Troubleshooting 10W solar panel

Discussion in 'Electronics & Electrics' started by splbound, Dec 7, 2017.

  1. splbound

    splbound Member

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    Hi All,

    Have purchased a 10W solar panel to trickle charge a Lead acid car battery.
    Using this as a test basis before I buy more panels to up the wattage.

    Am trying to find out if it is working.

    The panel comes with two adaptors:

    a) Crocodile clips
    b) Blocking Diode protected cigarette lighter plug.

    Testing the voltages before I plug it in using my multi meter.
    Open circuit (i.e. not attached to the battery I intend to charge)
    Panel receiving the same light (Consistent cloud covered day)

    1) The voltage direct from the panel is fine across the crocodile clips. Essentially the voltage supplied by the panel. Measured 17V
    2) Using the cigarette lighter plug adaptor with the panel. I measured 10V across the positive and negative terminals on the cigarette lighter plug.

    I thought these voltages should be much closer with the cigarette lighter adaptor reading 17V minus a small voltage drop across the diode?

    Am I thinking wrong here?

    Any insight will be appreciated.
     
  2. v81

    v81 Member

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    Generally you measure Voc (Volts open circuit) and Isc (Current short circuit) and verify that against whats on the panel.
    Sounds like you've already done the first.
    Anything inside the cig lighter plug?
    It might have an inbuilt reg.
    Got a 12v lead acid batt you can hook it up to ?
     
  3. OP
    OP
    splbound

    splbound Member

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    Thanks v81!

    I have decided to ditch this now and ordered a 5A solar charge controller to do the regulation.
    I'll test the Current short circuit on the panel with my meter when I get back home.

    I did pull the cig lighter plug apart and it had a fuse, blocking as well as a resistor & led combo.
    Diode tested OK, checking for resistance both ways on it without anything connected to it.
    Diode test using the multi meter showed approx 0.3V so everything tells me the diode is fine.
    Still don't know why the Voc across the cig lighter plug is so low against the Voc of the panel.
     
  4. merlin13

    merlin13 Member

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    That 10 volt measure almost sounds like what you'd directly see across the LED resistor for a 12 volt power level. But not for a 17 volt one...

    So if you've still got the plug thingy split apart then measure volts across all the bits.

    And trace the actual wiring out, on the offchance the plug thingy has been wired up arse-about. If the circuit layout is reasonably sane it "should" be something like Solar Panel -> Fuse -> positive end of the LED/Resistor combo -> Diode -> Output (or a few minor variations thereof).
     
  5. OP
    OP
    splbound

    splbound Member

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    Thanks Merlin13. I'll take it apart and create circuit diagram of it for reference. I may have been measuring the voltage across the Led Resistor all this time from that I remember the circuit to be.

    I have now received my charge controller and wired it up.
    All is working well, voltages reading as I expect now so looking at more panels for more wattage.
     
  6. merlin13

    merlin13 Member

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    Upthumbs. Try Bumtree etc for someone offloading used household panels cheap for more oomph, and occasionally up here in Bananaland there's an eBay seller offloading container loads of "seconds" at quite sane $$.

    Although if you're looking at charging a lead acid car battery from very low or dead flat charge state, even with lotsa panelling attached just be aware a 5 amp solar regulator miiiiight be grunting a bit when the battery wants to drag lotsa amps out of the charging hardware.

    What you've got "should" be fine providing you leave it all out in the sunlight for enough time.
     

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