AC on solar power

[cjsibley81]

Just trying to understand how this works. I'm planning on my build being all electric (if possible). How do I figure out how much solar power I will need. And is it possible to have RV roof mounted units on solar power?

[john61ct]

Possible as a technology demonstration, not practical.

Use a genset.

With a huge heavy storage bank, solar can be used to reduce its runtime.

A little.

http://www.skoolie.net/forums/f10/mi...tml#post297875

[david.dgeorge07]

No offense, but someone asks this question about once a week. The closest that I’ve actually seen anyone come to it is running a mini split unit in dehumidifier mode which is about half strength of normal air conditioning, maybe enough to cool one small room in real time off of solar.

[cjsibley81]

No offense taken at all. Thanks for teaching me!

[o1marc]

Some good info here. their interactive "wiring diagrams" make things easy to understand.


https://www.explorist.life/diy-campervan-solar/

[milkmania]

had actually just watched this guy before I logged in here

disregard the wind noise in the beginning
using a soft start method, several soft start modules online

https://www.youtube.com/watch?v=TMnxhqlyD-U

[john61ct]

Note that location gives max insolation conditions.

If anyone bothers sitting through that, please post the hard data.

What unit?

How big his bank in Ah? What chemistry? How often does the bank get back to 100% Full?

How many watts of panels? Up front costs?

Size of space cooled, how many hours per day, how well insulated?

No one's saying it **can't** be done.

Just a question of practicality and cost, compared to running a small quiet genset.

[roach711]

After watching the thing:

Air conditioner - Coleman Mach 1 Power Saver #48207C966 11,000 btu.

Soft start module - Micro-Air Easy Start #ASY-364-X30 (or X36 (blurry))

Battery - One 100AH lithium Ion L13 battery

Inverter - 2000W Go Power pure sine wave.

RV looks like a standard sticks and staples trailer.

He is in southern California in ideal conditions. His panels were putting out 13 to 17 amps while the AC was pulling about 11 running amps so the battery was just there to add a push to start the compressor then the panels would power the AC and some other small draws while throwing a few amps at the battery.

The lithium battery can be drawn down way further than lead-acid battery so he'd actually have a few hours capacity to run the AC at night.

Without the Easy start module the inverter was protesting when the AC started up but with it installed there were no warning sounds from the inverter.

So, doable technically without a huge battery bank. But that assumes good solar charging weather and no other large draws (and he still has to park in full sun). Whoda thunk it?

[Ninjakitty]

So... Rooftop a/c off solar is possible. I do it. Just not for a long time. Mini-split also, for longer periods of time.

I have 1400 watts of panels and a 12 volt 840 ah AGM battery bank.

Climate Right 12,000 btu mini-split.

Dometic Brisk II 15,000 btu rooftop.

(Side note, we are just starting to move into the bus. Have done one 3~ hour road trip)

On a sunny day, I can run the mini split all day while the sun is up and keep 100% battery bank. Not sure about over night as the nights we slept in it have been plugged in. Left it on dehumidifier on accident the other night, 70%~ battery bank in the morning.

Rooftop we ran on our trip, plugged into the inverter, mostly on the high setting. Hit 55%~ battery discharge after about 2.5 hours. (Side note, I had too all of a wire and plug size connected to a/c and burned a couple of fuses. I have corrected that. Will see of that affects power usage tomorrow on our trip.)

[Ninjakitty]

I'm in Central Florida

[cjsibley81]

Y'all are all amazing. My wife and I are still looking into different ideas. We are trying to get a few ideas down so we can start looking at cost of things before we buy anything. BTW I am in southeast Louisiana.

[john61ct]

Sure, running directly off the solar panels out in the desert is the easy part.

But means you **have to** park in the bright sun, and **only** get aircon when it is high in the sky.

Ballpark figure 100Ah extra capacity per hour you want to run it otherwise, pretty heavy, bulky and expensive, and don't forget batteries are a consumable.

So let's say 400Ah needed per day, how are you going to replace that every day?

If you want to run the aircon at the same time as needing to recharge the bank, now you need 3-4x the panels.

Got enough roof space? Can't park in the shade. . .

You really are in practice going to need a genset as well anyway.

so then it's just a question of hours runtime per day.

Solar's job is reducing that, and the fuel savings will vary enormously depending on weather conditions.

A **lot** of insulation and getting acclimated to the heat will help a lot.

[o1marc]

Originally Posted by john61ct

Sure, running directly off the solar panels out in the desert is the easy part.

But means you **have to** park in the bright sun, and **only** get aircon when it is high in the sky.

Ballpark figure 100Ah extra capacity per hour you want to run it otherwise, pretty heavy, bulky and expensive, and don't forget batteries are a consumable.

So let's say 400Ah needed per day, how are you going to replace that every day?

If you want to run the aircon at the same time as needing to recharge the bank, now you need 3-4x the panels.

Got enough roof space? Can't park in the shade. . .

You really are in practice going to need a genset as well anyway.

so then it's just a question of hours runtime per day.

Solar's job is reducing that, and the fuel savings will vary enormously depending on weather conditions.

A **lot** of insulation and getting acclimated to the heat will help a lot.

What Genset do you recommend? I see these Onan Genset Emerald Plus 4000. I see one locally for $650, then there's one for $450/make offer, but it's in Wash.

[bubb, the real one]

A tiny 5000 btu unit takes 4amps AC to run, this translates to 40amps DC, this means you need at least 600ah batt bank just to run it for 30 min until voltage drops below 11.5 and the inverter shuts off.
This Ac unit can cool the cab of a bus no more.

I have a 15000 btu window unit which cools the bus in the shade in Texas.
To run it by battery n solar I would need 2500 ah batt bank which would weigh at least 3000 lbs. and at least 3500 watts of solar, about 8ft wide by 40ft long.

IMHO

[john61ct]

You want pure sine-wave inverter type. Quiet is very important if you're camping near others.

Honda is best, eu2200i in this case x2 tied together, not sure about bigger ones.

Yamaha is good too.

Champion will be cheaper, tons of no-name Chinese out there too, maybe if you think likely to be stolen you don't care how many thousand hours the last.

[o1marc]

Originally Posted by john61ct

You want pure sine-wave inverter type. Quiet is very important if you're camping near others.

Honda is best, eu2200i in this case x2 tied together, not sure about bigger ones.

Yamaha is good too.

Champion will be cheaper, tons of no-name Chinese out there too, maybe if you think likely to be stolen you don't care how many thousand hours the last.

I offered $500 for this unit and they accepted. Is it worth it?
https://www.ebay.com/itm/Onan-4kW-Ge...4ba38631da9106

[BlackJohn]

Originally Posted by o1marc

I offered $500 for this unit and they accepted. Is it worth it?
https://www.ebay.com/itm/Onan-4kW-Ge...4ba38631da9106

I have one of those genny's. 35 years old. Worked great till governor let it run away last year. Let the smoke out then.
Sure wouldn't pay that much for that. Mine was original in MH but can't say it was much trouble till then. My fault I think, shut it down without taking the load off it first.


Make sure you get the remote start switch and wiring from the donor MH.
I won't tell you how much the points cost to replace, was shocking though.



John