Are generic MC4 connectors compatible?

MC4 type connectors were developed by the Swiss company Multi Contact, currently part of the Stäubli group, and soon gained market preference. They replaced their MC3 predecessors.

I didn't get to know it, but in the international market there was also – in the mid-2000s – the Radox, very similar to the MC3. Both had the risk of accidental disconnection as a weak point.

There were many types of connectors on the market and there was no standard. In some countries, connectors were now required to be locked, making accidental disconnection impossible, which made room for the Tyco Solar Lock (now extinct) and the MC4, which dominated the market.

Around 2010, it was still common to find photovoltaic modules manufactured with the Tyco Solar Lock, which for some time competed head to head with the MC4. The two connectors were completely incompatible. While the Tyco dominated the North American market for some time, the MC4 became common and grew in the European market – and later took over the world.

Although the original MC4 design was developed by Stäubli Multi-Contact, major manufacturers have developed compatible connectors, including Tyco itself. With its worldwide popularity, the MC4 standard has become the “bombshell” of the photovoltaic market. Currently there are countless manufacturers of generic connectors “compatible” with MC4.

MC4 connectors, generally speaking, are used on the positive and negative terminals of photovoltaic modules. They are also used in the cables that connect the strings to the stringboxes and from there to the inverters.

Many inverters already have electrical connections in the MC4 standard. Best practice recommends always using connectors from the same manufacture in photovoltaic installation, but market reality makes this very difficult.

More cautious designers and installers could look for connectors on the market from the same brand as those used in photovoltaic modules, but even this has become complicated. Module manufacturers that previously used connectors from well-known brands (such as Stäubli, Tyco and Amphenol) now use generic connectors.

In large volume purchases, it is still possible to require the module manufacturer to use a specific connector brand. However, in general this is very difficult. Although some manufacturers of modules, inverters and other equipment may still use connectors from well-known brands, this is not the rule, which makes standardization in projects practically impossible.

If it is impossible to standardize brands, an alternative would be to replace the original connectors of the photovoltaic modules. In addition to being costly, this practice increases the possibility of project failures due to manual crimping.

Furthermore, this practice would depend on the module manufacturer's consent to avoid voiding the warranty. Still, even if standardization is carried out on the module side, there are still connectors for other components (inverters, microinverters, etc.), which makes standardization unfeasible.

With the variety of manufacturers of modules, stringboxes, inverters, microinverters and power optimizers on the market, in addition to the infinite connector manufacturers, it is difficult to guarantee that all components of an installation use the same brand of connector. But is this necessary, since the connectors are supposedly compatible?

Although connectors from different manufacturers are apparently compatible and have the same type of fitting and can be combined indiscriminately, the reliability of electrical contact cannot be guaranteed.

In addition to precarious electrical contact between different brands of connectors (or between connectors of the same brand, which is not to be doubted when the quality is poor), there are differences in the materials used.

The thermoplastic in the generic connector shown in Figure 4, for example, is polypropylene. Connectors from more reputable brands (such as Stäubli and others) use a mixture of polycarbonate and nylon, which is much more weather-resistant and long-lasting.

What is the solution to the problem? The recommendation is to find out which suppliers of modules, inverters and components your distributor works with. Also find out which connectors are used by the manufacturers of modules and inverters that you will use in your project.

Although it is not easy to ensure standardization, any effort in this direction is worthwhile. If you identify module and inverter manufacturers that notably use connectors from trusted brands, consider adopting them as standard in your projects.

It is somewhat strange to define the brand of the inverter or module based on the connector it uses, as the connector is generally the cheapest and most trivial component present in equipment and installations.

However, the best manufacturers certainly employ good quality connections (even if they are not from well-known brands). Finally, the best recommendation, which is not difficult to follow: avoid, at any cost, the generic connectors that are dumped on the market, available in small distributors and even on internet shopping sites.

There are excellent brands of connectors available on the Brazilian market and it is not difficult to find them at the best distributors of photovoltaic materials. If standardization cannot be guaranteed, at least connectors from reliable brands known for their quality should be used.