Solar output

[clev]

I installed four 150 watt panels with 8.2 aH output and a 60 amp mppt controller. On the maiden 3-week voyage, the most output recorded in the middle of the day, full sun, no clouds, and no shade was mid 400’s for wattage and upper 20’s for amps. Is that normal? Is it unrealistic to expect the full 600 watts and 33 amps?

[Bob Denman]

70% percent or so... That's probably about what you can expect.
That's not to say that you can't coax more out of it...

[clev]

Thank you, Bob.

[Bob Denman]

When it comes to solar power: I've been doing a lot of looking, reading, and shopping!

[clev]

Me too; I spent hours and days, mentally putting this system together. Tech support was/is useless.

[scrubjaysnest]

Panel ratings are in the lab at 77 deg F. Dust on the panels, haze partial shading and temperature all impact output.
The biggest item is battery sate of charge. This determines how much the batteries will accept at any given time.
There are also other factors that come into play also. But the above are the biggies.

[Bob Denman]

You might want to check with Chance...
He's got MAD solar power knowledge!

[clev]

Scrub, thank you for the reply, and no offense, but I didn't understand a thing you posted. "in the lab at 77"????? "Dust, shade, hazing, temperature impact output"?? You did read, "New system, mid day, no clouds, no shade...etc"??? Right?? How does that answer my question?

[clev]

Bob, who is chance?

[Chance]

Originally Posted by clev

....cut..... Is it unrealistic to expect the full 600 watts and 33 amps?

I’m no solar expert, not even close, but will say that for the typical RV installation it is indeed unrealistic to expect 100% of panel rating. Most RVs install panels flat on roof which is most practical, whereas the “ideal” rating tilts panels so they are perpendicular to sun. Depending on where you are in US, and time of year, that accounts for a significant power reduction.

Systems “may” also have enough voltage drop in wiring from panel down to controller that it becomes significant. Because you are working with low voltages and high currents, any voltage drop due to resistance in wire becomes a larger percentage of the power being transmitted through wire (compared to what we’re used to seeing).

Also, the sun doesn’t always shine with same intensity. Just because it looks sunny, it may not be as intense as what was used to rate the panel. This obviously also depends on where you are — further North usually less solar power from sun.

I have no idea what your system is, or where you did your test, but in general I'm impressed you are getting 450 watts out of 600-watt rating. Obviously my comments assume you did a typical RV installation with panels mounted horizontally.

[wingnut60]

Yes, 75% of rating is pretty good....
And dust/haze/high,thin clouds/horizonal positioning, not perpendicular to sunshine, all hurt the solar input. I take a look at my panels about every 3-4 weeks, and they are definitely dusty and have to do a little cleaning. Sometimes a good shower does it for me.

[clev]

Thank you Chance & wing; very informative. Yes, my panels are mounted horizontal and connected to each other with 10 gauge wire. Final run from the roof to the controller is 4 gauge welder’s wire. Panels were clean and garaged up until we left on the trip. Texas to Indiana, then Ohio, KY, VA, and a southerly route back to Texas. I checked the controller a few times each day while traveling and parked. Output ranged from 200’s to 400’s watts and low teens to upper 20’s for aH. Having never had solar, I didn’t know what to expect.

[jpmihalk]

That is pretty normal. We have 400W of solar on our roof but on a good sunny day get around 280 watts due to sun angle and dust buildup on the panels themselves. On cloudy/rainy days it is substantially lower (but still has some charging capability.)

[Bob Denman]

Originally Posted by Chance

I’m no solar expert, not even close, but will say that for the typical RV installation it is indeed unrealistic to expect 100% of panel rating. Most RVs install panels flat on roof which is most practical, whereas the “ideal” rating tilts panels so they are perpendicular to sun. Depending on where you are in US, and time of year, that accounts for a significant power reduction.

Systems “may” also have enough voltage drop in wiring from panel down to controller that it becomes significant. Because you are working with low voltages and high currents, any voltage drop due to resistance in wire becomes a larger percentage of the power being transmitted through wire (compared to what we’re used to seeing).

Also, the sun doesn’t always shine with same intensity. Just because it looks sunny, it may not be as intense as what was used to rate the panel. This obviously also depends on where you are — further North usually less solar power from sun.

I have no idea what your system is, or where you did your test, but in general I'm impressed you are getting 450 watts out of 600-watt rating. Obviously my comments assume you did a typical RV installation with panels mounted horizontally.

This is Chance...
Thanks for chiming in at the exact right time!

[Chance]

Originally Posted by Bob Denman

This is Chance...
Thanks for chiming in at the exact right time!

Glad to help, but there is a lot I also need to learn. I mostly understand the engineering fundamentals from when I was in school a very long time ago.

I did build a mean solar oven as a class project that could cook biscuits. And the total cost had to be really cheap — like $10 (back then) which made it tough to find materials that would work.

[Bob Denman]

I figure that you know the "alternate fuel" stuff; even better than I know the best places to find good jokes!

[kcmusa]

The only think I can add is;
Did you have any 12V items on? or was that just what the battery's were accepting as a charge.?
It could be possible you have more available but the battery's were accepting all they could.
Just because you have 600 watts and 33 amps does not mean it all being used.

Turn on some 12v items and see what the meter says.

[juicesqueezer]

I'm still learning, reading and asking about solar myself. The wiring has a lot to do with the amount of gain or loss, panels you select and battery bank you are depositing the solar into. There are a few YouTubers who have put in some killer systems and it gives a breakdown of what products they used, etc.
Hebard's travels and Pau Hana are two that come to mind.
I have been in contact with Brian Boone, who is an RVer traveling the country doing solar installs. People rave about his knowledge and installs. From what I read and understand, 70% is about right. Keep in mind that with the panels laying flat, any shade from the air conditioner, satellite dish, etc. affects those panels as well. I'm planning on 5 200 watt panels for my system. We already have a 5500 generator and have the Auto Generator Start system to work in conjunction with the battery voltage. Just my thoughts on the subject.

[Chance]

Originally Posted by juicesqueezer

.....cut..... Keep in mind that with the panels laying flat, any shade from the air conditioner, satellite dish, etc. affects those panels as well. I'm planning on 5 200 watt panels for my system. ....cut.....

Shade concern is a great point, particularly as systems get larger in capacity.

If looking at 1,000 watts of nominal panel capacity, and you wire them all in parallel, the amount of current can get pretty high — like around 50 Amps.

In large systems some “experts” go with combination of series and parallel, which can reduce current significantly (normally in half), but then it risks losing a greater percentage of total installed capacity if some of the cells are shaded.

I’d assume that since you are looking at 5 panels (and odd number), that you must be planning on going with an all-parallel installation. In that case shade is bad, but not as critical.

[juicesqueezer]

Originally Posted by Chance

Shade concern is a great point, particularly as systems get larger in capacity.

If looking at 1,000 watts of nominal panel capacity, and you wire them all in parallel, the amount of current can get pretty high — like around 50 Amps.

In large systems some “experts” go with combination of series and parallel, which can reduce current significantly (normally in half), but then it risks losing a greater percentage of total installed capacity if some of the cells are shaded.

I’d assume that since you are looking at 5 panels (and odd number), that you must be planning on going with an all-parallel installation. In that case shade is bad, but not as critical.

Not sure yet how to wire system and may add a 6th panel and split the system into two MPPT boxes. Decisions, decisions!