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Old 07-07-2011, 14:31   #76
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Re: Four Solar Panels - Parallel , Series or Series-Parallel

in my view , two sets of serial panels, each with their own MPPT controller would be best, Paralleling with MPPT where one of the panels is in shade usually causes the controller to pick the wrong Vmp.


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Old 07-07-2011, 14:35   #77
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Re: Four Solar Panels - Parallel , Series or Series-Parallel

In that thread they agree with my view that if you get any shading, you're better off with either all in series or all in parallel, but no series-parallel combinations.

If you shade 1 cell on 1 panel in a 3x2 setup, you might loose 33.3% (2 panels of your power generation. If you do this with a 1x6 string you loose 16.6% (1 panel) if your panels have no internal diodes or even less if they do (only the section with the shaded cell).


Originally Posted by jaredko View Post
Demeter: Nope, sorry. All parallel sets will need to operate at the same voltage (unshaded panels are still running at max voltage). As shaded sections are bypassed, they no longer contribute, so the unshaded, unbypassed cells will be driven to a higher voltage, higher than the open circuit voltage, meaning that no current is produced, and that pair has no output.

Here's a thread with more detail and some great calculation. Running that same calculation for a string with only 2 panels in it shows that the cell voltage is pushed past the Voc.

Two Strings in Parallel with Unequal String Voltages - Solar Electric Power Discussion Forum by Northern Arizona Wind & Sun

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