MC4 stands for “Multi-Contact, 4mm” and is the standard for the renewable energy industry. Most of the larger photovoltaic panels have MC4 DC connectors. It is a round plastic housing with a single conductor in a paired male/female configuration developed by Multi-Contact Corporation. Multi-Contact is the official manufacturer of MC4 connectors.
MC4 DC connectors are terminated to each other by interlocking devices with notches, and in some cases special tools are required to disconnect. The interlock prevents the cables from being accidentally pulled apart. The MC4 DC connector also has weather resistance, UV resistance, and is designed for continuous outdoor use.
Small solar panels under 20 watts usually use screw/spring terminals or other types of automotive electrical connectors. These panels do not generate high currents and are intended to be used as stand-alone units, so the termination method is not important.
Larger panels or panels designed to be connected together in an array require standardized terminals to handle higher power levels. MC4 DC connectors fully meet the requirements, they appear on almost every solar panel with a power exceeding 20 watts.
Some people will cut off the MC4 DC connector on the solar panel and replace it with an Anderson power pole. However, the Anderson power pole is not designed for long-term outdoor use. Doing so will result in a solar panel that is incompatible with any other solar panel. If you insist on using a power pole, please make an adapter with an MC4 on one end and an Anderson power pole on the other end.
The MC4 DC connector has five parts: the main housing, the metal pressure contact point, the rubber water seal, the seal holder and the screws on the end cover. The male head uses different housings and metal contacts, and the remaining parts are interchangeable. If you want to disconnect, squeeze the two interlocks together and pull the connector apart.
Some versions of the MC4 have a detachable “safety lock clip” that can cover the interlock and provide additional protection against accidental disconnection. The connectors using these locking clips cannot be squeezed open by hand, and MC4 connector removal tool must be used.
Some special tools are required to use the MC4 DC connector. The only necessary items for installing the MC4 DC connector are an MC4 crimp tool and two MC4 wrench/disconnect tools.
The price of MC4 connector crimping tools varies greatly, ranging from less than US$20 to hundreds of US dollars. There are many good tools in the range of US$30 to US$60. As long as the MC4 crimping tool has a hinged out-swing contact holder, it will help make your terminals uniform and compliant. Some low-priced crimping tools do not have this function and should be avoided.
In addition to the MC4 crimping tool, you will also need two wrenches/disconnect tools. They are made of plastic and are easy to find, and a pair is less than $10.