Solar Upgrade

We’ve added panels to our solar setup and made additions to the solar shed. Our primary solar input is through 3 polycrystaline panels ranging from 235 to 250 watts each. They produce electricity as 24 volts DC. The 4 panels we added are 190 watt monocrystaline and produce electricity as 36 volts DC.

We have two Morningstar MPPT chargers for the panels. These chargers are able to take 24 or 36 volts input and adapt to charge a 12 volt battery bank. One charger has input from the 24 volt panels and the other charger has input from the 36 volt panels, with both charging at 12 volts for the batteries.

This photo was taken at 4 pm on December 4th.

We added the panels because for 4 months during winter the sun at the south is in almost always in the trees. We don’t get the same level of solar charging for our batteries. For 2 of those 4 months we generally don’t have to use a generator to charge the batteries (we have a 100 amp charger wired into our system). From November 21st through January 21st a series of cloudy days requires running the generator periodically to keep the batteries at a decent level of charge.

Our hope is that the extra panels will help keep the batteries at a better charge and require less running of the generator.

We have 3 of the 190 watt monocrystaline panels on a frame. All our other panels face solar south. These face southeast to get morning sun where there’s a break in the tall trees. Monocrystaline panels are affected by shading, unlike polycrystaline panels. Output will dramatically drop if there’s a shadow on a panel.

We had a wood frame supporting one of the polycrystaline panels. We put in rails so the wood frame would support 2 panels. The panel on the left is 235 watts polycrystaline and the one on the right is 190 watts monocrystaline. The larger panel is 50 pounds in weight, the smaller panel is about 40 pounds, easier to manage.

For most roof top solar panel installations a rail support system is used. The rails are aluminum and are designed with a groove for clips to hold panels on the top and another groove on the side for the T-bolt or similar mechanism for fastening to the roof. We used the K2 support system.

The end clips hold the panels securely. Since we had 2 different sizes of panels we had 4 end clips for each. A series of same-sized panels would have intermediary clips.

There is a junction box on the back of each panel at the top. Positive and negative cables leave the junction box and are connected to the wires to the solar shed with special connectors.

The connectors are male and female outer plastic shells. Inside the female shell has a male terminal and the male shell has a female terminal. I’ve taken a male connector apart and below the connectors are the components. The terminal is crimped to the wire. A cap is slid up the wire, then a compression cap, and then a white rubber sleeve. When the cap is screwed onto the connector the compression cap squeezes the rubber sleeve into the connector and around the wire creating a seal. If you look closely you’ll see the red o-ring on the black plastic male connector for an inner seal.

For attaching terminals to wire I have a special crimping tool. The blue tools at the bottom are for screwing the connector cap and body tightly together. These tools also have prongs for pressing retaining clips holding the connectors together so the connectors can be released.

We have a breaker box in the solar shed for wires going from the panels to the chargers. Square D QO breakers are UL listed for DC use and are the least expensive option. We have similar breaker boxes for wires going from the chargers to the batteries. Breakers at both sides of the chargers allows them to be isolated from the system. There is a similar breaker box for the wires from the 100 amp charger when we need to use the generator for charging.

December 8, 2021