Wiring the Solar Panels

Last month we got the solar panels up.

The next step was to research the best way to connect them and what we’d need to do it.

Each panel has a pair of wires (technically cables) with connectors.

One of the cables is positive, the other is negative. We had two options for connecting our three panels: in either series or parallel. There are advantages and disadvantage to each.

Series wiring connects negative to positive and positive to negative. This is the easiest configuration because it only requires plugging one panel into the next. It’s a good choice for longer runs of cable and can use smaller gauge (less expensive) cable. This set-up multiplies the panels’ voltages. Its disadvantage is that all panels must be in full sun. Even partial shade means no electricity. Or, if one panel isn’t working properly none of them work, just like a string of Christmas tree lights.

Parallel wiring connects positive to positive and negative to negative. Its disadvantages are that it requires adapters and heavier gauge (more expensive) cable for longer runs. Its advantage is that it begins to produce electricity when any part of the array receives sunlight. It isn’t up to 100% production until full sun, but at least it produces some. This set-up multiplies the panels’ amps.

For us, parallel wiring makes the most sense for several reasons. The first is that we want to take advantage of whatever sunlight is hitting the panels, even with partial shade. The second is that we don’t have a great distance between the panels and the battery bank.

We needed about 30 feet of cable to connect the solar panels to the battery bank. Dan will build a box for the batteries where the shelf unit is in the above photo.

The third reason is that we really don’t need additional voltage. Each of our panels is rated for 57.3 volts (VMP). Multiplied by 3 panels that would be almost 172 volts. That would be overkill for the small 12-volt system we need to power our freezer and a chest fridge. (See “Solar Pantry Part 4: The Plan“).

To connect the panels in parallel requires adapters.

They come in pairs, one negative and one positive. Connecting all three panels required two pair (for a total of four adapters, two positive and two negative).

The next step is to bury the cable, so let the digging begin.