Have any of you guys ever seen or heard of an electric 12v DC A/C compressor. I would like to be able to run my A/C with the engine off.

 

You could do it, I guess, but you're going to need a bigger truck to haul the batteries around in.

Steve

 

I got a pretty big truck, a small little generator and some good batteries.

 

I recall a thread somewhere where someone did the math on this. IIRC, the motor would draw somehere around 200-250 amps at 12V and the starting current would be much more. It just wasn't feasable at 12V. You would also need a ~30 amp cooling fan for the condenser and another ~15-20 amps for the blower motor. The 12v motor would also have to physically large at the specs needed. Again, IIRC, 7-10 HP and 1500RPM min. I don't recall the exact numbers, but hat's a darn hefty motor.

There's a fellow here on FTE who mounted a 115V window unit in his Econoline powered by a small Honda genset. He and the wife used it while parked overnight and as an auxillary while running. It was a pretty cool mod.

I've always heard that the hermetically sealed compressors in window units wouldn't stand up to the forces encountered in mobile use, but he didn't seem to have a problem. (No pun intended). He extended the rear bumper for the generator and other necessary travelling gear. I did a search but couldn't find the thread. Obviously this isn't practical for a pickup, but I thought it was really neat.

 

That sounds to me a little off, I got a couple 12v refigerators that only draw about 20 amps.

I do also have an inverter but was thinking a DC motor would be more efficent then going through the inverter.

Then again the generator pumps out A/C and ir rectified to DC so it's kinda a wash.

 

12 volt refrigerators usually don't use a compressor and cool a much smaller, much more sealed space. Most of those chill boxes use a Heated Wire setup to circulate the refrigerant. There may be some that use a small comnpressor, but I've never seen one. Look at the BTU rating on those boxes and compare it to the system in your truck. Most MVAC systems are rated at around 25,000 BTU.

Like I said, I don't recall the exact numbers. The current draw and HP figures were high enough to make the idea not feasable at 12 volts. You would need a 48 volt system to get the numbers even into the area of possibility. Remember, as the voltage goes up the current draw goes down. That's why cars went from 6volt to 12 volt systems.

 

Not even close "to a wash". The inefficiencies in your suggested power conversions are staggering.

Those little 12V refrigerators typically don't use compressor/refrigerant technology, they use Peltier modules to move heat from the well-insulated interiors of the box to the exterior.

The amount of electrical current needed to move the needed BTUs from a truck cab under all conditions, especially extreme ones, if very substantial.

Steve

 

Suggestions then, and please explain why? I'll admit I haven't yet put alot of thought into this. Just thought if there's a good why to run my in vehicle A/C without leaving that huge V-8 running.