Is it better to use slow chargers for NIMH batteries than the fast ones?

Discussion in 'Digital Photography' started by Mike Henley, Mar 28, 2006.

  1. Mike Henley

    Mike Henley Guest

    I'm going to develop a routine so that I charge 4 batteries every day
    regardless of my needs. If I need less then I'll just charge less
    often, every other day or less so. This means that I won't need a fast
    charger, but nonetheless will always have batteries ready. It will even
    be better than a 15 minutes recharger.

    Therefore, since I won't need a fast charger, should I stop using them?
    I already have a 15mins charger, a 1-2 hours charger, and a regular
    slow charger (~8 hours or more). Should I prefer to use the regular
    slow one?
     
    Mike Henley, Mar 28, 2006
    #1
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  2. Mike Henley

    ASAAR Guest

    Charging 4 cells per day might make sense if you rotate 50 or more
    of them through your chargers. Otherwise, each battery set probably
    should be charged no more frequently than every week or two if they
    aren't used, to minimize unnecessary extra work. Even with some
    self-discharge, after a week or two of sitting idle, the cells
    should have 90% or more of their full charge available. When
    charging this way, your batteries would probably last a little
    longer if you use your slowest charger, since it's unlikely to heat
    the batteries as much as the other chargers. And since the
    batteries (if they were unused) will have most of their charge, they
    shouldn't take anything like 8 hours to charge. Uh, that slow
    charger is "smart", isn't it? If it's a timer based charger, then
    I'd use the 1-2 hour charger instead, unless the batteries are well
    discharged. For my needs, I rarely use my 30 minute and 60 minute
    chargers. More than 90% of the time I use one of two other chargers
    that take anywhere from 4 to 7 hours before they're finished.
     
    ASAAR, Mar 28, 2006
    #2
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  3. Mike Henley

    Peter A. Guest

    Peter A., Mar 28, 2006
    #3
  4. Mike Henley

    SMS Guest

    Ah, life with NiMH.
    Batteries are now so inexpensive, that the marginal increase in the
    number of cycles that you get by using a slow charger isn't worth
    worrying about.
     
    SMS, Mar 28, 2006
    #4
  5. Mike Henley

    imbsysop Guest

    yeah sure .. let's make a substancial contribution to
    a) the depletion of available resources
    b) the ever increasing mounain of waste

    just by the mere argument of cheap consumables that lose their initial
    capacity after 6 months 'cos of inadequate use so they need an urgent
    cheap replacement ..

    that's a heck of an argument you are giving ..
    try google and type "toxicity Nickel" for a change ..
     
    imbsysop, Mar 28, 2006
    #5
  6. Mike Henley

    John H Guest

    I have been maintaining a large number of NiCad and NiMH packs
    that I want to be ready for use for perhaps five or six years. The
    method was suggested by a development engineer who worked with a
    battery manufacturer. It consists of using a simple clock timer set
    to turn on a C10 charger once a day for one hour. This has worked out
    well although packs should be cycled periodically if not discharged
    through use.

    John H
     
    John H, Mar 28, 2006
    #6
  7. To give as simple an answer as possible: In general, a slow charge will
    give a longer battery life than a fast one.

    However, many slow chargers are "dumb" meaning they don't have the
    ability to reduce current when the battery is full. They just charge at
    a constant slow rate, trusting the battery to dump the overcharge as
    heat - hard on the cell. SO, in some cases a "smart" fast charger will
    be better for the cell than a "dumb" slow charger.

    Also, my gut feeling is your charging regimen may be counter
    productive, unless you use you batteries a lot. There's reasonable
    evidence that rechargable batteries do best when stored at about 1/2
    charge. Constantly charging batteries that are only slightly depleted
    by self-discharge may in fact decrease their life.
     
    Scott Schuckert, Mar 28, 2006
    #7
  8. Mike Henley

    m Ransley Guest

    Nicads are best left discharged if use is infrequent and that is
    recomended by Sony for Nimh, I have 22 year old Nicads that still work
    by doing this. The packs that give me short life are the ones ive pushed
    to stay charged. Only Lead Acid are to be kept at 100% charge for
    longest life or they sulfate. Nimh and Nicads only have so many cycles
    in them, constant charging makes no sence to me. Slow is better but only
    a peak detection charger is going to safely not cook your cells from
    overcharging, unless you know how your charger monitors peak charge you
    might be shortening their life with all your units. Cheap chargers can
    be just that, cheaply designed.
     
    m Ransley, Mar 28, 2006
    #8
  9. Mike Henley

    Ron Hunter Guest

    You might find that your batteries last longer with the slow charger,
    but this has not been proven by any tests I have read about. In any
    case, NIMH batteries so so inexpensive, that it doesn't really matter
    much. Use whichever strikes your fancy.
     
    Ron Hunter, Mar 28, 2006
    #9
  10. Mike Henley

    John H Guest

    Topping off at C10 for an hour a day for certain packs that I
    want constantly available is worth a small sacrifice in service life
    for me. I just replaced a four cell Sanyo NiCad pack that was
    maintained this way. The EE code dates it at May, 2000. They were
    put in service shortly afterward. They makes the cost about $2 per
    year. For that I could grab the device they powered and go at any time
    without having to worry about charging up beforehand.


    John H
     
    John H, Mar 28, 2006
    #10
  11. Mike Henley

    Paul Allen Guest

    Yup, that's what I do too. I have three sets of batteries. One is
    always in the camera and the other two are in slow chargers on a timer
    that turns on for an hour a day. When discharged batteries come out
    of the camera they go in a charger overnight with the timer set to
    an appropriate value. The timer automatically reverts to 1 hour on
    per day, so I never have to think about it. And I always have fresh
    batteries.

    The popularity of ultra-fast chargers seems to come from the same
    source as the popular mania for more megapixels. And SMS is probably
    right that it doesn't make economic sense to worry about the slight
    lifespan reductions you'll get from using a fast charger. The real
    issue is that your next camera will probably use a proprietery battery,
    and then you'll be stuck.

    Paul Allen

    Paul Allen
     
    Paul Allen, Mar 28, 2006
    #11
  12. Mike Henley

    Paul Rubin Guest

    15 min chargers get the batteries fairly warm, which can't be good for
    them. Also, the Energizer charger should NEVER be used on cells that
    are already charged, to above 75% or so (i.e. past where the charger
    notices the negative delta V transition). It can overcharge severely
    and get the cells very hot if you do that.

    If you're planning to do all that charging because of self-discharge,
    you might look into the new Sanyo Eneloop cells or the Titanium
    equivalent (called Endura or something like that), which have much
    slower discharge. In general though, NiMH cells made recently have
    good charge retention over a several month period. Don't think
    they'll be almost flat if they go for a week without charging. I'd
    say don't worry about it if you've charged them in the past two
    months. They won't be at 100% full capacity after that long, but
    should be well over 50%, so just use them normally and recharge when
    they need it. With Eneloop/Endura they'll be over 90%.
     
    Paul Rubin, Mar 28, 2006
    #12
  13. Mike Henley

    ASAAR Guest

    Any particular reason why, or was your reply intended for someone
    else? A small amount of quoting is generally more useful than none.
     
    ASAAR, Mar 29, 2006
    #13
  14. Mike Henley

    Guest Guest

    Batteries probably won't make the "mounain" much higher.
    Esp if you recycle them.
     
    Guest, Mar 29, 2006
    #14
  15. Mike Henley

    Ron Hunter Guest

    That depends on the batteries! I have a Kodak pack of NIMH that will
    discharge almost completely in a week. I have some Energizers that take
    a couple of months. Motto here is, charge before you go, and always
    keep disposables appropriate for your camera as backup.
    That said, my wife just returned from a 7 day cruise, and took over 100
    pictures with those Kodak batteries, and it went to battery warning when
    I was reviewing them in the camera. I guess I can live with that.
     
    Ron Hunter, Apr 2, 2006
    #15
  16. Mike Henley

    Ron Hunter Guest

    Yes, but one look at the subject line makes the reference clear.
     
    Ron Hunter, Apr 2, 2006
    #16
  17. Mike Henley

    stauffer Guest

    The faster the charge, the more heat. Heat is not the friend of your
    battery. So slow charge is always better for the battery. However,
    one has to consider practicality and the need to sometimes charge in a
    hurry. If you are SURE you never will need a fast charge, then indeed
    a slow charger only is fine.
     
    stauffer, Apr 2, 2006
    #17
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