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I can't wait that long to charge the batteries!

Discussion in 'Electronic Components' started by Caspian, Jul 26, 2007.

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  1. Caspian

    Caspian Guest

    Some domestic appliances come with rechargeable cells that need charging
    for many hours before their first use.

    For example, I have a Panasonic DECT phone with two AAA NiMH cells which
    needs charging for 7 hours.

    But maybe you can't wait that long for some reason and you simply
    "must" use the appliance!

    How much would cell life be reduced if such an appliance is used after,
    say, only 30 to 60 minutes of charging instead of the 7 hours?
     
  2. First, take care that NiMH and NiCd are different, Nicads have a 'memory
    effect' that makes this unwise. You've got Nickel metal hydrides, so you
    can do it. Most of the charge goes in during the first part of the charge,
    the increase isn't linear.

    That means you can grab a useful charge in the first hour of charge, but to
    make sure the full charge is properly applied, use up that charge before
    trying to recharge, then give it the full time. Don't try to guess how much
    is needed if you charge from empty for an hour, use for half an hour, and
    such, you'll probably overcharge the batteries.

    In short, you can get a lot of capacity from a charge of as little as one
    third of the time for full charge, but whatever you do, always start the
    charge on a freshly discharged MiMH battery so you know where you are.
     
  3. GregS

    GregS Guest

    I have done the quick test of a device sometimes without even plugging it
    in, or after a short charge. I don't try to drain the device, and I never
    seemed to have a problem. Here is a fairly neat page on battery effects......

    http://www.dansdata.com/gz011.htm

    greg
     
  4. (GregS) wrote in
    NiMH doesn't have memory effects so that's not an issue in my post.

    I don't understand what you're saying exactly, but it's undeniable that if
    you part-charge a NiMH battery during a third of its charge time, then
    discharge only a little, you can't charge it for the full time unless it IS
    drained first, for the obvious reason that you'll overcharge it if you try.
    Some battery chargers might detect the true state of charge, but most
    assume the battery is really low, and have a very simple timer, if there is
    any means to prevent overcharge at all.
     
  5. GregS

    GregS Guest

    I have no idea what my chargers know.

    I took my camera on vacation after not using it for a couple years and
    used my older NiMH's. I charged them with two different chargers.
    One charger would not stop charging. The camera would die very rapidly
    using these cells. Allthough they are the highest capacity of the dozens
    I own, I'm wondering if they are permanantely worthless, at least
    in my camera. I was going to try some brand new cells and check
    that first. I had to use Lithium backups on vacation for my Minolta.
    I have a lot to learn about using NiMH cells,even though I have been
    using them in cheap chargers for many years, but wish there was
    something better.

    I want to make a fixture to discharge my NiMH's down to 1 volt.
    I was planning on using a diode string to generate a 1 volt zener and
    using another series current limit resistor. Soon. I'm wondering
    if that will help my current cells I own.

    greg
     
  6. (GregS) wrote in
    I've recently got a pair of small CR123A lithium rechargeables, 880 mAH.
    Very nice. The charger cost a bit more than with NiMH types, but only maybe
    50% more. Those batteries prefer to be discharged lightly and can be
    recharged at will and taken off charge at any time for use, and the
    chargers have to be accurate to sense the battery condition to be safe, so
    if you can get one that's ok, you might get more out of them that with
    NiMH. Less weight for a start.

    The small chargers for 'SureFire' K2 LED torches found on eBay are worth a
    go. I was nervous about mine at first, the risk of nasty accidents, but
    it's well behaved and will safely stop charging when it's done. Each
    cell is handled seperately by the charger. The cell charge voltage should
    never rise above 4.2V for a 3.6V cell, and I think there are other critical
    points to watch, but if these things increase in sales without a rise in
    disaster reports, then all's good. It's dangerous tech, but so are NiMH's,
    if they get a short circuit.
     
  7. Top posted just this once...

    AT LAST! SOMEONE THAT SCTUALLY KNOW THE PROPER TERMS FOR THE DEVICES HE
    USES!

    Thanks dude... I needed that.

    There, english TARDS.

    Put that in you enema bag and shove it up your asses!
     

  8. Wrong.

    Single cells have ZERO "memory effect" when charged singularly.

    A BATTERY of cells MAY develop a "memory effect".

    Most modern charging systems incorporated into the devices the cells
    are placed into themselves, however, have "watchdog circuits" that insure
    that all cells get "topped off" properly.

    You are about five years behind, as are the cell types you attribute
    this "problem" to.
     

  9. The "watchdog" circuit protect devices and cells from this problem as
    well, these days. No overcharging here...
     
  10. Wilscombe

    Wilscombe Guest

    A simple solution might be to use standard disposable AAA batteries
    until the others are fully charged. There might be a problem if these
    batteries are left in for a long time but I imagine the risk would be
    minimal. Most manufacturers have Helplines who could advise.
    Can anyone tell me what a "Tard" is,let alone an English one? I
    imagine "Spurious Response" is a Redneck? Curious breed!
     
  11. "Voltage Depression occurs primarily in NiCad batteries. NiMH batteries are
    almost never affected and Li-Ion batteries are NEVER affected."
    http://www.zbattery.com/memoryeffect.html

    I was partially remembering this:
    "If a cell becomes reverse-charged, or is left flat for a long time, small
    metal whiskers can grow across the plates."
    http://cucc.survex.com/archive/jnl/1992/nicd.htm
    I remember that partial formation of those 'whiskers' can be related to
    partial charge/discharge cycles.

    If the OP had asked questions about memory effect specifically, I'd have
    checked for current info before posting, but he didn't ask that. It's a
    side issue, as he asked if his NiMH's can be safely part charged then used.
    I think my answers to the actual question were right.
     
  12. It would if it had one, perhaps. If all it has is a timer, the obvious
    thing to do is charge for full time on a freshly discharged cell. If there
    really IS a non-obvious and different method, I'm not sure it's wise to
    recommend it to someone asking a very basic question about battery charge.
    Far better to take the safest course.
     
  13. GregS

    GregS Guest

    Partially true. Only if the cell is abused, especially overcgarging, or
    perhaps if its been used a lot. I have let cells lie around and they
    don't go bad. I have had cells practically brand new that shorted
    after harsh charging. I am referring to NiCad's.

    Yes, my Johnson walkie talkies still have German Nicads that still
    work, and never go dead. I charged them a couple years ago. They
    are 43 years old.

    greg
     
  14. clifto

    clifto Guest

    It's short for "retard", which itself is shorthand for "mentally retarded
    person".
     
  15. I have often wondered that myself. I see this warning ONLY with
    consumer appliances. When I buy cells, the data sheet never says
    anything about needing to charge them fully before the first use in
    order to avoid some sort of permanent damage or capacity reduction.

    I have since ignored the warnings about needing a full charge before
    first use, with no observed ill effects.
     
  16. Nope. The term retard can be referring to such a person, but it also
    means taking a step back.

    Take some techno-person, watch him state something utterly ludicrous,
    and just like the "retarded" timing on an automobile, viola! We have
    someone that is acting retarded.

    They are rampant in Usenet.
     
  17. Jerry G.

    Jerry G. Guest

    Have several sets of batteries with external chargers. While you are
    gabbing away on your phone, you can be having some batteries on charge.
    When the batteries in use are running low, you do a battery swap.
    Calculate the number of sets of batteries and chargers you will need,
    and then go for it!

    By the way it sounds, I would guess you will need three sets of
    batteries and chargers.

    --

    Jerry G.


    Some domestic appliances come with rechargeable cells that need charging
    for many hours before their first use.

    For example, I have a Panasonic DECT phone with two AAA NiMH cells which
    needs charging for 7 hours.

    But maybe you can't wait that long for some reason and you simply
    "must" use the appliance!

    How much would cell life be reduced if such an appliance is used after,
    say, only 30 to 60 minutes of charging instead of the 7 hours?
     
  18. No. You have several cell in external charging devices, which been
    improperly monikered as "battery" chargers.
    No. You have some cells on charge.
    When the cells run low, you should swap ALL of the CELLS that comprise
    your device's BATTERY, as swapping only those you perceive as being
    drained is asking for problems.
    Unrelated stupid shit.
    Unrelated stupid shit.
     
  19. If it excercises you so much, instead of lambasting someone just because
    you can, write a letter to the Times or something. Submit an article to a
    journal. Or at least write to every maker of commercial gear who
    transgresses. There's more to understanding something than getting the
    exact words right. Sure it's misleading, but most people know how to avoid
    the problems. If you really want to evangelise on this point, get a job
    writing manuals for a major company, as that's the way you'll most likely
    shape public usage of these terms. You certainly won't reach them this way.
     

  20. Learn how to attribute your quoting correctly, and/or quote the actual
    post you are replying to.
     
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