homemade 12v AC system?

[dmartin1]

Ive posted a thread about this a long time ago,but never really got anyone thinking or talking about it.

is there an ac system out there thats solely powered by 12v power?
like, the compressor bolt up to the existing trucks ac system,but the compressor run off of 12v somehow?


I was thinking maybe if you found the right electrical 12v engine, you could run a V belt pulley(or any other belt you decide on) on the electrical engine driving an AC compressor originally driven by the gasoline engine?providing you hooked it all up right with relays switches etc(im not a pro at electrical..).

am i just nuts for thinking of this? or do you guys think it could be done? whats your thoughts?

[379redneck]

not mine

[379redneck]

Does your truck already have ac in it that just doesnt work?

[dmartin1]

no my truck has perfect air conditioning.

im just curious if i can run an AC compressor off of an electric motor instead of the gas engine(just for fun,see if it works type thing).

wanna see what guys say about this....technically its the same thing as the gas engine spinning it,except for variations iin RPM's.

i would think as long as it gets spun, it would pump the freon?

[379redneck]

Look up how the window ac units work, they have to move the freon around somehow. Im sure there are other people on here that know a lot more about this stuff than I do that could figure something out.

[dmartin1]

hmmmm...anyone? im real curious on this subject?

[lilpoindexter]

I think it would work. I work on Tow tractors...I had to do AC on one with a cramped engine compartment...so we went with a compressor driven by hydraulic fluid...the compressor was stuffed under body somewhere...as you said, as long as you turn the shaft, you should get AC.

[tucsonjwt]

There are 12V AC units made for commercial applications (trucking) which run of extra batteries, but they are big packaged or "mini-split" systems (like home A/C units. They cost about $4K-$6K+ the last time I checked. They are designed to allow 18 wheelers park with A/C on and not run the truck engine or generator.

http://www.dcairco.com/index.php/dc-9000-1224-vdc

[Eyegore]

What are they using in these new hybrid cars lke the chevy volt?

[tucsonjwt]

That's one for Volt engineer Keith. I think some hybrids run electrical accessories off the battery at times, including A/C.

[dmartin1]

EXACTLY..how do the chevy volt or the nissan leafs get AC? or all these hybrid deals?

if i can find the right 12v engine i may be trying this in the next few weeks.

it would be sweet to have the AC run off 12v,i imagine less tug on the engine,less over heating (i live in a 120 degree summer area).

i imaginer you could hook the hot wire for the electric motor with the hot wire for the compressor clutch so when the switch is flipped it engages the clutch on the compressor and spins at once. hmmm?

any electrical nuts out there?

[dmartin1]

thats a cool link, tuscon.
but i wanna just run the compressor off a strandard electrical engine on a switch, so basically takin it off the engine brackets,and mounting it and a electric motor inline with each other on the inner fenderwell driven by a V belt

[tucsonjwt]

My guess is running straight off battery power will drain the battery quickly, assuming you are talking about hooking an electric motor to 12V DC. A hybrid or pure electric has a huge battery bank. If you add an extra battery or two you will have to charge them while driving, and I think it will take a lot of driving to charge them. You would need to calculate the amperage draw of the compressor X 12V = total watts consumed to determine what type of power demand would be consumed by the compressor, then determine what battery size you would need and how much it would take to keep it charged. My guess is you would have to crank up the engine speed to keep enough electrical generation to power the electric motor, like the fast idle circuit when the A/C is on, so I don't see the benefit there. Charging extra batteries from your household circuit might make more sense, until you ran out of battery capacity while you were on the road.

[379redneck]

Would running a bettery only for the ac work? I know some work trucks like the ones the fire departments have use two batteries, one to start the truck and one to power everything else. I have never noticed a difference in the rpms with the truck we use and theres a lot of stuff hooked up to it. You might also need a second alternator, I cant remember how its set up right now. That would only work if you had simething like what might be in the electric cars, but like tucsonjwt said, those cars have huge batteries in them so it might not be enough. Maybe you could hook up one of your other pumps to move the freon, like how the diesel engines used the power steering pump for the brakes. I dont know a lot about it but its just a thought.

[Eyegore]

But what if you went with whatever system these smaller cars are using, they have small motors but the truck cab size would still be equal to whatever size they have. Sorry if off the thought line for this thread but the it would help witht e pull off the motor.

[Pyrotechnic]

I know the Toyota hybrids use some sort of electric A/C. You can sit there parked with the engine off and the AC on. Whether it runs on 12V or not I don't know.

The simple answer is to take a 12V electric motor and couple it to the compressor with a V-belt. You may want to upgrade your alternator or even run a second one to feed the new load. An additional battery (deep cycle) might be a good idea too.

[Psycho71]

Hmm, I'll start off by saying I'm an A/C man first, and know a very little bit about electricity. And barring some of the new technology being used in electric cars, my thoughts on the subject are this;

Running an a/c compressor off of a 12v dc motor would not be practical for general automotive use. The 12v motor would draw a very large amount of amps, which would have to be replenished from somewhere or the battery would drain very quickly. This would require a large charging source (alternator?), and that would place a drain on the engine equal to the compressor, in theory (to every action there is an EQUAL and opposite reaction). Then there's the reliability factor of the 12v motor itself. If it were used as a sole source of a/c in an area like Tx. where a/c is used 9-10 months out of the year, that 12v motor would not last very long at all. And given the size motor it would require, replacement would be very expensive.

Is it possible, yes. Anything is possible. Is it practical? Not really IMHO.

I've seen compressors ran off of hydraulics myself. Lots of them. Hydraulics are capable of gobs of power with little taxation on a pump that might be designed to run much larger systems. This is very practical. In fact, ingenious in some applications.

Again, I'm not up to speed on how it's done in the electric cars out there today. But, the motors running those cars are very large motors, designed to move around cars weighing thousands of pounds. So the energy required to run an a/c compressor is a fraction of their capability. They also have forward momentum charging systems to recharge the batt's. under deceleration. So the power consumption of an a/c compressor sized to cool the interior is minimal in the gran scheme of things.

[7T2]

As far as using a 12VDC motor to run a compressor pump, I think you will go to a lot of work and fabrication to come up with a system that ultimately doesn't gain you anything over what is available now.

I have a couple sirens on my ambulance that use electric motors that are roughly the same as a starter motor. I would imagine you would need something similar for an AC compressor. I can tell you that those sirens pull more than 100 amps when you start them up, and anywhere from 60-75 amps to keep them spinning. Most vehicles come stock with an alternator that is considerably less than 100 amps. Based on what I have seen, you would probably have a maximum of 3-4 minutes of cold air until your battery is completely dead, engine running or not, unless you significantly beef up the charging system. Add in the cost of that and it makes sense to just stick with the old engine-driven system.

[tucsonjwt]

Actually, modern mini split household A/C units run on a DC inverter - that is taking 120 volt a/c and inverting it to DC (not sure of the DC voltage). This allows the DC motor to run at variable speeds to match the load of the A/C, causing it to be more efficient than standard "on or off" AC voltage motors. Some 18 wheeler tractors bolt mini splits to the back of the cab to take advantage of this, but they are producing mega power, or use a separate AC generator mounted to the frame of their rig.
I see only two options:
1) run the A/C off the crank pulley somewhere (just like a normal automotive
A/C compressor, which will drain power from the engine
2) install a separate power source for the A/C unit, like 2 extra batteries which you charge at home on a charger every night. That might give you a couple of hours of cooling before the batteries die, and that would shorten the battery life a lot. The batteries would power a DC motor with a pulley to turn the normal automotive A/C compressor.
3) Install a small generator to power a motor to turn a compressor.
Any way you cut it, you don't get power for free. Either you burn gasoline or electricity from a home charger. Modern automotive A/C compressors are lighter and more efficient, but they still take a toll on gas mileage.

[68longhorn]

I can only speak for Ford but their Fusion Hybrid has a electric A/C compressor which runs off the high voltage traction battery, not the 12 volt battery. The high voltage side of that car puts out around 280volts or so. I've heard UNVERIFIED claims that the electric A/C compressor off the Fusion can be retrofitted to run off the 220volts in your house and cool your garage.

[motornut]

check for rv's type?
i don't have one in my 20 foot square box(see terry below) but i know that some newer units have some low powerd AC units......12v from what i hear but i duno i'll ask around the camp this weekend

[motornut]

k forget that idea
lol could try swamp coolers

[Eyegore]

They already did this on old volkswagons, it used to hang off the passenger window.

[jonfarrugia]

I am in the same boat with my build...I have no room to mount a compressor so I've been looking at other options like an electric compressor i could mount in the trunk.
I came accross transport truck sleeper compressors that run at 12vdc and draw 31amps.
would something like this work in the automotive world?

http://www.alibaba.com/product-gs/38...ioning_of.html

[dmartin1]

some neat info in this thread. it sounds like it could be done if you really wanted to but its not practical at all. i wish i had the funds and time to atleast try it to say that i did it.

on the charging baterys at home every night topic, instead of having to charge the batterys every night to run the motor for the ac, couldnt you fab up a high-output alternator and charge the batterys while running? i know that would put just as much strain on the engine as a compressor, but like i said, it seemed like a neat topic and ive never seen it done before.