How to calculate Energizer NiMH Charging Times

Discussion in 'Digital Photography' started by newsgroup2003@gmail.com, Apr 29, 2006.

  1. Guest

    I have the Energizer CHDC charger and I checked online and I cant
    figure out how htye are calculating the charging times:
    http://data.energizer.com/PDFs/chdc.pdf

    I have a set of 2300 mAH Energizer batteries and I don't want to charge
    them too long.

    Anyone know what "math" Energizer seems to be using?

    Thanks
     
    , Apr 29, 2006
    #1
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  2. Bob Salomon Guest

    Bob Salomon, Apr 30, 2006
    #2
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  3. ASAAR Guest

    On 29 Apr 2006 15:25:02 -0700, wrote:

    > I have a set of 2300 mAH Energizer batteries and I don't want to charge
    > them too long.
    >
    > Anyone know what "math" Energizer seems to be using?


    For AAA cells, dividing the mAh rating by 100 will give you the
    identical results shown in Energizer's charging time table. Their
    math wasn't quite as precise for AA batteries, but if you divide the
    mAh rating by 300 you'll get very close. So for your 2,300 mAh AA
    cells, 2,300 / 300 == 7.7 hours.

    But you might want to do yourself and your batteries a favor.
    Get a better charger, one that stops when the batteries are fully
    charged, and use this CHDC charger only as a backup. These are
    called "Smart" chargers. The problem is that to calculate the
    correct CHDC charge times you'll need to use a more complex formula
    that will reduce the 7.7 hours based on two factors.

    The first is that your battery's capacities will progressively
    diminish as they age, so while using 2,300 when they're new will
    work, a year from now they might have dropped to 1,900, and that
    would mean that the batteries would now only need 6.3 hours to reach
    a full charge. Keeping them in the charger for the full 7.7 hours
    that new 2,300 mAh batteries need would only help to further shorten
    their lives.

    The second factor is the charge state of the batteries when you
    put them in the charger. If they're fully discharged, then 7.7
    hours would be an appropriate amount of time to leave them in the
    charger. But you'll often be putting the batteries back in the
    charger before they've been fully discharged. Just because a camera
    or other device says that the batteries need to be recharged, that
    doesn't mean that the batteries are fully discharged. Put them in
    some other devices and they may continue operating for hours!

    Another example. Suppose that you fully charge a set of batteries
    and don't use them for a month or two. Due to self discharge, they
    might have lost 1/2 of their charge. Put these back in the CHDC
    charger and they'd only need 3 or 4 hours to reach a full charge, so
    if you let them charge for 7.7 hours they'd be "overcooking" in the
    charger for several hours, and that would also shorten their lives.

    That's the bad news. The good news is that this is a very slow
    charger, faster than a trickle charger but not by a lot. So the
    batteries won't be severely overheated, and the amount of their life
    that's lost by overcharging will probably not be a lot. Instead of
    them lasting for 3 or 4 years, they might only last 2 or 3, and
    after a couple of years, even if they're still performing fairly
    well, you might want to replace them with a new set of 3,300 mAh
    batteries. :)
     
    ASAAR, Apr 30, 2006
    #3
  4. wrote:
    >I have the Energizer CHDC charger and I checked online and I cant
    > figure out how htye are calculating the charging times:
    > http://data.energizer.com/PDFs/chdc.pdf
    >
    > I have a set of 2300 mAH Energizer batteries and I don't want to
    > charge them too long.
    >
    > Anyone know what "math" Energizer seems to be using?
    >
    > Thanks


    Too many variables to have an accurate answer. Get a good charger and
    don't worry.

    --
    Joseph Meehan

    Dia duit
     
    Joseph Meehan, Apr 30, 2006
    #4
  5. Guest

    Thanks everyone. What's a good charger that can keep up with
    increasing capacity of the batteries? I recall the Energizer has (at
    least in the past) capped the maximum mAh in their larger chargers.
     
    , Apr 30, 2006
    #5
  6. Guest Guest

    Thanks everyone. What's a good charger that can keep up with
    increasing capacity of the batteries? I recall the Energizer has (at
    least in the past) capped the maximum mAh in their larger chargers?
     
    Guest, May 2, 2006
    #6
  7. Bob Salomon Guest

    In article <dRC5g.105075$P01.77643@pd7tw3no>, <>
    wrote:

    > Thanks everyone. What's a good charger that can keep up with
    > increasing capacity of the batteries? I recall the Energizer has (at
    > least in the past) capped the maximum mAh in their larger chargers?


    The new Ansmann Energy 8 Pro is rated for AA NiMh up to 6400 mAh.

    --
    To reply no_ HPMarketing Corp.
     
    Bob Salomon, May 2, 2006
    #7
  8. wrote:
    > Thanks everyone. What's a good charger that can keep up with
    > increasing capacity of the batteries? I recall the Energizer has (at
    > least in the past) capped the maximum mAh in their larger chargers?


    Maha C401FS .... it is an awesome little piece of equipment.

    --
    Thomas T. Veldhouse
    Key Fingerprint: 2DB9 813F F510 82C2 E1AE 34D0 D69D 1EDC D5EC AED1
     
    Thomas T. Veldhouse, May 2, 2006
    #8
  9. Guest

    Thanks again. Curious though, quick or rapid chargers are recommended.
    I was under the impression it's better for the batteries to be slow
    charged?
     
    , May 3, 2006
    #9
  10. SMS Guest

    wrote:
    > Thanks again. Curious though, quick or rapid chargers are recommended.
    > I was under the impression it's better for the batteries to be slow
    > charged?


    The batteries will have a larger number of cycles if they aren't charged
    with a very high current. Probably not worth worrying much about, but
    the better chargers don't charge at a high rate.
     
    SMS, May 3, 2006
    #10
  11. SMS Guest

    wrote:
    > Thanks everyone. What's a good charger that can keep up with
    > increasing capacity of the batteries? I recall the Energizer has (at
    > least in the past) capped the maximum mAh in their larger chargers?


    Technically, they have a timer that times out, after what used to be
    sufficient time to charge even the highest capacity batteries. I'm sure
    that they'll come out with updated models that don't have this
    limitation. The timer is supposed to be a fail-safe way of terminating
    charging, if the other detection methods don't work for some reason.

    The charger makers may want to put a switch on the charger for high
    capacity batteries, to increase the duration of the timer from three
    hours to maybe six hours.
     
    SMS, May 3, 2006
    #11
  12. ASAAR Guest

    On 2 May 2006 21:51:21 -0700, wrote:

    > Thanks again. Curious though, quick or rapid chargers are
    > recommended. I was under the impression it's better for the
    > batteries to be slow charged?


    Yes, if you're using an old timer based charger, since there were
    many ways that the charger could end up charging the batteries well
    beyond the point where they reached a full charge. If a fast
    charger was used, the batteries could be severely overheated,
    shortening their lives. With "smart" chargers, even if the very
    fast ones aren't quite as gentle as the slower chargers, significant
    damage won't occur, and you'll get long life (many charge cycles)
    whether a fast or a slow charger is used. I use a slower charger
    more often, but only because it's smaller and more convenient. I
    rarely need to quickly charge a large number of batteries, but that
    need arises, I've got several fast (30 and 60 minute) chargers
    available. More important than whether you get a fast or slow
    charger, is to get one that charges each cell independently. If you
    find a charger that only charges batteries in pairs, skip it. :)
     
    ASAAR, May 3, 2006
    #12
  13. wrote:
    >
    > Thanks again. Curious though, quick or rapid chargers are recommended.
    > I was under the impression it's better for the batteries to be slow
    > charged?
    >


    It is better to charge slow, mostly because of the fact that a battery will
    take a charge more efficiently and take more of a charge when it is cool in
    temperature. Fast charging raises the temperature of a battery. There are
    other reasons I believe, but that is a large one.

    --
    Thomas T. Veldhouse
    Key Fingerprint: 2DB9 813F F510 82C2 E1AE 34D0 D69D 1EDC D5EC AED1
     
    Thomas T. Veldhouse, May 3, 2006
    #13
  14. Bob Salomon Guest

    In article <44589d85$0$277$>,
    "Thomas T. Veldhouse" <> wrote:

    > It is better to charge slow, mostly because of the fact that a battery will
    > take a charge more efficiently and take more of a charge when it is cool in
    > temperature.


    Some chargers, like the Ansmann Digispeed and Digispeed Ultra have a
    temperature controlled exhaust fan in the charger to draw heat off from
    the cells when the temperature rises during charging. These automatic
    fans keep the batteries at the proper temperature even in the Digispeed
    Ultra which charges most cells in 10 minutes to full charge.

    --
    To reply no_ HPMarketing Corp.
     
    Bob Salomon, May 3, 2006
    #14
  15. Bob Salomon <> wrote:
    > In article <44589d85$0$277$>,
    > "Thomas T. Veldhouse" <> wrote:
    >
    >> It is better to charge slow, mostly because of the fact that a battery will
    >> take a charge more efficiently and take more of a charge when it is cool in
    >> temperature.

    >
    > Some chargers, like the Ansmann Digispeed and Digispeed Ultra have a
    > temperature controlled exhaust fan in the charger to draw heat off from
    > the cells when the temperature rises during charging. These automatic
    > fans keep the batteries at the proper temperature even in the Digispeed
    > Ultra which charges most cells in 10 minutes to full charge.
    >


    I'll tell you what. If a fan is required, then the core of that battery is
    going to be hot ... and it will not charge efficiently. Also, heat is not the
    only fact, resistance is another, and of course, how the battery has been
    conditioned (the better Maha chargers claim to have an algorithm they use to
    charge the battery that eliminates the need to condition a battery).

    10 minutes ... I suspect the charger is manufacturer is figuring that its
    users would prefer to replace batteries more often then to charge slowly. I
    find it a rare case that I actually need to quick charge. I keep a couple of
    batteries charged as spares and then charge at slow speeds for most charges.
    There are cases I want power fast and I will use the fast charge (like a
    spontaneous photo opportunity and I need to power my flash), but they are few
    and far between.

    --
    Thomas T. Veldhouse
    Key Fingerprint: 2DB9 813F F510 82C2 E1AE 34D0 D69D 1EDC D5EC AED1
     
    Thomas T. Veldhouse, May 3, 2006
    #15
  16. SMS Guest

    Thomas T. Veldhouse wrote:

    > I'll tell you what. If a fan is required, then the core of that battery is
    > going to be hot ... and it will not charge efficiently. Also, heat is not the
    > only fact, resistance is another, and of course, how the battery has been
    > conditioned (the better Maha chargers claim to have an algorithm they use to
    > charge the battery that eliminates the need to condition a battery).


    The ultra high-rate chargers such as the Ansmann Digispeed and Digispeed
    Ultra should be avoided. There is rarely a need to charge the batteries
    that fast, and the high charging current and high heat has a very
    negative effect on battery life. The fan will dissipate the heat into
    the air, but it doesn't help the battery life.
     
    SMS, May 4, 2006
    #16
  17. Bob Salomon Guest

    In article <4459726d$0$96921$>,
    SMS <> wrote:

    > The fan will dissipate the heat into
    > the air, but it doesn't help the battery life.


    Certainly has not hurt the cells to date.

    --
    To reply no_ HPMarketing Corp.
     
    Bob Salomon, May 4, 2006
    #17
  18. "Bob Salomon" <> wrote in message
    news:...
    > In article <4459726d$0$96921$>,
    > SMS <> wrote:
    >
    >> The fan will dissipate the heat into
    >> the air, but it doesn't help the battery life.

    >
    > Certainly has not hurt the cells to date.


    Is there any evidence for that, e.g. a link to some research? I'm
    serious, all I've ever heard/read over the years is that rapid
    charging reduces useful life of NiCd/NiMH batteries. It's to do with
    the heat generated when the cells reach approx. 80% of their capacity,
    more heat changes the chemical ability to recharge. I'd love to see a
    good study on that subject.

    Bart
     
    Bart van der Wolf, May 4, 2006
    #18
  19. Paul Rubin Guest

    "Bart van der Wolf" <> writes:
    > Is there any evidence for that, e.g. a link to some research? I'm
    > serious, all I've ever heard/read over the years is that rapid
    > charging reduces useful life of NiCd/NiMH batteries. It's to do with
    > the heat generated when the cells reach approx. 80% of their capacity,
    > more heat changes the chemical ability to recharge. I'd love to see a
    > good study on that subject.


    The rapid chargers that I know of stop charging when that happens.
    They switch over to a slow charge, so to get a complete charge takes
    several hours. But being able to get the cells up to 80% in 15
    minutes is very useful.
     
    Paul Rubin, May 4, 2006
    #19
  20. SMS Guest

    Bart van der Wolf wrote:
    >
    > "Bob Salomon" <> wrote in message
    > news:...
    >> In article <4459726d$0$96921$>,
    >> SMS <> wrote:
    >>
    >>> The fan will dissipate the heat into
    >>> the air, but it doesn't help the battery life.

    >>
    >> Certainly has not hurt the cells to date.

    >
    > Is there any evidence for that, e.g. a link to some research? I'm
    > serious, all I've ever heard/read over the years is that rapid charging
    > reduces useful life of NiCd/NiMH batteries. It's to do with the heat
    > generated when the cells reach approx. 80% of their capacity, more heat
    > changes the chemical ability to recharge. I'd love to see a good study
    > on that subject.


    Remember, Bob Salomon is the distributer for the Ansmann chargers. So of
    course he's going to say what he says.

    The fact is that high rate charging, which raises the temperature of the
    batteries considerable, reduces the number of charge cycles.

    As Isidor Buchmann writes "High temperature during charge and standby
    kills batteries."

    It'd be interesting to test the number of cycles of the same battery
    type using both a normal rate and a high rate charger to see just what
    the difference in the number of cycles would be.

    It's not usually necessary to charge batteries at such a high rate, so
    those very high rate chargers should be avoided unless someone really
    needs a super-fast charge.
     
    SMS, May 4, 2006
    #20
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