What is the maximum cable length for solar panel? | Calculator
Most people who want to install a solar system wonder how far should the solar panels can be from the house.
In some cases, you may have to install solar panels far away from the rest of the system components because there is not enough space to install them or to avoid obstacles that could cast shadows on the panels.
Leaving the solar panels mounted wherein it will just be blocked by shade of trees and buildings will leave the panel useless since the light energy which is sourced from the sun does not reach the photovoltaic cells.
On the other hand, installing the solar array away from the load, whether it is batteries or inverters, is not always the best way to ensure maximum power, because the system will be subject to power loss due to resistance to flow in the cables, but this can be reduced by using a large cable diameter.
The satisfactory preparation between avoiding shading, line loss, and extra costs due to purchasing a large-sized section is knowing the maximum cable length to use with your solar panels.
In this article, I will reveal to you the distance that must be respected for your setup.
Why is it important to respect the maximum distance of the cable?
Avoid voltage drops
When the length of the cable is long for a certain current flow and wire size, the electrical voltage that will reach the load, whether it is charge controller or inverters, will be less, and the device may not work to charge the batteries properly, as the charge controller is not designed to compensate the voltage drop (raising the voltage to reach the battery voltage, learn more).
As the cable length increases, voltage drop is inevitable even if you use thicker cables.
However, this voltage drop can be reduced to a reasonable level.
As a general rule it should be kept below 3% as recommended by the National Electrical Source Code (NEC). Source
Note: You may find in some sources a rate of more than 3%. In fact, you can work with any value between 3 and 10%. A voltage drop of 10% is acceptable for non-critical loads, such as lights, because they usually have a wide voltage range in which they operate.
But you should not have a voltage drop of more than 3% for any critical loads, such as solar water pumps.
Avoid risk of fire
Choosing the right cable diameter for your PV installation is not only important to ensure minimal energy loss between solar panels and the battery bank, but also to avoid a fire when using a small cable.
If the distance between the solar panel and the charge controller is too large, the cables may overheat constantly, which may lead to their damage quickly, and there is also a small risk of fire. Source
What is the maximum distance between battery and charge controller?
When talking about the maximum cable length for solar panels, we mean the length of the cable that extends from the photovoltaic array to the location where the charge controller or inverter is located.
As for the other solar components, it is agreed that they should be close to each other. The battery should be close to charge controller and/or inverter, in this case the cable wire gauge (AWG) between the batteries and the charge controller is determined by the ampere capacity of the charge controller.
A table below shows which gauge of wire should be used to connect the battery bank and charge controller.
| Controller to Battery | |
|---|---|
| Charge Controller Size | Cable Wire Size |
| 15 amp | 14 gauge |
| 20 amp | 12 gauge |
| 30 amp | 10 gauge |
| 40 amp | 8 gauge |
| 60 amp | 6 gauge |
| 80-100 amp | 4-3 gauge |
Remember that the charge controllers should not be more than 3 feet (1 meter) from the battery bank!
What size wire should I use for my solar panels?
For higher wattage solar panels (50 watts and above), thicker wires may be needed to reduce voltage drop and ensure efficient power transfer. Wire gauges such as 10 AWG may be recommended in some cases to handle current effectively over longer distances or for installations where the flowing current can reach up to 30 amps.
However, the specific wire gauge required can vary based on the solar array configuration, so if you set up a solar array in parallel, a 2 to 8 AWG array will be needed to safely transfer power to the charge control unit or inverter.
What is the Maximum Cable Length to Use with your Solar Panels?
Here's what this calculation looks like for a 12V and 24V PV system:
The transition from 12V to 24V makes it possible to reduce the size of cables required and therefore the installation cost.
Example: Let's take a system of 4 100W panels installed in parallel. At Vmp 18V, the maximum current is 400/18 = 22.2 amps.
Looking at the wire capacity column, 10 AWG is the smallest gauge wire that can be safely used with 25A DC 12-volts system.
Next, we look at the Maximum Cable Length row, and select the column corresponding to the distance between the solar panels and the load, whether that be batteries or inverter.
To stay within the 3% loss parameters you can see that with a 12V system a 10 AWG wire pair only supports a cable length of 10 feet!
The same solar panels, if you install them in a different configuration, such as the 2S2P configuration (two panel wired in series and two in parallel with them)
In this configuration, the maximum current is Icc = 12 amps.
Following the same steps as above you can see that with a 24-volt system a 16 AWG wire pair is the smallest gauge wire that can be used safely.
To stay within the 3% loss parameters you can see that a 10 AWG wire pair supports a cable length of 40 feet.
The same applies to the 48V system voltage.Calculating Solar cable size
Most of the time you will be wiring your panels in series. This is because MPPT charge controllers have a high input voltage and it's cheaper to wire theme in series. in this case, you can use the calculator bellow to calculate the maximum cable length for solar panels:
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Output Voltage (n x Voc: e.g. 21.3V for 1 x 100W panel):
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Maximum Amperage (n x Isc: e.g. 6.07A for 1 x 100W
panel):
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Cable Size:
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Conductor:
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Select the acceptable Voltage Loss (%):
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Result:
For example, if we are going to install a 3kW solar power system with 9 panels connected in series. The solar panel rating is 340W, Voc = 40V, Ics = 9.53 Amps.
In a series connection, the current is 9.53A. The array voltage is calculated by adding the voltage of all panels (9 x 40) to get 360 V.
- We are going to use cable Size = 12awg (4mm²) copper.
- Voltage drop is as we choose, i.e. 1%.
Conclusion
It should always be remembered that for solar panels to work at their maximum capacity, they should be positioned and placed to a mount correctly.
Strong cables and ropes should be considered when mounting the solar panels to roofs. These cables will secure the correct alignment of the panels and will fit them to the roof. Another issue that the cables secure is safety. If these cables are loosely fitted to the panels, and in the event these falls off to the ground, it will render the surface on the panel broken and can even hurt someone if these panels falls off to people on the ground.
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Mohamed Bellamine
I'm the blogger behind Goo SolarPower. As a solar engineer, and a strong supporter of renewable energy. I've always been interested in Solar devices. I loves to write articles, guides, and tutorials about solar PV technology. Through goosolarpower.com I want to help people build and understand how solar power systems work.