On an IV curve, increased series resistance makes the section between the maximum power point and Voc less steep. It also shows up as a lower fill factor and a more rounded knee. At array level, check first for damaged or undersized cables and for poor connections at module or array interconnects. A long cable run can produce the same curve shape, so repeat the trace closer to the array if you suspect this. Inside the module, the extra resistance can come from failing cell interconnects or junction box connections, from metallization corrosion, or from cell cracks. An infrared scan helps locate high-resistance faults. Defective connectors and poorly soldered interconnects show up as local heating, even before the electrical change can be measured. Corrosion is often visible to the eye and comes with a lower Isc. Interconnect failures and cracks are hard to see, so use EL imaging to find dark regions or crack lines. With cracked cells, most of the power loss comes from lost current rather than from series resistance.
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observed_asc1 verified · fact Shallow IV slope near Voc
Higher series resistance makes the IV curve less steep between Vmpp and Voc. Long cable runs can produce the same shape, so the model should account for them or the test should be repeated closer to the array.
sec=D.6 h=f87aef72de6fverified by: joshuahamsaverified on: 2026-10-20
c2 verified · fact Reduced fill factor
Seen with metallization corrosion (together with lower Isc), with early-stage interconnect failure and with cell cracking.
sec=h7 h=7c7e8aa5f488sec=h5 h=5f9cbfc08864sec=2.3.3 h=b6c82133fe8cverified by: joshuahamsaverified on: 2026-10-20review note: support check: partial - Corrosion with lower Isc and interconnect failure with fill factor decrease are stated, but cell cracking is only described with a 2% absolute FF drop, and 'early-stage' interconnect failure is only loosely matched (stage 1).
c3 verified · fact Rounded IV curve knee
Reported for interconnection failures where redundant interconnects still carry the current.
sec=h8 h=9f1fbad653f1verified by: joshuahamsaverified on: 2026-10-20
c4 verified · fact Reduced Vmp/Voc ratio
In cracked-cell modules, a falling Vmp/Voc ratio points to series resistance. Light and dark IV curves, or light IV curves at two intensities, measure it best.
sec=2.3.3 h=b6c82133fe8cverified by: joshuahamsaverified on: 2026-10-20
c5 drafted · lead Hot electrical connection
In the first phase of a connector failure, extra resistance produces heat that thermography can show, even when the electrical change is too small to detect.
sec=D.6 h=f87aef72de6fsec=h6 h=e7691a95e9d7c6 drafted · lead Localized IR hotspot
Poor solder bonds in cell interconnects dissipate more power and heat up locally.
sec=h8 h=9f1fbad653f1typical_power_lossc7 disputed nominal 0.1 PERCENT
Conditions: Per cut cell interconnection in cells with 4 busbars, from a series resistance increase of about 1%
sec=h5 h=5f9cbfc08864review note: possible conflict with c8 (same source; check the conditions)conflicts with: Increased series resistance (c9)
Conditions: Per cut cell interconnection in cells with 3 busbars (less redundancy)
sec=h5 h=5f9cbfc08864review note: possible conflict with c7 (same source; check the conditions)conflicts with: Increased series resistance (c9)
c9 verified · fact nominal 2.6 PERCENT
Conditions: Part of a 10% module power loss from induced cell cracking that is caused by a series resistance increase of 0.5 Ohm cm2
sec=2.3.3 h=b6c82133fe8cverified by: joshuahamsaverified on: 2026-10-20review note: reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement
presents_as c13presents_as c13presents_as c14presents_as c15presents_as c11