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Just wondering, Ni-cd charger used on Ni-mh

Discussion in 'Boat Electronics' started by Syntax, Mar 28, 2007.

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  1. Syntax

    Syntax Guest

    I know it is not the right place to ask, but maybe some of you know the
    answer.
    I got a bunch of Ni-mh batteries, and a charger that supports normal and
    Ni-cd charging, so what charging method is the best for these batteries?

    Puuuf, there goes my brain :)

    Wkr Syntax
     
  2. Larry

    Larry Guest

    Set the charger to charge NiCd batteries and it will charge the NiMh just
    fine...albeit a little slowly as they are probably much larger in AH
    capacity. I'm currently buying NiMh "AA" cells at 2.5 AH!

    Larry
     
  3. Syntax

    Syntax Guest

    Okay, now i know it is safe to use.

    Mine are 2 and 2.5 AH, but they actually take less time to charge on the
    Ni-MH setting than on the normal setting.

    But thanx.

    Wkr

    Syntax
     
  4. Larry

    Larry Guest

    Yes. The NiMH setting charges at a higher current. Ni-Cd chargers will
    charge them, but at the slower rate...which isn't a bad thing at all.

    Larry
    --
     
  5. You have to be carefull though. NiCD is usually charged either at C/10 rate
    of at high current, where a drop in voltage is used to detect the end of the
    charging cycle.

    The C/10 charge with NiCD cannot overcharge them.

    However, NiMH batteries show a much smaller voltage drop when full, which
    might not be detected by a fast NiCD charger. Also, overcharging NiMH at
    C/10 will certainly damage them. So be careful!

    Meindert
     
  6. Jack Erbes

    Jack Erbes Guest

    Meindert Sprang wrote:
    So for routine purposes and otherwise healthy NiMH cells, what would you
    use? As an aside, I finally figured out that C/10 means 1/10th of
    capacity and that C/20 or C/30 is a much better idea.

    I have a DuraCell quick charger that is identified as a "Class 2"
    charger but does not tell me much more than that. Do you know what the
    charge rate on a Class 2 charger is? Output is 1.6V @ 1800mA.

    I'm about to throw away the DuraCell and get a Maha I think.

    Jack
     
  7. I must corrent myself here. C/10 is fine for NiMH. Faster than C/10 will
    overcharge them when not stopped.
    No idea but the specs suggest that it pumps 1800mA in the cells. The
    efficiency of NiMH is 66% so when you have a 2500mAh cell, it needs
    2500/0.66 = 3800mAh for a full charge. That equals 3800/1800 = 2.1 hrs with
    your charger. So to see if your charger works, put the empty cells in, and
    check after 2.1 hrs if the charger has shut off of does so within the next
    15 minutes or so. If it doesn't, disconnect it yourself.

    Meindert
     
  8. Jack Erbes

    Jack Erbes Guest

    Thanks Meindert,

    The cells I have a Energizer NiMH 2300mAh AA's. They have been charged
    a couple of times now. The DuraCell quick charger charged them in about
    15-20 minutes (blinking LED stopped blinking) on the first use, it took
    more like an hour after the second use.

    The batteries show a stable 1.37V aftet they are charged, removed from
    the charger, and rested for a day or so. I haven't checked to see what
    they come off the charger at, I need to do that though.

    But the thing irritates me a little because I have no idea what it is
    doing and no control over anything. I think I'll treat myself to a
    better charger and feel a little better for better just for knowing what
    is going on there.

    I don't use a lot of batteries and am more interested in getting a good
    charge that will provide longer service life on things like my Garmin
    76Cx handheld than I am in getting fast charges.

    I decided to try the NiMH's for awhile simply because I think it is
    better for world in the long run, I don't think it will save me any
    money in the long run over the 35 cents or so I pay for the disposable
    alkalines I have been using. I'm probably wrong about that too though.

    Jack
     
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