# Air Conditioning Questions



## retrodog (Sep 17, 2007)

Yeah, I'm a noob here so maybe there is a thread that you can point me to.

I'm in the planning stages of doing a car conversion and since I live in the Houston area there would be about 6 months that I need ac of some sort. I'll probably be using an RX-7, Miata, or MR2 so I won't need tons of cooling. I've seen some 1.5 hp motors for running the ac compressor and power steering pump. Do these work or is that inadequate for this work load? 

Also, do I just build a new bracket system for mounting the existing compressor and pump so that the existing plumbing reaches adequately?

I have a small machine shop (drill press, cut-off saw, MIG welder, etc.) so I could custom-build the brackets.


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## Greenflight (Sep 13, 2007)

Hey retro- there aren't a whole lot of guys running A/C, so you're kind of on your own here.

I would imagine one of those small Ametek tape drive motors would be adequate. Can't say for sure though.

And of course, if you want to fill it with ice every so often: http://www.instructables.com/id/Portable-12V-Air-Conditioner---Cheap-and-easy!/

As far as power steering goes, I've never thought that it's really necessary. Especially on cars in this size range. Heck, I drive my truck without it.

Good luck!


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## moldiebrownie (Aug 29, 2007)

Like greenflight says, alot of guys don't run it because of the extra weight and or battery drain. Those that do, either run the compressor from a small electric motor via a v-belt like this guy http://www.geocities.com/electric_honda/civic/civic3.html
or they buy a dual shaft drive motor like this http://www.evparts.com/shopping/product_details.php?id=536&product_id=1123 and install a pulley on the other side to drive the compressor like this guy http://www.saabrina.blogspot.com/ who is actually running a/c and p/s off it. 

One other alternative (of which I know nobody doing it yet probably because of price and availability) is to use one of the new compressors from Nippondenso that comes stock in some hybrids. Denso has married a electric motor to a compressor in one neat package. They did this because when hybrids stop at a light or something..the gas engine is off and the traditional belt driven compressor will not function..hence no AC. For the same reason...there are now electrically driven steering racks. Here is link to one of these compressors being sold on Ebay http://cgi.ebay.com/ebaymotors/2004...ressor-OE_W0QQitemZ320015485444QQcmdZViewItem
This particular one is Toyota part # 88370-47010 and happens to retail for $961.58 (US) new at a Toyota dealer. If you do go with a regular compressor and run it off a small electric motor...you can use a very small compressor like from a Geo metro since you say you don't need much ac. I attached a pic of the Denso compressor since after the ebay auction the link will be useless.


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## pandaran (Nov 13, 2007)

Greenflight said:


> And of course, if you want to fill it with ice every so often: http://www.instructables.com/id/Portable-12V-Air-Conditioner---Cheap-and-easy!/


That's genius! I was wondering how I'd get a/c, and that looks like a distinct possibility! Plus I like the cheapness. ^_^


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## KiwiEV (Jul 26, 2007)

I like that idea too. It's almost summer here and I'm keen to try and make one myself out of foil-lined flexi-pipe and a big chilly-bin. The next EV will definitely have proper air conditioning for those 2 or 3 months of the year that it can be uncomfortable to be sitting in traffic with your back adhering to the seat. 

I also just thought of something to make it even more impressive - buy "dry ice". Dry ice is simply frozen carbon dioxide. It's cheap to buy, stays cool a long time in a chilly bin and is something like -70° C (-94° F) when frozen. A bag of it would last a few days in a chest at home, and you just pour some into your portable cooler when you're heading out. It evaporates leaving no moisture too so there's no water to remove!
I like it! I think I'll try that this summer!


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## pandaran (Nov 13, 2007)

So, would you just have dry ice in a box with fans blowing the air out, instead of having the water circulating through the heater core?


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## KiwiEV (Jul 26, 2007)

Oooo that's a good question. I haven't thought of it in detail. The idea bowling around in my head is that You'd have a large chilly bin in the back seat with some foil flexi-pipe - like you use with home ventilation systems - running between the front seats and aimed at the driver.

Let me whip up a picture of what I had in my mind...

There! It's very simple but you get where I'm coming from. Perhaps having the air travel through a sealed metal box at the bottom of the ice water would help too? For me to create it, it would have to be ultra simple and cost effective too.


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## elevatorguy (Jul 26, 2007)

pandaran said:


> So, would you just have dry ice in a box with fans blowing the air out, instead of having the water circulating through the heater core?


I'm not a chemist, but wouldn't that be piping carbon dioxide into the car? 
I think keeping the dry ice in a bin and exchanger would be a good idea


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## pandaran (Nov 13, 2007)

I like the idea of the dry ice being colder, but the thing that really draws me to regular ol' water ice is that I can make it in my freezer, or stop off at any sort of Kwik-E-Mart for more along the way.

Of course, I'm completely new to these sorts of projects, and it would be wonderful to see a different take on that a/c. More options = good!

One thing that would be nice is finding a way to make the ice last longer. The long drive I make the most often is to Sacramento and takes me a bit over an hour and a half. It'd be annoying to have to stop on the way for ice. Then again... I still have to do research to see if I can get that kind of range on an EV in something resembling my price range in the first place. (I love your on-the-cheap take on things, Mr. kiwiev. I'm already planning on implementing your heater design! ^_~)


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## KiwiEV (Jul 26, 2007)

Hehehe, you're very welcome. I should find out if the heater works this weekend if I can get all my main cables in. I'll blame Nick Smith if it doesn't work.


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## Mr. Sharkey (Jul 26, 2007)

I just have to poke my nose in here and kick my own A/C system. Depending on what type of car you choose to convert, you may not need to do too much of anything to take advantage of the cooling power of ice:










That's two bags of ice cubes in the "rain tray" of my VW Rabbit EV, with room for at least two more. All of the air that enters the car's ventillation system has to pass over the ice on it's way into the passenger compartment. No pumps, no additional circulating fans, has automatic melt water draining, the whole works, built in at the VW factory!


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## mattW (Sep 14, 2007)

I wonder if it is possible to kill two birds with one stone by combining the pressure pump for the AC with the vacuum pump for the brakes. I realise that AC is usually using freons or something instead of just air. But it seems stupid to have one pump to bring things up to pressure and another to bring other things to low pressure. Does anyone have any ideas about how to combine these two functions? Is there such a thing as a pressure exchanger like you can do with heat? It might even make the vacuum pump a bunch quieter!


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## pandaran (Nov 13, 2007)

Awesome! How much would you say it cools the passenger compartment with passive cooling like that? It gets pretty toasty here during the summer (105ºF/40ºC+) and a/c can be more than just a matter of comfort on some days.


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## Mr. Sharkey (Jul 26, 2007)

It's not like having "real" A/C, but neither is one of those cooler units. Just having some cool air blowing on you can help. Personally, I would refuse to live anywhere that the temperature extremes require life support.


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## pandaran (Nov 13, 2007)

Haha, yeah... sometimes it's a pain, and I definitely don't like the sheer number of people (since most of them are grumpy too much of the time), but it's sure nice to be within a two to three hour drive of the ocean, the snow, lakes, mountains, rivers, and desert! Although, I haven't really had a huge urge to visit that last one.


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## Nick Smith (Oct 26, 2007)

And if it _does _work you can all address the checks to me... I need lithium (ion) for my condition.


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## mattW (Sep 14, 2007)

Ok here is my idea for relatively efficient AC based on no experience and a dodgy knowledge of what it is I'm talking about. Get a slightly larger vacuum pump then you would have otherwise and install a really small used turbo on the 'exhaust' of the pump. Rather than using the turbo to compress the air going into the engine you could use it to compress the gasses in the air conditioner. This is based on a bunch of assumptions but it works in my mind. I'm a bit worried about the scale of the turbo to the amount of air exiting the vacuum pump and also whether or not the turbo even could be used to compress AC gas but if it could work, or could be made then you would only be using slightly more energy to do twice the work. What do you think?


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## xrotaryguy (Jul 26, 2007)

mattW said:


> I wonder if it is possible to kill two birds with one stone by combining the pressure pump for the AC with the vacuum pump for the brakes. I realise that AC is usually using freons or something instead of just air. But it seems stupid to have one pump to bring things up to pressure and another to bring other things to low pressure. Does anyone have any ideas about how to combine these two functions? Is there such a thing as a pressure exchanger like you can do with heat? It might even make the vacuum pump a bunch quieter!


You can do this with the power steering pump and a hydo-boost brake booster. You can't do this with an air conditioning compressor.


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## xrotaryguy (Jul 26, 2007)

I think you guys are on the right track with the ice in the cowl. This is similar to keeping the ice in an ice chest and blowing air through it. Here in Arizona, many golfers actually buy systems like this for their golf carts. Here is one example.
http://www.swampy.net/golfcartairconditioner.html








The unit on the top blows cool air onto the cart's occupants while the ice chest in the back supplies the icy cold reservoir of ice. This system uses a 12v fan to move the cool air, but it has no capacity to freeze the ice.

I think that the best way to go would be to install a small recreational electric ice chest that can be run off of a 120v household ice chest. That way it can refreeze the ice when the car is charging. 

I wouldn't simply toss an ice chest into the car and run an extension cord to it though. I would probably fill the ice chest with water and submerge a heater core in the water. The heater core would have antifreeze in it and would be plumbed to the car's evaporator core or to its heater core. Using the evaporator core would probably make more sense. That way the air conditioning controls/vent doors, etc would still function properly. A small fluid pump would be required to move the antifreeze. The car's stock blower motor would be used to blow the cold air.

This has the potential to be totally transparent to the driver. In other words, the driver could be totally ignorant as to how the system works, yet he could still operate it as though it were a standard automotive air conditioning system. 

Some manufacturers, like this one make coolers that can cool their contents to as low as zero degrees Fahrenheit (or -18 degrees celsius for those of you who aren't lucky enough to use standard measurements ), so the air coming out of the vents could potentially be VERY cold! 

This system would use an extremely small amount of the traction pack's energy. Only the system's small fluid pump and the car's blower motor would be consuming energy. This is in contrast to the design that was linked to earlier in the thread.








Holy Crap! That's a HUGE compressor drive motor. That thing must shorten range considerably! That's not "cool" at all. 

Here is one more link to consider for cooling your car with ice.
http://www.kooleraire.com/index.htm


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## Mastiff (Jan 11, 2008)

KiwiEV said:


> I like that idea too. It's almost summer here and I'm keen to try and make one myself out of foil-lined flexi-pipe and a big chilly-bin. The next EV will definitely have proper air conditioning for those 2 or 3 months of the year that it can be uncomfortable to be sitting in traffic with your back adhering to the seat.
> 
> I also just thought of something to make it even more impressive - buy "dry ice". Dry ice is simply frozen carbon dioxide. It's cheap to buy, stays cool a long time in a chilly bin and is something like -70° C (-94° F) when frozen. A bag of it would last a few days in a chest at home, and you just pour some into your portable cooler when you're heading out. It evaporates leaving no moisture too so there's no water to remove!
> I like it! I think I'll try that this summer!


Gavin I'd recommend against leaving Dry Ice evaporating in a closed environment, that's a quick way to get dead. 

I'd do like someone else suggested and keep the Dry ice outside the passenger compartment and use a heat exchanger, that would be safer.

If you did use that system, I think you'd also have the only Pure Electric Vehicle that also emits Carbon Dioxide. 

I'm not sure how much power it takes to run an A/C compressor but I think the simplest way is to power the A/C off of a small Permanent Magnet motor for maximum efficiency.

Maybe a small 1/4 or 1/2 Horsepower Permanent magnet motor, probably a 12 volt.


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## aeroscott (Jan 5, 2008)

car a/c are vary powerful units in part to cool our hot and sweaty bodies down. The other part is we have a huge furnace burning 4 gallons of gas per hour. That's about 400,000 btu's per hour soaking into our little world. Man that's about 4 house furnaces .our ev's have to deal with oh about 5kw or 17000 btu's of this heat depending on load.A lot less in most cases like slow traffic.


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## Dennis (Feb 25, 2008)

I don't understand why many conversions use the 12 volts from the DC-DC converter to power a one horsepower motor for the A/C compressor. The overall efficiency is terrible going this route. For example DC-DC converter = .78*motor .85 = 66.3% overall efficiency and thats not even including the I^2R losses of the high current flowing through the wires which makes the result much worse.

It seems more logical to me that if a conversion is using 144 volts then buy a 180 volt permanent magnet motor. The benefit is the current will be far less to develop one horespower allowing one to save money in copper wire costs as they can use smaller gauge wire, and the efficiency will be much better since no DC-DC converter is used and current flow is less in the wires. So now the overall efficiency is more like .85*.90 for the wire = 76.5%.

There not hard to find either if you go to electricmotorwarehouse.com. I found one that costs just  $362.44 here: http://www.electricmotorwarehouse.com/dc_motors.htm


EDIT: I see now why one would not want to go that route. The current surge would be severe for the initial star up of the motor that it might destroy it. I am going to design a start up controller for this then. I'll be back on here to post the schematic..


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## aeroscott (Jan 5, 2008)

it's even worse then that even permanent magnet motor at 12 volts is 50% eff. if I remember right . But it gets way better even at 24 v, at 100 v it's in 95% range.


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## Dennis (Feb 25, 2008)

Okay I have come up with a way to limit current inrush to a 180 volt permanent magnet motors. Most of the current limit inrush parts can be salvaged from an old dryer.


ON/OFF A/C

http://img132.imageshack.us/img132/703/aconoffpt4.png


Current inrush limit controller


http://img85.imageshack.us/img85/1134/motorcurrentlimitzb3.gif







This device works by using Nichrome coiled wire to limit inrush current. As current flows through the coils they begin to heat up red hot, as a result the heat from these coils will activate a snap action thermal switch to close; energizing the contactor coil which engages the main contact to feed full pack voltage to motor and engages the auxiliary contact. The auxiliary contact "locks" the coil on such that as the snap action thermal switch opens up from the coils cooling down, will not have any effect on the contactor coil since the auxiliary contact keeps the current flowing to the coil.


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## MrCrabs (Mar 7, 2008)

Has anyone tried using a Peltier heater/cooler junction? (aka TEC or Thermoelectric cooling)

They take between 12-16 v dc, and one side gets hot, and the other side gets cold.

Here is my idea for a heating and cooling system...

Attach several peltier devices to the stock radiator. Attach heatsinks to the other side of the peltier device. Setup several 12 vdc computer fans (or similar) to blow air past the heatsinks.
Connect plumbing and a fluid pump so coolant is moved thru the radiator, into the heater core, then back into the radiator.

When cooling is desired, give +V to the peltiers, they will cool the radiator, and fluid inside. The heatsinks and fans will cool off the hot side, so the peltiers can keep working somewhat effiecently. The pump moves the cold coolant into the stock heater core, cooling off the driver.
When heating is needed, give -V to the peltiers, now they will heat up the radiator. I'm not sure if you would need to run the fans over the heatsinks.
Now the pump is moving hot coolant to the stock heater core, warming up the driver.

I don't know how the total efficency would compare to using a separate motor to drive the stock A/C compressor. But it would be nice to have a combo heating/cooling setup.


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## aeroscott (Jan 5, 2008)

peltiers have a very low cop (coefficient of performance).compressors are able to move 300% or better( cop 3 or 4 ) more heat then the power they use .a window unit takes 300 watts hr. to run , 300 w . hr. x 3.4( watts to btu) =1020 btu of electric power but will do 4000 btu cooling. a window unit run off a inverter would be low power draw . some bigger ones come with heat pumping ev-1 had heat pumping that's taking the hot side of the ac for heat. saves power when heating. a car unit running at variable speed per load will be hard to beat lots of power to get cooled down then slow compressor down as car cools down. it better then on and off.remember no big hot engine to heat us up.


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## the slashmaster (Feb 24, 2008)

Wether it be a gas car or electric I was wondering why no one gets the smallest house air conditioner they can find, then hook it up with a power inverter from the accesories battery and hoses to bring the cool air in. This way you can remove it in the winter. I also think they already make rv air conditioners that run on 12 volts. What happens if you just use one of them?


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## aeroscott (Jan 5, 2008)

get a inverter and house unit or the 12 volt unit.


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## MrCrabs (Mar 7, 2008)

the slashmaster said:


> Wether it be a gas car or electric I was wondering why no one gets the smallest house air conditioner they can find, then hook it up with a power inverter from the accesories battery and hoses to bring the cool air in. This way you can remove it in the winter. I also think they already make rv air conditioners that run on 12 volts. What happens if you just use one of them?


Here you go!
http://i3.photobucket.com/albums/y86/lubricant/air.jpg


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## KiwiEV (Jul 26, 2007)

MrCrabs said:


> Here you go!
> http://i3.photobucket.com/albums/y86/lubricant/air.jpg


Crikey, is that legal?


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## Cornelius (Sep 15, 2007)

I am currently experimenting with something along the lines of what has been mentioned here. In my S-10, I have an Iota 75 amp DC to DC converter. It supplies the 12v needs for the truck and feeds into a Xantrex inverter made for Idling Solutions commercial truck air conditioning. I also have a 12v battery to handle the inrush current for a second or two (the inverter can take it, but the Iota can't). Connected to the inverter is a 6000 BTU Kenmore (made by LG) air conditioner. There are 5000 BTU air conditioners available, but this model was the smallest size physically. It is also Energy Star rated, and draws only slightly more power than a 5000 BTU.

I have tested everything electrically, although the air conditioner is not yet installed in the truck. I'm still trying to decide exactly where to mount it, and whether to keep it as a single unit or have a repair shop make it into a split system. The air conditioner draws 560 Watts on high, equivalent to about 3/4 HP. That's less than others that have used a 1 HP motor, and you would still have to add the blower motor power. Of course there are losses converting the 144 VDC traction pack to 12v and then to 120 VAC. I would prefer to have a 144 VDC air conditioner and avoid all this, but I don't have the resources of GM or Toyota...

I originally got the idea for this from my Roadtrek camper van which has a Fedders 5000 BTU air conditioner installed at the back roof area. After I started on this, I read that GM is actually doing something similar to this on their prototype fuel cell vehicles.

When I have tested all this, the air conditioner is still sitting on the garage floor. Any thoughts or suggestions regarding the air conditioner installation are appreciated. The original factory air was trashed by the previous owner, and has been removed, so I have plenty of room under the hood.

Edit: RV air conditioners, such as for my Roadtrek camper, run on 120 VAC. To run an RV air conditioner, you need to use the generator or be at a campground with power.


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## xrotaryguy (Jul 26, 2007)

I was recently wondering why it is that some hyperbolic-array-type solar generation systems use salt deposits as a heat sink. 

If you're unfamiliar with this technology, the system basically makes LOTS of heat from the sun and uses it to power a steam turbine. However, when the grid doesn't need so much power, the array will sink the heat into an under-ground salt (NaCl) deposit. The salt will hold the heat until the grid actually needs electricity and then extract the heat and run it through the steam turbine.

Also, Ford pioneered the sodium-filled exhaust valve for NASCAR decades ago so that the exhaust valve could withstand higher temperatures. The sodium in the exhaust valve is a simple heat sink that has high energy input to temperature change ratio, or a high specific heat.

As a point of reference, the specific heat of water is generally regarded as being very high at 4.18J/(g deg K). That means one gram of water requires 4.18 joules of energy to increase its temperature by one degree kelvin or Celsius. 

So what is the specific heat of salt? One site claims that the specific heat of salt is 854J/(g deg K) at zeor degrees C. WOW! Here's a link to the site.

http://www.korth.de/eng/503728952d091450d/503728952d0b6863b.htm

Is that accurate? If so, I am NOT going to design a ice based air conditioning system. I'm going to use salt. This would make a HUGE difference in the mass of the heat sink required. A small amount of salt could be chilled and kept cool for hours. Heck, a chilled salt based cooling system could probably be designed to stay cold for more than a day with out too much trouble.

Can anyone verify this? Is the specific heat of salt really that high?


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## xrotaryguy (Jul 26, 2007)

KiwiEV said:


> Crikey, is that legal?



We like to say, "only in America."


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## xrotaryguy (Jul 26, 2007)

Sweet, a whole salt brick only costs $20.00. Just get one of these, maybe cut it in half and set it in a small on-board grid-powered refrigerator. Duct air through the fridge when you need cold air.


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## xrotaryguy (Jul 26, 2007)

Oh wait... the specific heat of salt is 854J/kgK. That's 0.854J/gK. Oops, water still beats that. I guess I'm back to using ice.


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## X1/9jm (May 2, 2008)

An exchanger is a must for dry ice. I used to work beside a dry ice factory and a guy came in and bought a cooler full for a party. He went out to his car (middle of summer) and with the windows up he drove off. He got to the end of the road (about 1/4 mile) before passing out, running the stop sign, and plowing into a brick walled sign across the road. Fortunately it broke the windshield out so he could get fresh air.


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## retrodog (Sep 17, 2007)

X1/9jm said:


> An exchanger is a must for dry ice. I used to work beside a dry ice factory and a guy came in and bought a cooler full for a party. He went out to his car (middle of summer) and with the windows up he drove off. He got to the end of the road (about 1/4 mile) before passing out, running the stop sign, and plowing into a brick walled sign across the road. Fortunately it broke the windshield out so he could get fresh air.


Yeah, I guess it's not a good idea to flood the cabin with the same thing that the human body exhales. If that worked, we could go diving with just a bag to breathe in.


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## Phyber Optik (Jun 4, 2008)

*Insulation?*

I've been researching AC while gathering info for my first EV conversion.

I'll be in PA by then, so it will be used only seasonally - and on the hottest days. For me AC is a must...I'm very heat intolerant and sweat like a pig above 76*.

* Anyhow, my approach to the cooling dilemma will be two-pronged:*

- Obviously, an efficient cooling unit, whether it be the Ice-Cooler method or a small 120vac window unit.

- *Vehicle insulation.*


Cooling an automobile has the same challenges as mobile homes - they are poorly insulated metal box ovens. 

But insulating a vehicle is an easy, relatively inexpensive and passive addition to aid the overall efficiency of the cooling system, which may be overlooked. (not to mention added heat retention in the winter)

Most cars have next to nothing above that cardboard headliner and the "insulation" found elsewhere such as in doors and body panels serves the primary purpose of a sound deadener rather than R-value.

I used to work as a residential installer of Icynene spray foam insulation. The stuff was amazing. Besides it's excellent R-value, stability and light weight, it was tenaciously adhesive and filled the most minute cracks and gaps like nobody's business. The houses were practically airtight.

It also has excellent sound deadening value, and is extremely fire-resistant. You could spray the interior of body panels, the firewall, and of course the roof and literally trim the bubbled excess to a perfect fit with a serrated steak knife or pruning saw.

The stuff wasn't cheap, but for such a small application it could probably be done for a couple hundred bucks tops - maybe even cheaper if you brought your car to one of their job sites where they were already set-up and spraying.

Also, the addition of window tinting reduces heat significantly. I tinted the windows of my 99 merc cougar (ICE - sorry) and it reduced the temps significantly.

My tint is about 20% and is also illegal. But a $20 bill gets me through state inspection every time.

One could also take the approach that many school buses use, and paint their roofs white. I have even heard about a special paint with an amazing R value. Even Sno-Seal would help with the solar heating.

Combine this with a "real" central vent/circulation fan - not the gimmicky as-seen-on-tv junkers - to keep the interior temp down while the car is parked in the hot sun while you run into Walmart...and overall efficiency might make AC much more palatable.

Has anyone already addressed insulation as part of their cooling systems?

Any thoughts?


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## judebert (Apr 16, 2008)

I've always wanted to insulate the whole car. And at R3.6/inch, that stuff is pretty good. 

Still, that's per *inch*. I'm more likely to get 1/8" or so inside the doors. There's just not that much room!

If I've got the time, maybe I'll go with a polyurethane or something. Oh, for infinite time and money...


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## Phyber Optik (Jun 4, 2008)

Even 1/8" of icynene would do ya nicely.

The biggest heat sink is the roof, if you could get 1/8 or 1/4" up in there, it'd be the biggest bang for the buck. (headliners sag for a good reason  )

The spray can foam would also suffice and would be cheaper and more convenient, although I'm uncertain of it's r-value.

I imagine that any method of insulation - even the foil faced bubble-wrap looking stuff would greatly improve efficiency and would be a cheap and relatively easy addition.

A ventilation fan for parking could be routed to suck relatively cooler air from the bottom of the car which is in shade and isn't roasting from the catalytic converter. A small solar panel on the trunk lid might run it just fine.


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## SuperChuck_A11 (May 29, 2008)

Cornelius said:


> . There are 5000 BTU air conditioners available, but this model was the smallest size physically. It is also Energy Star rated, and draws only slightly more power than a 5000 BTU.
> 
> . I would prefer to have a 144 VDC air conditioner and avoid all this, but I don't have the resources of GM or Toyota...
> 
> .


http://wagners12voltair.com/product.htm
*5000 BTU, l ow amp draw system for 24, 36, and 48-volts*


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## Phyber Optik (Jun 4, 2008)

That looks to be a nice DC solution...but $2500 dolla....ouch!

Could buy a some extra batts with that.

-Running a small Honda E1000 generator just to power the AC seasonally has also crossed my mind....stick him right on a hitch receiver mount.

-I also wonder if gutting one of those mini-fridges and using just the small (colder) metal ice cube tray maker part in a small cooler setup could be utilized with less juice.

What the heck did the EV1 use? Anyone have any info on it?

I think we really need to get this worked out now with Global Warming upon us.


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## willitwork (Apr 9, 2008)

Hi,
if I use the Warp 9 motor with dual tail shafts, and I turn the A/C pulley with one, I believe I am reading that when I am at a standstill, the motor will not be rotating the pulley. So the worst is that you would have no A/C while standing still??
I also know the power the compressor will draw might be substantial, but if I am willing to not have A/C while at a standstill, is it possible to have several 12 volt batteries in parallel (assuming space is available) to handle the electricity requirements so that the traction pack will not be drained?

I am assuming it can't be this easy, but I haven't seen this possibility addressed. (In the back of my mind I am thinking that if I still have the power going to the A/C to engage the clutch and the tailshaft of the motor is not spinning this would not be good, unless the A/C is smart enough not to engage the clutch if the pulley isnt moving)
thanks for any insight


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## SuperChuck_A11 (May 29, 2008)

You could just "idle up" the controller so your foot off pedal is still 300 rpm...by pulsing the motor, of course you'll have to have a clutch or a torque converter, not direct drive.


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## Jacob Riskin (Jun 10, 2008)

This may sound like a silly question, but I'm a newb in this forum. Has anyone tried to use the air-conditioning system out of the 2004-2008 Prius? I did a quick parts search and while I'm not sure it includes everything it seems to be roughly $1200-1500 in parts. I also read in a Prius forum that it is a very complicated system, but, it seems like it might be worth it for someone to give it a try. I would have to imagine it's one of the more energy-efficient methods.


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## mattW (Sep 14, 2007)

The problem is the prius system runs on AC at the prius voltage, not an easy swap for DC conversions.


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## Rook (Jun 5, 2008)

I’m still in the research or design phase for a future EV, but I’ve been thinking about air conditioning. I have an idea and I’m curious what you all think. A while ago the dehumidifier in my studio died. I believe it was a freon leak because the unit still ran. For those of you who haven’t focused on it a dehumidifier is just an air conditioner with both sets of coils back to back so the air is cooled, drops its water, then is heated up again by the back coils. The compressor is small, about a 4 inch cylinder 8 inches high. I plugged the working replacement dehumidifier into my Kill-A-Watt and it uses 3.66A at 120VAC (with a 12A starting surge). It seems like with an inverter and some creative plumbing it would make a decent (although weak by car standards) EV AC unit. I like the idea because it would be isolated from the rest of the car so if I want to focus range I could turn it off and it wouldn’t put any drag on the car. Think it would work?


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## SpeedTek (Jun 13, 2008)

I have been pondering over this same question for the last few years. I was thinking of building a heat pump system or take a 240VAC home pump and put it in the system. My friend said the Home A/C pump is not designed for jolts and jostles of a car.


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## Manntis (May 22, 2008)

has anyone here experimented with piezoelectric cooling?


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## Madmac (Mar 14, 2008)

If using a separate motor to run an AC compressor has any body considered using a salvaged motor out of a recent washing machine. Not having much knowledge on white goods other than seeing data sheets for control IC's they seem to be induction motors these days. The open design might need an enclosure.

If the control electronics follow the usual motor control configuration then there is a power factor correction stage producing a DC voltage rail for the motor inverter. In the US the DC rail should be about 140 Volts and in Europe about 340 Volts. Motors are about 1 KW rating.
The control allows variable speed operation, which would allow current drawn to vary depending on cooling requirement.

With a small remote (or timer) the AC could be switched on before going out to the car, an advantage over an ICE car. Could do the same for the heater so no getting in a cold car on a winter morning.

Madmac


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## judebert (Apr 16, 2008)

Madmac, that's the best solution I've heard yet. It sounds like you could get a motor and controller at surplus prices.

I'm willing to go to the scrap/junk/surplus place. Unfortunately, I'm as clueless as can be, especially with respect to AC. Can you give me an idea on how to identify a suitable motor?


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## MrCrabs (Mar 7, 2008)

Manntis said:


> has anyone here experimented with piezoelectric cooling?


You mean Peltiers?
I believe the peltier cooling method would be inferior to the efficiency of a modern auto a/c system.
Now if you wanted to make a seat pad, that had coolant running thru it (to cool off the drivers body) then peltiers might be good enough.

http://en.wikipedia.org/wiki/Thermoelectric_cooling
http://watercooling.co.nz/node/66

Hmm apparently they can be more efficient than an AC unit at low duty cycle (20% of rated voltage)
I wonder how many it would take too cool off the cabin. Even if you could design the peltier system to be more efficient, it might not be cost effective.


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## Manntis (May 22, 2008)

MrCrabs said:


> You mean Peltiers?


No, I meant piezoelectric. High efficiency oscillating bimetals in place of lower efficiency, power consumptive rotational fans.


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## MrCrabs (Mar 7, 2008)

Manntis said:


> No, I meant piezoelectric. High efficiency oscillating bimetals in place of lower efficiency, power consumptive rotational fans.


I see, I should not have assumed 

Is this a relatively new area of research? All I can find on google are journal articles (many you need membership to read) and patent applications.


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## Manntis (May 22, 2008)

MrCrabs said:


> I see, I should not have assumed
> 
> Is this a relatively new area of research? All I can find on google are journal articles (many you need membership to read) and patent applications.


Not really  - you can already buy piezoelectric camping coolers:

http://www.sailboatowners.com/upload/pix.tpl?folder=73237853523&sku=111032238017259982&fno=39

If you have your E.Eng or M.E. you should apply for an IEEE online membership - tons of great articles!


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## MrCrabs (Mar 7, 2008)

That is a peltier cooler. A google search for igloo piezoelectric cooler turns up that picture, and thats about it. 

http://www.sailboatowners.com/upload/display.tpl?folder=73237853523&fno=39
Here is the guy's writeup about the cooler, with a link to the pic you posted. He mentions it only cools 40 degrees below ambient temp, which is pretty standard for all peltier coolers.

A google search for Igloo Kool Mate 56 turns up many links describing that unit as a Thermoelectric cooler (aka peltier)
http://www.walmart.com/catalog/product.do?product_id=3353216

I've finding lots of research about using small piezoelectric devices to create a pump, but they are very small scale. I doubt they can be scaled up to anything useful (or cost effective compared to fans/compressors) otherwise we would have had them by now.


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## Manntis (May 22, 2008)

MrCrabs said:


> I've finding lots of research about using small piezoelectric devices to create a pump, but they are very small scale. I doubt they can be scaled up to anything useful (or cost effective compared to fans/compressors) otherwise we would have had them by now.


We do have them by now: http://www.piezo.com/prodfan0nav.html

The _Peltier effect_ is a thermal differential that allows for heating or cooling, depending on current flow direction, by running electricity through dissimilar conductors. This is used to make thermocouples.

The _converse piezoelectric effect_ is _motion_ induced by electric current applied - the opposite of creating electric current by mechanical stress - and specifically uses electricity, not an ambiguous heating or cooling source, to create that motion. This is used to make oscillating fans.

Thus you'll often see devices with Peltier elements and piezoelectric actuators - two separate things - which is probably what the Igloo cooler in question uses, hence the confusion.


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## MrCrabs (Mar 7, 2008)

I have a Vector travel heater/cooler that uses Peltier devices to keep the cooler cool, and it uses standard 12vdc fans to blow air across the hot side. Inside the cooler area is just the cold sink, no fans blowing air around inside the unit.

I think the guy who wrote it up about his boat was just confused, anyways those Piezo fans look interesting, but what can you use them for? Maybe cooling off an IC or CPU but how could they be used for cooling off the interior of a vehicle?


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## Manntis (May 22, 2008)

MrCrabs said:


> I have a Vector travel heater/cooler that uses Peltier devices to keep the cooler cool, and it uses standard 12vdc fans to blow air across the hot side. Inside the cooler area is just the cold sink, no fans blowing air around inside the unit.
> 
> I think the guy who wrote it up about his boat was just confused, anyways those Piezo fans look interesting, but what can you use them for? Maybe cooling off an IC or CPU but how could they be used for cooling off the interior of a vehicle?


A small bank of them fanning the heating/cooling element, whether said element is Peltier type or not. It's desirable to have air circulation in a vehicle, hence the requirement for a fan, but you'd be surprised how much power a rotational motor fan takes when compared to piezoelectric counterparts

It's sort of like replacing incandescent bulbs with LEDs. on the surface of it, the original didn't seem that power hungry... but the cumulative effect over time can result in significantly less battery drain. Every bit helps!


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## MrCrabs (Mar 7, 2008)

I did a quick comparison of CFM/W.

http://www.primelec.com/Shop/Control/Product/fp/SFV/31734/vpid/5176351/vpcsid/0/rid/124330
This fan draws 1.2 W and moves 13.7 CFM which is 11.4 CFM/W
The low voltage piezo you linked to draws 42 mW and moves 0.75 CFM which is 17.8 CFM/W.
So they do are more efficient.... but did you see the pricing on them? It would cost a small fortune to move the same amount of air that a $3 fan could.

What about a small personal cooler? Something where a piezo fan cools off the hot side of a peltier, and the cold side is strapped to the back of your neck, with something to spread the cold around the back of your neck.


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## Manntis (May 22, 2008)

MrCrabs said:


> did you see the pricing on them? It would cost a small fortune to move the same amount of air that a $3 fan could


Same argument I often hear against lithium ion batteries vs. SLAs 



MrCrabs said:


> What about a small personal cooler? Something where a piezo fan cools off the hot side of a peltier, and the cold side is strapped to the back of your neck, with something to spread the cold around the back of your neck.


new headrest design, here we come!


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## BigAlum (Jun 12, 2008)

Hey, Guys -
As for "cooling while standing still," why not a rather large diameter heavy-rim flywheel between the traction motor output and the compressor clutch to tide the rotation over for a few minutes? Flywheel could possibly be engaged automatically before the stop by application of the brakes, thus assisting the stop (mechanical regen?). Of course, the coupling would also have to be overrunning or completely clutched...Thinking out loud again.


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## Manntis (May 22, 2008)

BigAlum said:


> Hey, Guys -
> As for "cooling while standing still," why not a rather large diameter heavy-rim flywheel between the traction motor output and the compressor clutch to tide the rotation over for a few minutes? Flywheel could possibly be engaged automatically before the stop by application of the brakes, thus assisting the stop (mechanical regen?). Of course, the coupling would also have to be overrunning or completely clutched...Thinking out loud again.


Principally because an electric accessory motor turning the A/C compressor and, if needed, power steering pump is less mass than a large flywheel-and-clutch assembly, and needs nothing more to engage it than a switch.


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## Jacob Riskin (Jun 10, 2008)

I'm thinking three things

1. We need DC equivalents to all of the belt driven accessories

2. Until they exist its best to go the least complicated path, which in my mind means a small DC motor to power any needed accessories.

3. The other possibility is that AC motors and controllers come down enough in price and we start using AC powered accessories.


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## Phyber Optik (Jun 4, 2008)

BigAlum said:


> Hey, Guys -
> As for "cooling while standing still," why not a rather large diameter heavy-rim flywheel between the traction motor output and the compressor clutch to tide the rotation over for a few minutes? Flywheel could possibly be engaged automatically before the stop by application of the brakes, thus assisting the stop (mechanical regen?). Of course, the coupling would also have to be overrunning or completely clutched...Thinking out loud again.


IMO, your idea sounds DIY doable for the AC. Or at least worthy of some serious thought.

Perhaps a double electric clutch on the AC compressor to isolate the flywheel power from the traction motor output (?)

For powering idle AC, I have a sneaking suspicion that the mechanical energy transfer in a simple flywheel (which is engaged only when the AC is on) would be more efficient than using all of the regen to capture juice to the traction pack which will then return it back to the AC compressor.

Maybe you could modify a set of Wheel Spinners to solve the problem. 

I've been looking at F1 KERS systems (Kinetic Energy Recovery System) which will likely be implemented for the 2009 F1 season.

 It uses an 11lb flywheel (total KERS system is 55lbs) powered by braking energy which spins it at 65K RPM on ceramic bearings in a vacuum chamber - which is _un-cooled. _

For F1, it gives an 80hp "boost" for 6 seconds at the push of a button.

Best part, it is pure mechanical energy transferred straight to the tranny and is 70% efficient, vs electric KERS (basically the regen braking systems on electrics/hybrids) which is only 35-45% efficient.

Since most EV's don't have trannies, I'm sure it could be pumped to a generator for direct juice straight to the drive motor(s), and perhaps optionally (and at less efficiency) - the charging system.

It would eventually cost around $1000/car if put into mass production. Thats cheap.

This could eventually be the way to go with the kinetic braking energy, instead of trying to pump it back into the batteries at less efficiency. 

Could boost you off from stop lights and boost you up hills or into passing/merging speeds to save batt power, or be ECM managed to bleed out before depletion on flatland or highway driving for battery charging.

*A couple linkies for those interested:*

http://www.motortrend.com/features/editorial/112_0803_technologue/index.html

http://www.flybridsystems.com/


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## Drizzle (Jun 17, 2008)

Rook said:


> I’m still in the research or design phase for a future EV, but I’ve been thinking about air conditioning. I have an idea and I’m curious what you all think. A while ago the dehumidifier in my studio died. I believe it was a freon leak because the unit still ran. For those of you who haven’t focused on it a dehumidifier is just an air conditioner with both sets of coils back to back so the air is cooled, drops its water, then is heated up again by the back coils. The compressor is small, about a 4 inch cylinder 8 inches high. I plugged the working replacement dehumidifier into my Kill-A-Watt and it uses 3.66A at 120VAC (with a 12A starting surge). It seems like with an inverter and some creative plumbing it would make a decent (although weak by car standards) EV AC unit. I like the idea because it would be isolated from the rest of the car so if I want to focus range I could turn it off and it wouldn’t put any drag on the car. Think it would work?


 
I've been thinking of something very similar for a while...

I understand there is a question about the compressor handling the bumps and jostles of life in a moving vehicle -- and I'm still waaaay too early in my learning-curve on this project to have figured out the details of electrifying it without having start-up surges potentially damage components, but... 

Has anyone tried taking the compressor out of a refrigerator or window A/C unit and just pluming it into the car's A/C plumbing in place of the car's original compressor? It would be lighter weight, wouldn't add the necessity of additional weight and space consumption like a drive-motor for the original A/C -- and I THINK it would use considerably less power. 

I understand that this compressor would likely not produce as much "cool" as the original compressor did -- but I'd happily accept half as much cooling power with the simplification factor. And like Rook mentions above, it would be easy to fully disengage when you didn't need it (or your range-needs trumped your need for comfort!).

Anyone???


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## Phyber Optik (Jun 4, 2008)

Drizzle said:


> Has anyone tried taking the compressor out of a refrigerator or window A/C unit and just pluming it into the car's A/C plumbing in place of the car's original compressor? It would be lighter weight, wouldn't add the necessity of additional weight and space consumption like a drive-motor for the original A/C -- and I THINK it would use considerably less power.


A household fridge might still pull some substantial amps, however one from a mini-fridge might work and drain less juice.

I'm also one who could settle for "cool" vs. "cold" air with less drain.

I'd love to know the amp draw on big and little fridges vs. the amps to run a motor to spin a stock automobile compressor.


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## Drizzle (Jun 17, 2008)

Phyber Optik said:


> A household fridge might still pull some substantial amps, however one from a mini-fridge might work and drain less juice.


What got me to thinking along this vein was reading an article recently that mentioned that newer household refrigerators consume less than 1 Kwh per DAY. (And that would include lights, fans, and icemakers...) To me, that sounds _very_ likely that an automotive setup would facilitate less drain than a 1/2 horse motor running the original compressor...


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## Manntis (May 22, 2008)

Drizzle said:


> What got me to thinking along this vein was reading an article recently that mentioned that newer household refrigerators consume less than 1 Kwh per DAY. (And that would include lights, fans, and icemakers...) To me, that sounds _very_ likely that an automotive setup would facilitate less drain than a 1/2 horse motor running the original compressor...


Could ditch the compressor and refrigerant entirely and use a Peltiers element, keeping it all electric rather than electric to mechanical to refrigerant


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## O'Zeeke (Mar 9, 2008)

Manntis said:


> Could ditch the compressor and refrigerant entirely and use a Peltiers element, keeping it all electric rather than electric to mechanical to refrigerant


 
I just went with el cheapo for about $45 and it works great. Yes it is a pain in the ass to dump it out and add more ice but my range is limited to about 1 [email protected] 50 mph and the ice lasts longer than that and very little amp/hr drain http://www.instructables.com/id/Portable-12V-Air-Conditioner---Cheap-and-easy!/


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## BigAlum (Jun 12, 2008)

I just read the links to the flywheel regen technology articles. I am very impressed. If the big three don't jump on this technology with all four feet, they'll be missing a great way to boost their CAFE numbers. Looks like a great idea for home-brew electrics, too. I've always had an idea that mechanical storage of energy, if sufficiently drag-free bearings and a suitable means of transfer were developed, would be the most efficient. Check out the links - Very impressive!


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## stevejamaican (Oct 27, 2010)

Along with the traditional solutions, you can also use Peltier modules to build an AC solution, or you can use a compact compressor from a company like Masterflux. 

I found an example of a build using the Masterflux solution on this site: http://www.evdrive.com/BMW_project/AirConditioning.html


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