Rapid charging good or bad for NiMH batteries?

Discussion in 'Digital Photography' started by Bruce W.1, Feb 6, 2005.

  1. Bruce W.1

    Bruce W.1 Guest

    In my research I found that some people say that rapid charging is good
    for NiMH batteries and others say it's bad, so I'm confused.

    Can anyone shed some light on this matter?

    Thanks for your help.
    Bruce W.1, Feb 6, 2005
    #1
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  2. Bruce W.1

    Rudy Benner Guest

    "Bruce W.1" <> wrote in message
    news:tpuNd.1884$...
    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    Now that you are confused, you will fit in well here.
    Rudy Benner, Feb 6, 2005
    #2
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  3. Bruce W.1

    deacon Guest

    Bruce W.1 wrote:
    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    The conventional wisdom is that it's bad, but at less than $2.50 for 2300 mah
    AA's, why use a slow charger? There may be a definitive analysis of the number
    of recharges using fast vs. slow charging out there, but I haven't seen it.
    deacon, Feb 6, 2005
    #3
  4. Bruce W.1

    Ralph Mowery Guest

    That is what I say. When most cams take either 2 or 4 of the AA size and
    you can get them and a charger for about$ 15 why worry about it. Not sure
    about all the cams but even the non AA batteries cost about $ 20 for a new
    one and usually last atleast a year.


    "deacon" <> wrote in message
    news:xZuNd.2205$...
    > Bruce W.1 wrote:
    > > In my research I found that some people say that rapid charging is good
    > > for NiMH batteries and others say it's bad, so I'm confused.
    > >
    > > Can anyone shed some light on this matter?
    > >
    > > Thanks for your help.

    >
    > The conventional wisdom is that it's bad, but at less than $2.50 for 2300

    mah
    > AA's, why use a slow charger? There may be a definitive analysis of the

    number
    > of recharges using fast vs. slow charging out there, but I haven't seen

    it.
    Ralph Mowery, Feb 6, 2005
    #4
  5. Bruce W.1 wrote:

    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.


    It reduces the number of cycles that the battery will last. I'd get the
    Maha MH-C401FS which has a selectable charge rate. You can slow charge
    overnight, or do a fast charge when needed. Then there are the
    "ultra-fast" chargers, which should be avoided. These are like 3.4A
    charging rate.

    See: http://nordicgroup.us/chargers/
    Steven M. Scharf, Feb 6, 2005
    #5
  6. Bruce W.1 wrote:
    > In my research I found that some people say that rapid charging is
    > good for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    I don't have the facts on it, but I work under the expectation that slow
    is better but fast is not a problem IF they don't overheat. I don't expect
    either to be a real problem and I have never lost any sleep over it.

    --
    Joseph Meehan

    26 + 6 = 1 It's Irish Math
    Joseph Meehan, Feb 6, 2005
    #6
  7. Bruce W.1

    Harvey Guest

    "Bruce W.1" <> wrote in message
    news:tpuNd.1884$...
    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    Rapid charging, while convenient, is not good for any battery. Rapid
    charging is accomplished by increasing the average current flow into the
    battery in order to save time. Increased current flow means increased heat.
    The increased heat will tend to boil off more of the chemicals in the
    battery than slow charging. For every 18 degrees F increase in the
    battery's temperature, the reaction doubles. This boiling off of the
    chemicals in the battery will eventually lead to a decline in the battery's
    storage capacity. That all being said many people do not care if they get
    only 100 cycles versus 500 cycles of a Ni-MH battery and are willing to make
    the trade off.
    Harvey, Feb 6, 2005
    #7
  8. Bruce W.1

    Bob Salomon Guest

    In article <0XvNd.3851$%>,
    "Harvey" <> wrote:

    > Rapid
    > charging is accomplished by increasing the average current flow into the
    > battery in order to save time. Increased current flow means increased heat.
    > The increased heat will tend to boil off more of the chemicals in the
    > battery than slow charging. For every 18 degrees F increase in the
    > battery's temperature, the reaction doubles.


    Which is why the fast Ansmann chargers have an automatic fan that comes
    on automatically to maintain the optimal temperature in the cell while
    charging a 2500 mAh NiMh cell in 10 to 40 minutes. Naturally, being a
    smart charger, it switches each sell to trickle charge mode as that cell
    reaches full charge.

    http://www.ansmann.de/en/index.htm?view=detail&pid=614&tab=description&pr
    2id=&appid=

    --
    To reply no_ HPMarketing Corp.
    Bob Salomon, Feb 6, 2005
    #8
  9. Bruce W.1

    Ron Hunter Guest

    Bruce W.1 wrote:
    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    Some batteries, and chargers, are made in a special way for fast
    charging. If using those, it probably doesn't cause any harm. Fast
    chargers are likely to cause the batteries to warm up more than is good
    for them, and may shorten there useful life. But with NIMH batteries
    running less than $1 each, why worry about it?


    --
    Ron Hunter
    Ron Hunter, Feb 6, 2005
    #9
  10. Bruce W.1

    Harvey Guest

    "Bob Salomon" <> wrote in message
    news:...
    > In article <0XvNd.3851$%>,
    > "Harvey" <> wrote:
    >
    > > Rapid
    > > charging is accomplished by increasing the average current flow into the
    > > battery in order to save time. Increased current flow means increased

    heat.
    > > The increased heat will tend to boil off more of the chemicals in the
    > > battery than slow charging. For every 18 degrees F increase in the
    > > battery's temperature, the reaction doubles.

    >
    > Which is why the fast Ansmann chargers have an automatic fan that comes
    > on automatically to maintain the optimal temperature in the cell while
    > charging a 2500 mAh NiMh cell in 10 to 40 minutes. Naturally, being a
    > smart charger, it switches each sell to trickle charge mode as that cell
    > reaches full charge.
    >
    > http://www.ansmann.de/en/index.htm?view=detail&pid=614&tab=description&pr
    > 2id=&appid=
    >


    Interesting. You need to use special fast charge batteries with that unit.
    Harvey, Feb 6, 2005
    #10
  11. Bruce W.1

    Bob Salomon Guest

    In article <crxNd.3865$>,
    "Harvey" <> wrote:

    > You need to use special fast charge batteries with that unit.


    No you can use any NiMh or NiCd cell. These are smart chargers not dumb
    ones charging with brute force.

    --
    To reply no_ HPMarketing Corp.
    Bob Salomon, Feb 6, 2005
    #11
  12. "Bruce W.1" <> writes:
    >In my research I found that some people say that rapid charging is good
    >for NiMH batteries and others say it's bad, so I'm confused.


    >Can anyone shed some light on this matter?


    There are multiple ways to charge a NiMH cell, not just two.

    Fast chargers, that charge in 3 hours or less, are *good* - compared to
    most other chargers. They detect when the cells have reached full
    charge, and stop charging at the high rate. (They may continue trickle
    charging at a very low rate).

    There are timed chargers that simply charged for a fixed amount of
    time, and if the cell wasn't fully discharged before starting, it may
    be badly overcharged. These are probably the worst for the batteries.

    There are 14-hour chargers that also overcharge the cells, but at a
    lower rate that won't cause much damage. Still, you don't want to leave
    cells in these for more than 24 hours or so.

    So, among these types, fast chargers are best.

    On the other hand, if you compare fast chargers only, there are
    differences. Ones that monitor each cell individually are better than
    ones that charge multiple cells in series or parallel. And one-hour or
    faster chargers are likely to give you fewer charge cycles than the
    slower 2- or 3-hours chargers, so *when comparing fast chargers* faster
    may not be better. On the other hand, faster is convenient, and the
    cells are cheap, so you have to balance the convenience against longer
    life.

    Dave
    Dave Martindale, Feb 7, 2005
    #12
  13. Bruce W.1

    Paul H. Guest

    "Bruce W.1" <> wrote in message
    news:tpuNd.1884$...
    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    I've used the same twelve AAA no-name NiMH batteries in my wireless
    headphones for over two years, charging a pair of them every other day on a
    one-hour Ray-O-Vac quick charger and I've never had a battery fail yet. I
    also use the same charger for my digital camera AA's and have never had a
    battery failure or apparent weaking over the same two years of very hard
    service.

    Seems to work OK for me, but even had I experienced some failures, the
    convenience would have been worth it.
    Paul H., Feb 7, 2005
    #13
  14. In article <tpuNd.1884$>,
    "Bruce W.1" <> wrote:

    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    There's a sweet spot in the charging rate. While the physical effects
    of fast charging versus slow charging are debatable, 3-hour to 1-hour
    rates are where electrical and thermal indicators of a complete charge
    are the strongest. Outside of that, the signs are vague and the
    batteries are likely to be over charged or under charged.

    Unused batteries don't always show electrical signs of a full charge.
    It's best to put them in a trickle charger for the first couple of
    cycles. They can become very hot before a 1-hour charger detects the
    heating.

    The ultra-fast chargers use a pressure sensor because gassing is the
    best sign of overcharging at higher currents.
    Kevin McMurtrie, Feb 7, 2005
    #14
  15. Bruce W.1

    Alan Meyer Guest

    Dave Martindale wrote:
    > ...
    > ...
    > There are 14-hour chargers that also overcharge the cells, but at a
    > lower rate that won't cause much damage. Still, you don't want to

    leave
    > cells in these for more than 24 hours or so.
    > ...


    I've got one of those. I've used it to charge the AAA batteries
    for my ancient Palm VIIx and, after about 2.5 years, the
    batteries seem to last about as long as ever.

    Alan
    Alan Meyer, Feb 7, 2005
    #15
  16. Bruce W.1

    Harvey Guest

    "Bob Salomon" <> wrote in message
    news:...
    > In article <crxNd.3865$>,
    > "Harvey" <> wrote:
    >
    > > You need to use special fast charge batteries with that unit.

    >
    > No you can use any NiMh or NiCd cell. These are smart chargers not dumb
    > ones charging with brute force.
    >
    > --
    > To reply no_ HPMarketing Corp.


    Perhaps but that is not what the manual says, for what that is worth.
    Harvey, Feb 7, 2005
    #16
  17. Bruce W.1

    Harvey Guest


    >
    > The ultra-fast chargers use a pressure sensor because gassing is the
    > best sign of overcharging at higher currents.


    Gassing? Surely you jest.
    Harvey, Feb 7, 2005
    #17
  18. Bruce W.1

    Don B Guest

    Bruce W.1 wrote:
    > In my research I found that some people say that rapid charging is good
    > for NiMH batteries and others say it's bad, so I'm confused.
    >
    > Can anyone shed some light on this matter?
    >
    > Thanks for your help.


    I've always been told heat is the enemy of rechargeable batteries, so if
    that's true, it makes sense the cooler you can keep them when charging
    the better.
    Don B, Feb 7, 2005
    #18
  19. Bruce W.1

    Ron Hunter Guest

    Bob Salomon wrote:
    > In article <crxNd.3865$>,
    > "Harvey" <> wrote:
    >
    >
    >>You need to use special fast charge batteries with that unit.

    >
    >
    > No you can use any NiMh or NiCd cell. These are smart chargers not dumb
    > ones charging with brute force.
    >

    You need special batteries for chargers that work in less than 1 hour.
    If they aren't properly vented, fast charging could be dangerous. Note
    that smart chargers can detect what kind of battery you are using, and
    adjust their charging approach automatically. Buy a good charger!


    --
    Ron Hunter
    Ron Hunter, Feb 7, 2005
    #19
  20. Bruce W.1

    Ron Hunter Guest

    Don B wrote:
    >
    >
    > Bruce W.1 wrote:
    >
    >> In my research I found that some people say that rapid charging is
    >> good for NiMH batteries and others say it's bad, so I'm confused.
    >>
    >> Can anyone shed some light on this matter?
    >>
    >> Thanks for your help.

    >
    >
    > I've always been told heat is the enemy of rechargeable batteries, so if
    > that's true, it makes sense the cooler you can keep them when charging
    > the better.
    >

    Yes, and no. Most batteries are designed to withstand some heat during
    charging. If your charger heats them to a point where you can't stand
    to have your finger on them, then it probably isn't doing the batteries
    any good.


    --
    Ron Hunter
    Ron Hunter, Feb 7, 2005
    #20
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