"Solar Power" LED Flashlight - Too good to be true...

Discussion in 'General Electronics Chat' started by tom66, Nov 14, 2011.

  1. tom66

    Thread Starter Senior Member

    May 9, 2009
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    This thing was 99p. I thought, wow, that's a big solar panel and three LEDs for 99p. How can they do that?

    A simple dissection shows that the circuit is very simple. There's a lithium battery, CR2016, 3V. Famed for its rechargeable nature. :)eek:) A PCB switch mounted on a small piece of PCB. And three LEDs in parallel... no limiting resistor, although not usually required as the lithium cells have such a high ESR that they limit the current sufficiently.

    But wait, how does the solar cell come into it?

    Well, it doesn't... or at least, nothing is connected to the panel. And in fact, the torch does not work with the battery disconnected.

    So, I thought, why would they bother with such a large solar panel? Those panels would be quite expensive - about £3 to £5 each - and there's no way they could sell these at 99p. Then I looked carefully, and I noticed something didn't look right with the cell. There were these red wires, running out of line with the electrode wires. Also, the cell has several holes in it. So it's basically for show.

    I measured the cell as putting out less than 1mA short circuit, and about 2.2V open circuit, so it's pretty dead.

    Now I'm not that bothered, after all it was only 99p but it really seems shady (puntended) to me to sell these as solar powered!
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    Haven't you seen cheap solar/battery calculators that have a photo of a solar cell instead of a real one?
     
  3. Markd77

    Senior Member

    Sep 7, 2009
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    Oh well, no great loss, I've bought a few "solar powered" calculators with fake cells.
    These ones are real:
    http://forum.allaboutcircuits.com/showthread.php?t=44754
    and also if you have a "Poundland" near you they have one with a carabiner clip which is pretty similar inside, but has 2 LEDs and a resistor.
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    [​IMG]

    You have several latent prints on the solar cell forgery. I would present this to Scotland Yard so they round up the usual suspects and put an end to this tragic consumer abuse.
     
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Free market in action..... somebody came up with a way to make money off reject solar panels that don't work.:D
     
  6. tom66

    Thread Starter Senior Member

    May 9, 2009
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    The panel is a QFSOLAR panel. Shenzen China solar technology. Must be rejects; I wonder what they paid for them? Would make interesting silicon wafers, perhaps for experimentation with fabricating my own transistors. :)

    The panel is 3722-9L; the same as in Mark's torches.
     
  7. jimkeith

    Active Member

    Oct 26, 2011
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    Hey guys, if we add a good solar cell, can't we turn it into an above unity flashlight? :):):)
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    Unless the solar cell is huge and expensive, it is a dim, cheap solar garden light.
     
  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    As the proud owner of many solar powered garden lights I can attest to the fact that while they are all dim they are rarely cheap.



    (Fortunately I discovered a food store dumping their summer merchandise with a rather large supply of solar garden lights on 75% discount. I got 12 lights for under a buck a piece.)
     
  10. Audioguru

    New Member

    Dec 20, 2007
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  11. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    You could swap out the battery and the panel with one that is made to be recharged, and a solar panel that works. A solar charging circuit is incredibly simple, and shouldn't be hard to fit in. The flashlight will still be garbage, but at least it'll do what it's supposed to :D
     
  12. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    I wonder if these are the same folks that sold DVD rewinders. :)
     
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