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What is a bypass diode?

On most solar panel datasheets you will find the section “Diodes” followed by something along the lines of “3 Bypass diodes serviceable” found on Peimar modules’ datasheet or “IP67 / 4 diodes” found on Solaria modules’ datasheet.

What is a “diode”?

Diodes are basic electronic devices that function to ensure power flows in one direction only. In solar there are two types of diodes: “bypass diodes” and “blocking diodes.” They’re essentially the same. Bypass diodes are between solar panels, while blocking diodes are between the panels and the external load, controller or batteries that the panels are connected to. The majority of solar panel manufacturers include both types of diodes in their modules, which is why you don’t see any on sale at RENVU.

Aside from helping the current flow in one direction, bypass diodes also help solar panels mitigate shading issues.

The problem:

Shade falls on part of your solar panel, and the entire panel stops producing power.

Bypass diodes to the rescue:

Bypass diodes allow current to pass around the shaded cells and supply power at a reduced voltage rather than none at all. So if you have 3 bypass diodes, and shade falls in a small segment at the top of the panel, the series of panels’ production is reduced to 2/3rds it’s usual (imaging the solar panel split into 3 parts, with one part not functioning due to the shade). Note that diodes do not replace the benefits of microinverters and optimizers, which prevent the entire string being affected by shading issues.