Electric A/c conversion

[lovemysan]

I want to convert may a/c system from the belt driven compressor to hermetic type compressor. Does anyone know the aprox btu output of a small cars a/c system. My guess would be not more than 8000 btu for my car. I would think that the 7 amp compressor could easily keep up. Of course this all arm chair theory. BTW I take 20% loss of economy running the a/c.

[Daox]

The only tid bit I can offer is that the Prius' electric AC compressor is run off the main battery pack instead of the 12V system.

[lovemysan]

Yes I read that also. Its because the higher voltages allow for smaller parts. I found a 5k btu Marine 12v system that draws 45 amps 12 v dc. The compressor will cycle so its not a constant voltage. The goal is to do this as cheaply and easily as possible. I'm thinking of running a test. Put a 5k btu a/c in the trunk blowing into the cabin via the seat folded down. Running on my small generator. This would tell if its feasible. I'm pretty confident it would be enough. The next question would be where or how to find a 12 volt compressor that would work well with the current hard parts in the car. Mainly the condensing coil and evaporator coil. My current a/c is horrible. How many HP does it take to make 45 amps?

[dremd]

I've heard that the average car's A/C system is powerful enough to cool a normal 2000 square foot home in Atlanta.

Might look in to a variable displacement compressor (Love mine!) before going electric.

[gascort]

You also need a way to push a lot of air through the condenser in the trunk. The efficiency of your unit will depend a lot on this.

If you know someone in the refrigeration industry, maybe you could have them hack up the 12V system and fab it into your evaporator and condenser.

[Daox]

Originally Posted by lovemysan

How many HP does it take to make 45 amps?

45A * 12V = 540W

540W = .72 hp

I've heard (not from an expert) that an car's AC system is comparable to a household window unit. Of course those vary widely in size so...

[extragoode]

I would think that in WI you would be in the same situation as I am here in IA in that you have the A/C for dehumidification as much as cooling, so it may not require the SAME size system as the car anyway. I just wanted to mention this in case you hadn't already thought of it. I know for me, I just need a little more something than the vent, cause they don't do much when it's hot and humid.

[lovemysan]

Originally Posted by dremd

I've heard that the average car's A/C system is powerful enough to cool a normal 2000 square foot home in Atlanta.

Might look in to a variable displacement compressor (Love mine!) before going electric.

I have a variable displacement compressor. However mine is mechanically controlled and resource hog. Some of the more advanced units are electronic and more efficient. I had a standard system in my old nissan truck that was more efficient because it rewarded the judicious a/c user with intermittent cycling. MY VDC doesn't cycle and never seems to change the amount of power necessary to provide the minimum amount of cooling. I tried setting the fan to low and different temp settings to no avail the FE was all the same. The temp control on my car merely mixes hot(drawn from the heater coil) and cool air together causing increased loss of eff. I find that manually cycling the compressor does yield increased FE. This thing siphons off a serious amount of power I est. 8-10hp.

[metromizer]

I think you will be disappointed with driving the compressor with an electric motor, that is driven off the alternator. Reason? every time you convert one form of energy to another, you loose efficiency. I have wondered about efficiency ratings for compressors for years, but it seems to me that unless your car is an EV, the most direct drive approach will be the most efficient.

Running that a/c compressor and coupled electric motor off a bank of 'on board batteries' however, that you charge up from a solar photovoltaic system, might have running your car's a/c system for nothing.

Originally Posted by lovemysan

I had a standard system in my old nissan truck that was more efficient because it rewarded the judicious a/c user with intermittent cycling....

I owened couple of 'hardbody' Nissans in the 90's and really liked that a/c feature. I would turn off the a/c buttom while getting on a freeway or climbing a grade. Too bad the 2.4 liter wasn't a little more frugal with the fuel

Originally Posted by lovemysan

MY VDC doesn't cycle and never seems to change the amount of power necessary to provide the minimum amount of cooling.... The temp control on my car merely mixes hot(drawn from the heater coil) and cool air together causing increased loss of eff.

It just doesn't seem right, almost ridiculous, doesn't it? Yet most automobile a/c systems are set up that way.

[elhigh]

If somebody comes up with a really feasible idea, let me in on it, okay? My truck has no AC at all, and here in the Bible belt we get pretty hot and really humid - opening windows just stirs the sticky around, and swamp coolers have no effect whatsoever.