Solar Panel Micro-Cracks — Causes, Detection & Impact on Performance

What Are Micro-Cracks?

Micro-cracks are tiny fractures in solar cells that are invisible to the naked eye. They occur from mechanical stress during manufacturing, transport, or installation. While not immediately dangerous, micro-cracks can grow over time due to thermal cycling, reducing cell output and potentially causing hot spots.

Common Causes

• Transport damage: Vibration, impacts, or improper stacking during shipping
• Installation handling: Stepping on panels, dropping them, or over-tightening clamps
• Thermal cycling: Repeated heating and cooling expands micro-cracks over years
• Hail damage: Large hailstones can create new micro-cracks
• Snow/wind loads: Excessive mechanical load can stress cells

Detection Methods

Electroluminescence (EL) Testing

The gold standard for micro-crack detection. An EL camera captures images of the panel under reverse current, revealing cracks as dark lines or areas. All LONGi panels undergo EL testing at the factory before shipment.

Visual Inspection

Severe cracks may appear as visible lines or "snail trails" (silver-coloured tracks following crack lines). However, most micro-cracks are only visible under EL imaging.

Impact on Performance

Not all micro-cracks cause immediate problems. Small cracks that do not disconnect cell portions may have negligible impact. However, cracks that isolate cell areas can cause:

• 5–15% power loss in the affected cell
• Hot spots from current mismatch
• Accelerated degradation over time
• Potential warranty claims if output drops below guaranteed levels

Prevention

• Use panels with half-cut cells (LONGi Hi-MO) — smaller cells are more resistant to cracking
• Follow manufacturer handling guidelines during installation
• Use appropriate mounting clamp positions (typically at 25% and 75% of panel length)
• Never walk on panels
• Store and transport panels vertically, not flat

Frequently Asked Questions

Are micro-cracks covered by warranty?

Micro-cracks present at delivery (from manufacturing) are covered. Cracks caused by improper handling, installation, or external damage are not. LONGi's rigorous factory EL testing minimises the chance of shipping panels with pre-existing cracks.

Do half-cut cells crack less?

Smaller cells are more resistant to thermal and mechanical stress. Half-cut cells in LONGi Hi-MO panels are more robust than full-size cells.

Can micro-cracks be repaired?

No. Once a cell is cracked, it cannot be repaired. However, if the crack does not isolate significant cell area, the panel can continue operating effectively.