Electric AC?

[TheDude]

Has anyone tried out an electric AC compressor? I've been seeing more and more of these around. Originally they seemed to be aimed at RVs and large trucks but I've keep reading things here and there about them being used for retrofits and hotrods. I like the idea of this as it could keep the engine less cluttered and should be less parasitic and I think it could be cheaper as well but have yet to find anyone in the real world using one and very few videos etc that I've found of people using them.

Here's one example of a full kit, but I think you can just use the compressor only and use other components that support modern refrigerants

https://qualyair.us/collections/a-c...rdash-electric-compressor-air-conditioner-12v

 

[giantpune]

Seems like it would require a manlier alternator and wiring. Maybe even converting to a 3G alternator.

And how does the math work out about being less parasitic? It takes a certain amount of energy from the motor to run the AC compressor. In the old configuration, the motor directly turns the compressor via a belt. In this configuration, the motor sees extra load via the alternator. The energy needs to be converted to electrical energy and then back into mechanical energy. That seems like both of those conversions would be wasteful.

If you want less parasitic loss than a belt driven compressor, I think the answer is pulley swaps to underdrive it.

 

[TheDude]

Seems like it would require a manlier alternator and wiring. Maybe even converting to a 3G alternator.

And how does the math work out about being less parasitic? It takes a certain amount of energy from the motor to run the AC compressor. In the old configuration, the motor directly turns the compressor via a belt. In this configuration, the motor sees extra load via the alternator. The energy needs to be converted to electrical energy and then back into mechanical energy. That seems like both of those conversions would be wasteful.

If you want less parasitic loss than a belt driven compressor, I think the answer is pulley swaps to underdrive it.

Yes, very possible it'll need a beefier alternator although I don't thing anything extravagant from what I've seen.

Less parasitic maybe isn't the best way to phrase that. They are more efficient in a number of ways from just the way the power is generated to not relying on engine speed to produce cooling. They can be turned off when not in use where a belt driven compressor is always turning and does draw a bit of power all the time.

Having said that, there will be drawbacks like what you mentioned the possible / likely need for a bigger alternator and that they often aren't going to be as powerful as a similarly sized belt driven compressor.

I'm actually less interested in an efficiency gain as the just the flexibility in installing them and the possible cost savings. While I'm not going to do this, I like the idea that one could stash the compressor in the trunk or inside a fender well etc. to keep the engine bay less cluttered and leaving easier access to the engine when working on it.

 

[Don C]

Seems like it would require a manlier alternator and wiring. Maybe even converting to a 3G alternator.

And how does the math work out about being less parasitic? It takes a certain amount of energy from the motor to run the AC compressor. In the old configuration, the motor directly turns the compressor via a belt. In this configuration, the motor sees extra load via the alternator. The energy needs to be converted to electrical energy and then back into mechanical energy. That seems like both of those conversions would be wasteful.

If you want less parasitic loss than a belt driven compressor, I think the answer is pulley swaps to underdrive it.

I agree, the compressor requires the same amount of power, assuming the effectiveness and cooling capability is the same, whether it is powered directly by the engine or by the electrical system. The battery has the capacity to power the compressor for a short period of time, but has to be recharged or the complete electrical system will shut down. The alternator has to be able to recharge the battery, as well as power the a.c. compressor, ignition, blower motor, lighting system, and accessories. I looked online and the electric a.c. compressor I saw for cars requires up to 63 amps.

And, I agree, converting engine power (mechanical energy) to electricity and back to mechanical energy both have losses that are dissipated as heat, requiring more engine power to run than running the compressor directly from the engine.

Electrical a.c. compressors came about from necessity to be able to provide a.c. for electric powered cars, not for efficiency.

 

[giantpune]

They can be turned off when not in use where a belt driven compressor is always turning and does draw a bit of power all the time.

Belt driven type just disengage the clutch when the AC doesn't need to run. The pulley spins, but not the rest of the compressor. It doesn't use any more power from the engine like that than an idler pulley. It actually should use less power from the engine, since the circumference of the AC pulley is like twice as big as an idler pulley.

One would think that if these really did work great, we would already see them used in production vehicles. I'm sure the big auto industry has already tried them out in concept and beta cars over the years and decided against using the in production runs for one reason or another.

EVs do use electric AC compressors. So it is starting to become a thing. They are being forced into using it because there simply isn't a crank pulley always spinning that they can connect to. Maybe as EVs force them to use these more, they will fix whatever issue they saw with them and the technology continues to improve.

 

[TheDude]

Really wasn't looking to get into a debate about efficiency about this. We can quibble over details see electric compressors in some higher end non EV / non hybrids, but regardless, I don't really care about that so again sorry I brought it up.

My point in looking at this is more about flexibility and maybe cost savings.

 

[Steve McMahan]

It seems to me, beyond the methodology of producing work, an electrical compressor would in itself be able to be designed to be more efficient, because it can be optimized to work at a very specific range. An engine driven devise has to work at all inputs, while an electrical unit can be designed into the sweet spot. So, sub-optimized. It may use more energy to produce the same work, but nonetheless, it might create different under hood looks as compressors could end up anywhere in the vehicle. I think it’s cool.

 

[Don C]

Really wasn't looking to get into a debate about efficiency about this. We can quibble over details see electric compressors in some higher end non EV / non hybrids, but regardless, I don't really care about that so again sorry I brought it up.

My point in looking at this is more about flexibility and maybe cost savings.

Nothing wrong with bringing up an issue like this. Interesting topic. Definitely offers flexibility, in not needing the engine mounted brackets, idler pulleys, and crankshaft pulley. And, it is doable. Selection of a mounting point may be critical, depending on how noisy they are. Please let us know if you proceed with it, and how it comes out.

On projects like this, all aspects, positive and negative, need to be reviewed, see if the positive outweighs the negative. Cost is only one of the things to think about. Things like ease of installation and maintenance, and aesthetics, that don't have a direct monetary value, also need to be considered.

 

[will e]

One would think that if these really did work great, we would already see them used in production vehicles. I'm sure the big auto industry has already tried them out in concept and beta cars over the years and decided against using the in production runs for one reason or another.

This was my thought too. Although it usually takes a few years to adopt.

I did a quick search and it appears that many of the AC compressors for cars us a much higher voltage (144v or greater). That's just a 30 second review but it makes sense. That's going to be one of the downsides for retrofitting.

 

[giantpune]

Nothing wrong with bringing up an issue like this. Interesting topic. Definitely offers flexibility, in not needing the engine mounted brackets, idler pulleys, and crankshaft pulley. And, it is doable. Selection of a mounting point may be critical, depending on how noisy they are. Please let us know if you proceed with it, and how it comes out.

On projects like this, all aspects, positive and negative, need to be reviewed, see if the positive outweighs the negative. Cost is only one of the things to think about. Things like ease of installation and maintenance, and aesthetics, that don't have a direct monetary value, also need to be considered.

You could get pretty sneaky with where you mounted it, too. Like mount it inside the fender, hidden behind the splash shield.

 

[TheDude]

Nothing wrong with bringing up an issue like this. Interesting topic. Definitely offers flexibility, in not needing the engine mounted brackets, idler pulleys, and crankshaft pulley. And, it is doable. Selection of a mounting point may be critical, depending on how noisy they are. Please let us know if you proceed with it, and how it comes out.

On projects like this, all aspects, positive and negative, need to be reviewed, see if the positive outweighs the negative. Cost is only one of the things to think about. Things like ease of installation and maintenance, and aesthetics, that don't have a direct monetary value, also need to be considered.

Thanks. Sorry just internet jaded about asking questions only to have people tell me you shouldn't do that when I understand the issue. That's never happened here which is something I've always loved about this site. No matter what dumb thing I've tossed out, people try and help. I've been toying around with this idea for a few years so I get most of the pros and cons and get that it's new subject to lob in here so people need to digest and dissect it a bit.

One comment about them in production cars. I think some of that is just cost. Car companies have been building belt driven ACs for decades, they know how to do it and it's cheap for them to make and support. The systems work and are reliable so why change it?

Beyond getting fancy about where its installed for looks, I just like the idea of mounting the compressor out of the way and not on top of the engine so it's less cluttered and easier to work on.

 

[donkost]

A interesting idea, and it's certainly ok to discuss. My wife's old 1999 Expedition Eddie Bauer had four wheel air suspension with the compressor located in the passenger side front corner of the engine compartment. Didn't kick on very often but when it did you could feel the vibration in the vehicle, and even hear it a bit. We owned that from new so it wasn't because rubber mounts were worn out etc. On the Navigator L it has rear-only air suspension and they must have done a better job of isolating the compressor since it is hard to detect when running. So for a electric AC compressor you'd certainly want to have all of that vibration isolated from the driving experience.

 

[Hemikiller]

Looking at the website, they're showing 600W, 60/70 amp draw. Other than having sufficient alternator capacity, it's a good idea and likely way more efficient than a York recip compressor. 600W is about 9/10 hp. You'll definitely be in 3G territory for an alternator, likely a double V-belt or convert to rib.

 

[giantpune]

Looking at the website, they're showing 600W, 60/70 amp draw. Other than having sufficient alternator capacity, it's a good idea and likely way more efficient than a York recip compressor. 600W is about 9/10 hp. You'll definitely be in 3G territory for an alternator, likely a double V-belt or convert to rib.

Do these kits have some mechanism to turn off the AC compressor when you stomp on the gas pedal? That 10hp they require doesn't matter as much when you're cruising around only using 50HP anyways. But you put your foot down and go WOT, you probably care more about the car going as fast as it can, so you want the AC to be disabled.

 

[Hemikiller]

That's a fraction - 0.9hp

1 hp = 745 watts

Fox Mustangs had a WOT AC cutoff switch, I'm sure others did as well.

 

[giantpune]

That's a fraction - 0.9hp

1 hp = 745 watts

Fox Mustangs had a WOT AC cutoff switch, I'm sure others did as well.

Oh, I read that as 9 or 10. Thats a bit of a difference.
I know the LS-swap-it-bro computers turn off the AC compressor at WOT.

 

[Hemikiller]

Lots of e-compressors out there in OEM land, think Prius, Tesla, C-Max etc. I'd assume pretty much any hybrid will have an e-compressor. Might be worth scavenging something off a wrecked vehicle, then you can get the power cables and connectors.

 

[Fabrice]

Without looking for electric, you could also look at small cars. Like mini’s,ford fiestas etc… their compressors are very light and work fine. I know my ex 2005 mjni cooper had airco and it worked fine. The diff is the time it takes before it is really cooling at max capacity. Takes a few minutes while I recall my 73 airco serving ice cubes within seconds.

 

[TheDude]

A interesting idea, and it's certainly ok to discuss. My wife's old 1999 Expedition Eddie Bauer had four wheel air suspension with the compressor located in the passenger side front corner of the engine compartment. Didn't kick on very often but when it did you could feel the vibration in the vehicle, and even hear it a bit. We owned that from new so it wasn't because rubber mounts were worn out etc. On the Navigator L it has rear-only air suspension and they must have done a better job of isolating the compressor since it is hard to detect when running. So for a electric AC compressor you'd certainly want to have all of that vibration isolated from the driving experience.

Same, I have an SUV that had an air suspension when we got it and while quiet, you'd notice while it was on. One of the other possible downsides is noise as you'd hate to hear this thing whirring away above the sound of the engine.

Do these kits have some mechanism to turn off the AC compressor when you stomp on the gas pedal? That 10hp they require doesn't matter as much when you're cruising around only using 50HP anyways. But you put your foot down and go WOT, you probably care more about the car going as fast as it can, so you want the AC to be disabled.

They claim that these things will draw power needed under load from the battery and so you don't need to turn off the AC when going up hills. Obviously no idea if that's true, but that's one of the Pros they list to these things.

 

[giantpune]

They claim that these things will draw power needed under load from the battery and so you don't need to turn off the AC when going up hills. Obviously no idea if that's true, but that's one of the Pros they list to these things.

These get their power from the battery, and the battery gets its power from the alternator. When you increase electrical load of 12v thingies on a car, the alternator puts more load on the engine to generate more power.

So unless their kit has some sort of switch that gets pressed when you hit WOT, I'm not understanding how the AC compressor is not robbing the energy that you would rather use to push the car faster.