Photovoltaic modules are almost always delivered with two permanently installed cables, almost without exception with type MC4 connectors. The cables are short and just dimensioned so that the modules can be installed side by side and connected in series. If you are planning a small balcony power plant, i.e. only want to connect a single module to a microinverter and place it directly behind it, this length is just about sufficient. But even with two modules next to each other that have to reach an inverter, things get tight – because the cables should not be laid under mechanical tension and also not pulled over sharp edges of the mounting material. A piece of extension is needed.
You either buy ready-made extensions or you get the cable by the meter – plus plugs and tools – and become a cable assembler yourself. If you only need two strings for a module of your own balcony power plant, you should take the first step and reach for the finished product. A cable with a length of one meter and two plugs costs between 5 and 15 euros depending on the shop, search terms are “MC4” and “PV extension”.
But experience also shows: It often doesn’t stay with a single balcony power plant and as a person interested in technology you become a multiplier for friends and family who are all standing in line. One is quickly faced with the task of “quickly” customizing such extensions. The following describes what you need for this.