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Solar peeps out there:

I have a section of roof that will take 9 panels. The 3 at the end are shaded by trees more than the other 6 til the late afternoon.

Should I run them separately as a string of 3 in series and the other 6 in series, then parallel those with branch connectors?

Just do the 9 together and accept the overall loss while those 3 are shaded? Or something that I’m not thinking of?

There are 3 other sections of roof that are more straight forward with 6-9 panels per string. They’ll all meet in a combiner box and run to (2) 6500w Inverter/charge controllers if that makes any difference. Thanks for any help!

#grownostr #solar #asknostr

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Discussion

Dark Sky Homestead and Herbs 2y ago

Assuming your panels have bypass diodes as most do, they bypass the under performing panel sections to prevent current from stopping.

The other concern is paralleling unequal panels in series. When paralleling they will match your lowest voltage. You said that other strings will be 6-9 panels if you can make them 6 panel strings and make more strings that can be placed with no shading then that would be best.

The lower voltage from the short string will have a higher impact on decreased current then the partial shading. If making more strings, then make sure the wire size from the combiner to the controller can handle the amps.

https://youtu.be/7CMe1oRXPFA

Dark Sky Homestead and Herbs 2y ago

Just an FYI, that's from my husband who is a journeyman commercial/ industrial electrician. Obviously not me!

Stacking Functions 2y ago

That makes a lot of sense. Tell him thank you!

I’m going to run this string as 9 in series, another 9, one 7 and one 6. Hopefully I can combine the 9&6 to one inverter and the 9&7 to the other with no problem.

I’ll probably run them to a 4-2 combiner box for lightning protection, fuses and disconnects.

Looks like watts24/7 has decent combiner boxes. If he has other suggestions please lmk.

Thanks again!

White The Crow 2y ago

Basicly if you have shaded pannels ina String Bypass diods will reduce the voltage of the string by the voltage of a pannel.

For better understanding with some basic numbers. A pannel Has 40V and 10A.

9 pannel no shade. 360V 10A

9 pannel 3 shaded. 240V 10A

9 pannel 3 shaded. 360V 1A

If you now have 2 Strings 9 pannel ea on one string 3 shaded. In parralel 360V 11A

Maybe 260V 18A if the mppt is controlling correctly

If you go for more strings in parralel do 3x6 pannel (string the shaded in one string)

Be aware that you will drastically increase the A on the mppt. Overpanneling on A only with very good cooling on mppt not recomanded.

Best case string out shaded pannels maybe use a microinverter for each pannel of the shaded ones.

If you charge a battery use a second chargecontroller for shaded pannels.

The drop in power for shaded pannels results havily on Amps. Eaven some light clouds can result in 10-25% power drop.

If you have still some questions feel free to ask.