Help CenterPerformance & Lifetime
Hotspot risk and bypass diodes
A hotspot occurs when a shaded or faulty cell, instead of producing current, starts dissipating it as heat — neighboring functional cells push current through it in reverse bias. Local temperature can exceed 150°C.
Bypass diodes, built into the panel's junction box (usually 3 diodes per panel, one per cell group), short-circuit the affected group once reverse voltage crosses a threshold, limiting heat dissipation.
A failed bypass diode (often invisible to the naked eye) removes this protection. An old panel, one damaged by lightning, or a low-quality one can have failed diodes with no visible sign until a hotspot appears.
| Sign | Interpretation |
|---|---|
| Local discoloration or burn mark on a cell | Active or past hotspot — thermal inspection recommended |
| Visible hot spot on thermal camera, no visual damage | Bypass diode likely functional, shading needs fixing |
| Burning smell, deformed junction box | Fire risk — take offline immediately |
Periodic thermal inspection (infrared camera, even a smartphone with a thermal module) catches a hotspot before it becomes a fire risk, especially on installations over 5 years old.
Common mistakes
- Ignoring recurring shade on a panel corner because "it's such a small area"
- Never thermally inspecting an aging installation
- Continuing to operate a panel with a visibly deformed or discolored junction box
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