12 VDC solar system

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I know that several of you guys are running your own solar/rechargeable battery systems for cheap around the house stuff. I was wondering if i could get some more specific info on this, like what specific parts you guys are using, where to get them, etc. Also, what are you running on this system? I was planning on making one this summer in my spare time, but it will primarily be for led lighting, so perhaps I should run a 6 V system?

Thanks.

Joe S.
 
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If your intent is to drive LEDs directly, your best bet is with individual solar cells, not panels.

A typical silicon solar cell provides 0.46 volt. Eight of them in series provides 3.68 volts, which is fine for most white LEDs.

Now we need to look at current. The area of the cell dictates its current; the basic rule is, 0.32mA per square millimeter. Large cells can be cut to provide the exact current required, or smaller ones can be wired in parallel to provide additonal current.

A Nichia draws 20mA, so 62.5 square millimeters are required. A square cell 8mm on an edge provides 64 square millimeters, so a string of eight of them will do the trick. Or the cells can be circular or rectangular, as long as the area of each one is at least 62.5 square millimeters.
 
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The only problem with hooking the LEDs up to the cells without a battery, is that the lights won't work when they are most needed, at night.

Joe S.
 

bikeNomad

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
If your intent is to drive LEDs directly, your best bet is with individual solar cells, not panels.<HR></BLOCKQUOTE>

Maybe I'm missing something, but if the sun's shining, why does he need an LED?
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Doesn't he need a battery in there somewhere?
 
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While a battery is not needed in order to drive an LED with a solar panel, I do admit a battery system has certain advantages
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Darell

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LOCO is more like it.
Most of the solar stuff out there is geared toward 12v and 24v. So I'd stick with 12 volt for all-the-shelf stuff. You can buy any size panel you want, and any size battery you want, of course. Then just string a bunch of LEDs together to get the voltage drop you need, or use resistors. I've purchased most of my stuff from Real Goods solar goodies.

It's a lot of fun to play with solar.
 
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