I've seen Jack Dirkes' Solar Panels mounted behind his boom gallows.
Where else have you mounted your solar panel(s), and what kind did you buy. Defender has a 100 watt system flexible system on sale right now with controller etc. for about $500.
Wouldn't a 20 watt system be plenty for charging a battery?
Thanks!
Ron
I have my boat on a mooring and this is what works for me. I use electricity to power my gps and occassionally, nav lights. I use a 10 watt panel. I Keep it in a cockpit locker, stored on edge in a protected spot and pull it out when my battery is about 12.4 volts. The panel is hardwired to my battery. As I'm leaving, I just place the panel on the cockpit floor. The controller prevents it from overcharging. When I come back (usually a day to two) the battery is all charged up.
Marc
According to Don Casey's book "Complete Illustrated Sailboat Maintenance Manual"(McGraw Hill), the output of a maintenance panel should be .3% of the total battery capacity. (maintainence means fixing capacity that deteriorates w time) His example is a 220 amp hour battery bank you need 0.66 amps, about what a 10 watt panel would produce. On my Suncat I have a group-24 battery with 65 Amp Hour capacity. That means my solar panel should be .19 amps for maintenance purposes only. At 100 deg F a 30 cell solar panel should be about 14.5 Volts (per Casey). Volts x amps = watts. Therefore I only need about 2.8 watts (.19x14.5) for maintenance. I use a 5 watt solar panel.
Now if I want to replace lost charge from using current on an overnight cruise, lets say (using Casey's numbers p 442 for device amp hrs - - anchor light 9.6 -12 hrs-, cabin lite 1.8. 8 hrs of depth meter for 1.6 and GPS for 4.0,) a total of 17 amp hours, then my solar panel at 5 watts (5/14 Watts/volts= amps) = .36 amps/hour = 47 hours at full output to replace the used charge. Because of sun angle inefficiencies, a fully sunny 12 hour day typically produces only 4 hrs of rated output (Casey) so it would take me approx. 12 fully sunny days (47/4) to replace that charge. (around central NY probably 3 weeks) For day sailing on the other hand, (my usual experience) I'd only use 5.6 amp hours or less (depth & GPS) and 15.5 (5.6/.36) hours of solar charging would work nicely, i.e. 4 days of full sun. These calculations appear reasonable and readily verified by my daysailing experience using my 5 watt panel. I usually use 4-6 hrs of sailing per week and in our area during the summer, there are usually 3 or 4 days/week of full sun. (Not so the rest of the year!)
I am happy with the 5 watt panel because I mostly day-sail since owning my SunCat, and a couple of weeks to recover once or twice a year from a one nighter is OK. A 5 watt 30 cell panel does not need a regulator but the voltage must stay above 13 volts. In hot southern climates, more cells and more voltage (Therefore more watts) is a good idea because of heat build up which causes voltage loss.
You can plug in your numbers and do the arithmetic for your situation but you need a good inventory of what you actually use to do this. OBTW solar panels should have plenty of ventilation to prevent overheating, an inch below them is recommended and a shadow on only one cell can shut the whole system down so placement is critical (cells are in series)!
Hope this helps.
Yes, Don, thanks very much for the thoughtful answer. I'll be adding up amps needed as I get closer to a purchase.
Ron