Observant friends may notice that several small diodes (bypass diodes) are usually installed in parallel in the junction box of solar panels. Today we will talk about why it is necessary to install bypass diodes? What is the purpose of this seemingly insignificant small component?
When team members go on strike: hot spot crisis
Imagine your solar panel is like a “power production team” composed of many small solar cells connected in series. When all team members (batteries) are in good condition, the current flows smoothly and the power generation is efficient.
But the problem arises, if one of the ‘team members’ unfortunately trips – such as being covered by a leaf, bird droppings, or shadow – the situation takes a sharp turn for the worse. Because the battery works in series, this obstructed battery cannot generate normal current and instead becomes a high resistance obstruction point. At this point, the strong current generated by other normal batteries is forced to pass through this “bottleneck”, resulting in concentrated heating at that location, which is the dangerous “Hot Spot Effect”.
Hot spots not only permanently damage the unlucky battery and its surrounding materials, greatly reducing the power generation efficiency of the entire board, but in extreme cases may even pose a fire hazard.
The savior appears: bypass diode
At this point, the bypass diode plays a crucial role! It is usually cleverly connected in parallel at both ends of a small group of batteries (such as a substring consisting of 20-24 batteries).
Under normal circumstances, the diode is in the “off” state, and the current flows obediently through the battery pack, making the diode appear transparent.
When a fault occurs, when a battery is obstructed causing a voltage drop in its group, the bypass diode will immediately sense and “turn on”, providing a low resistance “emergency bypass channel” for the current instantly. The current then cleverly chose this easy path, bypassing the problematic battery group directly. This clever design is like killing two birds with one stone:
① Avoiding hot spot effect: The current no longer accumulates at the blockage point to generate heat, protecting the battery and components.
② Saving power generation efficiency: Other unobstructed healthy battery groups on the solar panel can still output electricity normally, minimizing overall losses caused by local issues.
This small bypass diode, utilizing its unidirectional conductivity (based on the PN junction principle), silently safeguards the safety and efficiency of solar panels. It prevents local failures from dragging down the entire system and is the unsung hero that ensures the long-term, safe, and reliable operation of your clean energy investment. Without it, local shadows could mean high maintenance costs and even safety hazards.
