Solar Charging Station Project

This article describes the planning and construction of our club’s solar charging station.

I recently joined a second RC Club closer to my house.  The club recently had a major turnover of the club officers and is in the process of reorganizing things.  The first club I joined (South Jersey RC Society, of which I have been a member for many years, has a very capable charging station and I have become used to its convenience.  The new club for me (Jersey Sky Devils – AKA JSD) does not currently have a charging station.  So, when I go out to their field I either have to:

  • Bring pre-charged batteries
  • Bring a generator
  • Bring other batteries to be used to charge the flying batteries

This is very inconvenient.

The JSD members are used to not having a charger at the field.  They cope by:

  • Flying fuel, instead of electric planes
  • Use their large car / truck batteries
  • Bring a generator
  • Buy lots of batteries and pre-charge them at home

I have a nice 1800 continuous watt Westinghouse inverter generator which runs really well and uses little gas, but it is narrow and therefore unbalanced/unstable and once fell over in the back of my Prius.

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I have one of those 800 watt Harbor Freight generators, but they are relatively noisy for their size and I am unsure whether their relative “dirty” power might stress the circuit boards of my lithium polymer battery chargers.

One major obstacle to the club having a solar charging station has been that the owner of the small airport, next to which our flying field is located, has refused to allow us to construct anything on site onto/into which to place a solar charging station.  Finally we got permission to place a small structure for the purpose of housing the solar charging station.  It had to be under 8 feet in height and be placed so as to be way out of the way of the (alternate) landing area for large scale aircraft.

With permission granted for that, I researched the components needed to assemble a solar charging station.  Sources of information were the existing solar charging station at the South Jersey RC Society field, an article published in the AMA magazine, Amazon.com, google & YouTube.

I divided the project into modular components.  Many of the club members had skill sets better suited to specific modules and so we divided the tasks accordingly.

  • I put the overall plan together and was in charge of assembling the electronics and their configuration.
  • James Groff took on the task of building the shed at his house and later, the charging shelf at the field.
  • Brian LaBree recommended and supplied the deep cycle batteries at cost and built the heavy gauge battery interconnect wires and wires from the battery to the circuit breakers, cut-off switches, and charging bus.
  • I built the charging bus.
  • Bruce Cheeseman built the lockable box containing the cut-off switches.
  • Bert Armstrong organized the moving of the shed and the club work party at the field for the final assembly of the solar charging station.

The Shed:

The functions of the shed:

  • A mounting surface for the solar panels.
  • To house and protect the batteries, wires and solar controller.
  • To mount the charging shelf, charging bus, and charging bus cut-off switches.
  • To provide some storage space at the field.

I got the general idea for the shed from these pictures I found on the internet.  I looked up the panel pointing directions on the internet and took the average of the Spring-Fall and Summer angles (25 degrees) from vertical pointing SSW to optimize the light energy received during the flying season so that it would be unnecessary to keep repointing the panels from season to season.   The lean-to shed ended up being 5 feet deep and 8 feet long.  The high wall was 6.5 feet and the short wall 4.5 feet from the ground.  This yielded a roof slope of 25 degrees.

Pictures of actual shed are below:

After it was built we had to move it from James’ house to the flying field, 20 minutes away:

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The Charging Bus:

I made this out of 2 boards that were 8 feet by 3/4″ by 8″.  Grooves were made in one of the boards with a router to make a recess for the 4 gauge solid copper bus wire.  The bus wire was straightened by pounding it with a hammer on my concrete garage floor.   1  3/4 inch holes spaced 4 inches apart were drilled along the upper & lower section of the bus to create the charging ports.  Small holes were drilled in the center to allow the bus wires to exit to the connecting lugs in the back of the bus.  The shed is too small to be used from inside, so the charging will be done outside, but the wiring connections are inside and protected.   James created a 2″X4″ stud header for knock outs for the back of charging bus, the cut-off switch box, and possible windows to view the charge controller’s status LEDs from outside the shed.  Red & Black stripes were painted on the bus to make the polarity clear.   The club logo and lettering was printed on a color laser printer and attached with & covered by water based polyurethane.  The grounding/connecting lugs were obtained at an electrical supply store.

Cut-Off Switch Box

For safety and security reasons, we wanted to restrict access the cut-off switches which are on the outside of the shed.  Therefore, a weather protected, lockable box was constructed.  Bruce found an appropriately sized circuit box and built an aluminum flange around it so that it could be mounted in a cut-out of the wall of the shed and added a lock hasp.   I mounted the switches to the lower back of the switch box and cut holes in the back and bottom of the box so that the connectors to the cut-off switches could be accessed from within the shed without having to remove the switches or switch box.  I then placed a strip of plywood at the bottom of the box to isolate fingers from the connecting wires behind the switches.

Work Party:

Bert and James attached the charging bus to the side of the shed.  They then built the lower charging shelf.  An upper shelf was originally planned but it was later decided to “shelf” that idea and do it only if it were found necessary.  Bert cut 4 holes in the shed walls and mounted the vents.  Bill Froeder helped me transport a lot of my stuff to the field that I couldn’t fit into my Prius and helped generally with the various steps of the assembly of the solar charging station.

Brian LaBree, Bert and Edwin (Spin) mounted the solar panels to the roof. I cut a hole in the upper center wall and attached a conduit body to run the solar panel wires into the shed using drip loop.

Bert, Edwin & Brian inserted the 8 foot long 5/8″ diameter copper plated steel grounding rod into the ground.

 

Since Bruce had not yet completed the switch box at this point, finally assembly had to wait pending its completion.

Final Assembly:

Upon completion of the switch box, I cut a hole in the shed wall to mount the box.  I obtained/made the final cables for the battery/bus connections.  I used 4 Gauge welding wire for the battery to bus negative connections since that wire is half the price of “regular” automotive battery wire.  However, that didn’t come in red, and I didn’t want anybody in the future confused about the polarity of the wires.  I got 4 gauge automotive battery wire and crimped & soldered the appropriate copper lugs on them.  The batteries had 5/16″ posts,  circuit breakers 1/4″ posts and cut-off switches 3/8″ posts.  The connection at the charging bus was via a set screw, so those wire ends were solder tinned.  In-line fuses were placed on the positive wires of the panel to controller connection (15 amp) and controller to battery connection (30 amp).  The battery to controller was connected first and the controller to panel second.  Following that the connections of the battery to circuit breakers, circuit breakers to cut-off switches, and cut-off switches to charging bus were made.  Finally, the ground wire from the battery negative to the grounding rod was connected.

The batteries were place in a plastic storage bin to protect and isolate them.   Holes were drilled into the bin sides for ventilation.

LED lights were built into the charging bus board to serve as power light indicators indicating which side(s) of the charging bus were turned on.  They are simply wired from positive to negative across each side of the bus.

Finished Solar Charging Station!

Finished Solar Charging Station

Wiring Diagram:

Wiring Diagram

Wiring Diagram

The design allows for future expansion by adding more solar panels and/or batteries if needed.

If I failed to acknowledge anyone in this joint effort I apologize in advance.

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