Connecting solar panels in series: what you need to know

A string of solar panels is a method used to connect several photovoltaic panels together in order to increase the total system voltage while maintaining a regulated current.

This configuration is achieved by connecting the positive terminal of one panel to the negative terminal of the next panel in the string.

How series connection works

In series, the voltage of each panel is added to that of the others, but the current (amps) flowing through the system is identical to that of a single panel.

Example: if you connect three 12 volt, 5 amp panels in series, the total system voltage will be 36 volts (12V + 12V + 12V + 12V + 12V + 12V) and the current will be 5 amps.

Advantages of series connection

It is possible to use inverters that transform a higher voltage into alternating current (AC), which can be more efficient for transmitting electricity over long distances.

By increasing the voltage and decreasing the current, electrical losses in the cables caused by electrical resistance can be reduced.

The use of certain charge controllers and inverters specially designed for specific voltages is simplified by connecting them in series.

Disadvantages of series connection

If one of the panels is shaded or partially obstructed in a series configuration, this can have a significant impact on the performance of the entire string (string of panels connected in series).

The panel with the lower power restricts the amount of current that can be produced by the grid.

A mismatch can occur if the panels are not perfectly matched in terms of electrical characteristics (voltage and current), resulting in a drop in system efficiency. It is the smallest panel that influences the performance of the whole chain.

By connecting panels in series, each additional panel increases the total system voltage. This can increase the risk of electric shock during installation, maintenance or in the event of system failure, especially in large-scale systems where voltages can be extremely high.

It can be more difficult to expand a system of panels connected in series, as each addition must respect the electrical characteristics of the existing panels to ensure the efficiency and safe operation of the system.

Inverters must be compatible with the high voltage of series systems. This can restrict the available options and increase the cost of components.

Step-by-step series connection

Before we begin, here are some essential recommendations: To ensure a safe and efficient installation of your solar panels, it is vital to follow the manufacturer’s instructions for each component of the system.

The orientation and tilt of the panels should be matched to the latitude and annual path of the sun to maximise energy collection, and they should be placed in areas that are not shaded by trees or buildings during peak sunlight hours.

To keep the system in optimum condition, we recommend using compatible electrical components and regular servicing and maintenance. If you lack installation experience, it is advisable to use certified experts to ensure compliance with local regulations and energy efficiency.

Step 1

Make sure that all components are disconnected before starting the installation to avoid any electrical hazards. Check that the solar panels and cables are in good condition and have no visible damage.

Step 2

Check the specifications of the panels to ensure that they are in good condition and have no visible damage.

Check the specifications of the panels to ensure that they are compatible with each other in terms of voltage and current. Decide on the location of the panels, taking into account the possibility of shading during the day.

Step 3

Mount the solar panels on their support structure according to the manufacturer’s instructions.

Step 4

Locate the MC4 connectors or any other type of connector used by your panels, which are usually located in the junction box on the back of each panel.

Connect the positive (+) terminal of one panel to the negative (-) terminal of the next panel. Use appropriate solar cables to connect the terminals, making sure that the cables are long enough to be effortlessly accessible.

Repeat this process for each panel in your installation until all panels are connected in series.

Double check that all connections are secure and properly insulated.

Switch on the system and monitor the initial operation to check that everything is working as expected.

Step 5

Use a multimeter to check the total voltage of the panel string. This voltage should correspond to the sum of the individual voltages of the connected panels.

Step 6

Connect the string of panels in series to the solar inverter.

Connect the string of panels in series to the solar inverter, making sure that the string voltage and current do not exceed the specifications of the inverter. Secure all electrical connections with conduit or protective tape to prevent exposure and risk of short circuits.

Step 7

Re-check all connections to prevent exposure and risk of short circuits.

Recheck all connections to ensure that they are secure and properly insulated. Switch on the system and monitor the initial operation to check that everything is working as expected.

Conclusion: Safety tips

To avoid electric shock, we recommend that you disconnect the system from the power supply and wear personal protective equipment such as gloves, goggles and appropriate footwear.

Carefully examine all components, such as panels, cables and connectors, to ensure that they are undamaged.

It is preferable not to work in adverse weather conditions and to follow the handling instructions of the solar panels to avoid any damage caused by incorrect handling.

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