If you are wiring your own solar panels, there are two methods you can use: wiring in series and wiring in parallel. Lee Feliciano from New Use Energy (NUE) helps us understand why one method is used over the other.
Wiring Solar Panels in Series
Every solar panel has both a positive and a negative lead. When you are wiring in a series, you are connecting the negative lead on one panel to the positive lead on the other panel, end to end. It’s as if you’re connecting them in a row, like a string of holiday lights. This creates what is called a “series string”. You are left with the positive lead coming out of one panel and the negative lead coming out of the other panel. In the case of wiring 2, 18-volt panels together, you end up multiplying the voltage of the one solar panel by two. Ultimately, you have created a 36-volt solar panel series with two solar panels attached to each other.
Wiring Solar Panels in Parallel
In order to wire your solar panels in parallel, you will need to use a combiner cable. When wiring in parallel, take both positive cables from your 2 solar panels and attach them to the Y Branch Parallel Adapter. Then, take both negative cables and attach those to the adapter. What you should have is one negative and one positive cable coming from your two solar panels. You can think of it as creating two “parallel” lines into the parallel adapter to help differentiate this method from wiring in a series.
Why Would You Wire in Series vs. Parallel?
Now that you’ve learned the two methods of wiring solar panels you’re well on your way to powering and charging with solar! What are some reasons you would use one method over the other?
You would wire your solar panels in parallel if the voltage was at the correct voltage but you wanted to have redundancy or to speed up the charging process. For example, if you are using a 12-volt SunKit, that means it is installed with a 12-volt battery. In order to charge that battery, one 18-volt panel would be sufficient because 12 is less than 18. But if you wanted to double the charging speed you might want to add a second 18-volt panel to have it charger faster. Adding the second panel would allow your battery to charge twice as fast. In this case, you would want to wire your panels in parallel.
In the case of wiring panels in series what you’re trying to do is to wire them so you’re hitting a certain voltage window or output. This would be useful for something like charging a battery that needs to receive a certain amount of energy in order to charge. For example, our 24-volt SunKit includes a 24-volt battery. One 18-volt solar panel would not be sufficient to charge the 24-volt battery. In this case, you would use the parallel method to boost the voltage that your battery is receiving. Two 18-volt solar panels wired together in parallel will generate 36 volts, which is sufficient to charge the 24-volt SunKit.
Part of NUE’s mission is to make solar affordable and accessible for all. We hope this overview on wiring in series and parallel have helped you learn a little bit more about solar. Please share and spread the word about clean energy!