Another solar panel question

[Porthandbuoy]

Space to fit solar panels on Ladybird is limited. I have two realistic options:-

1) Forward of the mast there is enough room for a 20W panel. Shading by the forestay, sheets and shrouds when on her mooring would be minimal.

2) Aft of the mast I could fit a 30W panel, but it would be mostly in the shadow of the kicking strap.

So what's best? A 20W panel with an occasional shadow falling across it or a 30W panel rarely free of a shadow?

Both in parallel would, I suspect, be the best solution, but I can always add the other later.

 

[PaulRainbow]

Hard to be 100% certain, but i suspect there would be little difference. Both, in parallel would be the best option, as you suspected.

 

[lpdsn]

Space to fit solar panels on Ladybird is limited. I have two realistic options:-

I've an 18W panel just tied to the pushpit. I use it for trickle charging the battery I use for the trolling motor on the dinghy, but I'm sure I could put a number on the pulpit if I wanted them for the main batteries.

 

[sogood]

My experience so far of a 30 watt panel is that it provided very little, about 0.3amps when in the shade, ie. facing away from the sun. When I turned my boat around so now it faces the Sun, it shows up to 2.0 amps. I'd go smaller with less shade.

 

[Stemar]

I have a 24ft boat and managed to fit a pair of 20w panels over the hatch garage. I used rigid ones - much cheaper - and built a frame out of aluminium angle pop riveted together. The advantage of using a pair of small panels rather than one big one is that a small shadow can have an effect out of all proportion to its size. If one panel has a shadow on it, I may lose most of the output from it, but the other is usually in full sun, so working properly.

 

[Porthandbuoy]

Just thought I’d resurrect this thread and tell what I did, and the results.

I installed a semi-flexible 20W solar panel and a PWM dual-battery controller, both purchased from Photonics Universe. The controller has been configured to give 90% output to the house battery, a 110Ah Elecsol, with the balance going to the engine battery.

So far this summer, and no doubt helped by the cloudless sunny days we’ve been having, both batteries have been fully charged every time I’ve stepped aboard. Better still, the solar panel has been keeping up with the demands of the GPS, VHF, log&depth display, and autohelm.