Solar power extention

During our trip in the hot Adriatic seas, we have found out, that our actual 50W solar panel is not sufficient to be ultimately shore power independent. During that hot summer days we were able to keep the fridge running only for like 12 days before I had to recharge the battery from the shore.

One of the issue that was that our boom tent partially covered the panel during the day, so it has prevented the proper function.

So I've decided we need more solar panels. The question is the where to place it?
At first I was thinking putting them to the mast support or on the backstay.

solar panel on the aft mast support

solar panel on the backstay

However all these positions needs some maintenance and I think it's not really handy for a trailer-sailor when you need to simplify all the mast raising/lowering tasks.

A final decision was to get the semi-flexible panels and put them on the top of the cabin. The only possible free area for them is besides the mast base. Due to area limitation I was able to find these two suitable 20W ETFE semi-flexible panels from China with dimmensions of 600x300x2.5mm. You can also walk on these!

20W EFTE semi-flexible panel - model LS-20FX1

The installation is again drill-less using the 19mm 3M VHB acrylic double sided tape 49xx series, which has already proved to be working very well even on our hollow non-skid surface. It's just needed to degrease the surface with the isopropyl alcohol.

3M VHB double sided tape on the back of the panels

final placement

final placement

The next task was to create a junction box. I've created a simple circuit board inside a plastic junction box and glued it carefully under the existing 50W solar panel using Sikaflex 291i. It's important that this junction box is completely watertight to prevent any corrosion.

With parallel connected panels, each string to be connected in parallel should have its own blocking diode. This prevents current flowing from one parallel panel into a lower-current panel (shaded) and therefore helps to minimize mismatch losses arising in parallel connected arrays.

The best blocking diodes are Schottky's rectifying diodes like SB540 or similar. They have lower forward voltage drop around 0.3V instead of regular rectifying diodes which has around 0.7V.

junction box scheme with blocking diodes 

The new 20W panels are equipped with cables including the MC4 connectors already, so I've just bought two 1m long extension cables with MC4 connectors, cut them in half and used them as an input connectors.

inside the junction box

One hint here: to protect the circuit board from corrosion, it's necessary to coat the copper and the components with soldering rosin (flux) soluted in alcohol.

junction box glued with Sikaflex

The last step was to replace the old deck socket I've installed before. I bought some cheap China copy and the contacts corroded very badly just after a first season.

So I've decided to use some better connector with gold plated contacts and decided to use these type from Philippi Marine. You can also buy just the angular housing from Philippi and cheaper Weipu WA22 type connectors, which are not labeled "marine" as a primary use, but I believe it's the same quality - gold plated 16 Amps! That's what I did.

Weipu WA22 IP67 16Amp connector

The first test looks very promising and I hope that with a total of 90W, we will be shore power independent, at last.