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Volts but no amps from a (small) solar panel

Discussion in 'General Electronics Discussion' started by Jim N, Mar 7, 2013.

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  1. Jim N

    Jim N

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    Jan 28, 2013
    It was all going so well. This 12V 5W solar panel was intendeds to charge a lead acid battery that in turn powered some LEDs that look great on a home made Victorian lamp on top of a genuine old lampstand. The solar panel arrived from China and showed appropriate volts and amps on testing. But after wiring it all up I suddenly find nothing but static. Volts fine - up to 18V in sunlight on an open circuit. But absolutely zero amps. How is that possible? Has it failed spontaneously or have I done something wrong? Shall I just order another panel? (it won't break the bank, it seemed really good value for around £10
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Show us how you wired up the circuit. Did you use a reverse protection diode between the panel and the battery? Or even better a battery charger?
     
  3. Jim N

    Jim N

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    Jan 28, 2013
    Yes, the diode is on the positive lead from the solar panel to the battery and double checked with the multimeter to check it is in the right direction - it seemed fine. The LEDs are wired directly from the battery and work fine. I don't know how to draw a wiring diagram on this forum but my understanding is that there should be little room for error
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Post a photo of your setup, preferably with the wiring clearly visible and note where you are trying to measure the voltage and current.
     
  5. Jim N

    Jim N

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    Jan 28, 2013
    OK, here goes. Sorry, the close up is blurred but it should be OK. The graph is when I was plotting the voltage drop when the LEDs were on
     

    Attached Files:

  6. Electrobrains

    Electrobrains

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    Jan 2, 2012
    I can not see well on the photo how your cables are wired, but could it be that you have wrongly connected the red wire (+) of the panel to the black (-) pole of the battery?

    Are you really sure the polarity of the diode "is in the right direction"? The side of the diode without ring should be connected to the red wire coming out from the solar panel.
     
  7. Jim N

    Jim N

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    Jan 28, 2013
    It isn't clear, is it? Sorry. The black/white wire is the positive and the black the negative and I think it is wired right.
    What I don't understand is the solar panel. There is now totally zero amps even on the most sensitive DCA setting on the multimeter, even though there is voltage in sunlight. I am assuming some sort of shorted panel, although I can't see how it has happened, and ordered another panel
     
  8. BobK

    BobK

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    Jan 5, 2010
    It cannot show a voltage when shorted. Are you sure you are using your meter correctly? Did you disconnect it from the battery when you measured the current?

    Bob
     
  9. Electrobrains

    Electrobrains

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    Jan 2, 2012
    Or have you blown the (usually 2AF) fuse inside the multimeter?
     
  10. Jim N

    Jim N

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    Jan 28, 2013
    Thanks - THAT is what it is! The fuse inside the meter is indeed blown. That's why I like forums.
    Thanks again
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
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    Jan 21, 2010
    And it may be blown because you tried to place the ammeter across the battery.

    Don't make that mistake.
     
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