Can a 1v solar cell charge a 5v battery pack?

Discussion in 'General Electronics Chat' started by Oddy, Oct 10, 2014.

  1. Oddy

    Thread Starter New Member

    Sep 28, 2014
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    I just got landed with a pile of old solar lamps from a garage sale and after taking one apart and testing it i found the solar cell to produce between 0.3 and 0.9v depending on the clouds.

    I was just curious but could I use one of these solar cells to charge up say a pack of 3 AA batteries at 5v-ish using a boost converter or something similar? the lamp contained 2 AA batteries totalling about 3v so I'm assuming it must be possible but I was wondering if anyone could explain to me how easy it would be to do?

    Many thanks in advance
    Oddy
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    You could put a number of solar cells in series to add up to the desired voltage.

    Or you can use a boost converter such as LTC3105 or LTC3108.
     
  3. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    Last edited: Oct 10, 2014
  4. Oddy

    Thread Starter New Member

    Sep 28, 2014
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    Ah magic yes I was leaning towards just adding more solar cells technique but those boost converters do look useful.

    No IC's in sight just something which I'm assuming is a transistor but has no numbering or ID on it and a few other passive components (resistors, a cap and a photodiode/LDR I think).
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    If only one solar cell then the voltage is too less, so you need to increasing the voltage, in series some cells and using boost converter to raising up the voltage, and using the buck inverter or voltage attenuator to reducing the voltage and the output voltage should be great than the batteries a little.
     
  6. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi oddy,
    Has the 'transistor' got 3 or 4 wires.??
    E
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
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    1 volt could be boosted to charge a 5 volt pack, but 1 volt is getting awfull near the minimum voltage for transistors to operate normally. better to put on at least one more cell in series.
     
  8. Oddy

    Thread Starter New Member

    Sep 28, 2014
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    Standard 3 pin same package as a 2n3904 or 2n222 but theres no numbers on it so not certain, I'm guessing it's controlled by the LDR/photodiode; I'm not too worried about the circuit to be honest was just kinda wondering how possible it would be to run a microcontroller off of a pack charged by solar cells, maybe make a low power circuit to control a valve on a water butt with a soil damp sensor or something?
     
  9. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi,
    Its possible to connect in series, a number of PV cells to charge say, 3 *AA size batteries, dont forget to add a series blocking diode to the output of the series PV chain.

    The PIC will run OK from around 3V to make a soil moisture sensor.
    E
     
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