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Old 10-15-2008, 08:36 PM   #1 (permalink)
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Would you trade your AC for some extra MPG??

I've been thinking about a plug-in mild-hybrid conversion for my CRV..

Then, I started thinking about that fuel wasting AC compressor..
What if it went bad and I just got rid of it? (And all the other AC parts).

What if I used the compressor mounting hardware to install a small PM motor?

Two or three Green HP to assist my CRV up hills etc?

If you could get a 15 to 30% percent increase in your MPG for 30 miles, by dumping your AC?? Would you?

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Old 10-15-2008, 10:33 PM   #2 (permalink)
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nope..gets to hot here
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Old 10-15-2008, 10:36 PM   #3 (permalink)
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for a 30% increase, sure. I don't use it much anyways, just use the fan.
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Old 10-15-2008, 10:38 PM   #4 (permalink)
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Quote:
Originally Posted by Xringer View Post
I've been thinking about a plug-in mild-hybrid conversion for my CRV..

Then, I started thinking about that fuel wasting AC compressor..
What if it went bad and I just got rid of it? (And all the other AC parts).

What if I used the compressor mounting hardware to install a small PM motor?

Two or three Green HP to assist my CRV up hills etc?

If you could get a 15 to 30% percent increase in your MPG for 30 miles, by dumping your AC?? Would you?
If you're doing a mild hybrid conversion, you can always use an efficient higher voltage PM motor off the pack to drive the AC compressor. That way you'd be able to use a PWM controller to get exactly the amount of cooling you need regardless of RPM or load.
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Old 10-15-2008, 11:04 PM   #5 (permalink)
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Just beware that you'll have to recover the refrigerant before you cut any pipes. You'll need an EPA certification to do that. Unless, of course, the cause of failure was a broken pipe, in which case there will be no refrigerant left to recover.

The A/C compressor doesn't use that much power anyways. One datasheet (Danfoss BD250GH) referenced 230W at maximum capacity.

You can use a DC/DC converter to power the existing compressor from the high voltage batteries. If the high voltage is in the range of 150-350v, a PC power supply with active PFC can be modified into a DC/DC converter. The inrush surge might be a problem, but some multi-farad capacitors of the kind used in car A/V systems should fix that. If you need to replace the compressor anyways (which would require an EPA certification), you can check local HVAC supply shops for line voltage compressors (which can run from high voltage DC with a relatively simple MOSFET inverter), but some HVAC supply shops only sell to businesses.

There's also the option of silicon heat pumps, but they operate from low voltage DC, so back to that problem again. System design is also a little tricky.
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Old 10-15-2008, 11:07 PM   #6 (permalink)
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Quote:
Originally Posted by Clev View Post
If you're doing a mild hybrid conversion, you can always use an efficient higher voltage PM motor off the pack to drive the AC compressor. That way you'd be able to use a PWM controller to get exactly the amount of cooling you need regardless of RPM or load.
That's one complex way of turning grid juice into MPG..
Since I live in the NE, where my car AC gets very little use, it wouldn't be cost effective for me..

I'm thinking more along the lines of an old gas hog that maybe has a broken AC and they want $800 to repair it..
Plus, I'm sure there are a lot of hypermilers around that hardly ever use their AC..

When I was a kid growing up in south Texas, cars with AC were very rare.
But, somehow we lived with out ice cold air blasting on us..
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Old 10-15-2008, 11:31 PM   #7 (permalink)
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Xringer -

I would, but my wife and/or other passengers would probably not appreciate it. I do know that for my car (and probably many others), you can replace the AC with a pulley that matches the dimensions/location of the AC compressor pulley. Here is one I could put on my car tomorrow :

eBay Motors: 95 96 97 98 Saturn S Series A/C Bypass Pulley 1.9 (item 280268263281 end time Oct-17-08 12:26:34 PDT)
Click image for larger version

Name:	ac_bypass_pulley.jpg
Views:	33
Size:	10.8 KB
ID:	1934

Irony: My AC is broken right now anyway, .

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Old 10-15-2008, 11:31 PM   #8 (permalink)
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Quote:
Originally Posted by NiHaoMike View Post
Just beware that you'll have to recover the refrigerant before you cut any pipes. You'll need an EPA certification to do that. Unless, of course, the cause of failure was a broken pipe, in which case there will be no refrigerant left to recover.

The A/C compressor doesn't use that much power anyways. One datasheet (Danfoss BD250GH) referenced 230W at maximum capacity.

You can use a DC/DC converter to power the existing compressor from the high voltage batteries. If the high voltage is in the range of 150-350v, a PC power supply with active PFC can be modified into a DC/DC converter. The inrush surge might be a problem, but some multi-farad capacitors of the kind used in car A/V systems should fix that. If you need to replace the compressor anyways (which would require an EPA certification), you can check local HVAC supply shops for line voltage compressors (which can run from high voltage DC with a relatively simple MOSFET inverter), but some HVAC supply shops only sell to businesses.

There's also the option of silicon heat pumps, but they operate from low voltage DC, so back to that problem again. System design is also a little tricky.
I don't ever recall seeing a failed AC in a car that still had much refrigerant left in it..


Anyways, my post isn't asking how to better run or repair a car AC..
It's about the desirability of dumping your AC for better MPG..

Pretend it was a regular dealer option at a used car lot.
They both cost about the same..

Pick one:

A. 10,000 BTU AC system installed w/25 MPG unlimited miles.
(Until you turn on the AC, then it's 23.5 MPG).

B. Plug-In Mild-Hybrid system installed w/30 to 38 MPG for trips less than 20 miles.
(After 20 miles, it's back to 25 MPG).
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Old 10-15-2008, 11:32 PM   #9 (permalink)
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Quote:
Originally Posted by NiHaoMike View Post
The A/C compressor doesn't use that much power anyways. One datasheet (Danfoss BD250GH) referenced 230W at maximum capacity.
That model is only rated for a max charge of 300g.... I drive a midsize classed car (2000 Jetta), which is spec'd for a charge of 700g + 50g

Danfoss doesn't make a 750g model, but it does make a 800g max model... Which, under max load, draws 660W @24VDC

Now, 27.5 amps might not be too much compared to the KW the engine is putting out in total.... But, even daytime running lights (<55W per light) have an impact on FE. That and, I for one, see a drop in instant FE when I turn the a/c on....

Here's the data sheet on the bd350/350gh dual compressor
http://rc.danfoss.com/TechnicalInfo/..._ed100p202.pdf


That said, it would be cool to switch over to an electric compressor - there's some cool tricks you can do when you have finer control. I'd probably add a bigger accumulator, pwm the motor (as you mentioned) and move some componentry out of the engine bay Not to mention the option for a pre cooling cycle before getting into a car that has been well baked in Florida sun


EDIT
And to answer the thread....
Probably not given the current region I'm living in.... I wouldn't do this without installing an alternative cooling solution first.
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Old 10-15-2008, 11:54 PM   #10 (permalink)
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Quote:
Originally Posted by cfg83 View Post
Xringer -

I would, but my wife and/or other passengers would probably not appreciate it. I do know that for my car (and probably many others), you can replace the AC with a pulley that matches the dimensions/location of the AC compressor pulley. Here is one I could put on my car tomorrow :

eBay Motors: 95 96 97 98 Saturn S Series A/C Bypass Pulley 1.9 (item 280268263281 end time Oct-17-08 12:26:34 PDT)
Attachment 1934

Irony: My AC is broken right now anyway, .

CarloSW2
I think mine is still running. They say it's good to turn it one for a few miles at least once a month.

I did use it a couple of times this summer when my wife was with me.
But most of the time when it's hot out, she prefers we take her car.

You better order that pulley while they last!

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