Solar Panel Help

Discussion in 'The Projects Forum' started by ajnin, Aug 20, 2010.

  1. ajnin

    Thread Starter New Member

    Aug 20, 2010
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    0
    Greets,

    I have a large solar panel putting out on average 19 volts and about 1.3 amps shorted. Ultimatly I would like to make a nice portable power box for camping. It would be nice to have 2x12v car, 4 USB ports. I understand that they wouldn't all be usable at the same time. The need for the extra usb ports is for pesky cell phones like the iphone which needs a small circuit on the data pins. Also I would like to incorporate some batteries into the mix for some night use. I have a bunch of 6v SLA and a few 12v SLA batteries I was thinking about using. (unless thats a horrid idea)

    I recently used it on a camping trip to power my droid, a set of USB powered speakers, and another cellphone charger. I cheated however by using some 12v car chargers-to-usb for both the speakers and droid, and just a car charger for the other phone. I simply ran power from the solar panel to three female 12v cigarette jacks.

    This cant be the best way... right?

    I have thought about using 4 7805's and 2 7812's to achieve my desired results but I really am not sure if that is the most effecient use of the power provided from the solar panel or if those are even the proper regulators.

    Help I am pretty much a noob. Thanks in advance.
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    The solar panel, 15W+-, may be giving around 8 Ahrs, just a fraction of your load. Connect it to a 12V battery via a 2A reverse current diode.
     
  3. ajnin

    Thread Starter New Member

    Aug 20, 2010
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    So I have read that I need to charge 12v SLA batteries with around 13.5 ish volts. Is that not the case if I use a 2A reverse current diode?
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Sounds right to me. Most of the battery charging will be when AC power is available. A shottky diode may give another 2/10 V.
     
  5. ajnin

    Thread Starter New Member

    Aug 20, 2010
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    0
    So to charge batteries properly I should use a voltage regulator like a lm317 right?

    Will the lm317 eat the additional power "left over" from the solar panel? For example if the panel is outputting 18v and charging the battery is pulling 13.8+1.3ish using a lm317 do i have 2.9v left? Or does the lm317 suck up the additional voltage provided?
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    Forget the regulator.
     
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