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post #11 of 15 Old 01-30-2003
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solar power trickle charge

Connecting the solar panels to trickle thru the 12VDC lighter socket may simplify things, but that requires you to leave your battery switch in the closed position (as was stated).

My question: don''t most folks usually recommend that the switch stays open while the boat is unoccupied (and electric bilge pumps wire directly to the battery, bypassing the switch)?

Your thoughts on the pros/cons welcome.

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post #12 of 15 Old 01-30-2003
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solar power trickle charge

I the last 16 years I''ve left my batteries on for the entire season and turned them off only for winter storage. Never had a problem. In the application above this is the only way to benefit from a tricle charge.
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post #13 of 15 Old 01-30-2003
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solar power trickle charge

While it''s true that it''s a "good idea to turn your battery switch off while away" this only ensures the batteries will not be drawn down if you leave something else on ie. radios, lights etc. When you leave the boat after the weekend it is important to develop a procedure to shut down the systems while your away.

Another small point; if/when you measure the voltage from the solar panel without a load attached to it, it will not measure the ~16volts needed to charge the batteries. Don''t be alarmed, it''s just the switch which prevents back feeding the solar panel has not closed. Everything will be OK once you plug into the lighter socket.

Mike in Noank
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post #14 of 15 Old 02-12-2003
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solar power trickle charge

I use a 20 watt Solarex panel with no regulator. It works great, my batteries are almost always topped up when I arrive the next weekend. The 10 watt panel which I used previously didn''t seem to always quite keep up with the loads on my 33 foot sailboat.

I connected the panel directly to the two batteries through 2 diodes and 2 fuses. The diodes provide isolation between the batteries and also prevent discharging at night.

Leaving the battery switch on "Both" is not advisable. If the batteries are unequal, one will drain into the other and possibly both will be destroyed. I''ve had that happen. It''s also a possible fire hazard. If a battery shorts out, the other one will pump a lot of current into the bad one, heating it up. Not a good idea while the boat is unattended.

You can use just about any diode from Radio Shack as the current is low (less than 2 amps for a 20 watt panel). The fuses should be about 2 amps. The banded end (cathode) of each diode should be connected to the positive terminal on each battery through a fuse. The other ends (anodes) should be connected together and to the positive output from the solar panel. The negative output from the solar panel is connected to the negative terminals on both batteries. Using two diodes prevents any measurable current flow between the batteries while allowing the panel to charge both batteries.

Returning to the boat on a sunny afternoon I''ve measured nearly 13 volts at the batteries, but that doesn''t seem high enough to cause overcharging or loss of electolyte. I get five years out of my batteries and use this arrangement during the winter so I don''t have to take the batteries off of the boat.

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post #15 of 15 Old 02-20-2003
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solar power trickle charge

Jap shack has diodes that help the solar panel. I think they are 1n1004 diodes that trap the current from leaking back from the batts during the night or lack of sunshine. Called avalanche or cascade diodes. They dont allow current to flow untill 12 vDC is reached. Put one diode in series with the positive lead, easy to put in the plug, and watch for polarity again. I also think the diode will take up to 3 amps, but check on that.
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