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Testing a NiMH battery charger

Discussion in 'Electronic Repair' started by D, Oct 28, 2012.

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  1. D

    D Guest

    I have this battery charger which I use for NiMH AA cells:
    Some new cells I just bought do not seem to be holding a charge very
    long, and I'd like to check the output of the charger to be sure it's
    functioning fully. This charger uses temp to tell when the batteries
    are"full" (thermistor is present under batteries), then switches to
    "trickle". How can I tell by measurement if the thing is operating
    properly? I have access to a multimeter and oscilloscope for testing

    Any suggestions appreciated.

  2. Phil Allison

    Phil Allison Guest

    ** Are you for real ??

    The batteries get hot and you can feel that with your fingers.

    Means they are charged.

    ...... Phil
  3. D

    D Guest

    Are YOU "for real"????? Define HOT, smartass.

  4. D

    D Guest

    Thanks for the helpful reply. I appreciate that the batteries increase
    in temperature when they're charged, hence the thermistor, but "hot" is
    pretty non-specific, I was thinking there must be some charger voltage
    vs current curve which tracks the level of charge. I'll measure the
    voltage right after charging & see the result. These are 2,000 mAh
    cells. If nothing else, I suppose I could afix a suitable load, & see
    if the do indeed put out their rated current for the period claimed.

    Concerning your "friend" "Phil" with the social issues, I've been using
    this NG off and on for the better part of 20 years, back to when Sam
    Goldwasser was prominent (is he still around?), and I've always found
    the posters to be informative & civil. I don't recall ever seeing that
    kind of juvenile nonsense from anyone here before. Phil needs to get
    out of his mother's basement & make some friends.

    OK, "Phil", go ahead and unleash your childish, unoriginal,
    seen-it-before-from-a-million-losers-like-you tirade. I have no
    intention of reading it.

    And for god's sake, get back on your medication.
  5. Phil Allison

    Phil Allison Guest

    "Fucking DOPE "

    ** Charging is COMPLETE when the cells begin converting the charge current
    into heat.

    ** As anyone here can see, I posted a damn good reply to your absurdly
    stupid question.

    Then YOU came back with a gratuitous insult.

    YOU are way beyond merely STUPID and bad tempered.

    YOU are a fucking MORON and a stinking, fucking LIAR.

    Just like all anonymous cunts with Hotmail addys.


    ..... Phil
  6. mike

    mike Guest

    yep, be more specific.
    "not very long"

    NiMH batteries don't hold a charge for long.
    Especially high capacity ones.
    Especially cheap no-name ones.
    I'd not expect more than a couple of weeks of
    useful storage.
    Enloops or equivalent hold a charge much longer.

    Temperature charge termination is a BAD way to charge cells.
    It can work well if you fully discharge before recharging.
    Problem is that if you put in a nearly charged cell, you can
    do damage before the cell has a chance to heat up enough to
    trigger the termination.

    If you mean they don't put out as much energy as expected,
    that's a different issue.
    Depending on the load current and the device shut-off characteristic,
    internal battery resistance can cause the device to shut down long
    before it's used up. Cameras are especially bad in that respect.
    I've got cameras that run well on one battery vendor, but not at all
    on any other.

    It's like anything else. If you want long service life, buy
    premium cells and chargers.
  7. D

    D Guest

    Mike - Thanks for the reply. I agree temperature change sensing isn't
    as good as sensing voltage changes. The batteries are Harbor Freight,
    so they are cheap, but I've been using these types from them in AA & AAA
    for years with no issues in things like remote keyboards, lower drain
    items. Bought a new set for a CAMERA, as you said. The camera does
    have a setting for cell type, and a discharge function, which I've used
    to deplete them completely twice with recharging. I know this is
    especially an issue with cameras. Interesting about the internal

    You may be right about springing for better cells, at least in this high
    drain usage. Only trouble is my $$$ is a bit limited at the moment ;-/

  8. NiMH batteries don't hold a charge for long.
    Not so. I've put AA NiMH cells in a flash, that were charged months earlier,
    and they powered it well. This is an urban legend that has little basis in

    If it's the only method of termination, yes. But it's necessary to prevent
    overcharging, especially when the manufacturer recommends "slamming" the
  9. You may be right about springing for better cells, at least in this high-
    Good cells aren't expensive. A 16-pack of 2700 mAh MAHAs at Thomas
    Distributing is less than $3 per cell, and they throw in plastic cases and a
    carrying case.

    My experience has been that a 2700 mAh cell has about the same capacity as
    25-cent Costco (Toshiba?) cell. So you need to recharge them only about 12
    times before you break even. That's a good deal.

    I have two of these chargers, and paid about $40 for each -- when they were
    on sale. You might want to wait.
  10. Concerning your "friend" "Phil" with the social issues, I've been using
    That's nothing. He also ate the Chamberlains' daughter.
  11. mike

    mike Guest

    If you do the research, you'll probably decide that anything bought from
    HF is CRAP. That goes double for anything with a battery in it.

    They succeed because many people, like me,
    buy a tool for a job and rarely, if ever use it again.
    I have a boatload of HF stuff in that category, but I'd not buy it
    for a long-term use where reliability was an issue.

    Saving a few bucks on something that doesn't do the job is not being frugal.

    Use the HF cells in low-drain devices.
    Buy good cells for the camera and a new smart charger. The HF charger
    probably won't be friendly to your expensive cells.
    Enloops are highly regarded cells, but I guess it also matters what
    color the top plastic is. Japanese vs Chinese manufacture.

    Ebay cells are a crap shoot. I'm sure some of them are genuine,
    but I wouldn't bet money on it. My limited experience with EBAY cellphone
    batteries suggests that their specs are exaggerated.

    I've had several cameras that ran on AA cells. NONE of them were worth
    a crap.
    I don't know how they ever sold them new. Must be some degradation in
    the sensing circuitry that makes them all useless on NiMH now.

    Sometimes, you can find lower capacity cells with lower internal
    resistance, but I don't know how to tell without actually measuring it.
  12. D

    D Guest

    Thanks everyone for the great info on the batteries! I'll have to go
    back through all the links, but I appreciate the input!

    On Harbor Freight, my experience with them is that if you buy carefully,
    you can get what you need at a very good price. I've always had very
    broad interests (my downfall, some have suggested... ;-) and I
    personally own well over 20 grand worth of tools of all kinds which I
    have amassed over the years, from a tiny Swiss watchmaker's lathe to a
    full size PowerMatic cabinet saw and 8" jointer (woodworking is my real
    passion). I also have a complete set of professional grade automotive
    tools (mostly 30+ year old Craftsman & Snap-on). I do know good tools.
    I would not buy something requiring a high degree of precision, such
    as a jointer, from HF, but I have quite a few pneumatic nailers, impact
    tools, and even a compressor of theirs which have all served me quite
    well for years. I also have a very nice 3/4 HP drill press of theirs,
    as well as one of their tool chest side cabinets. All very servicable.
    Is everything they sell the best of its kind? No, of course not. But
    for the price (particularly if you combine a sale with one of their
    ubiquitous 20% off coupons) I have had no complaints overall, especially
    for tools I only use on occasion. And they're very easy with returns, if
    you do have a problem. I also have an HF clamp on multimeter which just
    yesterday I was using to measure the current drawn by a heater. Out of
    curiosity, I checked its readings against an inline measurement using a
    Fluke I also own. Dead on.

  13. Hi Michael!

    But it's knowing its place (rank). I have never seen an abuse posting
    to you by Phil...

    By the way, where is Eyeore?
  14. Phil Allison

    Phil Allison Guest

    "Daniel Mandic"

    ** A voice from the grave.....

    ** Responding to a rabid nutter like Terrell serves only to feed his ego.

    ** Think Eyesore wanked himself to death.

    Or maybe drank himself to the same end.

    ..... Phil
  15. Just a basic-electronics repairing selfmade-man...
  16. It's always a pleasure to me, Mr. Terrell!
    Phil is IMHO as Sommerwerck said, a capable electronics engineer, but.
    Only one Guru left in sci.electronics ;-). (more to come, I hope)
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