Will this mixed solar panel configuration work

Off Gridin' It

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I run a facebook group dedicated to teaching solar. Typically i advice against mixing solar panels because most of the time the efficiency losses are to high. So i will advice multiple charge controllers.

However this diagram was posted on my Facebook group. (This is NOT my design).
If you follow the math to it’s conclusion I get 98.44% efficiency.
However if you look closely at the diagram you will see he has mixed configuration creating sort of a 2P/2S/2P configuration.

My question is will this work. He has basically done one parallel string (2P) and then a series/parallel string (2S/2P). Then taken all that and put those in parallel as well.

Will this work? Theoretically the math comes out but can the Smartsolar 150/70 understand what is happening here and look at it as just a 2P config or will it freak out?

Thanks for your help.
 

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FilterGuy

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In general, if mis-matched panels are in parallel, it is best if the voltages are the same. If mis-matched panels are in serial, it is best if the currents are the same.

The arrangement has 4 strings. Two running at 215W and 37.4V and two running at 80W and 36.V. The voltage is not too far off but it is hard to predict what the result of having the mismatch will be.

The Smartsolar will try to adjust the operating point to maximize power. This means none of the panels will be operating at the Max Power Point(MPP). Since the current from the 215W strings will be so much larger than for the 80W strings, the operating power point will probably be much closer to the MPP of the large panels than for the smaller panels. This implies the voltage will be high for the smaller panels. Since the power drops off quickly as the voltage goes above the MPP, the reduction of output on the smaller panels could be significant. Meanwhile, the large panels will be operating at a voltage that is slightly less than it's MPP. The power rolls off slower for voltages under the MPP so the % impact to the large panels will be less.... So.... will the loss on the big panels be compensated by the addition of the small panels? Hard to say.
 

Porch

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FilterGuy has it right. This will work, but not be as efficient. However that said, solar panels are cheap now (if you shop around). So the efficiently losses from mismatched panels may not offset the cost of another charge controller and extra wiring.
 

sunshine

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Smartsolar 150/70 understand what is happening here and look at it as just a 2P config or will it freak out?
Break it down to actual cells. You have 4P72S
Since all the values are reasonably close the cc mppt wont know the difference and see this as 4P
 

Off Gridin' It

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FilterGuy has it right. This will work, but not be as efficient. However that said, solar panels are cheap now (if you shop around). So the efficiently losses from mismatched panels may not offset the cost of another charge controller and extra wiring.
Read my original post. This is not my design. I am curious if this usual configuration will be an issue for the charge controller. I recommended to the person that designed this configuration (Which is a beginner) to install two charge controllers.
 

FilterGuy

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Read my original post. This is not my design. I am curious if this usual configuration will be an issue for the charge controller. I recommended to the person that designed this configuration (Which is a beginner) to install two charge controllers.
The charge controler will work, but the gain from adding the smaller panels is questionable. You are correct that the best answer is to use two separate controllers.

If he proceeds with the design, ask him to test the output with and without the smaller panels. The result will be interesting.
 

Porch

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Read my original post. This is not my design. I am curious if this usual configuration will be an issue for the charge controller. I recommended to the person that designed this configuration (Which is a beginner) to install two charge controllers.
It won't be an issue at all. There is questionable benefit of still using the small 40 watt panels, but electrically, it will be fine.
Assuming the designer has the panels already, and there is not more panels then indicated, then I would even call into question in spending the extra money on a second charge controller for what might be little gain in efficiency.

I would like to see fuses on each panel string tho.
 

Off Gridin' It

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It won't be an issue at all. There is questionable benefit of still using the small 40 watt panels, but electrically, it will be fine.
Assuming the designer has the panels already, and there is not more panels then indicated, then I would even call into question in spending the extra money on a second charge controller for what might be little gain in efficiency.

I would like to see fuses on each panel string tho.
Yes he already has the panels. I did advise him to fuse. Thanks!
 
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