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Simple solar powered lights with a battery

Discussion in 'LEDs and Optoelectronics' started by nabberuk, Nov 16, 2015.

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  1. nabberuk

    nabberuk

    9
    0
    Jul 25, 2012
    hi,

    I have some fairy lights the are powered by a 3v battery, also I have a solar cell that's 6v and 4.5w/520mA. I would like to charge a battery pack (haven't got one yet, was thinking of a couple of a cells in series and parallel) with the solar and then power the lights at dusk - I believe I can use the solar to detect dusk.

    Other than that, I'm pretty stuck so if anyone could point me in the right direction
     
  2. donkey

    donkey

    1,289
    56
    Feb 26, 2011
    ok so how skilled are you?
    what size battery you looking at? amp hours matter
    what type of charger yo using? lipo and standard batteries (AA< AAA etc) use a special charging circuit from memory. SLA batteries take what you give them.
    what are you going to do with the 3volt battery?
     
  3. nabberuk

    nabberuk

    9
    0
    Jul 25, 2012
    Not very skilled at all when it comes to electronics!!

    Looking at standard AA batteries, unsure on the amp hours but would need a 4-5 hour run time. During the day the solar cell would charge the batteries.
     
  4. Alec_t

    Alec_t

    2,889
    773
    Jul 7, 2015
    White LEDs have a forward voltage of at least 3V, so you'd need 3 or 4 AA cells in series to drive them directly. Alternatively a DC-to-DC converter could step up the voltage of a single cell (as is done in most garden lights).
    Your solar cell rating is probably an optimistic one for full sun at the equator :), so don't expect 6V throughout the day.
     
  5. nabberuk

    nabberuk

    9
    0
    Jul 25, 2012
    Yeah I guessed that I wouldnt get the full 6 volts, I've been testing it in our gloomy weather and I've been getting around 4.5 volts.

    On the old solar that came with the lights, it contained a single aa cell so it was stepping up the voltage, it had other circuitry in to switch between flashing etc that I'm not fussed with.

    So I though I would build a separate one. Just not sure on how!
     
  6. Alec_t

    Alec_t

    2,889
    773
    Jul 7, 2015
    Is that the open-ciruit (no load) voltage, or when the cell is powering a load?
     
  7. nabberuk

    nabberuk

    9
    0
    Jul 25, 2012
    That's with no load
     
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