magic shine battery HELP!- Mtbr.com
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  1. #1
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    magic shine battery HELP!

    ok. i f**cked up. a couple of beers post ride will do that.

    my MS-872 wouldnt fully charge to the 8.4 v it did originally. it was only charging to 7.4v so would be blinking red immediately.

    advice on the web told me to rebalance my cells. so i decided to dissect the batt pack to check the voltages.

    the cells are B18650CA's. each measured 3.9v +/- 0.2mv.

    my screw-up is i didn't record how the cells were hooked up. i thought it was parallel.

    of course, then after i broke all the connections my etoh'ed brain wondered how does it generate about 8v with 4 cells in parallel at 3.9 v?

    i would like help to figure out where to go next. the original case is a beautiful aluminum with clear plastic lid.

    thanks

    dave
    spez roubaix
    fantom cross - stolen -
    crux
    moonlander

  2. #2
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    Why didn't you describe your pack more and sent a pictures I've asked? Again, make the pictures! You did not read carefuly I said you should measure cells or set(pair) of cells. Since you did not describe your pack enough I couldn't be more specific.

    Those Alu packs has one bad feature - parasite drain and has to be charged once awhile even if you don't use them. The cells are very likely BAK branded. They might became to deeply disharged and won't hold the charge.

    Now when you have totaly dissasembled it to single cells it would be hard to put them back to that case. There is very little room for repars and we still don't know what's wrong with cells for shure. There can be also something wrong with the protection circuit or cable.

    Do you have any single (or multibay) 18650 Li-Ion charger around? If you do charge the single cells. If the charge to 4.2V and holds the voltage for one day the cells are very likey good (still don't know if they hold capacity).

  3. #3
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    ...because I disassembled it to test the cells ( should have bought a charger first), figured out the polarity, soldered all the connections ( they were spot welded before). Big pain in butt to do all that.
    I doubt I could have gotten the pack together anyways. As you said small tolerances for sure and my soldering is pretty sloppy.

    But it's dead now so I'm buying new battery and charger.
    Thanks for the help anyways!
    spez roubaix
    fantom cross - stolen -
    crux
    moonlander

  4. #4
    RAKC
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    Well soldering these cells is a rapid way to kill them. Unless you have a high powered soldering gun and the know how to solder LIION cells, NEVER EVER TOUCH THEM WITH A SOLDERING IRON.

  5. #5
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    Lesson learned after researching li-ion batts.
    The protection circuit was attached to a pair of batteries in parallel.
    magic shine battery  HELP!-image.jpg

    I did survive the soldering though, but have been thoroughly chastised. I probably shouldn't have listened to the advice to "rebalance " the cells though.
    magic shine battery  HELP!-image.jpg
    spez roubaix
    fantom cross - stolen -
    crux
    moonlander

  6. #6
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    Finaly pictures! Sorry about the advice, but it is tipical simptom when you can't charge the pack to the full voltage. If you would send description and pictures of the pack at the begininig we could be more precise. I've take a look and see there are few different packs sold with MJ-872 lights, so I couldn't know which one you have.

    Now hopefuly you have restored cells the 2S2P setup and connect them to the protection module with all 3 terminals, did you? If you don't get any voltage out of the connector (or red/black wire solder point) your circuit module has to be reset. This is normaly done by connecting (good) charger for a few seconds. Hopefuly protection module is still working.

    Can you desribe your voltage measurments at different points?

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