Yea, 15 watts is going to give you 1 amp at 100% efficiency, which as you pointed out is rare. Sun must be 90 degrees straight overhead, no dirt on the panels etc. Realistically, a 15 watt panel is going to give you .5 amps on an average day. That's a notch above a trickle charge and frankly, not gonna power anything of value on my boat, but it would keep the batts topped off while I'm away.Highlander wrote:Excuse me !
2 Watts is trickle charging ! anything over 15 watts per battery will cook them in a very short time , 80 Watts is nice as long as you have some sort of charge controller , but depending on where you live that 80 Watts is most likely only going to be 30% to 45% efective , Solar power is way to expensive means of substaining hydro , cutting your hydro consumption with other options is the way to go & use a moderate solar system as a secondary back-up !
Nevertheless, on a perfect day you might push out 1 amp if the sun is bright and directly overhead in the summer. And you are right, THAT could cook your already topped off batteries, so a controller is in order.
For $66 bucks, you got a good deal and it's certainly worth using to keep batteries full if you are not a cruiser.