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Electric A/c conversion
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.
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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.
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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?
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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. |
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. |
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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... |
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.
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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. Quote:
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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.
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These may be of interest:
How much current does the A/C compressor draw? - GreenHybrid Prius Air Conditioning System [PDF] Electric Inverter A/C System for TOYOTA PRIUS Hybrid Vehicle [PDF] The third link shows that the Prius' electric A/C compressor uses 19% less fuel compared to the engine driven compressor of an older Prius version. Since the Prius' A/C system uses higher voltage, the compressor itself is 40% smaller and 53% lighter than a conventional electrically driven compressor. The Prius' system is electric to allow the use of A/C while in stealth (engine off) mode, so I wonder if this will be adopted in more cars as gas-saving engine start-stop systems become more popular? I guess that the major obstacle is the power needed. Running the A/C @ max at a 90-second red light may drain your battery enough to leave you stranded. High voltage systems, where are you? |
I was recently thinking of doing this to my car. It doesn't have air conditioning and is a mid-engine car so I was thinking of a front install.
I agree that any change of energy souce will add losses to a system - will not a DC motor do? Or more radical how about getting A/C from the alternator BEFORE the diodes while still allowing current to flow to them to feed the rest of the car? |
An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits
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Add a thermostat to turn your A/C clutch on and off. I designed and built my own out of parts I had laying around the house (I'm an electronics engineer). But, prior to this, I was using a household wall thermostat to control the A/C clutch. The reason I ended up building my own is that the wall thermostat I used (which was also laying around the house, hence, free) had too much hysteresis (wasn't cycling enough, would get too cold and then too hot, needed to switch more frequently), but it was better than nothing.
Maybe there are off the shelf thermostats that have adjustable hysteresis. I didn't research it as I was too cheap to buy a new thermostat and could quickly build my own for free. |
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Just so you know...I never did hook up my TCS module...but I still plan on using it on my truck fer something. ;) |
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