Long-term behaviour of PV connectors

Millions of them are installed on Swiss rooftops – connectors for photovoltaic (PV) systems. The international company Stäubli Electrical Connectors AG, with headquarters in Allschwil, is a global market leader in PV connectors with its MC4 brand product. It has tasked the Laboratory for Photovoltaic Systems at Bern University of Applied Sciences with investigating the ageing behaviour of PV connectors in actual use.


  • Lead school School of Engineering and Computer Science
  • Institute Institute for Energy and Mobility Research IEM
  • Duration (planned) 01.07.2021 - 30.06.2023
  • Project management Prof. Dr. Christof Bucher
  • Head of project Matthias Burri
  • Project staff Mischa Benjamin Müller
    Luciano Borgna
  • Partner Stäubli Electrical Connectors AG
  • Keywords Energy Strategy 2050, decentralised supply, photovoltaics, long-term behaviour of PV systems


PV systems have a long lifespan and require practically no maintenance except for operational monitoring, which is usually automated. The cabling in the module field is often used for decades without requiring any intervention. However, its performance also depends on the quality of the connectors installed and the correct handling during installation. The Original MC4 – made by the market leader Stäubli Electrical Connectors AG, previously called Multi Contact – is the most widely installed connector in Switzerland and has set the standard worldwide.


Logo Stäubli


This research project seeks to characterise the ageing behaviour of PV connectors in operation. A wide range of PV connectors used in various PV systems will be analysed at BFH’s Laboratory for Photovoltaic Systems. The ageing behaviour will be evaluated based on the following factors:

  • Age of the connectors
  • Situation where connectors are installed (protection from rain/sun/extreme temperatures)
  • Type of connector (original connector, cross connection)
  • Type of crimping (carried out by the manufacturer or in the field)

It is hoped the results will provide manufacturers with input on improving product quality while also giving the PV industry a better understanding of the ageing of a critical component of PV systems.

Various connectors used for PV systems. Enlarge image
Various connectors used for PV systems.


Firstly, a test procedure to analyse the connectors will be defined, combining requirements from three IEC, one UL and three EN standards. In particular, the test criteria of IEC 62852 “Connectors for DC-application in photovoltaic systems – Safety requirements and tests” will be applied. In addition to precisely measuring connector resistance under different current ratings, humidity and high-voltage testing will also be carried out.

The connectors will be tested on the widest possible range of PV systems. The following procedure will be used for testing the connectors:

  1. System operators and installation companies interested in participating can contact project leader Matthias Burri. Detailed instructions on supplying the connector samples will be provided.
  2. For each PV system, at least three connector samples must be provided between two PV modules and three samples between a PV module and cabling. When removing and transporting the connectors, it is important that the connector and cable are moved as little as possible. Under no circumstances must they be separated. Detailed requirements concerning the removal and transportation of connectors will be provided by the Laboratory for Photovoltaic Systems.
  3. The connectors will be tested at BFH’s Laboratory for Photovoltaic Systems in Burgdorf.
  4. The companies supplying the connectors will receive feedback on the condition of their connectors.

Stäubli will provide any replacement connectors and extension cable required free of charge. The cost of replacing the connectors will be borne by the parties wishing to test them. In return, they will receive information about the state of their components.