Mounting the Solar Panels

We chose to locate these on the main hatch cover.

The panels are 20V/20W each - so the total rig on a good day should deliver 40W. They were quite cheap on eBay - apparently, the guy had bought a whole batch for some sort of street-furniture job for the local authority and was selling the extras off.

Complete assembly.
The idea was to mount the panels on the hatch, run the wiring through a proper plug / socket to the inside and then provide a flexible connection to the control unit.

Parts List

• Solar panel mount:
  
• 2 x Solar Panel units. These consisted of 2 panels each in a hinged unit internally wired in parallel with protective diodes already in place.
• Strips of angle plastic for mounting brackets - from the hardware shop. This is the sort of plastic trim that you can put on bathroom cabinets.
• Screws / Nuts / Washers to mount the brackets to the panels and the hatch cover.
• Take Cable through hatch:
  
• Deck Connection Plug + Socket 2 Pin (Whitworths SKU: 33431)
• Cable Ties + 2-way adhesive bases.
  
• Flexible connection mount:
  
• Small plastic box - the sort of thing you would put a small electronics project in.
  
• Surface mounted cigarette lighter socket.
• Small length of choc-strip.
• Screws / Nuts / Washers for mounting.

How it was done

Making up mounting brackets for the panels

All the literature on the matter recommends keeping the panels as cool as possible - their efficiency drops off with temperature. I made up brackets to give a generous air-gap under the panels with angle plastic strips. These were cut to length, drilled and then bolted together with stainless fittings.

Cross Section through the mounting brackets.
Once the brackets are on the panels, mount the complete assembly on to the hatch cover - drill the holes and treat them with silicone sealant before tightening down. Make sure the cables are running the way you want them first.

Outer Wiring

The solar panels already had cables attached ending in croc-clips. They also had diodes. I left the diodes in place. When the panels generate power, they will charge the battery. When it's dark, they become a resistance across the battery and discharge it. The diodes stop this. I cut off the croc-clips.

Connect a length of cable cut off the solar panels to the Deck-mounted socket. Drill holes and mount the socket on the hatch not forgetting to drill a hole in the centre to let the length of cable pass through the hatch. Best to silicone the mounting screws. Put the plug in and lead the cable from the panels to the plug. Keep the cables permanently in place using cable-tie bases. These are self-adhesive but they really need to be screwed down.

Connect the panel wires to the plug. Make sure you get the polarity right - the positive goes to the big pin. Use a multimeter if in doubt. The panels should be wired in parallel - i.e. they produce the same voltage and, in theory, double the current.

Wiring in cable-ties connected to the plug.
Flexible Connection Mount

This part terminates the hatch-wiring and provides a connection point for the flexible connection. This connection allows the hatch to be opened and closed while everything is still connected and also keeps dangly stuff out of the way.

Assemble the connection box by mounting the cigarette lighter socket in the box and screw in a bit of choc-strip to take the wires (two connection points). Drill a hole in the top of the box to take the incoming cable from the panels. The cigarette socket I used had solder connections so I soldered a couple of pieces of wire from these into the choc-strip and then screwed the panel cable into this.

Screw the box assembly on to the hatch lid. I put this at the rear end. The problem with this is that, if anyone shoves the hatch back too hard, the box will hit the hull. You have to be careful.

Flexible Connection terminal assembly in place.
What should have been done differently

• The Deck-mounted connector is very high-profile - it almost interfered with the gull-sweep and it's a great little fitting to stub your toe on. As sod's law dictates, my local supplier got a load of low-profile connectors the day after the job was finished. If I ever need to change that fitting, I'll hold out for a low-profile one.
• The flexible connection mount is not in a very good place. One day, someone will give the hatch a good shove and it'll take some damage. I'm not really sure what to do about this. I guess a couple of adhesive rubber feet may help.
• Cigarette lighter fittings are not really marinised. They may be OK in an out-of-the-way part of the cabin but this is a little too near the big bad world for my liking. I had a setup on a dinghy and it didn't work at all. If this fails, I will have to revisit with some proper marine fittings.
• I didn't bother to silicone the hatch holes on the first attempt. A rainy night out solved that problem.