When connecting multiple solar panels in a system, you can choose between series and parallel wiring. Your choice depends on your specific needs. Let’s look at the differences and the best uses for each method.
What is a Solar Panel Series Connection?
In a series connection, solar panels are linked one after another. The positive terminal of one panel connects to the negative terminal of the next.
This setup has key features:
- Voltage Increases: The voltages of individual panels add up. For instance, connecting two 24-volt panels in series results in a total system voltage of 48 volts. This is ideal for systems needing higher voltage levels, like grid-tied inverters.
- Constant Current: The current remains the same throughout the series connection. The current is limited by the panel with the lowest current output. If one panel is shaded or not performing well, it affects the entire string’s output.
- Total Power Increases: The system’s total power output rises. Power is the product of voltage and current (P = V x I). Increasing voltage while keeping current constant raises overall power output.
- Shading Sensitivity: Series-connected panels are more affected by shading. If one panel is shaded, it can reduce the output of the whole series string. This makes series connections less ideal for areas with potential shading issues.
What is a Solar Panel Parallel Connection?
In a parallel connection, solar PVs are connected with all positive terminals together and all negative terminals together.
5 Key Characteristics
- Voltage Stays the Same: All panels have the same voltage. For instance, connecting two 24-volt panels in parallel keeps the system voltage at 24 volts.
- Current Increases: The total current output rises because the current from each panel combines. This setup is ideal for systems needing higher current, like off-grid systems with 24V or 48V battery banks. For example, two panels with 10 Amps each in parallel will result in a total current of 20 Amps.
- Consistent Voltage: The voltage across each panel remains constant. Shading or underperformance of one panel doesn’t significantly affect others.
- Power Output Rises: The total power output increases due to constant voltage and higher current.
- Better Shading Tolerance: Panels in parallel can handle shading better. If one panel is shaded, it won’t significantly impact the others.
Series and Parallel Wiring – Which Works Better?
When comparing series and parallel connections:
- Voltage: Series connections increase voltage. Parallel connections keep voltage constant.
- Current: Parallel connections increase current. Series connections keep current constant.
- Power: Both series and parallel connections increase power output.
- Shading Sensitivity: Series connections are more sensitive to shading. Parallel connections are more tolerant.
- System Requirements: The choice depends on the solar installation’s needs, system design, and the voltage and current levels supported by the inverter and battery.
Series vs Parallel, Which is the Better Choice for You?
The better option depends on your application.
Connecting solar panels in series is best if you spend most of your time in unshaded areas. This setup makes your system more efficient, performing well at the beginning and end of the day and on cloudy days.
Batteries need a higher voltage than their nominal value to charge. For example, lithium batteries need 14.4 volts to start charging. Most 100-watt solar panels output 18-20 volts. To charge your batteries, panels in parallel must operate at 75% capacity or more.
In contrast, wiring three panels in series gives an output of 54-60 volts. Your array would only need to operate at about 25% capacity to charge your batteries, easier to achieve late in the day or on cloudy days. An MPPT charge controller is required for this setup.
You can also wire solar panels together in parallel. MPPT charge controllers are expensive and may not be needed for small portable applications. For low-voltage systems in RVs or boats with variable lighting, a parallel solar system may work well. These systems work fine with a lower-cost PWM charge controller, saving you money.
Factors to Consider
When choosing a connection type for solar panels, consider key factors. The inverter and battery specifications are crucial. Different inverters have unique charge controllers and MPPTs that work at specific voltage and current levels. Matching the stringing configuration to these levels ensures optimal system performance.
A well-configured solar array charges the battery efficiently, following the battery’s charging curve and power draw at different stages. This setup also allows the inverter to maximize power output from the panels, increasing overall solar power system efficiency.
FAQs
Can you add more solar panels to your existing system?
Yes, it is possible to expand most solar energy systems. However, it isn’t always cost-effective. Adding solar panels can sometimes be more complicated and expensive than expected, but it is generally feasible.
Do solar panels charge faster in series or parallel?
Wiring in parallel usually results in lower voltage than wiring in series. With parallel wiring, panels must operate consistently to maintain the required minimum voltage. Generally, series wiring can lead to faster charging times. When wiring in series, it is crucial to connect each panel to the negative terminal of the next panel to maintain a continuous circuit.
Should two 100-watt solar panels be in series or parallel?
You need to connect two 100-watt 12V solar panels in parallel with your 12V battery bank to keep the voltage the same. In this parallel setup, connect your solar panels ensuring you have all positive terminals together and all negative terminals together.
