There are two ways to wire together your RV solar panels; you can wire them in series, or parallel. These two methods are both good, but you’ll get different results in different situations.
Wiring RV Solar Panels in Series
Wiring in series is similar to Christmas tree lights; it’s strung together on the same line. Wiring in series is appropriate if all of your solar panels are the same size, such as all of your panels are 100 watts. However, if you have different size solar panels, let’s say, a 100 watt, and a 175-watt panel, you won’t get 275 watts, you’ll get more like 157 watts. The smaller panels will drag down the bigger solar panels.
Also, wiring your solar panels in series has a higher output voltage while keeping the amperage the same.
One other downside to wiring in series is problems with shade on your panels. When solar panels are wired in series, if one panel falls under the shade, it affects the whole series. This won’t happen when wired in parallel.
How to Wire in Series
Wiring in series is done by joining the positive wire of one solar panel to the negative wire of another panel. This can be done with the usual MC-4 solar panel connectors.
Wiring RV Solar Panels in Parallel
Wiring your solar panels in parallel increases the amperage while keeping the voltage the same. That means, if you wire panels with different wattages, the overall outcome won’t be affected. So if you wire together a 100-watt solar panel and a 175-watt solar panel in parallel, you’ll get a total of 275 watts. However, if the solar panels are dramatically different, then there may be some discrepancies.
The downside to wiring parallel is that it can be more expensive; higher amperage needs very thick wires. Thick, copper wire can be very expensive. Also, parallel wiring also requires special branch connectors or combiner box, rather than the usual MC-4 connectors.
How to Wire in Parallel
A parallel wiring connection is made by wiring the positive wires of two solar panels together, and wiring the negative wires of each panel together. Usually, this is accomplished by using special branch connectors made just for this purpose. The branch connector has two inputs for the positive wires, which join into one. Likewise, there are two inputs for the negative wires, which join into one.
This is sort of a hybrid between the two systems and may be appropriate if you plan to install four or more panels. This involves creating two series, then wiring those two series in parallel. When you do a series-parallel connection on your solar system, you need to parallel two (or more) equal-sized series strings together. For example, you can wire two sets of four 100 watt solar panels in series, then wire those two sets in parallel to create an 800-watt array.
You’ll need to consider your options, and decide what is the best system for you.