Charge Regimen for NiMH batteries?

Discussion in 'Digital Photography' started by Bill Tuthill, Aug 19, 2007.

  1. Bill Tuthill

    Bill Tuthill Guest

    Reconditioning by full discharge was the recommended charging regimen
    for NiCd batteries, which had horrendous problems with memory effect.

    I am not sure it is the recommended charging regimen for NiMH batteries.

    In fact the Prius, which has larger-than-AA batteries of the same type,
    attempts to keep its batteries always between 3/8 and 6/8 charged.

    So isn't it likely that the same charging regimen would be best
    for NiMH batteries in AA size? Don't use NiMH batteries until dead,
    have a non-NiCd setting on the charger, and do not trickle charge.
     
    Bill Tuthill, Aug 19, 2007
    #1
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  2. It is not even recommended for NiCd's today.
     
    Joseph Meehan, Aug 20, 2007
    #2
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  3. Bill Tuthill

    Dave Cohen Guest

    First, there's a hell of a difference between getting maximum battery
    life in a Prius and
    in a digicam. Unless you're getting some special deal covering those
    batteries, replacement ain't gonna be cheap.
    OTH - who cares whether you get 500 or 1000 cycles in a digicam, just
    saw Kodak low self discharge in Walmart $7 for a pack of 4.
    I once did a search on best storing method. Some sites said to store
    discharged and I think other said the opposite. I concluded didn't much
    matter.
    Talking of Walmart, they never seem to have same item in all stores and
    same store will not always replace a given item on the shelf. I suppose
    they just go looking for large quantity bargains.
    I've seen Hybrids and Kodak in what I assume are eneloop equivalents
    although I've no idea if they are as good. Today I saw bundled charger
    and 4 eneloops for $19. First time I've seen eneloop offered in a Walmart.
    Dave Cohen
     
    Dave Cohen, Aug 20, 2007
    #3
  4. Bill Tuthill

    Bill Tuthill Guest

    So Joseph, are you saying SMS is blowing smoke?
     
    Bill Tuthill, Aug 20, 2007
    #4
  5. Bill Tuthill

    SMS Guest

    It is recommended to do this at least occasionally, in order to maintain
    full capacity.
     
    SMS, Aug 20, 2007
    #5
  6. Bill Tuthill

    ASAAR Guest

    It shouldn't hurt if used sparingly. If used more than
    occasionally it can do more harm than good. It's a 'feature' that
    was once fairly useful, but now mostly for users of extremely large
    numbers (tens to hundreds of thousands) of batteries that have the
    staff and expensive equipment that manage and condition pools of
    batteries to squeeze as much life as possible out of the batteries.
    For them, even a very small percentage gain can provide a nice cost
    savings. The same gain for you and me would probably be considered
    insignificant, and might not even be noticeable. The 'discharge'
    button on chargers is a feature that may help sell more, or justify
    a higher price, and I have it on a couple of my chargers. But I've
    found it to be more of a time waster than anything else, at least
    with NiMH cells. As far as blowing smoke is concerned, anyone
    paying attention to SMS's posts will have noticed that he'll use any
    rumor, substantiated or not, to push his biased propaganda campaign.
     
    ASAAR, Aug 21, 2007
    #6
  7. Bill Tuthill

    Ron Hunter Guest

    When NiMH batteries begin to exhibit signs of taking less charge, near
    the end of their use life, this MAY extend the useful life, for a while,
    but is it worth the trouble for something as inexpensive as a NiMH
    battery? It isn't to me.
     
    Ron Hunter, Aug 21, 2007
    #7
  8. Bill Tuthill

    Ron Hunter Guest

    Biased? SMS? Gee, I hadn't noticed.... GRIN.
     
    Ron Hunter, Aug 21, 2007
    #8
  9. Bill Tuthill

    ASAAR Guest

    And weird to boot. He posted a link not long ago to another of
    his web sites. For this one he lurks with his camera waiting to
    catch pictures of neighbors or other locals and expose them to the
    world. Better not roll through a stop sign, swing too wide into
    another lane when making a turn, or be caught holding a cell phone.
    I wonder how many other undisclosed web sites he has. He'd probably
    love to be given an FBI badge or be made a junior G Man. Shades of
    Elvis being handed an FBI Special Narcotics Agent badge by Nixon.
    Or maybe he'd settle for being appointed the USA's Lithium Czar. :)
     
    ASAAR, Aug 21, 2007
    #9
  10. Bill Tuthill

    Bill Tuthill Guest

    The thought has occurred to me that he might be paid off
    by the powerful lithium lobby.
     
    Bill Tuthill, Aug 21, 2007
    #10
  11. Nah .. more like taking too much lithium.
     
    Thomas T. Veldhouse, Aug 21, 2007
    #11
  12. Bill Tuthill

    Allen Guest

    I put SMS in my killfile long ago when he absolutely refused to tell us
    what technical qualifications he has for judging batteries.
    Allen
     
    Allen, Aug 21, 2007
    #12
  13. Bill Tuthill

    Dave Cohen Guest

    I agree, I suspect it will be me that will need a life extender before
    the NiMH give out.
    Dave Cohen
     
    Dave Cohen, Aug 22, 2007
    #13
  14. Bill Tuthill

    Bill Tuthill Guest

    Full discharge might not be advisable for NiMH batteries at any point
    in their lifecycle.
     
    Bill Tuthill, Aug 22, 2007
    #14
  15. Bill Tuthill

    ASAAR Guest

    "Full discharge" isn't as severe as the term implies. The
    discharge circuits used by battery chargers don't discharge
    batteries until the cells reach zero volts. They discharge them
    until a predetermined voltage is reached, usually 1.0 volts. At
    that point the cells retain virtually no capacity. While each
    discharge cycle takes its toll, as long as batteries aren't
    discharged too often, the overall battery lives won't be
    significantly shortened.
     
    ASAAR, Aug 22, 2007
    #15
  16. Bill Tuthill

    SMS Guest

    I agree, the regimen that maximizes capacity and charge cycles is too
    much trouble for an item that is so inexpensive to replace. Still, for
    those that keep claiming very high cycle counts, they should understand
    these are for batteries that have been subjected to the optimal charging
    regimens. Nothing wrong with this really, you wouldn't expect them to
    quote the cycle count for a battery that's not had the optimal charging
    regimen.

    Steve
    "http://batterydata.com"
     
    SMS, Aug 23, 2007
    #16
  17. I saw that at my local Walmart also. Does anyone know how good the
    charger is? Does it charge the cells individually or in pairs?
     
    Daniel Prince, Aug 23, 2007
    #17
  18. Bill Tuthill

    Bill Tuthill Guest

    NiMH charging is a matter of grave financial concern for Toyota Motors.
    They warranty the Prius (and other hybrid?) NiMH battery packs for 10 years.
    There are some early Prius models that have gone almost that long without
    main battery pack replacement. Assuming daily operation, this represents
    at least 3500 charge cycles.
     
    Bill Tuthill, Aug 23, 2007
    #18
  19. Oddly, they expect the battery to last 15 years. The 10 year warrantee is
    only valid for cars sold in states that have adopted the California emmision
    laws. I think that is eight states in all. The other 42 states have an 8
    year warrantee on the Prius battery.
     
    Thomas T. Veldhouse, Aug 23, 2007
    #19
  20. Bill Tuthill

    Bill Tuthill Guest

    Thanks, I did not know any of that.

    The key to 15-year lifespan has to be shallow discharge/recharge cycles
    and keeping the battery between 45% and 65% full.

    I am currently using NiCd batteries (left over from some cheap Chinese
    solar-assisted LED sidewalk lanterns) in my shaver. Given a complete
    discharge, they are lasting a lot longer than I expected. On the next
    pair, I'm going to count.

    IMO (supported empirically): fully discharge NiCd, but not NiMH batteries.
     
    Bill Tuthill, Aug 23, 2007
    #20
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