By Aimii | 10 June 2022 | 2 Comments
Connecting Solar Panels In Series Or Parallel
Solar panels come in different wattages. But we know that it doesn't mean more panels equals higher power. If you are considering mixing two or more panels, there are some things you should keep in mind.
Series wiring is to simply connect the positive (+) pole of one panel to the negative (-) pole of the next panel, which increases the voltage but keeps the current the same. You will get a total output voltage that is the sum of the voltage drop from all the single solar panels.
For example, you will get a total output of 72 volt 5 amp if you connect four solar panels of 18 volt 5 amp.
It has no need for fuses, and the wiring is easier and more cost-effective. Higher voltage means lower current through the wire. The smaller wire costs less than the larger wire.
Lower current means less heat loss in wire transport. So it will make the solar system have a higher work efficiency. And the less heat loss makes it allows you to use a longer wire to connect devices. As you know, high temperature is not good for the devices like charge controllers, inverters, and batteries. A longer wire makes it possible for them to work in the shade or cool room.
Second, each solar panel should be unshaded. Any one of the solar panels being covered by shade would affect the power output of the whole system. For example, if the current of any panel drops from 5 amp to 4amp, the total output power would drop from 360 watts we calculated above to 288 watts (72 x 4).
Third, if one wire was damaged, the whole system would not work.
Finally, you need to use an MPPT charge controller. It is a DC to DC transformer that converts power from a higher voltage to a lower voltage. The amount of power is unchanged (except for a small loss during conversion). For example, if your panel draws 18V, 6 amps, the charge controller will adjust the voltage to 13.8 and increase the current to about 7 amps. That way the battery can get more power because the overall charging power doesn't drop that much.
Parallel connection is to connect all the positive (+) poles of all panels and then all the negative (-) poles. This keeps the voltage constant but increases the current flowing into the controller.
Connecting the same solar panels (4 panels of 18 volts 5 amps) in parallel, you will get a total output of 18 volt 20 amps.
As each solar panel works independently, wiring solar panels in parallel is suitable for the mix-light condition.
In some conditions, like one panel is shaded and the others aren’t, you will not lose a lot of power compared to the series connection, because you still get enough voltage. Every panel works separately, and one would not affect the others. And due to the total voltage being low, it is much safer.
It is also suitable for low-voltage systems, such as some RVs and boats. As the parallel wiring doesn't change the total output voltage, you can choose the solar panels which have a similar rated voltage to your battery bank.
You can use PWM controller to reduce the output voltage of solar panels to make the batteries work well. And you know, the PWM controller is much cheaper than the MPPT controller.
Parallel connection requires thicker wire, fuses and connectors. If one panel is shorted, each panel must be fused at the junction of the connector. As the current increases, the wiring must be larger, which means a higher investment and heat loss in charging. If you plan to use a longer wire, you need to increase the size of the wire, that further increases your cost.
In addition, you’d better use the solar panels which have the same rated voltage, because the output voltage in parallel wiring would select the lowest rated voltage.
If you are sure there would be no shade covering, you can use series wiring. The high voltage makes more output at the peak of the sun.
If you are using an MPPT controller, you can directly connect multiple panels in series to obtain a higher input voltage, and let the MPPT controller control the charging. No need for combiners, fuses or oversized wires.
There are also other factors when you consider the series or parallels. One of them is the different ratings of the panels. A lower rating will result in lower power output. In order to minimize losses, we suggest you connect solar panels of different brands in series and connect in parallel for the solar panels of the same brand but of different voltages. The best and simplest way is to use the solar panels in the same brands and ratings (voltage, wattage). Also, do not mix the old and new batteries.
Let’s say, if you have a 200ah/12v battery, two 200w/24v panels, and an 850va/12v inverter, do you connect in series or parallel? You can connect them in parallel.
We know solar system setup can be difficult for most newbies. If you don’t know how many and what size of solar panels you need, our customer service team is standing by to give you some suggestions.
Table of contents
Wiring solar panels in series
● Voltage and current in series
● What it's best for
● Connection precautions
Wiring solar panels in parallel
● Voltage and current in parallel
● What it's best for
● Connection precautions
Which is best for you?
● Shade condition
● Batteries
● Charge controllers
Wiring solar panels in series
Voltage and current in series
Series wiring is to simply connect the positive (+) pole of one panel to the negative (-) pole of the next panel, which increases the voltage but keeps the current the same. You will get a total output voltage that is the sum of the voltage drop from all the single solar panels.For example, you will get a total output of 72 volt 5 amp if you connect four solar panels of 18 volt 5 amp.
What it’s best for
As wiring solar panels in series keep the current the same, it is suitable for the low-current system.It has no need for fuses, and the wiring is easier and more cost-effective. Higher voltage means lower current through the wire. The smaller wire costs less than the larger wire.
Lower current means less heat loss in wire transport. So it will make the solar system have a higher work efficiency. And the less heat loss makes it allows you to use a longer wire to connect devices. As you know, high temperature is not good for the devices like charge controllers, inverters, and batteries. A longer wire makes it possible for them to work in the shade or cool room.
Wiring precautions
First, all the solar panels should be in the same rated current, because the lowest rated current of any one panel would be the output current of this solar system.Second, each solar panel should be unshaded. Any one of the solar panels being covered by shade would affect the power output of the whole system. For example, if the current of any panel drops from 5 amp to 4amp, the total output power would drop from 360 watts we calculated above to 288 watts (72 x 4).
Third, if one wire was damaged, the whole system would not work.
Finally, you need to use an MPPT charge controller. It is a DC to DC transformer that converts power from a higher voltage to a lower voltage. The amount of power is unchanged (except for a small loss during conversion). For example, if your panel draws 18V, 6 amps, the charge controller will adjust the voltage to 13.8 and increase the current to about 7 amps. That way the battery can get more power because the overall charging power doesn't drop that much.
Solar panels connected in parallel
Voltage and current in parallel
Parallel connection is to connect all the positive (+) poles of all panels and then all the negative (-) poles. This keeps the voltage constant but increases the current flowing into the controller.Connecting the same solar panels (4 panels of 18 volts 5 amps) in parallel, you will get a total output of 18 volt 20 amps.
What it’s best for
As each solar panel works independently, wiring solar panels in parallel is suitable for the mix-light condition.
In some conditions, like one panel is shaded and the others aren’t, you will not lose a lot of power compared to the series connection, because you still get enough voltage. Every panel works separately, and one would not affect the others. And due to the total voltage being low, it is much safer.
It is also suitable for low-voltage systems, such as some RVs and boats. As the parallel wiring doesn't change the total output voltage, you can choose the solar panels which have a similar rated voltage to your battery bank.
Wiring precautions
You can use PWM controller to reduce the output voltage of solar panels to make the batteries work well. And you know, the PWM controller is much cheaper than the MPPT controller.
Parallel connection requires thicker wire, fuses and connectors. If one panel is shorted, each panel must be fused at the junction of the connector. As the current increases, the wiring must be larger, which means a higher investment and heat loss in charging. If you plan to use a longer wire, you need to increase the size of the wire, that further increases your cost.
In addition, you’d better use the solar panels which have the same rated voltage, because the output voltage in parallel wiring would select the lowest rated voltage.
Series or parallel, which is best for you?
When you read this section, I believe you’ve already known the pros and cons of both series and parallel connections of solar panels. But which wiring method is best for you? The answer is not black and white. It depends on your requirements. There are three main factors you need to consider.Shade condition
If you use the solar power in your RV camping life, wiring solar panels in parallel would be better. You may park your campervan under the trees, besides the buildings etc, so the shade would cover some parts of your solar panels. In that case, if you still use series wiring, the output power of your solar system would drops.If you are sure there would be no shade covering, you can use series wiring. The high voltage makes more output at the peak of the sun.
Batteries
When charging your batteries, the total output voltage from the solar panels must be higher than the nominal voltage of your batteries. For example, some 12V batteries requires 12.6 volt at start charging, while the output voltage of most solar panels are at 18 to 20 volt. In order to meet the voltage requirement of batteries, parallel wiring must take 70% of its capacity, while series wiring only need less than 30%. This 30% capacity would be easy to get even in the morning, late afternoon or cloudy day.Charge controllers
If you're using a PWM controller, you have no choice but to parallel. That means more combiners, fuses and bigger wires. All of which cost more money and installation time.If you are using an MPPT controller, you can directly connect multiple panels in series to obtain a higher input voltage, and let the MPPT controller control the charging. No need for combiners, fuses or oversized wires.
There are also other factors when you consider the series or parallels. One of them is the different ratings of the panels. A lower rating will result in lower power output. In order to minimize losses, we suggest you connect solar panels of different brands in series and connect in parallel for the solar panels of the same brand but of different voltages. The best and simplest way is to use the solar panels in the same brands and ratings (voltage, wattage). Also, do not mix the old and new batteries.
Let’s say, if you have a 200ah/12v battery, two 200w/24v panels, and an 850va/12v inverter, do you connect in series or parallel? You can connect them in parallel.
We know solar system setup can be difficult for most newbies. If you don’t know how many and what size of solar panels you need, our customer service team is standing by to give you some suggestions.
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