Diodes ‐ Bypass vs. Blocking Diodes

Today, almost every solar panel has BYPASS diodes.

Older Panels (3-4 yrs ago) did not have them: One shaded panel could stop production of the complete string.

Here is a nice video explaining the difference between the old and new solar panels (from 5 years ago, when diodes were a rarity): Solar Panels and Shade = Bypass Diodes

There is however something more: BLOCKING Diodes!

Below is a good example of where the could be used AND WHY THEY ARE NOT NEEDED! Shaded and non-shaded solar string in parallel. See what happens.

Important notice: The fuses this (crazy German) guy is playing with, THEY ARE NOT SUPPOSED TO BE SWITCHED UNDER LOAD! Do not do this at home...

The most important sentence you should know: Current always goes through the point of lowest resistance - And this is your charge controller! It is practically impossible that one string will be so shaded that the other string will manage to push electricity through it (instead of sending it to the charge controller).

However what happens if one of your solar panels fails and shortcuts (and the panel's diode does not work)? Then you may have a new point of lowest resistance! Here is a short video explanation about how things can go terribly wrong in a parallel connection: Solar Panels and Shade = Bypass Diodes

And here is a video explaining the difference between Bypass vs. Blocking diodes: Bypass vs. Blocking Confusion and why solar panels DO NOT act as a diode!