Ok you can tell me to stop thinking.

I have been playing around with this idea for a long time now of removing the AC compressor from the cooling circuit and replacing it with a small fractional maybe ½ hp. hermetic compressor and use an DC to AC inverter to run the motor.

But now that I have seen DC air conditioners for Marine applications and for aircraft it made me think.

I now find they have come up with a Brushless Direct Current compressor that to me looks like it might work.

So if my idea works the way I think it should I can run my air conditioner in my truck with the engine OFF.

With the blower running it should draw somewhere around 50-60 amps continuously on 12 volts, if I install a 24-volt battery system it would only draw ½ as much.

The blower and now required condenser fan would probably draw as much current as the compressor.

The only downside to my idea is the compressor and supporting electronics will cost around $500.00

What do you think of my crazy idea?
Jim

http://www.rparts.com/Catalog/Major_...ss/danfoss.asp

 

Every improvement or advancement starts as a crazy idea.

While I'm unqualified to critique this one (or even undertsand the concept at this point ), I can say from experience, that if anyone can make it work, and work well, it would be you Mr. Lane.

Rock on

 

sounds interesting, have you figured in if you will need to upgrade your alternator as well? that power has to come from somewhere. I would be willing to bet that the direct drive compressor is more efficient at the job than converting power to electrical, then using the electric to run the motor. As for being able to run the ac with the truck off, sure that would be nice, but for how long would it run? that seems like a lot of juice to run, consider deep cycle if you go for it.

 

I do have an 8-D Deep Cycle Battery in the rear and my alternator is 160 amps with 85 amps @ idle.

 

And you can plug it in at Home and precool the truck before you start it. Like an airplane at the gate. Sometimes the price of A/C parts makes me think about jaming a window unit in the rear window and throwing a generator in the bed. I have been thinking about something like that for the rabbit with no a/c but a gas engine driving the compressor and an extra altenator like an APU on an airplane. Also something that could put out enough juice to power the block heater and top up the battery for cold days when i don't have a plug. I day dream about stuff like this all the time.

 

sounds like a good idea, I would want to try and kill two birds with one stone on this one though. If no A/C compressor, how about install a regular compressor there to run air tools/airbags/airbrakes/airhorns?

 

I would leave the truck system intact and in perfect working order; then, I would do as above suggested (and Larry the Cable Guy already has done) and install a 110V (or 220) unit that could be powered in THREE ways at will, house-current, inverter current, and generator current; you could easily have all three.


With a set-up like that, you could plug in at the house or work and have a timer in the cord, such that it starts cooling a half-hour before you plan to enter the truck.


Look into the diesel-powered generators/A/C units that are becoming so popular in big-truck applications due to all of the poorly thought-out no-idle laws.


You have a topper, right ??; the unit could be mounted atop the topper, out of the way, and cool both compartments, providing you have/install a boot between the two.



Many of the so-called toy-haulers have these units mounted up top; even the candy-bar delivery trucks now have them, after years of having to eat already-melted chocolate bars.

 

Derr... never mind... half awake reading things... LOL
Still, I think an APU would be the way to go.

 

Check out an RV store like Camper's World or your local RV dealer.
Sometimes you can find ac units on clearance. I found one a couple of years ago for under $600.

 

The 2nd gen Toyota Prius uses an elec a/c comp. I can`t remeber off the top of my head tho what the voltage is, I KNOW it`s way more than 12v. I can ck on it next week when I`m back at work.

 

The only problem with the AC units for RV's is that they still require a generator or inverter to run them so the loss is in the conversion of DC to AC to run the compressor motor.

Ideally you could use a small 3-phase inverter to give you 208 Volts 3-phase and have it power a small rotary compressor of about ½ hp and it should also work but the inverter is expensive and it would draw a considerable amount of current.

I was doing some searching and I found a Marine AC unit and it looks like it is using the same compressor I was looking at.
Instead of an air over condenser this is using an exchanger and dumps the heat to the seawater instead.

http://www.dcbreeze.com/

Thinking about all of the Hybrids I think most of them still use a belt driven compressor that will cause the AC to stop working when it is on battery or stopped at a stoplight.


I think the Prius has a belt driven/ electric scroll compressor but the electric side is only large enough to keep it cool for short periods of time after it has already initially cooled down like when the engine is off at a stoplight.

On the Prius I think the battery voltage is something like 275 volts Direct Current and then an inverter converts the Direct Current voltage to 3-phase Alternating Current to drive the high voltage 3-phase motor but I am not sure of the frequency if it is 60hz, 400hz or somewhere in-between.

The DC circuits on the Prius is defiantly not something you want to go sticking your fingers into without knowing what you are doing.

Jim

 

You have the reserve capacity in those batteries to run it for short periods, say not more than an hour or two. If that's long enough for your purposes, you are definitely the man who can get it to work.

If you lived somewhere where it gets cold I'd push you more to the 125 volt side so you could run the block heater and a circulator pump in the winter.

 

you mean like this

(yes it works, but NO it is not mine)





more pics
http://rides.webshots.com/album/359668089RqnLfa

 

Jim,

Have you considered eliminating the mechanical aspects altogether and use Peltier devices?

http://www.peltier-info.com/

 

That is actually a killer idea.

You can replace that entire unit much cheaper than even thinking about working on the automotive A/C system; plus, that unit will freeze the doors shut in no time flat.


The one issue with that particular set-up that I would re-engineer is the bed/cab flexing and binding against the A/C unit.

He may have addressed that issue, but it is not evident in the photos.


I have seen beds twist as much as three inches higher/lower than the cab, just crossing a ditch or the like.



Larry the Cable Guy simply mounted his in the sliding back glass.