Photovoltaic systems are one of the world's most important renewable energy sources. Photovoltaic modules have three types of wiring: series, parallel and parallel series. This issue will introduce you to the basics of solar panel wiring.
1. Assembly tools and module types required for solar panel wiring
You should know the tools for solar panel wiring beforehand. These are crimping tools and solar connector assembly tools. The crimping tool is used to crimp the connecting plate of a solar connector to the bare wire.
The Solar connector assembly tool is used to fasten all components of the MC4 connector to the connecting plate. This tool is also used to unlock the connector after it has been inserted.
- Solar inverter
Solar panel inverters are one of the most important components in photovoltaic systems. This module converts the DC energy generated by solar panels into AC power suitable for your appliance. The output is pure sine wave with 120V AC voltage (US) or 240V AC (Europe).
- Solar wire type
The solar panel wiring can be completed by connecting the solar panels together using pre-installed wires on the module. But extending the wiring to an home solar inverter or service panel requires selecting the right wire.
For rooftop photovoltaic installations, you can use photovoltaic wire, which in Europe is called TUV photovoltaic wire or EN 50618 solar cable standard. For ground-mounted PV installations that require underground installation, you will need an underground service entry (USE-2) cable.
2. The way to carry out solar panel wiring
When building a solar power system, solar panel wiring is a key part of determining how much voltage and current the system outputs. The three main methods of connecting multiple panels are series, parallel and parallel series combination, and we will introduce them respectively below:
- In series connection
High efficiency solar panels have anode and cathode. Connecting solar panels in series means connecting the anode of a module to the cathode of the next, and so on. This type of wiring increases the output voltage.
For example, if two 12-volt panels are connected in series, the voltage can reach 24 volts, while the current is maintained as the current parameter of one panel.
- In parallel
The parallel solar panels increase the output current while keeping the voltage constant. The output current is the sum of all the currents produced by the modules in the string.
For example, if three 12-volt panels are connected in parallel, the voltage is maintained at 12 volts, and the current is 3x6 amps =18 amps. Solar panels in parallel must also comply with regulations.
This includes conductor size and overcurrent devices. This is calculated by taking the short circuit current too high by 125%, taking into account the number of modules in the system.
- Series-parallel connection
There is a combination of series and parallel solar panel wiring called series-parallel. The connection connects the solar panels in series to increase voltage by connecting the anode to the cathode and connecting these series in parallel.
All strings of parallel solar panels must have the same voltage. In all cases, the modules must be the same model in order to provide the best performance on the system.
For example, four 12-volt panels are connected in series in pairs and finally connected in parallel to obtain a voltage of 2x12 volts =24 volts and a current of 2x6 amps =12 amps.
3. Comparison of solar panel wiring in series or parallel
Many customers ask us what is the difference between series and parallel solar panels, how to choose, and how to share the difference between series and parallel solar panel wiring today.
- Benefits of series
Without increasing the current flowing through the output line, the total output power is increased. This saves the circuit from having to replace thicker output lines. The cost of wire is effectively saved, the current flow is small and the safety is high.
- Advantages of parallel operation
As long as the solar panels have the same output voltage, they can be connected parallel to the controller for use. And one of the damaged open circuits will not affect the overall voltage, only affect the power. The requirements for the photovoltaic voltage access range of the controller are not high.
- Shortages of series
When two or more solar panels are connected in series, if one of them is blocked or damaged by other objects and loses its power generation capacity, the entire circuit will be blocked and stop transmitting electricity to the outside world.
It is like the other electrical appliances in the series circuit are damaged, and the entire circuit becomes broken. The requirements for the photovoltaic voltage access range of the controller used are high.
- Disadvantages of parallel connection
Because the parallel voltage is unchanged and the total current is increased, the requirements for the wires used are higher and the cost is increased. And the current is large, but the stability is slightly poor.
Of course, whether the solar panel wiring is selected in series or parallel, it is best to choose the same specification for the panels. If you put different sizes of solar panels in series, the panels with the lowest current tend to have the highest current. In parallel, the voltage value tends to the minimum voltage of the panels, which is a waste of high-power solar panels in the same circuit.
4. Specific steps to connect solar panels
- Wiring sequence: First connect the battery, set the working mode of the load, then connect the solar panel, and finally connect the load.
- Wire diameter: min. 2 square mm.
The battery is connected to the anode side of the solar panel. So the voltage is the same.
- Fuse installation
We recommend installing a fuse between the anode extremes of the solar panels and the anode extremes on the charge controller. There is no need to install a fuse between each panel when connecting the panels in a series/parallel/series parallel manner.
The choice of fuse size depends on the amperage of the current, including how many solar panels you have put together and how they are connected (series/parallel/series parallel), and then use the above calculation to get the current amperage value of the solar photovoltaic group.
For example, if you have two 100-watt panels in series, each producing 5 amps of current, the total output current is 5 amps. We usually set an insurance value for the current, which is generally 1.25 times the current, so it is sufficient to choose a 6.25 amp fuse or a 10 amp fuse for this photovoltaic group.
5. How to connect solar panels and batteries
When the solar panel and the solar battery are connected, it is best to use a photovoltaic charging controller, which can control the output voltage of the solar panel, which can protect the battery from being overcharged.
At the same time prevent the battery from backflowing when the solar panel does not generate electricity at night. The connection method is as follows: Solar panel ---- photovoltaic controller -- battery -- DC load.
While solar energy is charging the battery, it is completely feasible for the battery to supply power to the outside. In this case, the power used by the load will preferentially use electricity directly from the solar panel, and the rest will be charged to the battery. On the contrary, if the power of the solar panel is not enough, electricity will be taken from the battery at the same time.
6. Precautions of solar controller installation
- Open the package and secure it in a suitable position (avoid direct sunlight and damp places).
- First connect the battery lead (so that the automatic recognition answer function does not cause errors).
- After the controller completes the identification process (the level indicator indicates the battery level), connect the solar panel lead.
- Connect the load line when the load is off. In order to use safety, do not load too much or add too many solar panels.
- Use a power source, such as a power generator, instead of a solar cell to charge the battery.
- When charging, remove the solar panel, and the charging current should not be too large.
- Pay attention to the anode and cathode terminals of the 12 volt 200ah lithium battery.
7. Can the battery be directly connected to the solar panel
No. If you connect the solar panel directly, it will form a solar panel to charge the 12v 100ah lithium ion batteries during the day, and the battery to discharge the solar panel at night, which has certain damage to the battery and the solar panel, so you must connect the controller.
After a simple understanding of the detailed knowledge of solar panel wiring, it is not difficult to find that although parallel will increase the cost of some wires, but not in the case of long-distance transmission, the increase of wires will not be much.
And parallel stability is higher, the circuit is not easy to completely paralyze. The above is the explanation of solar panel wiring. If you have any questions, welcome to contact us.