Solar trickle charger

[tweitz]

I will be keeping my new B323 at a dock near my house, incredibly convenient but without shore power. My prior boat had no drain on the batteries between uses, but I am expecting that the bilge pump, etc. on the new boat will provide a small, but measurable, drain on the batteries. I would therefore like to add a small solar trickle charger (reasonably priced) and am wondering what people's experience has been with these. Consider also that I am in the Northeast, where sun is not guaranteed every day and where the boat is in the shade for a part of the day. How much capacity do I need, and what are the strengths and weaknesses of each type and brand. Also, do you simply connect it to a lighter jack or does it need to be hardwired in in some way? Thanks for the help.

 

[Terry]

Trickle Charge

Basically when you main breaker panel is off there should be no current draw other than the normal internal discharge of the batteries. To determine the wattage needed, you need to know the amount of current being used and for how long each day. Say you have a 3 amp refrig running for 6 hours a day. This would be the current(3amps) times the hours(6) in a day the refrig is running, or 18 amps total a day.  The wattage used is amps/day used(18), times the battery voltage (12 volts) = 216 watts/day comsumed by the refrig. With a guess of 4 hours of sunlight a day, you would need to divide the total wattage consumed(216) by the available hours(4) = a 54 watt charge source needed. With only the normal discharge of a battery the current draw is quite low. Say 1% self discharge a day on a 200amp/hour rated battery would be 2 amps a day or 2amps x 12 volts = 24 watts. Again 24 watts consumed/4 hours of sunlight = 6 watt charge source needed to maintain the batteries.The quote below is from the link below."When using a small solar panel to keep a float (maintenance) charge on a battery (without using a charge controller), choose a panel that will give a maximum output of about 1/300th to 1/1000th of the amp-hour capacity. For a pair of 200 Am-Hour golf cart batteries, that would be about a 1 to 5 watt panel - the smaller panel if you get 5 or more hours of sun per day, the larger one for those long cloudy winter days in the Northeast."Sail on...Terry

 

[Terry]

Cable size

Sorry, forgot add to prev post.  As far as wire size, if you are just maintaining your batteries with a 10 watt solar panel or less, extension cord wire would be heavy enough. 10 watts is less than one amp. For a temp setup, I would just put aligator clips on the panel leads and clip them on the battery you want to charge. And make sure the panel is at least 12 volts. A larger panel or longer panel leads to the battery will need a bigger guage of wire.  Be sure to have a diode in series with one legs of the solar panel, or the battery will try to discharge thru the solar panel. And a fuse close to the panel would also be a good idea.Sail on...Terry

 

[tweitz]

Thanks

Thanks for the helpful advice.Ted