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NIMH battery charging.

Discussion in 'Electronic Repair' started by [email protected], Sep 23, 2005.

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  1. Guest

    What is the proper way to charge these cells. I have a number of AA's
    that are all weak. I have tried charging them at a constant rate of
    about .050A overnight and they seem to come up and they will work but
    don't last very long. Can these be charged manually as you would Nicads
    or is there a special trick to this? Thanks, Lenny Stein, Barlen
    Electronics.
     
  2. Ken Weitzel

    Ken Weitzel Guest

    Hi Lenny...

    Respectfully suggest that that's because you aren't charging them,
    you're just teasing them a little :)

    Unless 50 mills is a mis-type, that is.

    If you really have to charge them manually, then read the capacity
    (current "normal" is 2500 mah) and charge them 10 percent (250 mils
    in this case) for 14 hours.

    Or better, buy yourself a nimh charger. If the budget is a concern,
    then Walmart has an Eveready "dumb" charger that comes with two
    AA's, all for only a little under 10 dollars (cdn).

    If the budget isn't of concern, then there are "smart" chargers
    available that will on an individual cell basis pre-determine the
    state of charge, charge them to 100% quickly, and then leave them on
    trickle (about your 50 mil rate) until you remove them.


    Take care.

    Ken
     
  3. GregS

    GregS Guest

    I kinda wish someone would write up the best ideas that work about various
    batterys and charging methods, and methods to test each
    for quality. In working with NIMH, I have yet to gather enough
    information to really evaluate them properly.
    I have some that seem to shut down prematurly powering a digital camera.
    I think its just one cell acting up or something like that sometimes. I always wanted to build
    a charger, like one charging position for each cell. I never liked charging them
    in series or parallel. Each one should be individually handled.

    greg
     
  4. Bob Salomon

    Bob Salomon Guest

    The Ansmann Energy 16 will handle up to 12 AA cells treating each
    individually. It has a function that will automatically renew old cells
    that seem to be failing. It will do that by its refresh mode. Any cell
    that needs this will not effect the state of charge or the charge time
    of any other cell.
     
  5. Chuck Olson

    Chuck Olson Guest

    So far it seems Maha makes chargers that do a pretty good job. They have a
    couple that are said to rejuvenate cells - - the MH-C204F and the MH-401FS.
    I bought the more expensive MH-401FS because it charges and monitors each
    cell individually, and can be set for either 2 hr or 5 hr rate. So far, my
    NiMH AA cells are performing well in regular use in a 3-watt Luxeon
    flashlight that pulls about an amp out of a pair of Energizer 2300 mAh cells

    Chuck.
     
  6. Nostrobino

    Nostrobino Guest

    I agree. When a set of four is brand new they usually all charge in the same
    time, but as they age it seems that one or two cells in the set will become
    different from the others and will take much longer to charge. When that
    happens I don't see how two different cells can be charged properly if
    they're on the same circuit. That's why I like the Maha C401FS chargers that
    have individual circuits for each cell. I also have a couple of the older
    Maha C204Fs which reviewers all raved about, but because they charge cells
    in pairs I now use them only occasionally for the conditioning feature.

    N.
     
  7. Nostrobino

    Nostrobino Guest

    Well, the C204F can condition cells by automatically deep-cycling them. The
    C401FS does not have this feature.

    Yes, the C401FS is my favorite charger too. While it's not cheap, I doubt
    it's possible to get as good a charger at a better price. Absolutely, having
    a separate circuit for each cell is a good idea, and I appreciate the
    fast/slow charge switch too. Normally I use the slow rate because the cells
    stay cooler, but it's often handy to have the faster rate available when I
    need 'em in a hurry.

    N.
     
  8. jakdedert

    jakdedert Guest

    Yeah, I've got several devices which take *three* AA's...makes it kind
    of difficult to charge them, when my charger only does two at a time....

    jak
     
  9. Nostrobino

    Nostrobino Guest

    [ . . . ]
    Yes, I'll bet. I don't think I've ever had anything that took three AA
    cells.

    N.
     
  10. clifto

    clifto Guest

    All four of my FRS radios take three AA cells each. I've seen (but wouldn't
    own) flashlights that take three AAs.
     
  11. jakdedert

    jakdedert Guest

    At least half a dozen Motorola FRS radios and an LED flashlight, for
    starters....

    jak
     
  12. ASAAR

    ASAAR Guest

    Then you're missing out on a good thing. I have a small light
    that uses a high intensity Luxeon LED powered by 3 AAA cells. It's
    noticably brighter than 2D cell flashlights using krypton bulbs.
    The light pattern is better too, although as with most LED lights,
    there's no focusing.
     
  13. clifto

    clifto Guest

    My good LED flashlights take either two or four AA's. One of the "fours"
    has seven white LEDs, a decent if not pinpoint pattern, and turned out
    to be intrinsically safe in the bargain. (At least it's marked so; I
    haven't turned on the gas to experiment. :)

    Not having seen the Luxeon or any other LED lights with three cells,
    I was referring to some old-style krypton-bulb three-AA flashlights
    that just weren't worth the effort of carrying.
     
  14. jakdedert

    jakdedert Guest

    I believe I stated specifically an LED flashlight. It was one of the
    first ones available, from C. Crane. There are much better ones sold
    nowadays; but until this one dies, I'm keepin' it. I get 50 hours from
    a fresh set of alkaline AA's, and it will stay lit for an additional
    *100* hours at reduced brightness. I usually use discarded RF
    microphone batteries in it, but occasionally grab a set of NiMH's out of
    the charger if I've no mic culls around at the moment.

    jak
     
  15. What is the group's opinion of the chargers that Radio Shack sells at
    this time?

    And for that matter their batteries also.

    Thanks

    TMT
     
  16. ASAAR

    ASAAR Guest

    Several years ago when there were very few smart chargers
    available from any sources, their "timer" chargers were fair to
    good. They had one large smart charger that handled AAA through D
    cells, but it was a dud. I found that when it finished charging,
    the cells were only about 1/3 charged. I attempted to exchange it
    but found that that model had been pulled from all of the stores.
    As of early this year the only smart charger I've seen in any of the
    local stores is a tiny little thing, probably not high on too many
    lists because it's a fairly slow charger. But it has some nice
    features. It appears to have 4 independent charging circuits (but
    there's no easy way for me to verify this because it has only a
    single LED indicator). It charges up to 4 AA or AAA cells, NiCad or
    NiMH. Its best feature is that unlike my other finicky smart
    chargers that too readily refuse to charge what they consider to be
    marginal batteries, this one hasn't given up on any yet. And the
    batteries that the other chargers refuse to charge still have most
    of their original capacity and perform very well in everything I've
    put them in, except for the other "smart" chargers. This little
    charger, BTW, is the only one that isn't on the shelves with all of
    the other chargers. It's stored with the battery powered toy racing
    cars, with an Xmods logo. It sells for about $24, but comes with 8
    of Radio Shack's standard AAA NiMH cells. Even though I have more
    AAA batteries than I can use, I might get another of these chargers
    because what they do, they do well, and if RS stops selling them I
    doubt that I'll be able to find any other similar chargers.

    Their NiMH batteries are green, and have been for far too long.
    They're good batteries, but unless they were recently changed, still
    have the same modest 1800 or 850 mah capacity that they've had for
    several years. If you are considering getting their NiCads, watch
    out, as they have two types. One is OK, but the other has a
    capacity and weight that's only about 1/2 of the better type.
     
  17. Thanks for the response.

    I am a bit surprised that the market has not had better offerings.
    While I do not regularly follow this market (and that is why I ask the
    advice from those more knowledgable), I was under the impression that
    NiMH had been out for awhile and that I assumed that manufacturers had
    developed offerings to fill the market need...apparently not to the
    extent I had assumed.

    Could one determine if a charger is doing a cell individually by
    charging only one cell at a time?

    I also note that Radio Shack has an overnight charger and a fast
    charger that does AA through D sizes. Is there an advantage in having a
    slower charging rate? In other words, are the "fast charging" NiHM
    batteries have a problem that the slower charging batteries don't?

    TMT
     
  18. Darmok

    Darmok Guest

    When it comes to rechargeable batteries and chargers, I've found that
    this site offers a good selection, and decent prices.

    Note: I am in no way connected to this site, its owner, or anything;
    just thought it might be helpful to any who are looking for
    rechargeables or chargers.

    http://www.thomas-distributing.com/index.htm


    73 de Bill, KB8EB
     
  19. Thanks for the lead.

    While we are on the subject, what is the shelf life of NiMH batteries
    if they are left in their original containers?

    If one buys a package and puts it on the shelf for let's say five
    years, will the battery work as if you had charged it when you first
    bought it?

    I had also forgotten to ask...is there a FAQ for NiMH batteries?

    Thanks

    TMT
     
  20. Dave D

    Dave D Guest

    Theoretically speaking, slow charging will give more recharge cycles before
    the cell is worn out. However, with a decent delta-v charger doing fast
    charging, it's less of an issue these days. In the past, fast charging cells
    using the timer method was brutal and could often result in overheating and
    overcharging.

    Dave
     
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