info on their products and they replied that a gas system is the way to go. It is a nice thought, though. Easy to build and use, but if it does not do the job than is it really worth it. 

happy Holidays
HDS


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## Rook (Jun 5, 2008)

I imagine you’re thinking like I am that a small amount of cooling that fits your power scheme is better than a hot car on a Southern summer day. A while ago my wife’s van developed a slow leak in the AC system. It didn’t’ cool very well, but it wasn’t until it stopped all together that I heard complaints.

I didn’t know they made Peltier versions of dehumidifiers. I’ll have to look into it some time. A while ago I did the math based on a tiny peltier chip in a surplus catalog and it seemed like a unit with a large amount of cooling would use a huge amount of power. If that isn’t true of a larger unit it would have an advantage from a lack of moving parts or leaky joints. A disadvantage would be that a peltier cooler has a hot side and a cold side, so you can’t move the heat very far. You would have to dump the heat into the engine compartment.

I’m not an HVAC engineer so my dehumidifier idea might be harder to do than it sounds or it might not be possible at all. I just thought of it because when I opened it up it was easy to see the two coils and everything just bolted together. Probably if you were going to pursue it you’d want to mock up a prototype on the bench. If you lived anywhere near Titusville, Florida I’d give you my dead unit.

*Larry*


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## ga2500ev (Apr 20, 2008)

OK let's throw out a couple of oddball ideas.

1. Use the Einstein Refrigeration Cycle. You can find it here:

http://en.wikipedia.org/wiki/Einstein_refrigerator

No moving parts and all it needs is heat to operate. Sounds like you have plenty of that. 

2. Compressed air and a vortex tube. The vortex tube separates an incoming compressed air stream into hot and cold air components. Again no moving parts. Simply compress air into a tank before your ride and when it gets hot open up the tank into the vortex tube with the cold air coming into the cabin and the hot air expelled outside. The energy to compress the air happens when you charge the car, making it ready for use later. You can test with a high pressure paintball tank and a vortex tube.

ga2500ev


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## etischer (Jun 16, 2008)

Twilly said:


> One more issue is that your giant inverter will also need to supply a sine wave output. Most inverters produce AC by switching DC back and forth at 60hz, resulting in a square wave. And a square wave will not turn a motor.


I have run motors off my 12v inverter. I've run a vacuum cleaner and power tools without any issue. 

All AC motor controllers basically chop up DC to create AC. 

The original poster could always buy an inverter that run off pack voltage. I've bought several inverters that convert 300vdc to 115 ac for around 50 bucks. There are other cheap inverters that will convert lower dc pack voltage to 115, and these are also designed to run AC motors.


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## bbcb (Aug 2, 2008)

I think the link above regarding the Einstein fridge needs additional investigation.

At my uncle's lake house, the fridge & freezer (and everything else) is run on propane - most likely via a similar cooling cycle (http://web.archive.org/web/20061206174734/http://www.cam.net.uk/home/StKilda/electrolux.html). If you replace the propane burner with a wrap of heating elements (outside of the vehicle), would you not have created a heat pump of sorts?

In a similar vein, here's an option to power a swamp cooler (without the ice) http://www.instructables.com/id/Super-Beverage-Cooler/.This supposedly cools to 10 degrees F!! & can cool a can of room temp beverage to low 30's in about 2 minutes.

BBCB


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## HDS (Aug 11, 2008)

Hi bbcb

I bet your uncle's system that runs on propane is an absorber system. As I recall, the propane "purculates" a mixture of ammonia and water which separates them. The heat is blown off of the water vapor condensing it into a liquid. It is then reintroduced to an atmosphere of ammonia where it evaporates causing cooling. This mixture of ammonia and water then returns to the vat where the burning propane repeats the cycle.

It has been a long time since I read up on absorber systems, but I think that is the basic theory of operation.

Happy Holidays
HDS


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## morvolts (Jun 19, 2008)

HDS said:


> I think that it is important to keep in mind that most EV's have a run time of a couple of hours so the a/c only has to last for this duration. Another helpful option might be to be able to "chill" the vehicle prior to departing while still on utility power. That way the vehicle's a/c system is just maintaining the temp and not recovering from the vehicle sitting in the sun. Not so easy for the ride home unless you are fortunate enough to have a place to plug in while at work.
> 
> Best of luck
> HDS



With a large accumulator this would work for a while before needing a compressor.


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## Telco (Jun 28, 2008)

What kind of vehicle is this for? I've also investigated this, and it looks to me like a small window unit can work fine for a small cabin. Window units are designed to cool rooms that are roughly 8 to 10 times larger than the average small vehicle cabin, so should be able to cool a vehicle with no problems. If insulation is needed, lightweight insulation can be added. Besides, it worked for these people:
http://www.seniorark.com/Humor/*******%20Things/*******%20Images/*******%20air%20conditioning.gif
http://www.nextautos.com/files/wp-content/uploads/2006/07/*******%20central%20air.jpg
http://jokes.m3rlin.org/files/2007/09/001166-home-made-*******-car-air-condition.jpg


Heh heh... on mine, being as I have an ext cab truck, I envisioned building a shelf that set the unit in the bed, so that it lined up the bottom of the unit with the floor of the truck with the air coming in about halfway up the cabin wall in the back. The unit would be disassembled and rearranged to minimize bed intrusion, and a cutout would be made in the bed to cover what could not be rearranged. This cutout would then be worked in a way to give some locking storage like a bed box, to make it look conventional. The inside unit would be upholstered to look like it belonged, and the control panel would be disassembled rewired and reworked into a dash panel. And with a heat pump unit, you'd be able to eliminate the entire factory HVAC system. About the only issue would be the need for a defrost, but a ceramic heater with a tiny blower could handle that. If you have a car, no idea what you'd do.

Do NOT use dry ice for a vehicle AC system. Dry ice is frozen carbon dioxide, and as it evaporates it will odorlessly foul the air by reducing the percentage of oxygen in it. People have died in auto and small plane accidents because they put dry ice into a cooler, put the cooler inside the passenger compartment, then went to sleep due to oxygen deprivation and crashed. You may as well pipe the exhaust into the cabin for a heater







. Not trying to be abusive with my wording here, the fellow that recommended it may not have been aware of the danger.

That Einstein setup looks very interesting, I could see the heat source being a black plate on the roof with the works in the trunk, using the sun as the heater.

Another alternative is just a 1/2HP electric motor bolted to the side of the vehicle's factory air compressor with a belt between them. With this, you'd not need the clutch on the compressor, just a direct pulley. You could use the power wire that normally controls the compressor to run a relay that turns the electric motor on and off as needed. Electric motors can be had in any configuration, so you'd be able to get one that runs at the required RPM and be set to run off a tap on the battery pack as a whole. An AC motor would be the better way to go as it would be smaller. And, as it would no longer depend on the engine for direct drive power, the unit could be mounted anywhere on the vehicle.

Since you'd be able to control the motor speed, you could also get a smaller, more efficient AC compressor to do the same job. An AC compressor must be sized to perform at engine idle as well as cruising speed, but if it "always operated at cruising speed" then it would only need to be able to cool at cruising speed, not at "idle speed". This would be the simplest way to do it. If you choose to go this way, I'd suggest looking at a Dodge Durango compressor, 2002 or newer. The Durango has a very small compressor, and it seems to draw very little power off the engine for operation. Had to rent one of those crapbuckets once, and was surprised that I could not tell when the compressor was cycling. Normally I can feel a compressor cycle by how the engine is operating but that one I couldn't tell a difference.


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## VoltC (Jan 5, 2009)

Considering all the info I could find on the web, it seems that keeping the original AC system and running the compressor off the other end of the traction electric motor or with a separate small electric motor would be the simplest. Has anyone done any in-depth research regarding using the donor's car AC vs building something else?


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## sailfish11 (Sep 15, 2007)

TX_Dj said:


> 2) Better idea is to remove the compressor pulley altogether, and direct drive from a pack-voltage rated 2-ish HP motor via lovejoy coupler. Connect the compressor clutch signal line to a contactor that will switch on and off the motor instead. No drivetrain losses, simple construction, most efficient compromise, but difficult to find a motor at that power rating that matches your desired pack voltage without spending a small fortune.


Does anyone know where I can find a good selection of 2-ish HP motors? I'd need one that can run off of 312VDC.


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## etischer (Jun 16, 2008)

sailfish11 said:


> Does anyone know where I can find a good selection of 2-ish HP motors? I'd need one that can run off of 312VDC.


ebay, there are tons of AC motors to be had for less than 100 bucks. 

you need a 230v motor and an inverter. I bought my motor and inverter (runs on 312vdc) for around 100. My motor is even wash down rated.


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## sailfish11 (Sep 15, 2007)

Hmm... maybe this is something I can do.  But why would I want a 230V motor for my 312V system?


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## donmurray (Jan 21, 2009)

If the EV has a small cab, or if you can put a plexiglass partition behind the front seats, then the necessary AC will need less power. That is, the complete AC system can be smaller. Another idea is to modify the duct system so the driver gets all the blower air instead of trying to cool the entire cabin. Aim the air right between the legs and face. Up the dress would feel good if you like to wear dresses. 

As is usually the case with energy use, the most cost effective route is to conserve rather than generate more.

What seems to be needed is a compact integrated compressor and motor with built in controls. Mount it anywhere and control it with a manual or thermostat switch.

Saw an electric pickup system that had a typical ice cooler in the bed. Some lines were plumbed from the cooler to a small pump, radiator and blower mounted inside to the rear cabin roof. Apparently they dumped some ice and a little water in the cooler before leaving home, and that was adequate for some time. Probably depending on how much ice was put in the cooler. Only onboard power needed was the pump and cabin blower which was probably not much. I thought it was a crude but clever idea for a pickup EV.


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## Dillzilla (Aug 6, 2021)

voltmatic automaton said:


> I've been brainstorming an Air Conditioner idea recently and wanted to give you guys a note so you can give it a good going over with some constructive criticism.
> 
> The idea is to purchase $100 window unit a.c, a 12 volt inverter and hook these up to a battery to provide cold air.
> The housing itself would be stripped off and the piping inside would be modified to go where I need it.
> ...


I would look at RV air conditioners since they aren't much bigger than a window unit and is already prepped to be ducted. You also have the added bonus of being able to get a heat pump model to use as a heater as well


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## remy_martian (Feb 4, 2019)

I think you missed the $100 part


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## MattsAwesomeStuff (Aug 10, 2017)

I think you both missed that this thread is from the Bush administration era.


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