My son in law bought one for his camper. He is an electrical engineer and did all the computations. The camper will have solar panels on the roof and two giant lithium batteries. The camper isn't finished so I can't tell you if it worked out OK. The one he bought they use on boats, it's heavy and big and mounts on the roof. I don't think it would work on a car.
They EV cars use much higher voltage to power the compressor, i looked into this a few years ago and couldn’t figure how to make it work. Vintage Air won’t use electric compressors
I've thought about it and researched it to a degree. It stands a chance of working on a very small car, perhaps a Model A coupe, in terms of ability to cool the space in a relatively reasonable amount of time. It's not feasible in anything larger. It works in electric cars because the voltage is so much higher to power the compressor. It's not that it's impossible in a typical car, it's that it's not practical and would be less work, less cost and better to run a conventional system with a belt driven compressor. As cracked out as this sounds, what gave me the thought was just going to Home Depot, buying a small room air conditioner, pulling the guts out of it, and mounting it under the package tray in the trunk and putting the vents up through the back. It could be run with an inverter large enough to power it. It would be a totally self-contained unit. The problem is that it's actually a lot less powerful than a car AC unit, and would require a huge alternator to run, not to mention that without having the air blowing on you, the cooling effect would be much lower.
Yep the fact that cars only have 12 volts actually 13 + volts is the problem. Physics and simple math Power = Volts times amps that is 120 volts at 10 amps = 12 volts at 100 amps A 100 amp draw is huge and would require a #2 wire at approximately 1/4 inch diameter and most alternators can’t handle a continuous 100 amp output. AC takes power a lot of power, if you ever drove an econobox and had to turn the air off to p*** you know what I’m talking about. Dan
People don't realize that the average output of an automotive AC system is like 25,000 BTUs. That's enough to cool a large room. A window AC that size would require 11-12A at 230v, which is like 217A at 12v. That would take literally 2 high output alternators to run. So other functional practicalities aside, at best you'd be trading a belt driven compressor for a second alternator. Makes no sense.
You are absolutely right I used 10 amps at 120 volts just for a simple comparison 200 amps would require a minimum of 3/0 wire with 4/0 wire being better approaching 1/2 inch dia conductor. As stated above every time you convert from one energy type to another you loose some energy in the conversion due to inefficiency. Every automotive AC system I have seen has an idle air control valve or a control from the pcm Dan
What's easier: Built brackets to hold 3 extra alternators, and mount two more batteries, or: Build a bracket to hold one genuine Sanden 508? Which would be cheaper?
I’ve a pal who is a true master mechanic that fell on bad health in recent years due to a usps semi getting flipped in a tornado all that to say … 65 comet hardtop cant see a single wire or accessory under hood . Efi tbi gm fuel pump for p/s rack , alternator off pinion , electric vac booster brakes & an all electric a/c unit behind rear seat patron & it’s wildly cool if your into that kinda build
Well, this *is* the place to drop a few pis... . I like detailed stuff, style maybe not so much. IDK until I see it. Usually something good somewhere in any build. Marcus...
I'd like to see how this was done. If it's OT you can post it in the off topic builds forum, there is a place for this now.
It's one thing to install all that on a car... It's an entirely different proposition to make it actually work in the real world.
Some people just won't believe it but it is totally impractical on a 12 volt car. Period. End of discussion. The math don't lie.
While working for a HVAC company that specialized in off-road, construction, forestry, m*** transit, and military, I designed a oself-contained roof top unit for one of our up-armoured Canadian military vehicles during the Bosnian war. It was 12VDC powered. Had a 3 hp DC electric motor that belt drove a Harrison/Delphi V5 variable displacement compressor. Initially had issues with the vehicles catching on fire because the OEM refused to upgrade the stk alternator. Being DC powered, as the voltage drops, a motor will compensate by using more current. This resulted in the motor drawing hundreds of Amps, leading the power cable to overheat and catching fire. We used mil-spec connectors, cables, etc. The OEM eventually upgraded to a 145A alternator. IIRC, Amp draw was around 120A, with a cooling capacity of around 15,000 to 20,000 Btu/hr.
Was probably 1 or 1/0 AWG. Recall having issues as the wires had to soldered into the mil-spec connector. We ended up getting a solder pot IIRC. There was also the issue of supply as there were only one or two sources of supply (Bendix?), and they only made production runs once every 6 months. Yep, the good ole days. We also did other AC systems for other vehicles. One was for our Medium Logistics Vehicle Wheeled (MLVW - 6x6). These were all conventional pulley driven compressors off the engine. Initially they wanted the evap in the glove box. Told them it wouldn’t be big enough, but they insisted. We built the prototype with it in the glove box, and tested it. Of course it failed to cool the cab. It just amazed me how thick headed folks were.
The vehicle was essentially an Iveco truck, but because of political pressure, they wanted it built in Canada, so Western Star Trucks out in BC was awarded the contract. They (the engineers, and one in particular) had no clue about building this truck. It had a very small 4 cyl Diesel engine. Top speed was only about 90 kph. They/he thought they could get around the low power issue by going electric. Lol! We told them right up front about how much electrical power it would require. This meant the stk 90A? alternator was insufficient. We told them that, but they didn’t want to hear it. Went into production. Vehicles were sent to the war. They caught fire. They eventually had to retrofit the vehicles with the larger alternator. Being a mech Eng, and dealing with another engineer who refused to see the obvious was very frustrating at the time. Especially when they tried to blame us for the vehicle fires. Just another chapter in Canada’s sordid history when it comes to procuring logistics vehicles for the military.
I think things are the same everywhere I’ll bet it was frustrating, so my take is no net gain by using an electric AC unit and probably a slight net loss at the rear wheels running an electric AC vs running an AC compressor directly from engine. Is my ***umption correct or am I missing something. My hat off to you for making that system work. Dan
Yep. With today’s highly efficient scroll compressor designs, it’s a different story than with a belt-driven piston compressor , but I think it’s too complicated electrically speaking. We also later developed a “black box” that would limit the DC motor in-rush current which caused other issues ***ociated with EMI/EMC for the military radios in the vehicle.
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