Understanding how to effectively connect solar panels can be confusing, especially for beginners, and the way solar panels are wired has a direct impact on their efficiency and performance. This article aims to provide readers with a comprehensive understanding and application guide by delving into the differences, advantages and disadvantages of the two basic ways of connecting solar panels in series and in parallel, as well as which wiring scheme is best suited for your solar system.
How are solar panels wired together?
Wiring solar panels begins with specifying the voltage and current requirements of the system, as well as the specifications of the available solar panels. Before wiring, ensure that all connection points are clean and free of corrosion, and use appropriate connectors or soldering techniques to ensure a solid and conductive connection. When wiring, the positive and negative poles of the solar panels need to be connected according to the selected wiring method (series or parallel) and connected to the inverter or other power handling equipment according to the appropriate rules.
Solar panels can be connected in two main ways: in series and in parallel. These two wiring methods will not only affect the voltage and current output of the system, but will also affect the overall power generation capacity and safety.
Solar panels in series
Solar panels are connected in series by connecting the positive terminals of multiple panels to the negative terminals of neighbouring panels to create a current path. In this type of connection, the voltages of the panels are added together while the current remains constant. For example, if two panels have voltages of 24V and 24V, the total voltage of the system will be 48V when connected in series, but the current will still be the smaller of the two panels.
Pros:
- Increased voltage: for systems that require high voltage, such as utilities or large solar power projects.
- Reduced cable losses: Higher voltage means that less current is required for the same power output, thus reducing energy losses in the cables.
- Suitable for MPPT controllers: MPPT - Maximum Power Point Tracking - is an excellent device for efficiently utilising the maximum power output by digitally tracking the output of a solar PV panel and supplying the correct voltage to the rest of the system (battery and load). DC voltages (often up to 150 volts DC, depending on the manufacturer), thus allowing the use of larger solar PV arrays.
Disadvantage:
- Affects overall performance: If one of the panels is not performing well (e.g. shaded), the output efficiency of the remaining panels will also be affected.
- Higher voltage risk: in case of maintenance or faults, special attention needs to be paid to the safety risks posed by high voltages.
How to connect solar panels in series
Preparation for Connecting Solar Panels in Series
Before connecting solar panels in series, make sure that all panels to be connected in series have the same voltage specification and similar current output capability. This avoids any reduction in system efficiency due to differences in panel performance.
At the same time, check each panel for any damage or malfunction, especially check whether its positive and negative terminals are clearly distinguishable, and there is no short-circuit or disconnection phenomenon.
Steps for series connection of solar panels
- Connect the positive and negative terminals: Firstly, connect the positive terminal of the first panel with the negative terminal of the second panel through the connecting wire. Make sure the connection is firm and there is no loose or poor contact.
- Sequential series connection: according to the above method, connect the subsequent battery boards in series sequentially. For each connected battery board, check once whether the connection is firm and reliable.
- Installation of diodes (optional): In some cases, a diode can be connected in parallel between the positive and negative terminals of each battery board in order to prevent reverse current from damaging the boards. Please note, however, that the diode introduces a certain voltage drop, so the advantages and disadvantages need to be weighed in practice.
- Check the overall connection: After completing the series connection of all the battery plates, check the entire series circuit to ensure that there are no shorts, breaks or poor contacts. You can use a multimeter and other tools to test.
- Voltage Matching: When connecting solar panels in series, make sure all panels have the same or similar voltage specifications. If the voltage difference is too large, it may cause some panels to be over-voltage and damaged.
- Current Balance: Although series connection does not change the current, the current output capability of each panel may vary. Therefore, when designing and installing a system, it is necessary to consider how to balance the current output of each panel to improve the overall efficiency of the system.
Parallel connection of solar panels
Parallel connection of solar panels, on the other hand, involves connecting the positive terminals of multiple panels all together and the negative terminals all together to form multiple parallel current paths. In this method, the currents of the panels are added together while the voltage remains constant. For example, if two 24V panels are connected in parallel, the voltage of the system will still be 24V, but the current will be the sum of the currents of the two panels.
Advantage:
Increase system current output, suitable for application scenarios requiring high current.
Failure of a single panel will not affect the work of other panels, improving system stability.
Higher tolerance to shading, reducing power generation loss due to localised shading.
Better match with PWM controllers: If the panel voltage output and the battery voltage are almost the same, the efficiency of the charge controller will be higher than systems that have a severe voltage mismatch between the panels and the batteries, because there is no DC to DC converter like in the case of MPPT controllers. PWM controllers are cheaper and therefore can be affordable for common DIY solar applications.
Disadvantages:Cable Loss: Higher currents result in increased energy loss in the cable, especially over long distances.
Voltage limitations: if a higher voltage is required for the application then a parallel connection may not be sufficient.
How to parallel solar panels
Preparation for paralleling solar panels
Make sure that all panels to be paralleled have the same voltage specification so that they can operate at the same voltage. The current output capability can vary, as the parallel circuit will accumulate current.
Before paralleling, double-check that the positive and negative terminals of each panel are clearly identifiable and that there are no shorts, breaks or damage.
Steps for paralleling solar panels
- Connect the positive terminals: First, connect the positive terminals of all panels (usually the red wire or labelled ‘+’) together via the connecting wires. Make sure that each connection point is firm and reliable, with no loose or poor contact.
- Connecting the Negative Terminals: Next, connect the negative terminals of all the panels (usually the black wires or marked ‘-’) together via the connecting wires as well. Again, make sure each connection is secure and reliable.
- Checking the connections: After completing the positive and negative connections, check the entire parallel circuit to ensure there are no shorts, breaks or poor contacts. This can be tested using a tool such as a multimeter.
Precautions
Voltage Matching: When paralleling solar panels, it is important to ensure that all panels have the same voltage specification. If the voltage difference is too large, it may result in current imbalance or even damage to the panels or the system.
Current Balance: Although the parallel circuit will accumulate current, the current output capacity of each panel may vary. In practical applications, it is necessary to pay attention to the current balance of the system to avoid overheating or damage due to excessive output current of some panels.
Mixing series and parallel configurations
In order to eliminate the advantages and disadvantages of both configurations, it is recommended to mix the two to get all the advantages. You can connect multiple sets of solar PV panels in series for a parallel configuration. In this case, you get better energy yield, lower wiring costs, and can achieve better results with panels partially shaded.
Hybrid solar PV panels in the same series and parallel configuration can increase both voltage and amperage.
To ensure the highest efficiency, it is recommended to connect individual panels to separate inverters, as seen in solar PV panels with microinverters in grid-connected systems. Each panel connected with a microinverter will reduce the impact of partial colouring compared to a string inverter, as all panels can operate independently.
Solar Panel Series vs Parallel Connection Comparison Table
| characterisation | series connection | parallel connection |
| rationale | The positive and negative terminals of the battery plate are connected to form a series connection. | The positive and negative terminals of the battery plates are connected in parallel. |
| Overall Voltage | Sum of all panel voltages | Voltage per panel |
| amps | Current per panel | Sum of all panel currents |
| failure impact | One panel failure affects the entire series circuit output | Failure of a single panel does not affect the output of other panels |
| Voltage requirements | Output High Voltage | Output Low Voltage |
| Current Requirements | Relatively low output current | Can output high current |
| Cable Specifications | Smaller gauge cables can be used | Larger cable size required |
| Matching Requirements | The voltage and current of the battery plates need to be better matched | Lower requirements for voltage and current matching of panels |
| application scenario | High voltage applications | Ideal for environments with a lot of shadows where high current is required |
| Costs | Lower installation costs and higher space utilisation | Requires larger cables and more panels to increase costs |
Should I choose to connect my solar panels in series or in parallel?
Choosing whether to connect your solar panels in series or in parallel depends largely on your specific needs and installation environment. Here are some considerations to help you decide which connection is better for you:
Choose a series connection for your situation:
- High voltage required: if your inverter or system requires a high input voltage, series connection is a good choice.
- Limited space: In cases where space is limited, such as on a roof, series connection can provide the required voltage in a smaller area.
- Same conditions: if all panels have similar performance, series connection can effectively increase the overall output.
Choose the case of parallel connection:
- Shading effects: If lighting conditions are uneven or shaded, using a parallel connection prevents a failure in one panel from affecting the output of the others.
- High current required: If the system requires a high current output or is connected to a battery storage system, paralleling makes it easier to provide the required current.
- Multiple models: If you are using different models or different wattages of panels, a parallel connection may be better able to accommodate these differences.
The final choice depends on your power needs, equipment specifications and available installation space. For most home solar applications, many users choose to connect the panels in series for higher voltage, in conjunction with an inverter. At the same time, depending on shading and panel characteristics, parallel connection may be an option in some cases to ensure system stability.
FAQ
Can series and parallel be used at the same time?
Yes, series and parallel can be used together in the same solar system to achieve more complex voltage and current configurations. This hybrid wiring combines the advantages of series connections to increase voltage and parallel connections to increase current, making the system more flexible and efficient. However, it also adds complexity and design difficulty to the system, requiring more specialised knowledge and experience to ensure system stability and reliability.
Which is more efficient, series or parallel?
Efficiency is not determined by the wiring method alone, but by a combination of factors, including solar panel performance, mounting angle, shading conditions, inverter efficiency, etc. Under the same conditions, series and parallel connections have their own advantages, and the choice depends on specific needs.
Will the voltage increase indefinitely when connected in series?
No, it will not. The voltage will add up after series connection, but it is limited by the maximum input voltage of the inverter. Exceeding the inverter's tolerance may result in damage or loss of efficiency.
Does the current increase indefinitely when connected in parallel?
Again, no. Currents will add up when connected in parallel, but will be limited by the carrying capacity of equipment such as cables, connectors and inverters. The design needs to ensure that all components are capable of carrying the expected current load.
For shaded areas, should I choose series or parallel?
For shaded areas, it is recommended to choose a parallel connection. This ensures that the performance of one panel does not affect the output of the other panels.
