Is there a new type of AC Compressor

[si Banker]

I spoke to a friend who just purchased a Lexus Hybrid. He said that the compressor is electric in stead of belt driven. I have been told that the HP cost to run the ac compressor is about 7 HP.

Does anyone know anything about these Electric ac compressors.

[brads911sc]

Here is some info.

It runs off a separate battery. The real issue here is that what ever you gain in HP, you will lose in weight... well that and making it bolt up....

A/C compressor on hybrid - Club Lexus Forums

[jplucas]

It's purpose is so that the A/C can still run when the car is shut off at stop light or when in full EV mode (for the hybrids that have that mode).

[wwest]

Originally Posted by brads911sc

Here is some info.

It runs off a separate battery. The real issue here is that what ever you gain in HP, you will lose in weight... well that and making it bolt up....

A/C compressor on hybrid - Club Lexus Forums

"..you lose in weight.."

Quite possibly not.

Engine driven compressors must be sized large enough to provide coolig even during extended periods of idling, whereas an electrically driven compressor can simply speed up during those periods.

[brads911sc]

What I meant was...

You may gain abit in HP draw. But you may lose those gains in the seat of the pants dyno, if you add 50-100 pounds in a secondary battery to run the compressor... not sure what those batteries weigh but they are substantial...

Originally Posted by wwest

"..you lose in weight.."

Quite possibly not.

Engine driven compressors must be sized large enough to provide coolig even during extended periods of idling, whereas an electrically driven compressor can simply speed up during those periods.

[Chuck.H]

Originally Posted by jplucas

It's purpose is so that the A/C can still run when the car is shut off at stop light or when in full EV mode (for the hybrids that have that mode).

Exactly! My friends early Prius doesn't have this -- press the A/C button and the engine starts even if it's not needed to drive. I think this is where the electric power steering units came from also.

Chuck.H
'89 TurboLookTarga, 338k miles

[Jonny042]

Would provide a lot more options in terms of mounting - Imagine using a single front mount condenser and eliminating all the A/C hoses to the rear of the car? Would be nice to clean all that up, allow more room/clean up the engine compartment, etc.

Interesting!!!

[Jonny042]

Quick google search reveals that the toyota units use 200vdc - and that this is typical for electrics/hybrids.

No such thing as a free lunch, I guess. Or something like that.

[Porchcar guy]

Just read about this company ...... 24VDC
Brushless DC Electric Compressor For Vehicle A/C units:
1. Type: Integrated compressor with external controller.
2. Displacement: 36CC/r.
3. Input voltage: 24VDC, 48VDC, 72VDC and 96VDC.
4. Stepless variable speed...
5. Cooling capacity: 2KW at 2000RPM, 2.5KW at 2500RPM, 3KW at 3000RPM
6. Weight: 15KGS...

[brads911sc]

How does this compare to the Sanden 507 that comes in the Rennaire, Retroaire, Kuehl systems? How does it compare to stock Nippo (84-89) and York (-83)?

How much is power is that? What size battery would you need? Stock Alternator capacity?

Originally Posted by Porchcar guy

Just read about this company ...... 24VDC
Brushless DC Electric Compressor For Vehicle A/C units:
1. Type: Integrated compressor with external controller.
2. Displacement: 36CC/r.
3. Input voltage: 24VDC, 48VDC, 72VDC and 96VDC.
4. Stepless variable speed...
5. Cooling capacity: 2KW at 2000RPM, 2.5KW at 2500RPM, 3KW at 3000RPM
6. Weight: 15KGS...

[Porchcar guy]

Personally, I have no clue in a comparison..just throwing the info out there for others who have experience in this area to elaborate on.

[rpmgroup]

here's Denso unit. DENSO Automotive OEM Products

[djpateman]

It MAY be a little more versatile in terms of when it can run, and where it is placed.
However, it WILL be less efficient overall.
If the design requires an extra battery, then that is extra weight to carry, and extra cost.
It will likely require a larger alternator, and that is extra weight to carry, and extra cost.
The power conversion from mechanical to electrical and back again comes with losses in each stage so there will be more fuel consumed to provide the same cooling. In addition, any extra weight will require extra fuel to be consumed.

[wwest]

Originally Posted by djpateman

It MAY be a little more versatile in terms of when it can run, and where it is placed.
However, it WILL be less efficient overall.
If the design requires an extra battery, then that is extra weight to carry, and extra cost.
It will likely require a larger alternator, and that is extra weight to carry, and extra cost.
The power conversion from mechanical to electrical and back again comes with losses in each stage so there will be more fuel consumed to provide the same cooling. In addition, any extra weight will require extra fuel to be consumed.

"...less efficient..."

Uisng a 300HP Porsche engine, even idling, to turn a 7HP A/C compressor is what I call...LESS EFFICIENT.

7HP = 4900W = 400A @ 12VDC

BIG battery.

It only takes 1000W to run ("start" requires ~3000W) the 14,000BTU A/C in our MH, plus once the MH is cooled down the A/C compressor only runs about 50% of the time.

500W on the average isn't such a bad #

[djpateman]

7HP = 5220 Watts or about 380 amps at about ordinary system voltage.
Can you fit a 500 amp alternator in your 911?
How much crank horsepower would that require? More than 7 for sure.

5200 Watts is about the cooling capacity of 4 tons or 48,000 BTU
My house central air is only 18,000 BTU
The 911 AC is obviously engineered to cool in less than ideal conditions to a very high performance standard.

BTW, I used to work for an AC manufacturer, and for the last 20 years have worked as staff scientist for a thermoelectric cooler manufacturer. Heat transfer is my specialty.

[Scott R]

I did this to a home made car last year, it's not a good idea for normal car. You will need two 100AMP alternators in parallel and a three 12V lead acid batteries. You will be adding 200+ lbs of weight to the car to make this happen.

This does not even include the rest of the stuff you need to handle the current load and the safety issues. If you're still not convinced go for a ride in a LEAF with the AC on, you will not be impressed.

[brads911sc]

Yes. But WWEST is the resident Guru and a specialists on everything including AC. You have met your match. just ask Griff. LOL

Originally Posted by djpateman

7HP = 5220 Watts or about 380 amps at about ordinary system voltage.
Can you fit a 500 amp alternator in your 911?
How much crank horsepower would that require? More than 7 for sure.

5200 Watts is about the cooling capacity of 4 tons or 48,000 BTU
My house central air is only 18,000 BTU
The 911 AC is obviously engineered to cool in less than ideal conditions to a very high performance standard.

BTW, I used to work for an AC manufacturer, and for the last 20 years have worked as staff scientist for a thermoelectric cooler manufacturer. Heat transfer is my specialty.