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Up the voltage: How to connect solar panels in series in 5 steps

When you have multiple solar panels, you have to connect them somehow to build a system. You can wire solar panels in parallel or in series. In this article, we’ll take a close look at a latter type: here is a short step-by-step guide on how to connect solar panels in series. 

Series connection is common in home solar systems

Solar panels are wired in series when you want to increase the total voltage in a system. In this configuration, the voltage outputs of all panels add up while the current remains low on a level of what a single solar panel can provide.

Connecting solar panels in series increases the total voltage in a system way over the safe level. When you work with such a system, proper precautions and isolation mechanisms should be employed

The most common scenarios where people choose to wire solar panels in series include:

1. Home grid-tied systems. Grid-tied solar installations often require a specific voltage range for the inverter to function efficiently. Wiring panels in series can help achieve this level.
2. Long cable runs. In situations where there's a significant distance between the solar panels and the charge controller or inverter, using a higher voltage connection reduces power loss along the cables.
3. High voltage systems. If you need to charge batteries or operate devices that require a higher voltage than what a single solar panel can produce, you can connect multiple panels in series to achieve the required voltage. Sometimes, in off-grid systems with specific charging requirements for batteries, series wiring can help match the voltage requirements more precisely. 

Solar panels depend on each other

Solar optimizers or microinverters minimize the effect of a single shaded panel on the whole string even if panels are connected in a series

The biggest weakness of solar panels connected in series is that modules depend on each other. The entire series string performs as well as its weakest link. This leads to three important considerations:

1. Mismatch hurts the system. Solar panels wired in series should have matching voltage and current ratings. Ideally, you want the same models with the same power output. Using different panels brings down the production and damages panels in the long run.
2. Shade impact is high. If any of the panels in a series connection are partially shaded or obstructed, it will affect the performance of the whole string. Read about the ways to minimize the damage in our article “Shading analysis: How to pick a sunny spot for solar panels”.
3. A string is vulnerable. A series connection is more susceptible to system failure due to the breakdown of a single panel. Use high-quality panels and make sure your inverter meets safety requirements. It should be designed to shut down during power outages in the grid to protect your system.

Wiring solar panels in series in 5 steps

Time to connect the modules together! To wire solar panels in series, you'll connect the positive (+) terminal of one panel to the negative (-) terminal of the next panel, and so on until all panels are connected. The positive terminal of the first panel and the negative terminal of the last panel will remain open for connection to the rest of the system.

Step 1: Prepare the equipment

Put solar panels where you want them. Make sure that the place gets lots of sunlight and the place won’t get shaded. Solar panels should have matching voltage and current ratings. 

Make sure you have all the equipment: connectors if the panels don’t come with them, extension cords or appropriately sized cables, duct tape, wire cutters and strippers. The cables from the solar array usually go to either a charge controller or grid-tied Inverter. Some add a circuit breaker in between to protect the system from overcurrent or short-circuit faults. 

Cover the panels with cardboard or a blanket so that you don’t work with the voltage going through the wires

Step 2: Connect positive and negative terminals

Each panel has a positive and a negative cable coming out of its junction box. The cable either ends with a connector or you have you add one yourself. Usually, MC4 connectors are used: male and female. You can read about how to replace a connector in our article on types of solar connectors.

Before connecting, make sure you know which cable is positive and which one is negative. Look for the markings or use a voltmeter. As a rule, the female MC4 connector is attached to the positive lead. Take the positive terminal of the first solar panel and connect it to the negative terminal of the second solar panel.

Repeat the process, connecting the positive terminal of each panel to the negative terminal of the next panel, until all panels are connected in a chain. The idea remains the same whether you have two solar panels in series or ten. If you need to connect two solar panels at a distance, use an extension cord with a female MC4 on one end and a male connector on the other one. 

Step 3: Connect the open terminals 

In the end, you’ll have a positive and a negative cable from panels on the opposite ends of your array. Connect the open positive terminal of the first panel to the positive cable going to the charge controller or the rest of the system. Similarly, connect the open negative terminal of the last panel to the negative cable. Check out our article on solar wires to learn more.

Step 4: Secure and protect the wiring

Properly secure and protect all the wiring connections to prevent accidental disconnections and to ensure the system remains weather-resistant. Color code your wires with duct tape if you haven’t already. Mark the positive cable with red color and the negative one with black

Step 5: Test the system 

Before putting the system into full operation, conduct a test to ensure that all connections are secure and functioning correctly. Use a multimeter to measure the open circuit voltage (Voc) and the short circuit current (Isc) across the positive and negative terminals of the first and last panels. The voltage ratings of panels should sum up while the current should stay low across the array. 

Andrey Gorichenski
Senior Editor

Andrey had been a news editor and freelance writer for a number of medias before joining A1SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.

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