Best way to wire panels for shade

Billybobthethird · Jul 4, 2021

I have a small 12 volt system with a panel array with 5 in a row, all series right now. I'm looking to add another 5 and I'm also replacing the now dead fla batteries with lithium, so I figure now is a good time to re wire the panels for shade, since I have rolling shade from both sides

Billybobthethird · Jul 4, 2021

I'll try to post pictures when I get home

Billybobthethird · Jul 4, 2021

Billybobthethird · Jul 4, 2021

That's the sunniest spot in my back yard. The new panels will go below them, and possibly one on stage right off the existing array

Billybobthethird · Jul 4, 2021

The obstacles to work around

snoobler · Jul 7, 2021

More in parallel means fewer panels impacted from shading of cells other panels.

Assuming shading hits the tops and bottoms of your panels, re-orienting them horizontally would help. If you shade ANY row of cells of a vertically mounted panel, you kill the entire panel's output.

Not knowing any details of your system, a 2S5P system would probably be a good place to start.

1000W/12V = 83A, so if you have a MPPT charge controller with < 80A charge rating, you're over-paneled and losing available solar. If you deal frequently with bad weather or cloud cover, then over-paneling a lower rated MPPT controller is fine.

Rider · Jul 7, 2021

If the panel sets (2 sets of 5) go into the shade at different times, consider 2 SCCs, one for each set of 5 panels, to minimize the shading effect over all 10 panels. If you do that, you can also point them in slightly different east/west angles to get more sun earlier/later in the day.

Billybobthethird · Jul 7, 2021

The sun moves left to right, shading whole panels at times, especially in winter. I have a 40a mppt rover charger, which I was of the impression I could parallel some panels and have up to 100v input on, even with a 12v battery. I'm planning on possibly getting a 24v inverter at some point. I use most of my power during the day, but will have a 6.8kwh of lifpo4 cells as a buffer. There are many days where I have clouds, which is one reason for the 1000w of solar, but I do want to be able to use it on the sunny days to do laundry and dishes, charge tool batteries, ect..., so I don't want to leave capacity on the table. I can change the orientation of the panels, but the shade generally won't miss just the tops, so not sure if it will help?

snoobler · Jul 7, 2021

If whole panels are shaded at a time, orientation doesn't matter much.

40A means the unit is limited to 40A of charging, i.e. 40A * 12V = 480W. In reality, you can get up to 40A * 14V = 560W depending on the MPPT spec. Your power profile will look like this:

Solar Charge controller, how many amps?

I want to install 600 watts of solar on my van. After performing a basic calculation of 600/12 = 50, it seems that I would need at a minimum a 50 amp charge controller. I am a little confused as I am looking at starter kits from Grape solar and Rich solar 3 X 200-watt panels with only 40 amp...

diysolarforum.com

Except your "red" zone is about the same size as the blue zone; however, your "green" zone will be bigger as well.

If you want the potential to get 1000W, you need to get a 2nd 40A controller with 5 panels on each. Given your shade concerns and the fact that you are at 12V, I would just parallel all the panels.

If you shade the top of a vertical panel, it's essentially disabled. If you shade the top of a horizontal panel, you only disable a portion of it, typically only 1/3 or 1/2 the panel depending on design.

Alphacarina · Jul 7, 2021

In your situation, wiring all panels in parallel will give you the most power when some panels are shaded. You will probably need all new cabling in larger wire sizes and probably a larger or a second SCC to handle the amps. When you string panels in series and one panel gets shaded, you lose almost all power output, whereas panels in parallel would still give you partial power output

Don

Billybobthethird · Jul 8, 2021

Thank you, I will get a second mppt charger and parallel all the panels. What is a decent price charge controller?

Billybobthethird · Jul 8, 2021

Also, what are people doing to parallel this many panels?

snoobler · Jul 8, 2021

Billybobthethird said:
Thank you, I will get a second mppt charger and parallel all the panels. What is a decent price charge controller?

If the Renogy is working for you, it's probably not a bad choice. Will lists several MPPT on his site:

DIY Off Grid Solar Charge Controllers

Building a vehicle mounted solar power system? Let me help.

www.mobile-solarpower.com

Personally, I only recommend Victron or other Tier 1 equipment (midnite solar, outback, etc.).

Billybobthethird said:
Also, what are people doing to parallel this many panels?

Combiner box is the best option, but pretty spendy.

Since you're going to have 5 panels in parallel, you'll need a fuse/breaker on each panel

One of these for each 5P array:

MidNite Solar MNPV6 Solar Array Combiner

MidNite Solar MNPV6 Solar PV Array Combiner Box

www.solar-electric.com

Plus whatever breaker amperage your panel stickers say for a max fuse. I'm guessing 10A:

Midnite Solar MNEPV 150 Volts 10 Amps DC Circuit Breaker

NOTE: There is a new version of this breaker available. The new part number is MNEPV10-150-1PNP.

www.solar-electric.com

Billybobthethird · Jul 9, 2021

Thank you. Wiring and fusing upgrades are a must, but I am wondering about something like a buss bar to parallel the panels, put both banks into series through the wall, then both controllers would be identical, in parallel to the batteries?

HRTKD · Jul 9, 2021

Why not put the panels on the roof of the buildings?

Billybobthethird · Jul 9, 2021

Access, I would get zero output without constantly cleaning them

HRTKD · Jul 9, 2021

My neighbor has had panels on their second story roof for a few years. Not once have they cleaned them.

Billybobthethird · Jul 17, 2021

Billybobthethird said:
Thank you. Wiring and fusing upgrades are a must, but I am wondering about something like a buss bar to parallel the panels, put both banks into series through the wall, then both controllers would be identical, in parallel to the batteries?

rin67630 · Jul 18, 2021

Alphacarina said:
In your situation, wiring all panels in parallel will give you the most power when some panels are shaded.

These are 100W 36 cells panels with Vmp around 18V, right?
The best is to wire them pairwise (ideally to get shaded together) to get 36Vmp (where MPPT works ways better) and then parallel the pairs to minimize the effect of shading.
If you have 2x5 panels, orienting 5 pairs distributed: 2E, 2SE, 2S, 2SW, 2W will give you a longer solar power time with a flatter day curve, which is good to be nice to the battery and limit the overall current. But of course if the price is much longer cables, you should balance the advantages.

2009Bounder2020 · Jul 19, 2021

HRTKD said:
My neighbor has had panels on their second story roof for a few years. Not once have they cleaned them.

depends where you live, im on a farm and we have to spray ours down fairly often or they get dusty and you can see it on the output

Best way to wire panels for shade

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