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Charging Li-ion batteries

Discussion in 'Electronic Design' started by Paul Burridge, Oct 30, 2003.

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  1. Hi,

    I've got some rechargable lithium-ion batteries; 3.7V/1100mAh.
    Is there any problem with conventionally charging these or does it
    require some sort of dedicated charger with all sorts of protection to
    do the job properly? I was just going to hook 'em up to say 4.2V for a
    few hours. Will that be okay?

    p.
     
  2. Ian Stirling

    Ian Stirling Guest


    Probably.
    Current limiting to around an amp, and terminating the charge when
    the current has fallen to 50ma or so is probably a good plan.
    Don't go much over 4.2V, 4.20V is probably what you should shoot for.
    If you drop the voltage to 4.1, the cells will last more cycles.
     


  3. I've heard some horror stories about Li-Ion batteries literally exploding if
    not properly charged! Use a dedicated Li-Ion charger, or read more about how
    they must be charged and follow the guidelines. I wouldn't use NiCd or NiMH
    chargers on them.

    Costas
     
  4. mike

    mike Guest

    try
    sci.chem.electrochem.battery

    Several issues. Some types of cells can take only 4.1V. Make SURE
    you have the 4.2V cells. Bigger problems if you try to charge them in
    series. Take care NOT to discharge them too much. How much is too much?
    Not a clue. 3V maybe???
    Cells that have been overdischarged can get reeeel hot when you charge 'em.
    mike
    --
    Bunch of stuff For Sale and Wanted at the link below.
    laptops and parts Test Equipment
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    Honda CB-125S
    400cc Dirt Bike 2003 miles $550
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  5. Well, do not connect them directly with 4.2V supply.
    Make constant current source say 100-250 mA & connect batteries to it.
    For schematic, mail me at
     
  6. mike

    mike Guest

    Just to clarify, make sure your constant current source is voltage
    limited at the correct voltage for the chemistry of the cell you have.
    I'd use 4.1 myself because you usually can't tell by looking at the cell.
    And that's not
    "about 4.1V" it's 4.10000V max, max, max not a millivolt more...
    Monitor the temperature.
    mike

    --
    Bunch of stuff For Sale and Wanted at the link below.
    laptops and parts Test Equipment
    4in/400Wout ham linear amp.
    Honda CB-125S
    400cc Dirt Bike 2003 miles $550
    Color LCD overhead projector
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  7. Mike

    Mike Guest

    Exactly how does one determine if ones Li-ion cells are the 4.1v type
    or the 4.2v type ?. I'm using some BLC-2 cells (as used in Nokia
    batphones) in a project, being charged by a TI BQ24001 charge chip
    which has this option pin strappable, and there seems to be no info
    out there as to the preferred diet of the cell.
    cheers
    M
     
  8. budgie

    budgie Guest

    That's probably the essence of what is needed, with under/over-temp
    precautions. Current-limited constant voltage (CLCV) is the regime to
    use.

    It's not a horror story, but precautions ARE necessary. For an
    in-depth read of the care_and_feeding, the O/P and others considering
    playing in this field should download the spec sheets of dedicated
    Li-Ion (not multi-chemistry) controllers from Maxim, Linear Technology
    or Benchmarq (TI). We use the MAX1737 in our commercial chargers.
     
  9. Ian Stirling

    Ian Stirling Guest

    Well, there is probably a right way to measure this, popping the battery
    out of my nokia, and measuring the voltage (I diddn't measure it on
    charge) of the BLC-2 gave me 4.17V, so it's a pretty safe bet that it's
    4.2.
     
  10. mike

    mike Guest

    SAFE BET???
    An explosive recommendation based on a HUNCH??? and a single measurement
    that.s 1.6% over 4.1V on a phone that may or may not be the same???
    And your meter is accurate...and...your phone chip is not on the high
    side of spec...and...

    Safe for YOU maybe, cause HE's gonna be the one at risk.
    mike
    --
    Bunch of stuff For Sale and Wanted at the link below.
    laptops and parts Test Equipment
    4in/400Wout ham linear amp.
    Honda CB-125S
    400cc Dirt Bike 2003 miles $550
    Color LCD overhead projector
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  11. Well I managed to take a peek at the dedicated charger for this cell
    in a store yesterday and it is actually marked as 4.2V out (as I'd
    anticipated) at 600mA. (which I hadn't - seems a bit low). So whilst
    4.1 would work okay, 4.2 is optimal and perfectly safe, it seems.
     
  12. Ian Stirling

    Ian Stirling Guest

    The battery (BLC-2) is constructed in such a manner that I don't believe
    it's likely that it has the capability of signalling 4.1/4.2 voltage, and
    it's very unlikely that there are both 4.1 and 4.2V cells.
    Checking again (after charge) the voltage is 4.18
    Given that nokia are unlikely to produce a phone that is that inaccurate,
    I believe 4.2 is almost certainly the intended voltage.

    The meter is accurate, at least to within +-10mv on that range.
    I have an old standard cell that I checked it with.
     
  13. mike

    mike Guest

    See, you do the research and you find the answer. And you didn't have
    to rely on a SWAG represented as a safe bet.

    I have some first-hand experience trying to use (NiMH) cells from a cell
    phone in a computer application. They couldn't take the fast charge of
    the computer.
    mike

    --
    Bunch of stuff For Sale and Wanted at the link below.
    laptops and parts Test Equipment
    4in/400Wout ham linear amp.
    Honda CB-125S
    400cc Dirt Bike 2003 miles $550
    Color LCD overhead projector
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  14. What does "SWAG" mean? I've only ever seen it used on this newsgroup.
     
  15. onestone

    onestone Guest

    reuest a couple of sample bQ24013 chargers from Ti. These run from the
    USB port even. there is also a free sample EVKit, but I don't know if
    it's available still.

    Al
     
  16. I'm not aware of who "Ti" is/are, but I'd imagine one has to be some
    sort of corporate client to be able to successfully request a freebie
    from 'em?
     
  17. Mark Zenier

    Mark Zenier Guest

    Scientific Wild Ass Guess.

    Mark Zenier Washington State resident
     
  18. Ian Buckner

    Ian Buckner Guest

    Paul, you may not be aware of this but there have been 2 instances
    recently of batteries exploding in Nokia phones in Holland. Nokia
    are investigating, but I don't know what they came up with. They
    suggested initially it might have been due to people using non-Nokia
    supplied batteries.

    Regards
    Ian
     
  19. Thanks, Ian. I have to say I've faced worse things in my life than an
    exploding phone battery, but nevertheless, I decided I couldn't be
    arsed to build a suitable charger myself so I've now bought the
    dedicated one. And if that blows up, I'll sue! :)
     
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