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Re: Will Solar Panel Trickle Charge Battery?
It depends upon the type and size (Ah capacity) of you batteries, but you'll probably need a larger solar panel than just one of the those little "trickle chargers" (along with a good charge controller). Most of the panels marketed as such are between 1 and 5W. I have a total of 275 Ah of batteries on my boat (2 x 225 Ah 6V golf cart batteries and a 50Ah 12V reserve battery), and a 20W panel is just about right for keeping everything "topped off". If you have a smaller total Ah capacity, particularly if you are using AGM batteries, you may be able to get away with a 10W panel. But I wouldn't count on anything below about 10W having enough output to avoid the consequences of long-term undercharging of your batteries.
The rule of thumb is that wet cell batteries lose about 1% of their charge per day (AGM batteries self-discharge at a rate of only about 10 or 20% of that, or about 0.1 to 0.2%). So, discounting that a small part of the total battery capacity on my boat is in the form of AGM, that means that I need to supply about 3Ah a day (rounding to the nearest whole Ah) to maintain the batteries. A 20W panel, in a fixed position on the push-pit rail, can supply slightly more than 1 amp at charging voltages, or about 5 to 7 Ah per day (a bit more on a sunny summer day, quite a bit less on a stormy winter day). Allowing for various inefficiencies in the system, and counting on the system having to "catch up" after cloudy/stormy days, that works out to be just about the right size.
"If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most." --- E.B. White
Last edited by Puddin'_Tain; 06-26-2014 at 04:30 PM.