True battery powered AC/not swamp cooler

[egfasdsdsz]

Originally Posted by redbarron55

Please let's not argue about semantics especially when almost everyone knows what is meant.
Amp hours are often use with batteries and the whole time you are drawing power the voltage is dropping so the energy (if you like) is changing the entire time.

You are correct, I believe most of us who rely on rechargeable batteries understand the correct use of “Amp-hours”. My concern was the use of this term in the calculation of power factor, which is incorrect (should be “Volt-Amps”).

[trainman]

It does come a time when it's just easier to stay at home, or camp in cooler weather. All that being said, Boondocking is a seasonal sport for us, when it's hot we either stay home, or camp where 120V is available. I live in Texas where it will be 103 today, did the yard yesterday when it was cooler, 101 if I remember.

trainman

[John in Santa Cruz]

Originally Posted by Shullj

Please keep us posted. Domestic and others are now making small DC refrigerators/freezers that are far more efficient than thermoelectric or Peltier coolers. This is very similar technology to that required for an AC unit.

AC units are ALL compressor based now, this zerobreeze thing is just a smaller variant, not some radical new idea.

and yeah, 2700 BTUs of cooling is hardly nada. at 350 watts, thats about 30A at 12V, so will suck a typical RV battery down hard in a couple hours.

[redbarron55]

Originally Posted by John in Santa Cruz

AC units are ALL compressor based now, this zerobreeze thing is just a smaller variant, not some radical new idea.

and yeah, 2700 BTUs of cooling is hardly nada. at 350 watts, thats about 30A at 12V, so will suck a typical RV battery down hard in a couple hours.

That is my point and if there is a conversion from 12 to 120 volts the current is going to increase by approximately a factor of 10.

The power required will increase by the losses in that conversion and also the power will also be increased by the power factor of the AC unit.

As to.....

[RogerDat]

Way too many snarky comments directed at members! Now someone has to go through and clean out the name calling and criticism so people can find the useful information without wading through the unpleasant exchanges.

If one is going to disagree one needs to be able to do so without being disagreeable, maybe even state your own opinion or thoughts without any reference to the comments of another. The community rules really boil down to be courteous and nice.

From the forum rules

Be Courteous!
Our philosophy is that we want the forum to be an online reflection of the RV'ing community. Treat each other with respect, just as you would around a campfire. Here are some general guidelines that we expect you to follow:....

For the complete list please see:
https://www.fiberglassrv.com/forums/...ork&page=rules

[Air Doug]

I vote for more respect and civility too.

So I know the topic is real AC, not swamp cooling, but Shullj posted pics of his 5 gallon bucket swamp cooler and it got me to thinking if part of the answer for "real AC" is some sort of hybrid system. In other words, start by precooling the trailer with the swamp cooler and run the "real AC" on pre-cooled air. The swamp cooler gives the the AC a head start. The first obvious problem is that the swamp cooler is flow-through and is constantly exhausting air to the outside, so any air cooled by the AC would be exhausted to. But I am just brainstorming the problem. Maybe run a swamp cooler to cool the air gap between the roof-mounted solar panels and the trailer? Makes the trailer cooler and the solar panels more efficient?

By the way, I built a 5-gallon bucket swamp cooler following the FIGJAM design and got 30 degree F temperature drop in 100 degree Nevada weather. The FIGJAM thread on the Burning Man forum is now up to 144 pages! If you build one, start at the end and work backwards - there have been design improvements.
https://eplaya.burningman.org/viewtopic.php?t=33842

[redbarron55]

Swamp coolers can work well in dry climates, but where the humidity is high not so much.
Also if you do use a swamp cooler and raise the humidity to cool you still have the energy to remove the latent heat of all of that water vapor in the air.

[Byron Kinnaman]

Originally Posted by redbarron55

That is my point and if there is a conversion from 12 to 120 volts the current is going to increase by approximately a factor of 10.

The power required will increase by the losses in that conversion and also the power will also be increased by the power factor of the AC unit.

As to.....

I would like to clearify this statement and correct a small but important misconception.
Goring from 120 volts to 12 volts the current in the 12 volt system increases by 10. (1 amp at 120 volts = 10 amps at 12volts.) This is the main reason batteries run down rapidly when trying to run a refrigerator on a 12 volt battery.

[John in Santa Cruz]

Originally Posted by Byron Kinnaman

I would like to clearify this statement and correct a small but important misconception.
Goring from 120 volts to 12 volts the current in the 12 volt system increases by 10. (1 amp at 120 volts = 10 amps at 12volts.) This is the main reason batteries run down rapidly when trying to run a refrigerator on a 12 volt battery.

yeah, I really prefer to convert my battery capacities into watt*hours for comparing...

a pair of 6V golf cart batts rated at 220AH is 12V * 220AH is 2640 watt*hours, *BUT* lead acid really should never be discharged below 50% if you want them to last, so the typical 2000 watt RV air conditioner would run about 40 minutes before you're at 50%, *and* you'd need a 2000 watt solar system to keep up with that A/C if its running full power at 100% duty cycle in hot weather. thats 12X the 'capacity' of the factory solar option on my Escape, and probably 20X its actual useful output mid day.


btw, living out here in the arid west, where if its hot, its almost certainly very dry, swamp coolers *do* work pretty well. now, I live on the left edge of this continent, within spitting distance of the Pacific Ocean, so extreme heat isn't something we get here at home hardly ever, but a few miles inland, its an all summer thing.

[TucsonAZ]

I'm a homesteader type, interested in practice and not theory. For me there are things that will work, things that will work well, and things that will work ideally. I choose based on the importance of said project as well as the point of diminishing returns.



I'm simply stating as somebody who is a fabricator/homesteader type what has worked for me.



Once in which in the Bay area I spun a bearing on a stepvan/motorhome conversion. My fault of course, should have repacked them before the trip but anyway, the damage was done and the race and castle nut were welded to the spindle. This was as I recall a 14k i-beam front axle and I couldn't find another to save my life and I was still 950 miles from home. So I'm broke down in an old K-Mart parking lot that was a City sanctioned homeless refuge during the heatwave in 2014 with my son and a baby pied ball python (don't ask).



I had options but what I ended up doing was cutting/chiseling the nut and race off. Filing the spindle back to as smooth as possible grinding the spindle threads off, retapping and using two very thin nuts to lock things back in place as there was no 3/4x16 castle nuts. Thankfully it was on the passenger side and not the drivers.



The point to my story is this worked, not well, not ideal but got me home. I sold the van and told the guy about it, oddly he didn't seem phased and is still driving it around like that as a food truck so you may even say it worked well?


This was real life though, on paper I would have been way too worried about thread depths, the metallurgy of it and a dozen other things.

Originally Posted by dbdbgriggs

Tucson, keenly interested in the details of your 5000btu ac mods. Presume this is a window unit? Thanks

Basically I pulled it all apart, taped everything to seal gaps and so on. I added a hard start capacitor to lower the startup amps as well as a replay and time delay of 5 seconds so that when you turn on the AC on high fan it spools up the fan to high before kicking on the compressor. This all drastically reduced the current at startup to allow for use use on a 1,500 watt inverter and likely would be fine on 1,000 watts.

[TucsonAZ]

I'll share a little info on one of my setups here as well. This is the rig I was traveling in:


https://www.cheaprvliving.com/forums....php?tid=10114


This is comparing solar in full sun versus clouds:


https://www.cheaprvliving.com/forums....php?tid=11549


Here are my solar panels, I think they're 230 each, total of 1,340 watts.



This is my inverter, breakers, shunt, charge controller and so on.



This is my battery bank, I had to fabricate the seat mounting to fit two Honda Passport seats and mount the five AGM batteries under it securely.






I can tell you with absolute certainly what you can do with a system like this without discharging the battery bank below 50%.

[Defenestrator]

Originally Posted by StevenMaria

2360 BTU requires 690 watts at 100% efficiency let’s say that unit is 75% efficient .That 2360 would require about 900 W not the 210 they’re quoting. Something is fishy

Not so fishy, actually. Air conditioners are heat pumps, so they "cheat" by using ambient temperature and can move around more watts than they use. So, it's basically removing 690 watts of heat from the cold side and dumping 900W (690+210) to the outdoors. It works because "outdoors" is a sort of infinite heat sink.

I agree that ~2000BTU isn't enough for anything but a tiny massively-insulated travel trailer. The 11.5K unit on my extra-insulated Escape is overkill, but anything below 7K would fall behind on hot days. Maybe if you coated a Boler with a couple inches of foam on the inside and radiant barrier around the outside it would be enough. I do expect it to exist, since it's actually their second-generation product and the first gen did get delivered. Seems to be slightly lower-efficiency than the rooftop ACs though, much less a window unit or mini-split, so not really a great option for running on batteries regardless.

The dehumidification mode is kind of interesting. It looks like it's a bit smaller than any of the existing compressor-based dehumidifier options, which is nice. Price is too high to be worth it just for that, though. For that much money I might as well swap out the roof AC for one with a dehumidification and heat-pump mode.

[John in Santa Cruz]

gawd, i'm glad we live where we don't need an AC at home. I hate the sound of those things.

[Raspy]

Originally Posted by John in Santa Cruz

gawd, i'm glad we live where we don't need an AC at home. I hate the sound of those things.

Me too. And the electric bill to run them!

The only time I've been glad to have one on the trailer was on a business trip to Las Vegas and Phoenix, in August one year. They work, but the noise is terrible.

[Fred762]

Saw an ad for this device, but was wondering how it gets rid of heat and condensation..

Zen Cooler

https://www.smore.com/qfxrk-zencoole...ws-price-facts

[Jon Vermilye]

Originally Posted by Raspy

Me too. And the electric bill to run them!

The only time I've been glad to have one on the trailer was on a business trip to Las Vegas and Phoenix, in August one year. They work, but the noise is terrible.

While I hate the sound as well, I have to admit I added a 10,000 BTU window at home unit this year. Living on Lake Ontario in upstate NY, we used to have <90° summers with the nights cooling to the low 60's. Over the last two years, many 90°+ days & only down to the 70's at night - I don't know if it is old age or climate change, but it is getting too hot!

[Fred762]

How could this work w/o outlets to outside air??

https://www.prime8.com/cool/?gclid=E...SAAEgKyY_D_BwE

[TucsonAZ]

Originally Posted by Fred762

How could this work w/o outlets to outside air??

https://www.prime8.com/cool/?gclid=E...SAAEgKyY_D_BwE

It's just an evaporative cooler, works the same way misting yourself with water on a hot day would work.