After receiving great information about what type diodes to fit to more than one solar panel. I Thankyou. HOWEVER , after reading extra articles and trying to understand about fitting extra solar panels (ie: adding extra power generation) in this esteemed magazine. I can not find any comments about the importance/need to fit a blocking diode to prevent a panel that is in the shade drawing power from the other solar panels in the one setup.
Some time ago I read an item on the Redarc site which stated they no longer bothered with diodes on their solar panels. I assume it would still be there.
My opinion informed by my reading and experience. It is difficult to find any current information that is definitive but they were always recommended previously. Newer panel have sealed junction boxes so who knows what is in there.
I believe if you are using 12V panels and batteries then you could probably not bother with blocking diodes when using parallel panels without worry. Redarc say that they do not fit them to their panels. https://www.redarc.com.au/forum/discussion/664/blocking-diodes Of course you must use a controller/regulator (which normally prevents reverse current).
If you use panels in series then the voltages are higher, so series strings in parallel do give higher voltages for more reverse leakage. And at 24V doubled again. So the reverse current under adverse conditions of one string in shade and high panel temperatures may cause much higher reverse currents that could lead to damage. It certainly happens to flexible panels sometimes I believe, even used as only single panels in parallel and some are not recommended for parallel use at all. But in the heat on the flat roof top thermal runaway may destroy semiconductors as we know.
Sooo what is the answer. A good sized schottky diode is cheap and easily fitted. Why not ! Make sure it is over rated x2 or more and has some air space for cooling.
AIUI solar panels are constructed with one or more strings of cells connected in parallel. I guess it would be unlikely for one string to be shaded and the other not, but if this were to happen, then there would be no diode protection.
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First off, do you mean blocking diodes or bypass diodes, from your description it would appear your referring to blocking diodes.
I have found blocking diodes are not required if your using panels or strings with similar OCV specifications.
