Air conditioning on solar

Doesn't it state directly on the compressor inside the A/C unit what the draw is in amps and Watts? I tried this once and found the info by looking through the side vents. The compressor was labeled. The rating on the unit itself doesn't include compressor start up.

BTW, I would rather have a window shaker in my rv than the obnoxious roof air. It is too large for my 24ft TT, vibrates the whole unit and makes a loud droning sound. My window unit (5000) is super quiet and runs on the Honda 2000 for 14 hours without revving up.

Today it was 78 f out and I wanted to test the new panel vs the old and play with the air conditioner again.

Using the 245w Bosch mono and the 250w Navajo poly with a pair of Eco-w's on the combined 345 Ah bank I was able to run the window shaker for four hours.



The draw was higher than before once it got the pressure up but no higher than it's rating. I kept it in the sun to keep the compressor on.

Watts


Volt amps


The inverter was pulling 35a and under meaning the two panels tracking was almost keeping up. Once the voltage dropped a bit the controllers cranked it up to 200w + and I saw the occasion 17.75a each on the controllers.



Like I said the panels were almost enough and the bank was ever so slightly lossing the battle. After four hours the voltage under load did get below 12v after sitting just above 12v for a hour.



If I can do this for the limited times we need it with three panels flat, I will be thrilled. We don't need the trailer to be a ice box, just below 80f is nice.

Now I have to find out where to send the Power verter because it's as squirrely as the last one.

Thanks folks for all your help and suggestions! I apologize to the OP for the off-topic time these discussions took ... hopefully through all this a little bit of sunlight has been shown on all aspects of RV solar systems.

I'll probably go the MPPT controller route and use whatever panel technology is the most rugged (won't break if blown over). BTW, from the picture it appears that the Roc-Solid portable kit is using poly panels.

Just for fun and to be thorough, I'll take a hard look at various ready-to-go foldable portable systems at Quartzite next month before deciding whether or not to put together my own system ... as I've got a lot of other Spring projects lined up already!

P.S. Unfortunately, I probably won't wait for ultra-high efficiency graphene solar panels to become available and affordable, even though I just can't get out of my head the factoid I recently ran across that in plants Mother Nature converts sunlight to energy at efficiency rates of 97-98% !!!

Phil

Since I have been here, all I've heard was "don't buy the kit" Buy the components and put them together yourself. That changed some when Solarblvd, Eco-worthy, Windynation and others started producing affordable and functional kits but there is still a lot of snake oil and Koolaid out there.

It's pretty simple. Pick out a panel or set of smaller panels. A 50 ft run of COPPER 10 gauge solar wire is $50. Want to spend money on a MPPT controller but not the off brands, buy a Morningstar 15a MPPT for $200. It will get you that little bit of extra power and all the features you want while being able to hold your head up high. For the money you will have a set up tuned to your needs and that's the most efficient way to go.

Phil, panel efficiency has nothing to do with its amps output. Panel efficiency is to do with its watts per square inch so a smaller panel with the same wattage is more efficient. Both can have the same amps.

Solar for Rving is hugely inefficient and inconsistent due to the weather, so you can't fine-tune it. Just grab some and use it. It will give you more amps than not using it. Forget efficiency and just get the most Isc per dollar (forget dollars per watt --you are buying Isc amps not watts with PWM)

Or buy whatever, play with it, discover what we told you here was right after all, and then play solar-set trading on Craigslist like Jim does till you get it right :)

EDIT--missed Phil's above-- the 120w panel gets its wattage rating by looking at its IV curve where you get the Vmp at its knee. The Imp is whatever the amps are at that Vmp point.

Poly panels have typical Voc of 21.x and monos 22.x Polys have higher Iscs with the lower Vocs (and the Vmp/Imps) Iscs are pretty much proportionate to wattage with the polys at that same voltage.

An 80w will be 5.1ish, a 100w will be 6.3ish, 120w 7.6, 130 8.2.
That is how I can use my 130w panel specs to estimate the "expected amps" from any wattage---it is all in proportion. Monos are less amps of course with that higher voltage.

However Imp means nothing in either PWM or MPPT. With PWM you just care about Isc and with MPPT you care about watts and Vmp.

The Roc thing is so expensive because it has MPPT which costs way more than PWM. It likely has a Tracer MPPT since it mentions that 13.8 Float voltage. They cost about $140 just for the controller.

A PWM 120w kit with the same panels will have a controller worth about $20.

BFL13 wrote:
A 120w poly has Isc of 7.6a,

What 120 watt poly panel has an ISC of 7.6a?

If you mean "every 120W poly panel", then are you ruling out any new poly technology improvements that just may yield more than 7.6a ISC?

I guess it depends upon what "120 watts" means in the solar advertising world. I (erroneously?) thought that a 120 watt panel meant the real estate size of the panel ... assuming some kind of commonly available technology being used in the poly manufacturing -> hence maybe newer technology poly panels being capable of higher currents than panels of the same size but of older technoloy.

This begs the question: Since the "120 watt" Roc-Solid portable set is so expensive ... does this mean that it's physically smaller than competitors' "120 watt" systems because of superior technology?

The spec says maximum charging current.

What in the spec implies that this means only a 10 amp charge controller is used?

Bear in mind that only a very slight improvement in the efficiency of any given solar charging system can give a dramatic improvement in performance (amperage output) - since most run of the mill solar systems are so inefficient as delivered. Not counting the variations in solar panel controllers, the solar panels themselves range in efficiencies from the low 20% range to the high 40% range.

What I assume is that maybe paying high bucks for a solar system will occasionally get one a higher efficiency system - which will translate into higher charging currents and hence a higher wattage rating for their system as a whole. Roc-Solid may be doing this for their "120 watt" portable system.

Looks to me that it is designed in Oz but not built there.

A 120w poly has Isc of 7.6a, which you will get with PWM so with MPPT doing amazing things it might hit 10amps.

The 13.8 is the Float voltage of the controller. If they are using , EG, an EP Solar Tracer MPPT ($140 maybe) that has the same fixed charging profile as the EP Solar PWM LandStar one like I had. It takes the battery up to 14.6v then holds it there for 2 hours and then drops to 13.8v Float for the rest of the day.

I was happy enough with that profile but prefer to leave it at 14.6 longer than two hours sometimes depending on various factors. I like my Solar30 way better.

They don't show the actual panel specs that I noticed anyway.

IMO forget that whole deal and just get a 120w panel and a $35 Solar30 controller, which has the desired adjustable voltage so you can set it to 13.8 or whatever all you like.

It is more controller amps than you need but it has the amps readout and adjustable voltage that most in that price range or below don't have, so it is worth the extra $15 over the typical eBay job that would still work ok.

I assume you means the 10a max charge rate? I believe that means it has a 10a charge controller, not that you will see 10a out of 120w.

I keep coming back to this site and getting intrigued by the specs of their 120WFSP portable set:

http://www.roc-solidsolar.com.au/assets/manuals/80W%20&%20120W%20Solar%20Panel%20Brochure.pdf

Look at that great 13.8 Vdc float spec (perfect for our AGM batteries) and that great maximum charging current spec for only a 120 watt panel. I can't figure out if it's using mono or poly panels - can anyone tell from the picture?

I really don't want to spend that kind of money UNLESS that maximum charging current spec is somehow correct. However I do respect Australian RV products and in general, their advertising ... assuming it's a product that's actually manufactured there.