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Dorfie

Well Known Member
I have been attracted to the all electric air conditioner system to install in the RV 10. However, it needs a 24V system, which I am not really interested in. Is it possible to have a 24V alternator, two 12V batteries in series which will supply 24V to AC system. Then tap the two 12V batteries in parallel to supply 12Vpower to rest of all aircraft systems? I think it sounds silly and far fetched that it will work (been stalling posting this for a long time), but would like to get some understanding why and why not, what is possible and what not. Just thinking!!
Thanks.
Johan
 
Pretty sure you can do such a thing, using the right diodes.

The "right diodes" may be a bit of a problem??
 
There is no reason you could not consider a 28V system for your aircraft. Most avionics will accept 28V, If you were planning on a Vertical Power system, I don't believe that would work. The real issue is designing a system with an essential bus. It sounds like a lot of batteries. It's not a far fetched idea.
 
Dorfie said:
I have been attracted to the all electric air conditioner system to install in the RV 10. However, it needs a 24V system, which I am not really interested in. Is it possible to have a 24V alternator, two 12V batteries in series which will supply 24V to AC system. Then tap the two 12V batteries in parallel to supply 12Vpower to rest of all aircraft systems? I think it sounds silly and far fetched that it will work (been stalling posting this for a long time), but would like to get some understanding why and why not, what is possible and what not. Just thinking!!
Thanks.
Johan
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I think you can do it, but what systems are you worried about needing 12V?

Most modern electronics and avionics will run on anything from maybe 10 to 32 volts without complaining.
 
Power Converter

I would just use a power converter. There are several different options available on Aircraft Spruce. 12-to-24 and 24-to-12, depending on which way works best for you.
 
I don't think it would be advisable. One of your batteries would have more load than the other and that would cause problems. I build boats for a living and this set up would be great for us, but we have to use converters .
 
It takes a lot of grunt to run that a/c. If you don't want a 24V system for the plane, why not add a 2nd alternator regulated at 24 V & AGM battery(ies) that run nothing but the a/c? With proper switching network & a 24>12V converter, it could become your backup supply for an 'essential' bus to run avionics, etc in the event of a main 12V system failure.

If you haven't done it already, I'd suggest signing up for the Aeroelectric email list. A lot of this kind of stuff gets covered there.

Charlie
 
What you described will not work. You cannot have 2 batteries simultaneously in series (for the ac) and in parallel (for the aircraft).
 
Too many amps to run an electric compressor at 24/28 volts, if that is what you have in mind. Big wires, big switches, big batteries and short run time.

Heavy batteries, unless you want to use LiO Polymer.

A standard belt driven compressor system would be much less weight to actually keep the cabin cool.

Happy hunting for a "cool" solution.
 
I have one

I have the Harbour system in my Air Tractor running two 24 volt (standard) batteries. It draws 75+ amps and is hard on my starter/generator, but then again, so is 95? under a helmet, all day long.

Call Harold Harbour in Texas for advice or his son, Scott 806 879 2392.

Best,
 
Bill.Peyton said:
There is no reason you could not consider a 28V system for your aircraft. Most avionics will accept 28V, If you were planning on a Vertical Power system, I don't believe that would work. The real issue is designing a system with an essential bus. It sounds like a lot of batteries. It's not a far fetched idea.
Click to expand...

Thanks Bill,
I would prefer to stay with 12V system since 12V items are common and easily obtainable and common to automotive products. I am planning on installing Vertical Power as well.
 
Thanks for all the responses. It is indeed informative.
The AC system I am referring to was one on display at Oshkosk last year. I have now forgotten the vendor's name (I have it somewhere, needs digging out).
Like Pierre said, it draws about 70 Amp on a 24V system at full cooling function. The total current drawn can be controlled. I must also admit that other than seeing and feeling it demonstarted at Osh I have not heard reports on its effectiveness. This stuck in the back of my mind and seemed simpler to install since it is pretty much self contained, and might even be removeable during winter months. Other than needing 24V to run the AC, I am not really keen on a complete 24V system, hence my thoughts on something hybrid. More people told me it cannot work than it can work, and as Ron said others have also commented that the load on the batteries will not be even (not that I understand the why). I am not an electrical engineer and can do the basic stuff only.
Johan.
 
BobTurner said:
What you described will not work. You cannot have 2 batteries simultaneously in series (for the ac) and in parallel (for the aircraft).
Click to expand...

I have an all electric ac in the -10 that has the same setup that you described.

As posetd by someone above..if you center tap an additional "12 volt" load from the battery array you will have one battery with a higher amp draw than the other and over time you will see one battery voltage drop lower and lower while the the alternator continues to produce 28 volts. this means the other battery will be seeing higher and higher voltage. 15-16-17 volts as the other battery is 13-12-11 volts.

To remidy the problem there are several options.

The most desirable options for our application is:

1) Get a 24-12 volt converter with a high enough amp rating to handle the 12 volt load.

In the old days this was relatively inefficent and weighed a lot -10-15 lb for something that would handle 10-20 amp.

Nowdays you can get a switching power supply that is very efficent (92-98%) and is fairly light (cant remember but 3 lb should get you 20 amps or close to it.


2) get a battery equalizer. This is basicaly a 24-12 volt converter except instead of outputing a steady 13.8 volt regardless of input. It will output 50% of the input voltage. This is then used to charge the second battery (maintain an equal charge) the benifits of the equaizer are you can have an intermitant 12 volt load (fuel pump, landing light, flaps, trim, etc.) that exceeds the amp rating of the converter and then when the intermitent load is removed the equalizer will exchange charge from one battery to the other.

I have the equalizer set-up and have had no problems whatsoever.

This is what I used. You only need a big enough converter to recover the charge imbalance during normal cruise.

If you decide to go with a 24-12 volt converter I have a new in box Redarc CE20-13.8 which is a 20 amp converter that I would sell.

IMAG0618.jpg
 
Dorfie said:
Like Pierre said, it draws about 70 Amp on a 24V system at full cooling function. The total current drawn can be controlled. I must also admit that other than seeing and feeling it demonstarted at Osh I have not heard reports on its effectiveness. This stuck in the back of my mind and seemed simpler to install since it is pretty much self contained, and might even be removeable during winter months. Other than needing 24V to run the AC, I am not really keen on a complete 24V system, hence my thoughts on something hybrid.
Johan.
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My A/C system (Compressor, Evaporator fan motor, condenser fan motor) draws about 62 amps at 27.5 volts.

About 1 month ago I installed a Plane power ALT-FLX alternator which produces 150 amps at 28 volts.

Fit under the stock cowl with plenty of clearance and only weighed 12.5 lb.

I can run the A/C no problem idling at 800 rpm.

The Flightline A/C system is advertised at 50lb wihich is correct for the components but you will need a slightly heavier alt, slightly heavier wiring, slightly heavier everything :rolleyes: I would guess the total weight ends up around 65-70lb but is worth it to me.
 
I opted for a 28V system in my RV-10. It is running through a VP-200; don't know if the VP-X has a problem with 28V but I'd expect that it would be just fine. I'm not doing the all-electric A/C because I wanted to balance the weight rather than sticking everything in the tail. I'm not sure why people think 28V components are hard to get; they are actually easy to find. The biggest mod I had to make was building a battery box for a 24V battery; I basically enlarged the kit-supplied part in outline out of .060 stock, using the original as a drilling template, and used U-channel, also pressed from .060, to make the sides of the box. I think I posted it here in a thread, so I'll either add the link or post the pictures again. Anyway, the only real advantages of the all-electric version are that it can be run without the engine running (if you have ground power) and you don't have to run hoses to a compressor in the engine compartment. That said, I'm not trying to talk you out of the all-electric version but I do think you should reconsider the 28V vs. 14V system decision.

And here's the link to the thread about my battery mount: http://www.vansairforce.com/community/showthread.php?t=58209&highlight=battery+box.
 
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flion said:
I'm not sure why people think 28V components are hard to get; they are actually easy to find.
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They are indeed easy to find - just not so much fun to pay for. The price differential for 28V versus 14V can be substantial.
 
A/C

If you can build an airplane you can build an A/C for your plane go to the junk yard and get the smallest compressor from a compact car and take the coil out of dash mount it in a box and you have a homebuilt a/c go for it and post pics so others can do it to.
Bob
 
6 Gun said:
If you can build an airplane you can build an A/C for your plane go to the junk yard and get the smallest compressor from a compact car and take the coil out of dash mount it in a box and you have a homebuilt a/c go for it and post pics so others can do it to.
Bob
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Neat idea and sounds real easy when you put it like that. So you addressed the evaporator coil but what about the condensor condensor coil typically built into the car's radiator?
 
Problems with AC in an AC..

I too would love to have AC in my 10, but after researching the solutions available, they each have their drawbacks: 1) Engine driven systems are lighter and cheaper, but steal HP when in use, 2) Electrical-driven systems can be made to be removable, but weigh more and take up baggage compartment space when used, 3) all solutions are expensive, but rolling your own may not be so simple. Perhaps it's best to go with an icebox solution (i.e. cheap, removable) or just fly with less clothes on.;) In Colorado, AC isn't so necessary, but for trips to hot/humid areas, it sure would be nice.
 
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