solar panel wanted

[bobg]

I want a simple solar panel just for keeping batteries topped up. Some on offer seem to say not waterproof, but does this mean you cannot do scuba diving with them? Are they really rain and spray proof but the manufacturers limiting product liability by saying not waterproof? I have also been told by the sage voices in the boat hut that as long as I get one that has a low trickle charge, there is no need to worry about having a cut-out device when the battery is topped up.

But the main question is what's the best deal around for a cabin mounted solar panel (rigid or flexi) used just for trickle charging a krankie battery and a deep-cycle battery linked together?

 

[Gin]

I went for a 30W Solarex semi flexible- it's sufficiently flexible for the cabin top and waterproof.

This one does NOT have a reverse current blocking diode to prevent battery drain at night- I particularly didn't want that to avoid either a bigger hole in the topsides to pass the diode through or the need to sever the cable and rejoin it in case that made for a non- watertight joint.

This set up suited me as I fitted a charge regulator so that as one battery was filled it would switch over to the other- to be honest I doubt this happens as whilst I went for the biggestpanel I could accommodate, what with shadow and inappropriate angle to sun for much of the time and living half under the sprayhood it really can only deal with the secondary battery to which the primary charge is directed. Probably if I removed the sprayhood when I leave the boat it would be very much more efficient .

As to cost, the retail price was a whopping £325 which I simply would not have paid just for this experimental installation but fortunately I got a brand new one on e-Bay for £125 which was quite enough!

 

[bobg]

Mucho thanko. More advice welcome.

 

[VicS]

FWIW I have a 5 watt panel to keep a small leisure battery topped up. I have found that quite adequte but my electrical consumption is low. I get virtually nothing from the outboard engine though.

I had the perfect place to mount a panel that size and no regulator is required.

You will need something a bit bigger but for just trickle charging not much. I would not parallel the batteries though. IMO you would be better off connecting to each battery via suitably rated diodes. A small diode splitter in other words. You do not need to worry about volts drop across the diodes as the open circuit volts of a solar panel is more than high enough to overcome that. If deck space lends itself to installing two small panels rather than one large one then you could consider a separate panel for each battery.

If you search through the websites you will find recommendations on the max size of panel you can use vs. battery capacity without needing a regulator. I can't quote a url off hand.

Be sure to fit fuses, as close to the batteries as possible, rated to protect the wiring between them and the panel(s).

I can't comment on the water proofness. Mine came from a chandlers and I assumed it was suitable for the intended use. It would seem foolish to me to go to all the trouble of installing something that was not suitable only to have to rip it all out after a couple of years and buy the more expensive one that you should have bought in the first place anyway.