[Charlie B]

They are good as a battery maintainer to keep a battery topped off. If you keep your boat in the water at dock or on a mooring they will keep up with self discharge and occasional bilge pump usage or other very light loads but not much more than that. Do the math a small panel is about 15 by 30 inches or so and puts out maybe 15 watts. Even a small 10 amp battery charger puts out a little over 14 volts at 10 amps and that works out to be about 140 watts. So you see you would need about 10 panels to roughly equal a small 10 amp charger...Charlie