What Are By-Pass Diodes in Solar Panels?
By-pass diodes play a crucial role in solar panels made up of individual solar cells, especially when cells are shaded or covered with dirt. But how exactly do they work?
Most crystalline solar panels, which dominate the market, consist of numerous individual solar cells connected by electrical wiring. Standard panels typically have 60 or 72 cells, arranged in a 10x6 or 12x6 configuration. SunPower panels, for example, have slightly more—usually 13x8 cells (totaling 104).
These cells are connected in series along the length of the panel, as illustrated in the diagram (with the red line indicating the flow of electricity).
Electricity flows through all the cells, but what happens if one cell is damaged and no longer conducts electricity? The entire panel—or even the whole system—could stop generating power.
Overflow Valve
That’s why all solar panels are equipped with by-pass diodes, which act like overflow valves. If the current gets blocked at one point, the by-pass diode provides an alternative route, allowing electricity to keep flowing.
Typically, each panel contains three by-pass diodes, as shown in the diagram. The black arrows indicate the by-pass diodes.
Blocking Effect
If a single cell is damaged, electricity won’t flow through the entire panel as usual. Instead, one-third of the panel will be bypassed, as shown in the diagram. The red cross marks the defective cell, and the red line shows the rerouted current.
By-pass diodes are incredibly useful. Without them, even a minor defect could severely impact energy production. In some cases, an entire panel can be bypassed if electricity is rerouted through all three by-pass diodes.
By-pass diodes also play a crucial role in mitigating shading issues—something we’ll explore in more detail in another article.
