28 panels. 3 MPPTs. Shading. Now what?

[WorldwideDave]

Hello! I am trying to get the maximum out of my MPPTs and panel configuration. I think the goal is to push more current to recharge batteries. So parallelling more panels should be employed. This sound right?

I have 3 SCC MPPTs (250/70, 150/100, and 100/20) I am trying to get the maximum production out of them (all victron).
I have 28 panels, but 7 are in one array, and 6 are in another.
The rest I can lay on ground or lean against wall until I come up with a plan.
Panels are 200w. All figures are with winter overages/safety: 30.8 VOC, 8.6 ISC (amps).

7 panel array I have 2 series, 3 parallel, using 6 of them. They produce the most. In shade in morning and again in afternoon. This is currently connected to the 150/100 SCC. That is 62 V, 26 A in this arrangement. I have room for another 74A and 88V remaining available to that SCC. Most I can do safely is 3 series, 3 strings OR 2 series 4 strings OR 4 series 2 strings. Strings = parallel. This is 8 panels max, or 1600 W. I believe this is correct.

There is one panel on the end; right now that single panel is plugged into the 100/20. I could be paralleling another panel. That's it for this MPPT - that would be 62 VOC, 17 A. That one is done.

the 6 panel array is the 250/70, and is all in series right now. it has a lot of shade until about 12:30 in the afternoon, and even then has some shading on 1 of the panels pretty bad. I think this one is 185V, but just 9 A. That leaves 65V and over 60A still available to this SCC. I could parallel this 3 and 3 but probably better as 2s3p due to shading at one end. I also believe that this SCC can support 8 series 3 parallel with my panels.

I can also remove panels from the shady ends of both (or leave disconnected) as they are in the shade. However, I get about 500Wh from the single panel alone, so hesitant to remove that one.

Removing shading not an option - power pole and neighbor's hedge creating shade. Asked, but not going to cut it so I can produce more solar. I can move panels anywhere if needed (except roof due to permit).

I am open to suggestions.

 

[quantum`]

Sell or throw away those 200 watters. They're more than three times that power now.

Check the CCRs of your HOA. Maybe it doesn't allow panels on the roof where they can be seen.

The average 90266 home value is $2,967,633, down 1.3% over the past year and goes to pending in around 34 days.

 

[WorldwideDave]

Sell or throw away those 200 watters. They're more than three times that power now.

Check the CCRs of your HOA. Maybe it doesn't allow panels on the roof where they can be seen.

No HOA or CCRs. City/County. Flat roof. They would be seen by everyone - all neighbors have 2-3 stories. This is one story - 70 year old house, would need new roof due to age and weight.
Not throwing away panels, ever. Got these for $20 each about 6 months ago. Can use in many places/projects. Have 4 seperate solar projects, and possibly 2 more abroad. Learning. ROI on all my setup will be met in 3 more months. That's about 10 months total for all projects. Hard dollars saved that instead of going to Edison goes to batteries, inverters, and yes, these panels.

 

[Solar Guppy]

No HOA or CCRs. City/County.

You may think that but your in CA and they definitely have codes where you are located ( zip code shows Manhattan Beach CA ), you need to read up on NEC2020, building code is 2022 and the state as soon to be NEC2023. This would be where your building department is.

 

[WorldwideDave]

You may think that but your in CA and they definitely have codes where you are located ( zip code shows Manhattan Beach CA ), you need to read up on NEC2020, building code is 2022 and the state as soon to be NEC2023. This would be where your building department is.

I agree with you 100% - I was saying that there are no HOAs or CC&Rs from builder or this plat/subdivision. There are a lot of codes in this city, county, and state...not to mention very nosey and curious neighbors who are bored and call code enforcement and parking enforcement and all types of enforcement for sport.
We have street sweeping one day a week. If we move our cars and park in front of a neighbor's house any time before or after street sweeping even for a minute, they will call the parking enforcement, and leave a nasty note on your windshield. Doesn't just happen to me, happens to all the neighbors. Just some real a-holes in this town. But the parking enforcement guy is nice - he'll come knock on your door and tell you to move it because he received a complaint filed. If you aren't home you'll get a ticket or worse - towed.
Anyhow, I'm not putting SQUAT on my roof, and not grid-tied or hybrid in my solar stuff - just some batteries, some inverters, some MPPTs that run some equipment around the property. We are still grid connected and our power bill is $250 USD a month, but was $400 a month our gas bill is much lower now that some stuff running on solar.

 

[Crowz]

My new method for handling shade is more charge controllers to divide things up so the shaded ones are on their own controller. Your going to loose power to shade no matter what but with it being more subdivided amongst more controllers you can limit the penalty from it.

You just have to make sure the shaded stuff is on its own string.

 

[Chuck E.]

Just my 3 cents, since I have fought shading many ways.
I think it comes down to any array that you have will make maximum power with the most panels possible WITHOUT being in the shade. That may mean a 6 panel array may have to be a 4 panel array. I think you can monkey around with this realizing ONE panel shaded significantly will cut down the full array to half or less of its capable output (best estimate, but its a huge reduction). If you have a way to see each individual array's outputs this can help with the musical chairs of sort I think you may have to do.

 

[quantum`]

Ok. Money is an object.

It is not credible that rooftop solar is outlawed, especially in CA.

I-I-I am out of ideas... actually I have a couple but they would be unacceptable.

 

[WorldwideDave]

You just have to make sure the shaded stuff is on its own string.

I have 3 SCC. Just 1 of them can handle all panels. With 2 of them I could easily handle a few thousand watts more. With the 3 I have I think I can handle 9000 watts or so, but I don't have that many panels or space for them all.
Wait a second...let me see if I understand...
Are you suggesting that I use one MPPT and run 2 parallel strings - one with 6 panels in the sunny array, and one with 6 panels in the shade - and parallel them up? I mean one of them is producing zero until about 11:30 AM, while the other array starts producing 2 hours prior. That would free up a SCC to run a 4th string somewhere else.

 

[Chuck E.]

More smaller (but still functional voltage wise) arrays is the way I solved a lot of my shading issues. Cost is more wire, connectors and breakers pretty much.

The overall best solution to shading is micro inverters But thats expensive.

 

[WorldwideDave]

Just my 3 cents, since I have fought shading many ways.
I think it comes down to any array that you have will make maximum power with the most panels possible WITHOUT being in the shade. That may mean a 6 panel array may have to be a 4 panel array. I think you can monkey around with this realizing ONE panel shaded significantly will cut down the full array to half or less of its capable output (best estimate, but its a huge reduction). If you have a way to see each individual array's outputs this can help with the musical chairs of sort I think you may have to do.

I do have a way - but not when paralleling strings to the same SCC. Actually that's not true - I can always disconnect from the combiner one of the strings.
I am leaning towards putting a 2nd string of 6 panels below the 6 that are producing the most. Struggling with the space/angle. Might only be able to fit 4. But I am happy to test anything. I don't mind moving panels around when they're leaning against a wall or on the ground. I also wonder if panels mounted horizontally vs. vertically plays a factor. Right now all panels oriented same way (vertically) but 6 of them are flat vs. angled. they produce much less, but they are also the ones currently in the shade.
I have a stack of 13 more panels I'm not even using. Happy to run them anywhere and report back. Just need some direction.

 

[WorldwideDave]

More smaller (but still functional voltage wise) arrays is the way I solved a lot of my shading issues. Cost is more wire, connectors and breakers pretty much.

The overall best solution to shading is micro inverters But that's expensive.

I have lots of parallel connectors. I have one empty DC breaker box and rapid shutdown box not being used. But MC4 cabling I am running out of. And yes, 8 gauge at 50-100 feet is adding up fast. I could have easily had 30kWh in battery for what I have in cabling, fuses, DC breakers, rapid shut down devices and 3 different MPPTs now.
Friend has a box of unused micro-inverters. I think their purpose is to boost voltage/output, and you connect to each panel? I'd have to test each one. Been sitting in a box outside a long time.

 

[WorldwideDave]

You may think that but your in CA and they definitely have codes where you are located ( zip code shows Manhattan Beach CA ), you need to read up on NEC2020, building code is 2022 and the state as soon to be NEC2023. This would be where your building department is.

This is an unpermitted hobby I'm doing in my back yard. I'd love to go on roof, but not going to. have not touched the house's old panel at all. Do not want to involve them and not doing anything code compliant. I plan on building a home completely off-grid in the future on a beach somewhere. I'm learning here before attempting anything like that there.

 

[Crowz]

Lets use one of mine to show what I'm doing.

one array is sitting in a spot that is shaded until 10:30am. EVERYWHERE else has sun from 7:30am onward.
The array in the morning shaded area has its own scc. Not paralleled but on its own. Since it goes to the same battery bank it contributes when it can but it doesn't hinder anything when it can't.

Now in a roof setup I would do this.

Panels 1 thru 12 on a roof.

1 2 3 4 5 6

7 8 9 10 11 12

Now add a rogue tree.

As its shadow goes across the roof we loose 1 and 7 first

Then it gets into of 2 and 8 also.

Then 1 and 7 get sun again and 3 and 9 get shaded.

So the ultimate setup would be 6 controllers. 1,7 1st controller, 2,8 2nd controller etc. But this is kind getting ridiculous cost wise.

But 1-3 and 7-9 on a controller and then 4-6 and 10-12 on a 2nd controller actually increases your daily output.

For me its all about getting the batteries recharged so dividing things up helps ALLOT. Winter time is where this really pays off.

Summertime not so much since the total output for the day handles it all.

You know where the shading is and how it moves so you would have to figure out how to divide it up the best.

 

[Chuck E.]

Since I do not know your lot layout here are a few things to think about in how you set them up
1x Array (or string) of your panels will have about 8 amps of current
If you parallel two strings they need to both be exactly the same number of panels and amps will be about 16 amps (double when parallel)
If you parallel three strings it will be triple about 24 amps

I dont know victron but the numbers you posted look like some of the mppts will operate at 150 volts at 100 amps? or even 100 volts at 20 amps?

If this is correct splitting up to three panel arrays could be a good thing. 3 x 3 panel arrays would fit on the smaller mppt.

The point of parallel is just for example, if you have what I said above, 3 arrays of 3x panels and if a small amount of shading hits only one of the arrays then you would be only losing 50% of power on THREE panels, the other two 3 panel arrays will still function at full power.

I could add more but its more about principle than exact application that I'm trying to say here.

 

[WorldwideDave]

Ok. Money is an object.

It is not credible that rooftop solar is outlawed, especially in CA.

I-I-I am out of ideas... actually I have a couple but they would be unacceptable.

See you are in seattle. Lived on bainbridge island way back in the day for 15 years. Loved it. Miss it some days, but I like sunshine more.
yes money is an object.
But you raise a good point. I see 545W panels for $140 bucks all the time. They are much bigger than these panels, though, and might not fit/work. But I have considered the fact that instead of having 7 panels mounted vertically (1400W) I could probably fit 3 panels horizontally (1600W) and achieve same result. That would cost me under $500, but I have to weigh things like "do I want fewer panels on the array, or do I want to have another 200Ah of battery". Battery/storage always wins over spending more on panels. Heck the rack to mount panels cost more than my panels did.

 

[quantum`]

Plant a telephone pole and fix the panels to it in landscape, going up 20' high, lol.

 

[WorldwideDave]

Lets use one of mine to show what I'm doing.

one array is sitting in a spot that is shaded until 10:30am. EVERYWHERE else has sun from 7:30am onward.
The array in the morning shaded area has its own scc. Not paralleled but on its own. Since it goes to the same battery bank it contributes when it can but it doesn't hinder anything when it can't.

Now in a roof setup I would do this.

Panels 1 thru 12 on a roof.

1 2 3 4 5 6

7 8 9 10 11 12

Now add a rogue tree.

As its shadow goes across the roof we loose 1 and 7 first

Then it gets into of 2 and 8 also.

Then 1 and 7 get sun again and 3 and 9 get shaded.

So the ultimate setup would be 6 controllers. 1,7 1st controller, 2,8 2nd controller etc. But this is kind getting ridiculous cost wise.

But 1-3 and 7-9 on a controller and then 4-6 and 10-12 on a 2nd controller actually increases your daily output.

For me its all about getting the batteries recharged so dividing things up helps ALLOT. Winter time is where this really pays off.

Summertime not so much since the total output for the day handles it all.

You know where the shading is and how it moves so you would have to figure out how to divide it up the best.

Thank you. Yes I could see where having 12 panels on a roof with 6 SCC would be very costly.
I am doing my best to track where the shading is during the day, during the year. I've only been monitoring for 3 months or so. By 6 months I'll have a better idea. Just isn't something you pay attention to if you don't have solar and aren't considering it. Now that I have these panels stacked up, I want to use them.

 

[WorldwideDave]

Plant a telephone pole and fix the panels to it in landscape, going up 20' high, lol.

ironically, there is a power pole that I didn't even notice was there between 4 of the properties in the corner. That pole's shadow crosses all 7 of my panels in one array and 2 of the 6 in the other array. Didn't even notice it was there until after I put up the panels. Didn't realize it might impact production. The shadow it makes is about 6-8" wide, but slowly passes from my top producing panels to my least producing array. It has a transformer at the top, too - so at one point this big black blob shadow passes by 2 of the panels.

 

[Chuck E.]

I have lots of parallel connectors. I have one empty DC breaker box and rapid shutdown box not being used. But MC4 cabling I am running out of. And yes, 8 gauge at 50-100 feet is adding up fast. I could have easily had 30kWh in battery for what I have in cabling, fuses, DC breakers, rapid shut down devices and 3 different MPPTs now.
Friend has a box of unused micro-inverters. I think their purpose is to boost voltage/output, and you connect to each panel? I'd have to test each one. Been sitting in a box outside a long time.

If your only running 8 amps from an inverter to your back yard (I assume a subdivision with small back yard) 8 amps less than 50 feet you can easily downsize to 12ga wire, mabe even 14ga. I'm sure somebody with a wire chart handy can chime in here. HOWEVER this is if you run individual wires to each array, if you parallel AT THE PANELS and return to the inverter through one wire you do need 8 or 10 ga.

 

[Crowz]

Thank you. Yes I could see where having 12 panels on a roof with 6 SCC would be very costly.
I am doing my best to track where the shading is during the day, during the year. I've only been monitoring for 3 months or so. By 6 months I'll have a better idea. Just isn't something you pay attention to if you don't have solar and aren't considering it. Now that I have these panels stacked up, I want to use them.

Oh no doubt on not knowing where the shading is right off the bat. I planned out where to put my panels all summer long. That went out the window when winter set in. I wasn't even close to where they needed to be

 

[WorldwideDave]

Oh no doubt on not knowing where the shading is right off the bat. I planned out where to put my panels all summer long. That went out the window when winter set in. I wasn't even close to where they needed to be

I don't want to un-rack anything. I think smart people would put huge casters on their racks and then roll them around. I think some have pulled via tractors.

 

[Chuck E.]

I do have a way - but not when paralleling strings to the same SCC. Actually that's not true - I can always disconnect from the combiner one of the strings.
I am leaning towards putting a 2nd string of 6 panels below the 6 that are producing the most. Struggling with the space/angle. Might only be able to fit 4. But I am happy to test anything. I don't mind moving panels around when they're leaning against a wall or on the ground. I also wonder if panels mounted horizontally vs. vertically plays a factor. Right now all panels oriented same way (vertically) but 6 of them are flat vs. angled. they produce much less, but they are also the ones currently in the shade.
I have a stack of 13 more panels I'm not even using. Happy to run them anywhere and report back. Just need some direction.

90 degrees to the sun (or tangent) is maximum output, whatever angle that has to be on the ground depends on the location of the sun.

 

[WorldwideDave]

If your only running 8 amps from an inverter to your back yard (I assume a subdivision with small back yard) 8 amps less than 50 feet you can easily downsize to 12ga wire, mabe even 14ga. I'm sure somebody with a wire chart handy can chime in here. HOWEVER this is if you run individual wires to each array, if you parallel AT THE PANELS and return to the inverter through one wire you do need 8 or 10 ga.

Every day I am testing my system with about 1850 watts consistently, or just over 150 Amps, to run the pool equipment hard and fast to see what the system can handle. While I do have 2600W rack mounted array up (7x200; 6x200), I think the most I've produced at one time with all the shading I have at is about 1300W total across all 3 MPPTs. Plus older used panels, but really it's the shading and angles, I know it. The 6 panels (2s3p) angled correctly do almost 850 W at noon.

 

[Chuck E.]

A lot of stuff got said in a short time here. After back reading some of the input, I think your on the right track, essentially parallel and smaller counts on arrays benefit shading issues. Any array that has shading will be killed so any way you change that or isolate the shaded (or partially shaded through the day) stuff you will get overall higher KwH's per day. Not knowing your exact situation, I have done some temporary arrays back in the day with just THNN wire vs PV wire since it was "temporary", with no problems. Its cheaper. Maybe that can help get more wire within your budget ATM. I just think you will have a lot of wire to roll up on grass cutting days