Has anyone else pondered this question ? Even better have they come with a solution ?
P235 No 36 "Juicy Blue"
I replaced my solar panel about 2 years ago. I figured that there was little point having a permanently mounted panel as it most likely would always be in the way wherever I put it.
I went for a freestanding (and much cheaper) panel and controller bought from our beloved retailer; details below:
I had to add some additional rubber feet but it works fine. When I have finished for the day I simply leave it on the seat in the cockpit and connect. When I sail, it just sits below. I tend to sail every couple of days in the summer and it provides enough juice to power 2 radios, 2 instruments and the occasional use of the auto tiller – but I also get a little juice from the outboard.
Hope this helps
I had a solar panel fitted by Parkers on the coach roof forward of the hatch, it was about 2 foot square. That was over 10 years ago and solar panels no doubt improved since then. It powered two 85 Ah batteries in the starboard internal locker under the bench seat. The panel appeared to work well and a NASA battery monitor let me see how the batteries were doing. I just had to remember to pull the hatch back when using the boat which was not a big problem.
A shadow caused by the boom no doubt reduced the efficiency however the batteries always appeared to be fully charged when we went to the boat.
I have also seen a simple solution on other yachts of a fly lead and attaching a removable solar panel when the boat is not in use.
I sold Tarka in August after many years of happy ownership and she now resides in Rutland water, the new owner has joined the association.
I have a small solar panel (i.e. one not needing a controller) mounted on a (cheap) monopod camera pole attached to the aft starboard pushpit corner. The pole has a universal joint on the top so I can point the panel as I like. My battery is also on the starboard side, so it was relatively simple to fit a waterproof socket near the pushpit, and lead a wire to the battery above the aft berth. This arrangement has lasted quite a few years, and keeps the battery topped up between sails. I don't unship it when sailing as it doesn't appear to get in the way.
I mounted a 10watt panel over the forward hatch by bending a couple of thin bits of stainless to clip behind the hinge. I installed a waterproof socket nearby and fed the wire back to a controller which I bought from Maplin, sadly no longer with us. I dry sail and when the boat is on it's trailer it gets the sun for most of the day, fortunately. This keeps the battery topped up between sails and I know the thinking is a panel of this size doesn't need a controller, but on a sunny day it generates 1amp and charging continuously I feel it can't do the battery (110ah) any good. I normally leave it in place when sailing but sometimes disconnect it and take it below if the sea looks a bit rough!
I also have a small fridge with a Danfoss compressor and this uses less than 3 amps on average, connected to a dual voltage transformer which I plug into shore power when available. However when at anchor I have a 20watt panel mounted on a universal bracket on a pole which I assemble and then I plug this into the charging point near the engine, connected in parallel with the other panel.
I estimate the maximum current on a bright sunny day with the panel correctly aligned and the ambient temperature not too high, to be about 0.3- 0.35 amps ( "https://www.solartechnology.co.uk/content-files/cms/files/flexi-panels/Flexi%20spec%205W.pdf"). So far I don't think this has damaged the battery, though most of the time it won't have been in the best alignment, or the Sun would be obscured by clouds.
I found your last post interesting and followed your link. They did recommend a controller, admittedly the panel they were discussing was 10 watt but apart from controlling the current, it is also needed to prevent reverse charging of the panel.
I had always assumed my panels incorporated a diode to prevent this happening but when I was installing the 20 watt panel I needed to extend the cable and as the existing junction box, a black plastic moulding, bonded to the panel, was looking a bit loose I decided to remove it and connect the new cable directly at this point. I had always assumed the diode was also housed in this moulding but I was surprised that there was no diode and the original wires were soldered directly to the foil strips incorporated in the panel!
Without going to the boat I can't remember the make of the panels but they are well known German ones and I was intending to connect to a controller in any case. I have seen panels advertised as incorporating a diode so guess this is a feature worth checking when deciding to fit solar panels without using a controller.
I also thought there would be no danger of discharge through the cells. I see it has short circuit protection, but I suppose that is not the same. I leave everything connected during the sailing season, and there hasn't appeared to be a problem with discharging overnight. In the winter, I normally take the battery home, but due to the Pandemic , it has stayed on the boat this time, so we will see what state it is in when I am allowed back on board