Types of Solar Panel Connectors Explained

Ever wonder "which types of solar panel connectors should I use for my solar array?" This is a great question because discerning which one is right for your project can be a serious challenge. A myriad of third-party brands aside, you'll often find MC3, MC4, Helios H4, SolarLok, and Canadian Solar T4 brands.

By and large, MC4 is the premier connector for solar panels. However, these different models all come with a variety of unique aspects, including ingress protection, materials, and locking mechanisms. For more information on the different types of solar panel connectors and which one is right for your project, continue reading.

What Do Solar Panel Connectors Do?

Whether you're installing a solar array on your home or an off-grid system for an RV, your solar panels will have to connect to each other and to your projects. Solar connectors are the component used to achieve this safely and reliably.

The Importance of Solar Connectors

However, this hardware is relied upon to do more than just bridge two panels. They have to withstand the current sent through them while also maintaining a low resistance point to keep a constant flow of voltage.

And that's not all; These integral points of contact must survive a wide range of outside temperatures, weather, and moisture. If your connectors can't keep a tight seal and resist direct sun, they won't last the life of your panels, and you'll have to replace them.

Or worse, they could fail and compromise your solar system.

As such, these components require excellent engineering to consider all of these aspects while also complying with the National Electric Code. Several types of solar panel connectors exist to solve this problem, but not all are built the same.

MC3 Solar Connectors

Multi-Contact (the meaning of the abbreviation "MC") designed their simple MC3 connector in 1996. Friction and suction created the weatherproof seal and kept the unit from disconnecting. It featured male and female types to prevent users from accidentally connecting the wrong ports.

While this system was easy to work with, an update in the National Electric Code made them obsolete. However, due to their popularity at the turn of the decade, they are still easy to purchase. Many older systems still rely on them, and they are a great alternative for small-scale arrays.

MC4 Solar Connectors

After the National Electric Code started requiring a positive locking mechanism on solar connectors, the MC4 became the most popular unit. Its locking mechanism requires a special tool, adding to its reliability. As such, this model became the unofficial standard on the market.

In addition to its locking features, the MC4 has an IP67 (ingress protection rating). This means the component is entirely dust resistant and can resist moisture for 30 minutes submerged in water at a depth of 3 feet.

Similar to the MC3, this model's design features a negative male and positive female connector. This keeps the system setup easy for individuals, as users can always expect to know which port is which.

Check out our list of recommended MC4 Solar Panel Connectors here

Helios H4, Canadian T4, and others

The MC4 solar panel connector became so widely used that other companies started manufacturing compatible units. The Helios H4, for example, markets itself as a connector with a higher amperage capacity. The Canadian Solar T4, another popular brand, is built for more durability, touting an IP68 rating.

Additional benefits considered, these models perform the same essential functions as the MC4. They are entirely compatible and can be used conjunctively on the same project. However, MC4 recommends using the same brand for optimal reliance.

Obsolete Types of Solar Panel Connectors

While MC4 dominates the market, there are other types of solar panel connectors available to use. They perform the same functions as the MC4, although they are not compatible. As such, finding and installing them may require more effort.

SolarLok

Designed to add variance in the wire length of solar panel designs, the SolarLok designed its connectors to attach to each end of a wire. While this was useful in theory, it turned out to add a lot of complexity to its polarity consistency (eg, people often connected their panels wrong).

Radox

Designed with copper-beryllium contacts and a particulate-diffusing design, the Radox offered a cleaner and more efficient electrical current. However, the model fought regulations in the US and could not find its way out of Europe, where it was engineered.

MC3 vs MC4

If you're designing a solar array, you're likely to use either MC3 or MC4 (or comparable brand) solar connectors. While the National Electric Code makes the MC3 obsolete, it's still used in some cases. The main differences between the two connectors include IP rating differences and locking systems.

Ingress Protection

These two connectors have a considerable difference when it comes to water ingress protection. While both are impervious to dust, the MC3 has an IP65, whereas the MC4 has an IP67. This means that while both would handle a standard rainstorm, the MC3 might not hold up to major downpours or in areas that are prone to flooding.

Positive Locking System

When the National Electric Code started requiring positive locking mechanisms on connectors, the MC3 became obsolete. The component relied on friction and suction for its connection and had no way to prevent separation beyond that. The MC4 introduced a locking mechanism that required a special key to unlock, making it the most reliable connector on the market.

Choosing the Right Connector

Despite no longer being on the market, you can still pick up MC3 connectors for older model solar panels. You won't be able to use them on larger systems, but it fits the niche for specific projects. In general, you'll find the most success and universality using MC4 connectors.

Wiring MC4 Connectors in Series

When you connect the positive terminal of a solar panel to the negative terminal of another, you wire them in series. When you wire your panels like this, the voltage will add, but the amperage will stay the same.

For example, if you connected two panels, with each rated for 12 volts and 5 amps, your total voltage for the system would be 24 while the amperage would still be 5. This is important for systems working with an solar panel inverter that requires a certain voltage to operate.

When using MC4 connectors to wire panels in series, you'll use the components that are permanently attached to the panel to create the circuit. Just plug the negative male port into the positive female port until they lock together.

You'll use one pair of panel wires to connect to your project. As long as the distance from your project is reasonable in regards to your wire gauge, you can use any panel to connect to your project.

Benefits

With panels run in series, the current is separated with each solar connector, meaning you can run your system with smaller wires. This is a safer option for those concerned with the dangers of wiring your own electrical system.

Considerations

Panels wired in series are great when used with a Maximum Power Point Tracking (MPPT) charge controller because they're built to handle large voltages. Make sure to confirm which charge controller you have before you wire your system.

It's important to know that solar arrays wired in series will be less effective in the shade. Think of this system as a stream; If you blocked up the stream, less water would flow through. Similarly, when you cover one panel, the current is strangled.

Wiring MC4 Connectors in Parallel

When you wire the positive terminal of one panel to the positive terminal of the other, and similarly with their negative terminals, you've wired your panels in parallel. When your solar array is connected in this manner, the amperage increases, but the voltage stays the same.

If we were to use the same two panels from the previous example but wire them in parallel, their volts would stay at 12, and the amps would raise to 10. This is useful when working with inverters with lower voltage limits.

To wire your panels in parallel with MC4 connectors, you can't plug them together like you would in parallel. For this instance, you'll need a separate multi-branch connector for each type of port. The multi-branch connector accepts two of the same lead on one end and outputs a single current through the other.

Benefits

Solar panels wired in parallel do not struggle with the same issue with shade as panels in series do. Each solar panel produces its own energy, regardless of the condition of the panels around it. This is great for mobile systems with constantly changing conditions.

Considerations

Solar arrays wired in parallel typically work best with a Pulse Width Modulation (PWM) charge controller. These devices work better with higher amperage and allow you to connect more panels together.

These power systems have the potential to produce a lot of amperage, which can be hard to move. Unless located directly to its charge controller, a big system wired in parallel could require massive wires. As such, this type of system works best for smaller projects.