Development of Fixtures and Methods to Assess the Durability of Balance of Systems Components

David Miller, Greg Perrin, Kent Terwilliger, Joshua Morse, Chuanxiao Xiao, Bobby To, Sona Ulicna, Chun-Sheng Jiang, Laura Schelhas, Peter Hacke

Research output: Contribution to journalArticlepeer-review

2 Scopus Citations


The degradation of photovoltaic (PV) balance of systems (BoS) components is not well studied, but the consequences include offline modules, strings, and inverters; system shutdown; arc faults; and fires. A utility provider experienced a ∼30% failure rate in their power transfer chain, originally attributed to branch connectors. Field-failed specimen assemblies were, therefore, examined, consisting of cable connector, branch connector, and discrete fuse components. In this study, unused field-vintage specimens are examined using a benchtop prototype fixture to identify the most influential environmental stressors on BoS components as well as the effect of external mechanical perturbation. The prototype fixture was used to develop a perturbation capability for future use in the combined-accelerated stress testing chamber. The benchtop experiments were also used to develop the in-situ data acquisition of specimen current, voltage, and temperature. A significant increase in operating temperature (∼100 °C from ∼40 °C) and a different failure mode (arcing at the metal pins rather than overheating of the fuse filament) were observed promptly once periodic mechanical perturbation was applied. The current at failure was decreased from 35 A (measured for static specimens, with failure occurring in the fuses) to 15 A (for tests with mechanical perturbation, with failure at the male/female metal pin connection). After initial examination using X-ray computed tomography, the external plastic was machined away from failed specimens to allow for failure analysis, including the extraction of the internal convolute springs for morphological examination (optical and electron microscopy). Chemical composition analysis included energy-dispersive X-ray spectroscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy.

Original languageAmerican English
Pages (from-to)1341-1348
Number of pages8
JournalIEEE Journal of Photovoltaics
Issue number6
StatePublished - 1 Nov 2022

Bibliographical note

Publisher Copyright:
© 2011-2012 IEEE.

NREL Publication Number

  • NREL/JA-5K00-82867


  • Balance of systems (BoS)
  • branch connector
  • combined-accelerated stress testing (C-AST)
  • differential scanning calorimetry (DSC)
  • durability
  • Durable Module Materials Consortium (DuraMAT)
  • energy-dispersive X-ray spectroscopy (EDS)
  • Fourier transform infrared spectroscopy (FTIR)
  • fuse
  • reliability
  • scanning electron microscope (SEM)
  • X-ray computed tomography (XCT)


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