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capacity chart for alkaline batteries?

Discussion in 'Electronic Design' started by default, Dec 16, 2006.

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  1. default

    default Guest

    Anyone know where I can find some capacity information on regular
    alkaline Cells? I have an MP3 player that eats the single AAA cell
    and want to know what I can gain by wiring an external AA, or C cell
    in.

    Can't use NiMH types - dies at 1.2 volts.
     
  2. mkaras

    mkaras Guest

    You can see capacity information on battery data sheets from the
    manufacturer. Most battery compamies can provide this stuff on the
    "comercial" or "industrial" sections of their web sites.

    Here are some links to Panasonic Alkaline batteries for AAA, AA, and C
    size cells:

    http://www.panasonic.com/industrial/battery/oem/images/pdf/AAA_Ind_Alka_Bat_Data_Sheet.pdf
    http://www.panasonic.com/industrial/battery/oem/images/pdf/AA_Ind_Alka_Bat_Data_Sheet.pdf
    http://www.panasonic.com/industrial/battery/oem/images/pdf/C_Ind_Alka_Bat_Data_Sheet.pdf


    - mkaras
     
  3. Tam/WB2TT

    Tam/WB2TT Guest

    According to the Energizer Bunny:

    AAA = 1250 mah
    AA = 2850
    C = 8350
    D = 20500

    Since the C and the D cost the same, I would go with the D.


    Tam
     
  4. Joerg

    Joerg Guest

    Do you think it could work with two of those plus a couple of large
    enough Schottkys?
     
  5. Eeyore

    Eeyore Guest

    Note that end of life is specced at 0.8V !

    Graham
     
  6. Luhan

    Luhan Guest

    How's about a lithium-ion cell with a switching regulator?

    Luhan
     
  7. Joerg

    Joerg Guest

    That would be the high-tech solution with a very good nerd factor ;-)

    No idea what small Li-Ion cells cost but for the regulator there are a
    lot of modern and small footprint solutions available at TI, National
    etc. Could be a bit noisy though in case that MP3 player contains a radio.
     
  8. Guest

    I make it a point not to buy products that use AAA batteries. Capacity
    is propoertional to the square of the diameter, so using AA versus AAA
    is a big deal. Also, AA cells are quite cheap. Having done some
    capacity testing, get any alkaline. The difference between brands is
    small.
     
  9. Generally the manufacturers will provide some information:

    http://data.energizer.com/
    http://www.duracell.com/oem/primary/alkaline/alkaline_manganese_prod.asp
    http://www.panasonic.com/industrial/battery/oem/chem/alk/index.html#data

    Of these, the first had the most straightforward list of nominal
    energies in batteries of different sizes. It should be plenty for the
    rough ratio of AA to AAA information you are looking for.

    The short version cut-and-paste:

    Type Amp-hours
    AAA 1.250
    AA 2.850
    C 8.350
    D 20.500

    As for the NiMH, you have tried it, and not based your conclusion about
    the voltage cutoff based on the fact that the Alkalines that come out
    show 1.2v when it says they're dead, right? An alkaline which shows
    1.2v with no load will probably sag much lower when loaded than NiMH
    batteries would run.
     
  10. default

    default Guest

    Thanks for all the responses. It is looking like C may be my best
    option. This thing hangs from my neck in a hacked waterproof
    container for kayaking - the D size, unfortunately, won't fit.
     
  11. default

    default Guest

    I'm right with you there - hate the AAA for most things. Cost of the
    player was a consideration, and I'll add an outboard battery holder.
     
  12. default

    default Guest

    Yes I did try it. Considered two AA NiMH with some dropping diodes
    but that sounds wasteful too. At ~1.3 volts I hear an occasional
    thump after a loud passage - so I think it is borderline at 1.3.
     
  13. default

    default Guest

    I try not to get too involved or pricey with this stuff - I've upset
    the kayak a few times, so anything that goes with me is disposable or
    nearly so.
     
  14. default

    default Guest

    I'll try a C cell - it has to hang around my neck so light is helpful,
    and it might be nice if it floats.
     
  15. Ian Stirling

    Ian Stirling Guest

    NiMH AAA is _quite_ adequate for 90% of flash mp3 player use.

    I get about 10 hours from one cell.

    I would not hesitate in returning a MP3 player that died at 1.2V - it
    gets maybe 20% (IIRC) of the energy out of even an alkaline AAA cell.

    Modern NiMH AAA cells are quite good - I've got a torch that puts out 1W
    for >40 mins, on one AAA cell, and happily sits on my keyring.
     
  16. Ian Stirling

    Ian Stirling Guest

    Cheap and small.
    http://www.candlepowerforums.com/ should have links.
    They are used in flashlights and other stuff - for example, to get 3W
    out of an AAA sized cell.
     
  17. Your MP3 player dies at 1.2V?
    If that is the case then it is a very poor design, and I'd suggest you
    get a different one!
    A good design will use up all the capacity in the battery, down to 0.8V
    for Alkalines (or at least 1V), and also have a selectable software
    setting for using NiMh cells.

    Energizer & Duracell websites both have datasheets with capacity
    curves, like this:
    http://data.energizer.com/PDFs/E92.pdf

    In your case your MP3 player will use a DC-DC converter which will
    essentially be a constant power load, so use the constant power curve.
    A real test in the actual product is often the only way to get an exact
    figure though, but the graphs are good for ballpark stuff.

    Dave :)
     
  18. Agreed. There is a big market for the smaller size afforded by a AAA.
    If you don't like it you can always get a larger player that takes
    AA's.
    I get 15 hours out of my Creative MuVoTX/FM

    I don't know what voltage it dies at though, might have to measure
    it...

    Dave :)
     
  19. Tam/WB2TT

    Tam/WB2TT Guest

    He is more than likely measuring the no load voltage. That is not to say
    that it is 1.2V when the thing is running. I just went through that with a
    camera. A 6V alk cell measured 6.0, but would not work the shutter. A new
    battery fixed it. (It is an SLR; no autofocuss, no flash, battery was 10
    years old).

    Tam
     
  20. Joerg

    Joerg Guest

    I once had the beer kayak and sure enough I rolled it. Took us almost an
    hour to save all those cans.
     
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