Loading ...
Sorry, an error occurred while loading the content.

RE: [SeattleRobotics] NiMH battery charging

Expand Messages
  • Rob Purdy
    What s the best way to treat NiMH batteries to get the most overalllong-term useful life from them? 100% charge is ok. Like any battery the worst enemy is
    Message 1 of 4 , Aug 5, 2008
    • 0 Attachment
      "What's the best way to treat NiMH batteries to get the most overalllong-term useful life from them?"

      100% charge is ok. Like any battery the worst enemy is heat and vibration.

      NiMH are very robust. 100 to 10% is fine. Battery management is the bigger issue. Killing them flat is about the worst thing you can do to them. In a pure EV NiMH vehicle your charger will determine your battery life.

      Rob





      [Non-text portions of this message have been removed]
    • dan michaels
      ... faster self-discharge rate than a NiCd, so trickle charging them is a good idea, again, as long as you don t get them too hot. C/100 is always a safe
      Message 2 of 4 , Aug 5, 2008
      • 0 Attachment
        --- In SeattleRobotics@yahoogroups.com, "Dennis Clark" <dlc@...> wrote:
        >

        >
        > Another site I read, that doesn't like NiMh, says that they have a
        faster self-discharge rate than a NiCd, so trickle charging them is a
        good idea, again, as long as you don't get them too hot. C/100 is
        always a safe trickle charge (C = capacity of the pack). I don't
        charge mine faster than 1C, so it takes an hour to charge a battery,
        more or less, if it is fully discharged. Faster charge rates can be
        used if the pack is fully discharged (about 1V per cell), you want
        most of that current to go to the charge, not to heating, that is why
        it works best at fully discharged.
        >
        > If you want to get the best life from a NiMh then don't charge or
        > discharge them at more than 1C. Avoid getting them hot and they
        will last longer. There is no harm in fully charging them as long as
        (yes, I'm being repetitive here) you don't get them hot.
        >
        > If anyone knows more I'd like to know - Like, what is the typical
        negative delta-vee of a NiMh pack at full charge?
        >
        > have fun,
        > DLC
        >


        I've been using NiMH AA-cells for 4-5 years now. Just the regular
        cheapo variety, like from Nexcell, and the Eveready batteries they
        sell in Target. [some people buy specialty cells for far more than
        $2.50-3.00 per cell, so they might say something different].

        I bought the 15-min charger for the Eveready cells, and I'd say that
        was a mistake. Many of those cells died within a year or so. Even
        though the charger has a fan, I think the cells still get far too hot
        during charging.

        I also have 12 or 15 AA-cells that are 3-4 years old that I've been
        charging with the overnight [12-hr] chargers, and most of those cells
        are still functioning well.

        From what I've read, the negative delta-V is too small on NiMH
        batteries to be of practical use. It's much larger [about 10X, IIRC]
        on NiCad. I think the best way to charge NiMH is at about C/3, and
        monitor the cell voltage [max about 1.4v] and cell temperature, as you
        noted above.
      Your message has been successfully submitted and would be delivered to recipients shortly.