How to make a light duty solar panel junction box

If you have multiple solar panels and you want to connect them together to form an array, it is very helpful to create a solar panel junction box to help keep the wiring organized, and to also help eliminate reductions in voltage or watts coming from the solar panels.  In this write up, I will describe how to make a light duty solar panel junction box.  My definition of a light duty solar panel junction box is a box intended to be used to join low voltage, low amperage, low wattage solar panels together in parallel.  If you have 12 volt solar panels under 5 amps, that use 18-12 guage wiring – then this box will work for you.  If you have higher wattage solar panels that use MC4 connections, I recommend you view my write up for a heavy duty solar panel junction box.

When I created this light duty solar panel junction box, my intention was to create a solar panel array that was composed of 6 15 watt solar panels all wired in parallel.  This way the amperage and voltage would stay the same, but we would be increasing the joined wattage of the panels at the junction box.  I had started with two of the harbor freight 45 watt solar panel kits that use 12 guage wire and do not produce a lot of juice compared to larger panels.  I planned to install these panels on the roof of my garage, run the wiring to the junction box, and then run the junction box to a charge controller that would regulate my battery bank.  I wanted to keep the setup as simple and clean as possible.  The junction box you are creating is basically just an enclosed positive and negative bus bar that joins all of the positive leads of the solar panels to one bar, and all of the negative leads of the solar panels to the other bar.  Again, this is parallel wiring, so the amperage does not increase, the voltage does not increase, but the wattage does increase.

Step 1:

Go to Radio Shack and pick up the following items:

1) Project Box Enclosure

2) Barrier Strip – 8 or 12 position

3) Jumper Strip (if they do not have anymore, get a pronged electrical connector that can be used as a jumper

4) Grommets

5) 12 guage wire with two leads.  If they only have 1 lead, then get two reels – 1 red and 1 black

6) Super Glue

Step 2:

Take out the Barrier Strips and Jumpers and connect the jumpers to the barrier strip:

Step 2 option B if no jumpers are available:

Step 3:

Super Glue the new barrier strip with junctions inside the project box:

Step 4:

Drill a holes in the bottom of your project box large enough for two wire lead in the bottom of the junction box, and drill one giant hole (largest grommet size) in the top of your box for all of the leads from the solar panels, and install your grommets.  Connect one of your wires leads to one strip, and one wire to the other barrier strip.

Step 5:  Run all of the leads from your solar panels into the large top holes on your junction box.

Step 6: Connect all of the positive wires from your solar panel to one barrier strip.  Then connect all of your negative wires from the solar panel to the other barrier strip.
You will now have one positive bus bar, and one negative bus bar.  Your junction box just helped you to take all of those messy wires from the solar panel, and organize the
into one neat box that not only combines all of the panels together in parallel, but also now gives you two nice neat wires to work with.

Step 7: Connect the new single positive lead to your charge controller, and then connect the new single negative lead to your charge controller.

Step 8: Connect your charge controller to your battery.

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