TechnicalUp to date · Jan 15, 2026
Junction Box
An enclosure on the back of a solar panel containing bypass diodes and electrical connections where the panel output cables originate.
Why It Matters
Junction box quality affects long-term reliability. Water intrusion into a faulty junction box is a common cause of panel failure and potential fire hazard.
Related Terms
Bypass Diode
A small electronic component inside solar panels that allows current to flow around shaded or damaged cells, preventing them from becoming resistive loads that heat up and reduce output.
Backsheet
The rear protective layer of a solar panel, typically white or black polymer film (Tedlar, TPT). Provides electrical insulation, moisture protection, and UV resistance.