Why You Should Avoid Connecting Solar Panels in Series Only

If you are planning to install an off-grid solar power system for your home, cabin, RV, or boat, you may be wondering how to connect your solar panels to get the most out of them. Solar panels are the key components of any solar power system, as they convert sunlight into electricity that you can use or store in batteries.

However, not all solar panel connections are created equal. Depending on how you wire your solar panels, you may get different results in terms of voltage, current, power, and efficiency.

One of the most common ways to connect solar panels is in series. This means that you connect the positive terminal of one panel to the negative terminal of another panel, forming a single string of panels.

The voltage of each panel adds up, while the current stays the same. This may sound like a good idea, as it allows you to increase the voltage of your system without increasing the current.

However, there are some major drawbacks to connecting solar panels in series only. In fact, this is almost never done in practice, as it can severely compromise the performance and reliability of your system.

In this article, we will explain what a series connection is, how it works, and what are its advantages and disadvantages for wiring solar panels. We will also give you two reasons why solar panels are almost never connected in series only, and why you should consider other types of connections instead.

What Is a Series Connection?

A series connection is a type of electrical circuit where all the components are connected end-to-end in a single line. The current flowing through all the components is the same, but the voltage across each component is proportional to its resistance. The total voltage of the circuit is equal to the sum of the voltages across each component.

When you connect solar panels in series, you create a series circuit where each panel acts as a component. The current flowing through all the panels is equal to the current of one panel, but the voltage across each panel adds up. The total voltage of the string is equal to the sum of the voltages of each panel.

For example, if you connect four 12-volt 5-amp solar panels in series, you will get a string with 48 volts and 5 amps. The total power output of the string will be 240 watts (48 x 5).

There are some advantages to connecting solar panels in series. For instance:

â€¢ It allows you to increase the voltage of your system without increasing the current. This can reduce the electrical losses and lower the costs associated with wiring and transmission.

â€¢ It allows you to use smaller wires and fuses for your system, as they do not need to handle high currents.

â€¢ It allows you to match your system voltage with your battery bank voltage or your inverter input voltage.

However, there are also some disadvantages to connecting solar panels in series only. For example:

â€¢ It makes your system vulnerable to shading or damage on one panel. If one panel is shaded or damaged, it will reduce

the output current of the entire string. This will lower your system’s power output and efficiency significantly.
â€¢ It creates a high voltage drop across your string. The voltage drop is the difference between the input voltage and

the output voltage of your system. It is caused by resistance in wires and connectors. The higher your system’s voltage,
the higher your voltage drop will be. This will also lower your system’s power output and efficiency.

Two Reasons Why Solar Panels Are Almost Never Connected in Series Only

Based on these advantages and disadvantages, we can see why solar panels are almost never connected in series only. Here are two main reasons why:

â€¢ The impact of shading or damage on one panel. When solar panels are connected in series, the current flowing through all of the panels is the same. This means that if one panel is shaded or damaged, it will reduce the output current of the entire string. The power output of a solar panel is proportional to its current, so a drop in current will result in a drop in power. This will affect the performance and reliability of your system, as you will not get the expected amount of electricity from your panels.

To avoid this problem, you should connect your solar panels in parallel or in series-parallel. This way, if one panel is shaded or damaged, it will not affect the other panels in the system. The current and power output of each panel will be independent of each other, and the total power output of the system will be equal to the sum of the power outputs of each panel.

â€¢ The voltage drop across the string. The voltage drop across a solar panel increases as the current flowing through it increases. When solar panels are connected in series, the current flowing through all of the panels is equal to the current of one panel, but the voltage across each panel adds up. This means that the voltage drop across the string will also add up, and it will be higher than the voltage drop across a single panel.

The voltage drop reduces the effective voltage of your system, which affects its power output and efficiency. To avoid this problem, you should limit the number of solar panels connected in series in your system. You should also use thicker wires and connectors for your system, as they have lower resistance and lower voltage drop.

â€¢ Mismatched Solar Panels. One reason why solar panels are almost never connected in series only is because of the possibility of mismatched solar panels. Solar panels can have different voltages and currents, depending on their size, type, and condition. If solar panels with different voltages are connected in series, the output voltage will be limited by the panel with the lowest voltage. This can significantly reduce the overall efficiency of the system.

For example, if two solar panels with different voltages are connected in series, the output voltage will be equal to the voltage of the panel with the lowest voltage. If the two panels have voltages of 18 volts and 20 volts, the output voltage will be 18 volts. This means that the solar panel with the 20 volt voltage will not be able to operate at its full potential.

Another problem with mismatched solar panels is that they can create hot spots. Hot spots are areas on a solar panel that are hotter than the surrounding area. Hot spots can be caused by shading, dirt, or other factors. If a solar panel in a series string has a hot spot, it can reduce the output of the entire string.

Other Types of Connections

As we have seen, connecting solar panels in series only is not a good idea, as it can compromise your system’s performance and reliability. However, there are other types of connections that you can use for wiring your solar panels, such as parallel or series-parallel.

A parallel connection is a type of electrical circuit where all the components are connected across each other. The voltage across all the components is the same, but the current through each component is proportional to its resistance. The total current of the circuit is equal to the sum of the currents through each component.

When you connect solar panels in parallel, you create a parallel circuit where each panel acts as a component. The voltage across all the panels is equal to the voltage of one panel, but the current through each panel adds up. The total current of the array is equal to the sum of
the currents of each panel.

For example, if you connect four 12-volt 5-amp solar panels in parallel, you will get an array with 12 volts and 20 amps. The total power output of the array will be 240 watts (12 x 20).

A series-parallel connection is a type of electrical circuit that combines both series and parallel connections. It consists of several strings of solar panels connected in series, and then these strings are connected in parallel with each other.

When you connect solar panels in series-parallel, you create a series-parallel circuit where each string acts as a component. The voltage across each string adds up, while the current through each string stays the same. The total voltage of the array is equal to the voltage of one string, and the total current of the array is equal to the sum of the currents of each string.

For example, if you connect two strings of four 12-volt 5-amp solar panels in series-parallel, you will get an array with 48 volts and 10 amps. The total power output of
the array will be 480 watts (48 x 10).

Conclusion

Connecting solar panels in series only is almost never done in practice, as it can have negative effects on your system’s performance and reliability. There are two main reasons why:

â€¢ It makes your system vulnerable to shading or damage on one panel.

â€¢ It creates a high voltage drop across your string.

To avoid these problems, you should consider other types of connections for wiring your solar panels, such as parallel or series-parallel. These connections can offer more benefits for your system, such as:

â€¢ They increase your system’s tolerance to shading or damage on one panel.

â€¢ They reduce your system’s voltage drop and electrical losses.