Electric AC

[lilthom]

I’ve seen a couple videos on electric air conditioning kits. Anybody try this in our EBs?

 

[Broncobowsher]

Not on an EB. But I put one on my cargo van/RV. 12V mini split kit. Yes, it works. Not the full power of an engine driven compressor. They are only 10,000BTU or so. There are several different numbers depending on who is selling but I think they all interchange as far as performance. Draws about 60 amps for the compressor at full power, another 10 for the fans. On high I can see it pulling about 70A out of the battery bank. I have a very large battery bank and ~700W of solar to back it. For a full size cargo van parked in the sun it is good for about 25° off interior temps. I parked it at Costco on a 115° day, in full sun, let it run, came back and it was only 90 inside. Not that 90 is cool, but it is a lot cooler than the 140 it would likely have been just sun baking. I'll lit it run while out riding the bike on fair days and when I get back it is 72 in the van, the battery is being charged off solar while the A/C is running.

I've seen people mount them on the engine right where the belt driven compressor would go. I think that is a waste. If you are going to do that just run a belt and get better performance. I have mine (on the van remember) on the frame rail under the body.

If you want to run just a compressor, you can get just compressor kits and put that with the rest of your existing A/C system. There is a some trickery that isn't well documented. The battery leads can stay on the battery without issue. But there is a signal wire to make the compressor run. It is usually a 0-5V variable signal. 0V being off, and ramp up to 5V at full power. There are some that run 4.5V-9V. Look at the controller data plate/ model number/ part number. There is usually a 05 or 459 at the end or something like that.

Few more tips. LS engine swap A/C port adapters will work to convert the O-ring slip in ports to the standard screw on hoses. Also helpful if you keep the suction line distance reasonably short.

These are the same compressors that are used on 12V RV rooftop A/C units. I have one of those I need to install in a different project.

I feel the compressors are pretty efficient for the power going in vs the performance coming out. The are quiet and pretty smooth. Not silent, but neither are most belt driven ones as well. Do I consider them viable? Yes. Just not max perfromance. It's 112 and the start to the monsoon in AZ today, so humidity is up. It will struggle a bit, but better than none. If you want to blow ice cubes, go belt drive. If you just need to take the edge off a little bit, hot car after being parked, windows down just isn't cutting it afterall, I see it as viable.

One nice thing is you can mount the compressor someplace where it doesn't get direct heat soak that it has to fight. Not bolting it to an engine right next to the exhaust. Clean up the engine bay.

 

[73azbronco]

Park under a tree, anything with shade, anywhere.

 

[Yeller]

I think the electric tech has come a long way from the mid 20th century Cadillacs. I am doing a 12v roof top unit on my coach build.

 

[Broncobowsher]

I think the electric tech has come a long way from the mid 20th century Cadillacs. I am doing a 12v roof top unit on my coach build.

I'm courious how it works for you. Best I can tell it is a pretty good match for a smaller 110V rooftop unit (12k BTU). The one I have also uses an unusually small hole in the roof, 9x14 instead of the standard 14x14.

 

[Yeller]

@Broncobowsher it will be a while, I still need to buy it and install it, probably not until spring. Not in a huge hurry, have no plans for warm weather travel this summer.

 

[BroncoJimbo]

A friend has one on his Triumph TR6. It works well and is very quiet. He does have to run a HD alternator and wiring. He recommended Qualy Air
He said they were very helpful after the sale with his custom installation.

 

[lilthom]

Thanks, gentlemen. Not making a decision on this soon but will come back to this thread for a refresher.

 

[Steve83]

Remember that energy isn't free, and converting it from one form to another isn't, either. Try to imagine how much power it takes to spin a typical mechanically-driven A/C compressor at a couple thousand RPM (like it's doing when you drive normally). That's how much power the belt is taking off the harmonic balancer pulley (which is driven by the crankshaft) to drive the compressor. It's a very efficient process because the energy isn't being converted - it's mechanical from the moment the pistons are pushed down all the way to the compressor clutch turning the shaft to drive the compressor pistons.

But to get the same power from an electrically-driven compressor, the energy has to be converted from mechanical (in the belt) to electrical (in the alternator), then flow through wires, connectors, & relays with resistance into a motor that gets hot (which is a waste of power) to drive the compressor. So it actually takes MORE power from the engine to run the electric A/C than to drive a mechanical compressor of the same size. Or for the same power from the engine, you can only drive a smaller electric A/C. And in both cases, that extra power is wasted as heat in the engine bay (radiator) and in the electric compressor.

And that doesn't even address the oversize alternator required to convert all that added energy... It's not free, either. That's why you don't see electrically-driven A/C on production vehicles with engines. And on all-electric vehicles, the A/C is built like a house because the higher voltage allows it to run at lower current (Amps) meaning less waste. But that still takes a hoss of an inverter, and yours would still need a hoss alternator to power that, which would all be crazy-expensive & complicated compared to the factory A/C system.

 

[ntsqd]

Anecdotal footnote: My GP's had a 26' GMC motorcoach with the 455 that they put almost 200k on in the span of maybe 10 years. Grandad did some extensive testing and found that running the generator 5k?, 10k?) to power the 120VAC roof top AC actually made no real difference in the overall vehicle mileage, but made a dramatic difference in comfort as the dash AC could not keep up and running it did have a impact on the mileage.

 

[Broncobowsher]

Remember that energy isn't free, and converting it from one form to another isn't, either. Try to imagine how much power it takes to spin a typical mechanically-driven A/C compressor at a couple thousand RPM (like it's doing when you drive normally). That's how much power the belt is taking off the harmonic balancer pulley (which is driven by the crankshaft) to drive the compressor. It's a very efficient process because the energy isn't being converted - it's mechanical from the moment the pistons are pushed down all the way to the compressor clutch turning the shaft to drive the compressor pistons.

But to get the same power from an electrically-driven compressor, the energy has to be converted from mechanical (in the belt) to electrical (in the alternator), then flow through wires, connectors, & relays with resistance into a motor that gets hot (which is a waste of power) to drive the compressor. So it actually takes MORE power from the engine to run the electric A/C than to drive a mechanical compressor of the same size. Or for the same power from the engine, you can only drive a smaller electric A/C. And in both cases, that extra power is wasted as heat in the engine bay (radiator) and in the electric compressor.

And that doesn't even address the oversize alternator required to convert all that added energy... It's not free, either. That's why you don't see electrically-driven A/C on production vehicles with engines. And on all-electric vehicles, the A/C is built like a house because the higher voltage allows it to run at lower current (Amps) meaning less waste. But that still takes a hoss of an inverter, and yours would still need a hoss alternator to power that, which would all be crazy-expensive & complicated compared to the factory A/C system.

But there is more to the story. While a belt driven A/c will have more power behind it, at least it is easily capable of it. The belt drive is also at the mercy of engine speed. Asking an A/C compressor to have lots of power at low RPM, While surviving being zinged to the moon. While the electric runs at its own speed. Yes, there are conversion losses, but there is also performance gains of running the compressor at the RPM needed, not what it is forced to run at.

Electric cooling fans are technically less efficient because they go through the electric conversion and back to mechanical. Gut they are still used as they are more efficient running at the power level needed and not what is forced upon them. For very high load cooling systems they still use a mechanical fanas they can easily have more power. The loss in effiency is a compromise made to gain max fan power.

 

[Broncobowsher]

Anecdotal footnote: My GP's had a 26' GMC motorcoach with the 455 that they put almost 200k on in the span of maybe 10 years. Grandad did some extensive testing and found that running the generator 5k?, 10k?) to power the 120VAC roof top AC actually made no real difference in the overall vehicle mileage, but made a dramatic difference in comfort as the dash AC could not keep up and running it did have a impact on the mileage.

That is probably a not very efficient generator and the 120V rooftop RV A/C units are built to a price point with little given to the power used, so long as it doesn't trip the breaker.

 

[Yeller]

As to the efficiency it’s not about being free, or even more efficient. It’s about the packaging. In most of the electric systems the compressor is run PWM or VSR so there is no inrush current draw and they can run at whatever RPM is needed.

In my case the desire to run electric is to not be required to carry a generator. Can if needed for the desired activities but it is not required. As to the power consumed most applications that we are discussing either have plenty of alternator power or have bolt in options to get there.

 

[ntsqd]

That is probably a not very efficient generator and the 120V rooftop RV A/C units are built to a price point with little given to the power used, so long as it doesn't trip the breaker.

Which makes running it while driving and it having no impact on the vehicle's MPG even more interesting. Could cool the whole coach with the roof AC for less MPG impact than the pitiful cooling that the dash AC provided, and it did cost some mileage.

I like efficient systems, but at some point other considerations become more important. No doubt that the GP's generator was terribly inefficient as compared to today's generators. However, the combo of it and the roof AC were vastly more efficient than the dash AC employing an engine driven compressor. Have to look at the whole system and weigh it against the goals, can't just look at each component in that system and condemn the whole for one inefficient component.

If you're pulling 80A out of the engine driven alternator to run a 12VDC AC system is the engine really going to miss that ~1.5HP, and is that "missing" HP likely to have any significant impact on the vehicle's MPG?

 

[Steve83]

This thread is about A/C in an eB; not in an RV. There's no space for a generator, and bolting a 200A alternator to an antique engine would be expensive, and would produce a LOT of underhood heat, so the alternator probably wouldn't last long. Yes, efficiency isn't the only consideration, but performance isn't either. Cost, complexity, longevity, & the impact on the vehicle are also relevant.

 

[ntsqd]

Ever heard of "Compare and Contrast"?
I thought not.

 

[Broncobowsher]

130A 3G or 4G could run the A/C and still not be that stressed. But you pretty much need a serpentine belt to pull that off. Not doing it with a single V-belt. Personal experience is 70A all in will get the A/C running on high. That includes a dedicated condenser fan as I run mine parked and off a large battery bank.

200A on an antique engine isn't that big of an ask these days. You can get those from junkyard pulls if you know what you are shopping for.

 

[ntsqd]

I wonder if you can even buy matched set V-belts any more?

Ambulances and MDT's!