Recognising that the old solar system was end of life we’ve spent some time researching different replacement options. Laying flexible panels on the roof initially seemed like the obvious choice. It’s a large roof pointing skywards. But... flexible panels decay quickly, they are prone to overheating and damage from being stood on. Then the roof will most always have shadows from the boom, lines or helm station.

That moves us to option 2. Use fixed rigid panels on a solar arch. This frees up the roof, allows us to use higher efficiency more powerful panels, but requires the construction of an expensive stainless steel structure to support them above the davits. The positive by product is increased shade from the ‘extended roof’ shading the dinghy too.

Going through a few iterations of arch design we’ve ended up with a much more light weight solar wing sitting on the existing Bimini / Mainsail traveller vertical supports. This has cut the cost in half but also looks much more natural.

Maximising W / m2 led us to the Sunpower maxeon 3’s at 400W each for 100 x 170cm. But, non in stock. Probably due to the volatility in oil prices spiking home energy driving many to install solar. Next best option (in stock) is the Marlec 400W 100 x 169cm PERC panels. We did look at dual sided panels but the increase in output is negligible.

And then, selecting an MPPT controller that can handle the 1.6kw and output 133A at 12V seems to be beyond most controllers. Victron website very helpfully takes custom panel specs to determine the best controller for different combinations of series or parallel or both. We’ve ended up with two 150/70 controllers. Max 150V in and max 70Amp out. So two panels in parallel generate 150V open circuit and 66A at 12V out.

And then where to install them, high Amp end needs to be close to batteries. So next to 12V distribution bus. What I don’t understand is why the MPPT controller terminals are so small when the cables need to be large mm2 to avoid voltage drop and resistance. So that’s the theory, on to the install.

I’ve mounted the two controllers on a stainless steel sheet with two large holes cut out for the large computer fans switched by two 40C sensors. The 16mm2 cables from the controllers run to the 8mm terminal blocks. 25mm2 cables don’t fit into the controller terminals. With the two sets of solar cables routed from the bimini through to the floor compartment under the helm seat, which vents up and out, but I can create additional ventilation holes.

The panel installed in its’ new home with the cables running a short distance around to the main 12V distribution bus. Lots of fiddling with cable ties and clearance to make sure the cables don’t chaff or short. The last job is to connect up to the distribution bar, in place of the redundant starboard alternator cable.

Nothing is ever easy, disconnecting the alternator and winch cables, and fuses, we’re stuck being unable to remove the black plastic negative cover. If we could remove the negative cable then we could connect up the solar charges to the bus. I still need to remove the cable connection from the starboard alternator and the alternator belt.