homemade 12v AC system?

[Edahall]

Originally Posted by 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.

It would actually put more strain on the engine than the compressor. There is always a certain amount of loss with energy conversion (i.e. using alternator to charge a battery).

However, how about using the heat from your engine to run a boiler and a turbine that will power that A/C? As you know, the gasoline engine is only has an efficiency rating of about 20% so the rest of it is turned into heat. It sure would be nice to be able to capture some of that heat energy and turn it into propulsion energy.

[Stepper86]

Originally Posted by Edahall

It would actually put more strain on the engine than the compressor. There is always a certain amount of loss with energy conversion (i.e. using alternator to charge a battery).

However, how about using the heat from your engine to run a boiler and a turbine that will power that A/C? As you know, the gasoline engine is only has an efficiency rating of about 20% so the rest of it is turned into heat. It sure would be nice to be able to capture some of that heat energy and turn it into propulsion energy.

Oh man, I would love to see this one. Maybe it could be used to make Hot Dogs at the same time as it cools the driver down, add a camper and you would never have to leave your truck.

[wilkin250r]

I'm an Electrical Engineer, but the answer has already been given throughout the thread. Yes, it's possible, but you're honestly looking at a fairly big DC motor pulling quite a bit of power. A typical small window-mounted air conditioner for your house runs about 5 amps at 120V, which translates to 50 amps at 12 volts. That's a huge amount of power for a car. At the very least you're looking at an expensive high-output alternator if not a second alternator dedicated solely to your AC.

Now, it just doesn't make any sense to mount a second alternator to power your AC. If you've got the space for a second alternator, then why not just use an engine-driven AC pump?

And the typical starting battery has about 50 amp hours, so you've got one hour of AC use before your battery is dead.

And these are just the general guidelines, by the time you get into efficiency ratings of your power conversion, power losses in the system, ect ect you're going to reduce these numbers considerably.

[68shortstep]

Different power system, but when I was a kid my (mechanical inventor-type) uncle had a'60 T-Bird in which he had rigged a McCullough 2-cycle chainsaw motor to run the AC compressor for a below-dash mounted aftermarket AC setup.

It would run the chainsaw motor at not much more than an idle & just puttering along, it would keep the car cool inside when it was parked for hours with the car's main engine off. I remember that he did paint the roof white on what had been an all-black car, to minimize the added dark roof-color heat load.

Don't know how he had rigged the electric motor power for the blower of the underdash AC unit, but I remember that he had an extra battery in the trunk.

I think he quit using it & took it out because of having to mess with & carry the pre-mix oil & gas for the chainsaw motor.

[dmartin1]

Originally Posted by 68shortstep

Different power system, but when I was a kid my (mechanical inventor-type) uncle had a'60 T-Bird in which he had rigged a McCullough 2-cycle chainsaw motor to run the AC compressor for a below-dash mounted aftermarket AC setup.

It would run the chainsaw motor at not much more than an idle & just puttering along, it would keep the car cool inside when it was parked for hours with the car's main engine off. I remember that he did paint the roof white on what had been an all-black car, to minimize the added dark roof-color heat load.

Don't know how he had rigged the electric motor power for the blower of the underdash AC unit, but I remember that he had an extra battery in the trunk.

I think he quit using it & took it out because of having to mess with & carry the pre-mix oil & gas for the chainsaw motor.

now thats some engineering there lol! i guess anything can be done if someone really wants to.i wonder what people thought walking by the car off with a chainsaw motor pinging under the hood? lol

Originally Posted by wilkin250r

I'm an Electrical Engineer, but the answer has already been given throughout the thread. Yes, it's possible, but you're honestly looking at a fairly big DC motor pulling quite a bit of power. A typical small window-mounted air conditioner for your house runs about 5 amps at 120V, which translates to 50 amps at 12 volts. That's a huge amount of power for a car. At the very least you're looking at an expensive high-output alternator if not a second alternator dedicated solely to your AC.

Now, it just doesn't make any sense to mount a second alternator to power your AC. If you've got the space for a second alternator, then why not just use an engine-driven AC pump?

And the typical starting battery has about 50 amp hours, so you've got one hour of AC use before your battery is dead.

And these are just the general guidelines, by the time you get into efficiency ratings of your power conversion, power losses in the system, ect ect you're going to reduce these numbers considerably.

i understand, it was mainly just an idea like can it be done.I had never heard of this before( problly because its kinda stupid) but this has got a ton of interesting responses definately. thanks for the info!

Originally Posted by Edahall

It would actually put more strain on the engine than the compressor. There is always a certain amount of loss with energy conversion (i.e. using alternator to charge a battery).

However, how about using the heat from your engine to run a boiler and a turbine that will power that A/C? As you know, the gasoline engine is only has an efficiency rating of about 20% so the rest of it is turned into heat. It sure would be nice to be able to capture some of that heat energy and turn it into propulsion energy.

dam.I thought i had a crazy thought. a boiling turbine would definately be something LOL