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Subject: Simple DC light circuit design
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Date: 03/14/01 at 11:17 AM
Posted by: Paul Williams
I'm looking to make a small circuit incorporating two lights (KPR113 bulbs, Rated: 4.8v, 0.75A, 51 Lumens) connected to a rechargeable 12V battery (I plan on putting the bulbs in series...or would I be better off with a 6V and the bulbs in parallel?). I intend to recharge them with solar panels which must be within certain size constraints (approx. 3.5" wide and 30" long, or less). I would like the lights to come on at dusk and turn off after a set time limit (say, 4 or 5 hours)so I will need a photo cell of some sort AND I need some device to then turn off the lights after the alloted time period. Whew. Sorry it's so long.
Now the question. How? How do I determine the solar panel output I will need? How do they rate batteries per their output? I see 600mAh, etc, how does this factor into the equation? I assume using the bulbs I have in mind, they will consume approx. 18 Watts each (4.8V x .75A x 5Hours=18Watts)correct? That having been determined, I need to replenish that over one day's solar recharge. How do I calculate that and make sure I don't overcharge the battery?
It's been 15 years since my college engineering classes. Thanks for your help!
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