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Need help selecting components for solar a battery charger.

Discussion in 'Power Electronics' started by SimonF1, Jan 14, 2016.

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  1. SimonF1


    Jan 14, 2016
    First of all, Hello and hope everyone is having a great new year so far.

    I know very little about electronics and just need a little help getting the right components.
    I want to make a single cell AA solar charger that can charge a single AA 1900mAh eneloop battery in English winter time, So that's about 7hrs light per day.

    ive already got a 1.5v 0-300ma solar cell but for some reason even after 7 hours charging it does not have any power in the battery.
    Please I don't want a similar setup that I have to recalculate.

    I just need a link for the solar cell I need and from ebay uk would be best place for me to get it from.

    I already have some 1N4007 diodes that im hoping to use in the circuit, I place one diode in the live side from the solar cell wire with the stripe facing away?.

    Please can anyone post me a link for the solar cell I need please.

    Kind Regards
  2. MrEE


    Apr 13, 2012
    Try it without the diode. This type of diode will drop about 0.6V leaving only 0.9 for the battery.
  3. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    Get 2 more of the solar cells and connect them all in series. You don't need any diode.
  4. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir Simon . . . . . .

    " I want to make a single cell AA solar charger that can charge a single AA 1900mAh eneloop battery in English winter time, So that's about 7hrs light per day. "

    I gots to knows ?

    What is this light source type, and its voltage current specs, that you perceive is going to be consuming X amount of milliamperes from a 1.2 VDC @ 1900 mah AA Sanyo eneloop
    battery for about 7 hrs of light per day ?

    That voltage spec only meets an incandescant lamp of the penlight category . . .that I know of.
    That 1.2 voltage is also below common LED's operating thresholds, unless you use a germanium transistors converter circuit to up the 1.2 . . .and less . . . .voltage.
    In either case , this lighting level intensity, seems to be in the illumination magnitude of a nightlight or a reading booklight. . . . used "for a cold English winter time night".

    If you are figuring upon a total run time from the battery alone and computing it out as 1.2 Volts X 1.9 amps for a combined capable stored wattage of 2.28 watts.

    Recalculate . . . . . as you don't have that TOTALLY deep of a storage well.

    Figure on the lighting load gradually dropping the effective voltage of the cell to its safe recommended FINAL discharge state of .9 volt output.
    Sooooo figure on your having had a voltage decrease of 1.2VDC down to .9VDC as having supplied you with .57 watts of power
    during that discharge transition period.
    So, in re-figuring, what can you do with .57 watts of power, in computing, with the lights voltage and current requirements, in order to come up with an X period of operating time ?

    As far as the solar cells, I would be getting some "seconds"/ "cosmetics" / "breakers" from the larger 3 by 6 units that are MASS manufactured and used so PROFUSELY in large solar
    panel arrays, and figure the number of series cells at .5VDC that will get my required voltage and current requirements, along with being somewhat above the LEVEL of lighting wattage
    and time duration that you need.

    I'm DEFINITELY tending to overshoot on those solar panel series output voltage specs, with the number of overcast days and shorter winter daylight time .
    More initial voltage and current capability can readily be corrected thru a series FET constant current generator .

    The most common 3 by 6 cells can be bought and scored to like sizes with a cut off wheel chucked in a Dremel tool, and guided along a clamped on wood strip and then snapped and series soldered
    via jumpers to get the required multiples of .5VDC per cell.

    Surplus cells:

    Seems like youse U.K's guys have to pay thru the nose for postage !

    I usually just go for the cheapest items just out of the E-bay bidding threshold and just entering into the Buy it Now category, unless you like playing the E-bay bidding war . . . .or just having bidders luck .

    Now . . . .feedback . . . .on your lighting level needs aspects . . . . is it a night light level or booklight . . .or even . . . (put on sunglasses) MORE ?

    73's de Edd
    Last edited by a moderator: Jan 16, 2016
  5. SimonF1


    Jan 14, 2016
    Thanks for the reply's guy's I appreciate it.
    I have removed the diode and placed the cell in the window ledge and will see how it goes for 7hrs then check again, but if I do not use a diode will the battery not just drain back into the solar cell over night or in very overcast situations? if so is there not another diode I could use then? or would it be better if I replace the 1.5v solar cell for a 2v cell and use the 1N4007 with the .6v drop I would still have 1.4v for the battery.
    I would rather go overkill then not have enough power. so how about if a was to use a 3v solar cell with a diode and a resister? could that work?.

    @ 73's de Edd'
    That's a lot of text there and not sure I understand it all lol. but yes P&P is ridiculous here. for example a guy in china can send my neighbour a letter for under 15p but it would cost me 54p and the letters would be delivered by the same royal mail man. and buying from USA is a BIG NO NO. not only is it expensive but there is also customs to pay.

    Kind Regards
  6. SimonF1


    Jan 14, 2016
    ok so I left the solar cell in the light for 7 hours but the charge never goes above 1.278v so looks like I need more than 1.5v cell.

    so back to my original question :) can any one tell me what solar panel I need to charge a 1.2v-1.5v 1900mAh AA Battery?

    Just 1 panel and 1 battery and a diode or any way to stop backward drain of the battery.

    what I've learned is: 1.5v is not enough to charge fully a AA battery with or without a diode and that the 1N4007 diodes looses to much volt for my project.
  7. SimonF1


    Jan 14, 2016
    Maybe I would be better of asking these questions in a solar electronic forum, dedicated to solar energy,
    I realize its not your standard electronic questions so I think that's what I will do.
    Thanks to those that tried to help tho and im sure I will find my answers soon.

    Kind Regards
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