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NiMH AA battery charger

Discussion in 'Electronic Design' started by DG, Dec 25, 2003.

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  1. DG

    DG Guest

    I'd like to make a simple battery charger for AA batteries. My
    requirements would be:

    -Uses an AC->DC plug-in-the-wall adapter (I have a few of these laying
    -Will always charge 4 AA batteries at once (so I guess that's 6V in
    series, or should I charge them in parallel?)
    -I hope that the batteries will have the same initial charge when they
    are "dead". They will be used in my Canon A60 camera which takes 4 AAs
    -I'd like them to not get hot after they have finished charging. So I
    could either charge them non-linearly or have the circuit cut-off once
    they are "full".

    If there are any circuits available on the Internet, please let me know.
    Google didn't turn up anything for me so far.

  2. René

    René Guest

    Hi Dave,

    There are no doubt many hi-tec, possibly CPU controlled delta peak
    optimized fast charging systems around.

    I chose to go a different road.

    I use an older (NiCD intended) C/10 wallplug charger that once costed
    less than $10. (so charge current is ~ 100 mA). Every DIY market has
    those. No way to beat that price.

    A set of 4 x 1300 mAh NiMH's cost below $8 nowadays, so I purchased 2
    sets. While I deplete one set in my digicam, the other one is charged
    (takes ~ 24 Hours due to low charge current).
    And yes - I ususally forget to disconnect the charger and leave the
    batteries cooking for several days. Sometimes I even charge batteries
    that are not empy at all.
    All very bad and non politically correct. You know that, I know that -
    but the batteries do not. They can stand some overloading @ 100mA with
    very little degradation.

    The cheap NiMH AA sets do not mind and work reliably for over 2-3
    years now - giving reliable performance. If they eventually fail, I
    have to fork out another $8 for a replacement set (propbably 1800 NiMH
    nowadays). Always a fresh set of batteries when I need to go out

    -My 0.02....
  3. Active8

    Active8 Guest

    As much as I hate Radio Sheisse (SP scheiss?) unless I need an in
    circuit charging solution, I don't wast time. I'd check Wal-Mart

    I have 2 RS chargers. One for D cells and 9V batts and the Fast
    NiCd / NiMH charger that does 2,4,6,or 8 at a time. Takes an hour
    or less.

    I got some adapters at the dollar store, too. You can slip smaller
    batts inside and charge them in a D cell charger although they're
    really meant for *using* smaller batts, not charging them.

  4. Ken C

    Ken C Guest

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