Worked for me
I set up a solar panel to keep my 2 group 31 batteries charged over the winter. Worked fine one year, but a second year my batteries went dead due to the fact that the solar could not keep up with the battery drain. My boat was kept in the water that year and the bilge pump switch failed such that the pump kept cycling due to water sloshing in the bilge. No leaks, just no hysterisis in the switch. My cycle counter showed over 700 cycles! If your boat is high and dry, this problem won't occur. I would recommend that you disconnect the battery cables and connect the solar panel only to the battery. The solar panel should have a diode built in to prevent reverse leakage into the solar panel. I know the 4D is pretty large so any reasonable sized solar panel would not be too much power for it. Rule of thumb: You can trickle charge a standard wet cell at 1% of it's capacity without any damage. Assuming the 4D is about 250 AH (my guess), then a 2.5A continueous charge should be OK. My preference is to trickle charge at .25-.5% or 0.6-1.25 A in this example. Realize that the solar panel will only be at it's max output for 4-6 hours per day in the northeast, and I don't see any problem of overcharging. When you site the solar panel I would mount it on an angle, facing the sun and adjust the angle such that the panel is perpendicular to the sun during the winter months at your latitude. This angle can be found as the average of the declination of the sun during daylight hours for the mid winter months of storage. Consult any nautical almanac for this data or email me with your latitude and I will look up the number for you. This mounting will not only maximize the solar output, but will also help eliminate snow cover that would decrease output. Good Luck. Rich Stidger grstidge@capital.net
