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Latest batch is bad

  • desolder Top 10 Forum Poster Sunday, December 04, 2011 5:22 PM Reply
    This time i discharged at 200ma, instead of 1A. C/10 discharge is usually done for capacity claims. Stopped at 3.0v. Capacity was 2148mAh. It probably would have given me another 10% if i let it discharge down to 2.5V. So at least this particular cell is OK.
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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  • sheepish Top 10 Forum Poster Sunday, December 04, 2011 5:27 PM Reply
    What's the deal with termination voltage? Is 2.75V too conservative? Is <2.4V OK?
    DX has found a new way to deceive customers:
    Use reviews for different products that have not been bought
    by the person who wrote the review.
    http://club.dx.com/forums/forums.dx/threadid.1462252
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  • desolder Top 10 Forum Poster Sunday, December 04, 2011 8:39 PM Reply
    The recommended termination voltage varies. Some manufacturers, like sanyo and sony, recommend a 2.5V cutoff voltage. But samsung recommends 2.75V for their standard rate cells, and 2.5V for their high rate ICR series.
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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  • sheepish Top 10 Forum Poster Sunday, December 04, 2011 10:38 PM Reply
    I've just lodged a request for replacement.

    The pair are different sizes...

    http://www.dealextreme.com/customerphotos/quarantined/201112/20392-8ece6254-5475-437b-9a01-722b99111d82.jpg
    img src: http://www.dealextreme.com/customerphotos/quarantined/201112/20392-8ece6254-5475-437b-9a01-722b99111d82.jpg


    ... and different capacities.

    http://i39.tinypic.com/t6e3pt.gif
    img src: http://i39.tinypic.com/t6e3pt.gif



    Cell B (orange) is the older cell.
    Cell C (light green) is the new shorter cell.
    Cell D (dark green) is the new longer cell.

    The protection circuits of all these cells did not activate at 2.75V as claimed. The voltage of Cell C dropped under 2.40V before the protection circuit activated. I stopped the test at ~2.55V for the other two cells.

    Cell B got the sort of capacity I expected to get, 2310mAh down to 3.0V, or 2460mAh down to 2.55V.

    Cell C got only 990mAh down to 3.0V, or 1068mAh down to 2.40V. This is much less than half the capacity it should have, so it is clearly faulty.

    Cell D got only 1845mAh down to 3.0V, or 1873mAh edit - down to 2.40V. Note how suddenly it died compared to the other two. This is also well short of what it should be getting, just 78% of the claimed 2400mAh.
    DX has found a new way to deceive customers:
    Use reviews for different products that have not been bought
    by the person who wrote the review.
    http://club.dx.com/forums/forums.dx/threadid.1462252
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    post edited by sheepish on 12/7/2011 at 2:32 AM
  • sheepish Top 10 Forum Poster Monday, December 05, 2011 9:24 PM Reply
    I've just finished a test on my other "old" cell - Cell A - and no surprises it had a very close curve to Cell B.


    http://i43.tinypic.com/2nrbbm.gif
    img src: http://i43.tinypic.com/2nrbbm.gif



    The jump in voltage for Cell A part way through was when I realised the cell wasn't sitting fully in the holder, so at 79 minutes I pushed the cell in properly which changed the contact resistance. This is an old school test set up. :)

    It's still enough to show that the old batch were very consistent. The new batch have horrible consistency and quality. If this is what we can expect I'll buy quality cells from elsewhere for twice as much.
    DX has found a new way to deceive customers:
    Use reviews for different products that have not been bought
    by the person who wrote the review.
    http://club.dx.com/forums/forums.dx/threadid.1462252
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  • matrix-neo Moderator Monday, December 05, 2011 9:43 PM Reply
    interesting, in the previous graph the new longer cell holds the voltage slightly higher than the older(orange) cell up until about 800mah discharge, but this could just be typical lithium cell aging
    Resistance is futile-give in to DX gadget craving!
    also a voluntary mod-be nice please!
    Have an enquiry? https://cs.dx.com/ticket/index


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  • sheepish Top 10 Forum Poster Monday, December 05, 2011 9:56 PM Reply
    They're all pretty new, and there's so little difference between A (a few partial cycles) and B (almost new) - except for that caused by contact resistance - that I don't think ageing is a factor.

    I think the steeper slope of the discharge curve and the sharp roll-off are also indications of a significant change in cell construction or maybe even chemistry.
    DX has found a new way to deceive customers:
    Use reviews for different products that have not been bought
    by the person who wrote the review.
    http://club.dx.com/forums/forums.dx/threadid.1462252
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  • sheepish Top 10 Forum Poster Tuesday, December 06, 2011 6:11 AM Reply
    I've just seen manne's graph in http://club.dealextreme.com/forums/Forums.dx/threadid.960290 comparing these cells with the blue Trustfire cells, sku.5790. The general shape of those curves looks awfully familiar! Higher initial voltage, steeper discharge slope that's straighter to a lower voltage, and sudden roll-off at the end of discharge. The consistency is poor, too. Repackaged?

    Edit: Reposted graph because the original has gone.

    http://i45.tinypic.com/o74qc5.jpg
    img src: http://i45.tinypic.com/o74qc5.jpg

    DX has found a new way to deceive customers:
    Use reviews for different products that have not been bought
    by the person who wrote the review.
    http://club.dx.com/forums/forums.dx/threadid.1462252
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    post edited by sheepish on 11/18/2012 at 4:28 AM
  • sheepish Top 10 Forum Poster Tuesday, December 06, 2011 11:48 PM Reply
    matrix-neo said: the different colors and lengths would suggest a new manufacturer, let Dx know and they might switch suppliers, i know i would to avoid future problems

    Well, I've just had a response to my ticket suggesting I search the forums for a solution. I mentioned this thread when I opened the ticket.

    What's the best way of letting DX know there's possibly a problem with all the cells? Is there a product manager who could be notified?
    DX has found a new way to deceive customers:
    Use reviews for different products that have not been bought
    by the person who wrote the review.
    http://club.dx.com/forums/forums.dx/threadid.1462252
    Posts(23273) | Reviews | Tip post

  • BIBIwood Geek And Interns Wednesday, December 07, 2011 1:49 AM Reply
    Yes I'm following the thread and I'm actually running tests to see if their is a drop in the quality.

    The first results:

    Discharge @1A and terminaison voltage of 3V:

    http://s10.postimage.org/7ff58kv94/dscnew.jpg
    img src: http://s10.postimage.org/7ff58kv94/dscnew.jpg



    Charge @1A, the security timer stopped the charge after 2 hours:

    http://s10.postimage.org/qczczkoc8/chgnew.jpg
    img src: http://s10.postimage.org/qczczkoc8/chgnew.jpg



    I will test older samples to see if the capacity of the batteries decrease.
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