Mottled shade on solar panels not good?
I may have misunderstood, but I read something while on a trip (I can’t remember where I read it) that left me with the impression that it was damaging to the diodes on my panels to leave them operati...
Forum Discussion
BFL13 wrote:Simple, with PWM shading on a single cell will take out that whole column, the voltage for that panel will drop below what's needed to charge the battery, so you effectively lose the power from the whole panel.mike-s wrote:
It won't damage the diodes. They're there to bypass shaded strings of cells. But, especially if you use a PWM controller, shade on even a single cell can stop all power output from that panel for as long as it's shaded. But nothing gets damaged.
What does PWM vs MPPT have to do with it?
With MPPT (assuming you have 2 or more panels in series, or a higher voltage panel), losing a string just results in a partial loss from the panel, the remaining columns continue to contribute.
e.g. 2x 100W "12V" panels wired in parallel to a PWM controller. Shade one cell, you lose the output from the entire panel, and instead of 200W you now have 100.
The same 2x 100W "12V" panels wired in series to a MPPT controller. Shade one cell, you lose 1 column (commonly 3 per panel). The diode bypasses that column, but the other 2 continue to contribute because the voltage is still above the minimum needed by MPPT. You only lose 1/6 of the potential power, and instead of 200W you get 167.
(I probably should have said "column" in my first response, "string" more often refers to series panels)
