Cracked cell
A cell with visible thermal evidence of cracking — current crowding through the intact portion of a fractured cell. Small today, but cracks propagate with thermal cycling.
Thermal signature
An irregular warm region at part-cell scale, often wedge- or band-shaped where an isolated cell fragment has stopped conducting and the remaining area runs harder. Weaker and less sharply bounded than a mature hotspot, and confined within a single cell's outline.
Typical ΔT
5–15 °C above neighbouring cells across the affected part of the cell (typical industry interpretation aligned with IEC TS 62446-3).
What causes it
- Microcracks from manufacturing, transport or rough handling
- Hail or debris impact below the glass-breakage threshold
- People stepping on modules during installation or maintenance
- Thermal cycling and wind loading propagating existing microcracks
Power impact
Initial loss is small — often under a percent of the module — but cracks grow with thermal cycling, and an isolating crack can push the cell into hotspot territory or force its substring into bypass. The trajectory, not the snapshot, is the concern.
Recommended action
Monitor and re-inspect
Monitor. Record the finding with its location and ΔT, compare it against the next inspection, and escalate to module replacement if the ΔT grows, the affected area spreads, or the substring starts bypassing. Consider an EL test where crack extent matters for warranty claims.
Frequently asked questions
How do cells crack if the glass is intact?
Silicon cells are far more brittle than the tempered glass above them. Flexing during transport, a knee on the laminate, hail that the glass shrugs off — all of these can fracture cells invisibly. The damage only becomes apparent electrically, which is exactly what thermography and EL imaging detect.
When does a cracked cell justify replacing the module?
When the trend turns: rising ΔT between inspections, a growing affected area, or the substring dropping into bypass all indicate the crack is isolating more of the cell. A stable, low-ΔT crack on a producing module is usually watched rather than replaced.
Related anomalies
Suspect cracked cell on your site?
Fly the site, upload the thermal frames, and get every module graded against this taxonomy — severity-ranked, with flagged imagery and per-module locations. Quote your site size in seconds.
ΔT figures and abnormality classes on this page describe the typical industry interpretation aligned with IEC TS 62446-3 — indicative engineering guidance, not normative text from the specification. Temperature differentials are only meaningful when captured at ≥600 W/m² irradiance (per the TS) and verified on site before repair work.