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Li-Ion vs. -Poly

Discussion in 'Electronic Design' started by D Yuniskis, Jan 4, 2011.

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  1. D Yuniskis

    D Yuniskis Guest

    Hi,

    One of my portable DVD players uses a (nominal) 7.4V 2600mAH
    Li-Poly battery. One cell appears to be toast (*loaded* voltage
    RAPIDLY drops from ~3.5V to ~1.8V after ~10 minutes of use;
    other cell holds fast at ~3.5V).

    I was thinking of replacing them with a pair of 18650's
    as they occupy almost exactly the same space (different,
    though compliant, form factor; same volume -- of course!).

    It is my understanding that the charging technique for
    LiPoly and LiIon are identical (?). I'd prefer not to have
    to reengineer the charger (microcontroller controlled).

    [Given my druthers, I'd replace with NiCd but that would
    require way too much work!]

    Any other pointers to watch for (besides the usual, "OMG!
    You can burn your house down!!")?

    Thanks!
    --don

    P.S. pointers to a source/manufacturer of reliable *tabbed*
    18650's would also be welcome. (though I may just opt to
    cannibalize some laptop battery packs)
     
  2. Yep, charging LiPo and Li-Ion is the same and so is the pack
    protection.
     
  3. Lots of useful info on batteries at:

    http://batteryuniversity.com/
     
  4. The manual for one of my R/C chargers very explicitly states that
    Li-Ion batteries can not be charged with the LiPo program. My other
    charger has separate programs for LiPo and Li-Ion.

    I know LiPo has a nominal cell voltage of 3.7V, while Li-Ion is 3.6V.
    I do not know if that is the only difference.

    Some Li-Ion cells are marketed as "protected". I am not sure what that
    means, but maybe they have built-in protection against overcharge?
     
  5. Both types charge in the same way. Constant current followed by a
    float charge at 4.2V per cell.
    LiPo and Li-ion cells are flat at about 2.5V and fully charged at
    4.2V. The nominal voltage is pretty meaningless.
     
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