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Newbie Ni-Cd to Ni-Mh Battery Question

Discussion in 'Hobby Electronics' started by Han, Nov 6, 2006.

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  1. Han

    Han Guest

    Hi all,

    I have a cordless drill here that the battery pack has died on. After
    cracking it open (dead anyway) it's just filled with 12 x 1.2V 1200mAh
    Ni-Cd batteries to total 14.4V.

    My question is if I replace them with higher rated 1.2V Ni-Mh batteries,
    say 2000 or 2200mAh will the original charger for the drill be ok?

    The output on the chargers label is 15.0V DC 400MA.

    PS I know cordless drills are as cheap as chips these days or I could
    get them refilled at a battery joint, but it's more of a Cup Day project
    than anything else...

    This page was quite helpful
    I'm just not sure about the 15V charger and 14.4V total (or is it 1.2V?)

    Any assistance appreciated.

  2. Bushy Pete

    Bushy Pete Guest

    I've just changed the NiCd batteries in my "Bostik" soldering iron with
    NiMH. Runs and charges like a beauty, and I can get even more heat out of it

    It had two 1200mAh C cells and they were changed to 2700mAh. The original
    plug-pack charger works happily without getting too hot.

    Hope this helps,
  3. Don't use NiMh. NiCd have much lower internal resistance than NiMh so
    are more suited to high current devices like drills.

    Also, NiCd are much more robust and tolerant when it comes to charging.
    NiMh cells are exothermic during charging so they can get hot real
    quick and hence get damaged more easily.

    Stick with NiCd.

    Dave :)
  4. jasen

    jasen Guest

    no. most NiCd chargers can't correctly charce NiMh cells.

  5. Han

    Han Guest

    Thanks for the replies, much appreciated.

    I looked for NiCd's without success, seems NiMh are now the only readily
    available rechargeables available from the department stores / Jaycar /
    DSE / etc..

    With concerns about the charger too, in the end I decided against
    refreshing them ;) Thanks again for the advice.

  6. Jaycar have plenty of NiCD cells!
    Solder tab versions are available in AA,Sub C, 1/2 Sub C, 4/5 Sub C,
    and 2/3A
    Page 196 in the catalog.

    Dave :)
  7. jasen

    jasen Guest

    go to a battery place. not a toy shop.

  8. Han

    Han Guest

    Jaycar have plenty of NiCD cells!

    My local store didn't have any stock of the ones I thought I needed. The
    1.8AH SUB C were what I thought would be ok and better, the other 1.3AH
    would be much the same as the original batteries I thought and very
    little point in replacing given the cost.

    I was even going to try higher rated AA (as they would physically fit)
    but the highest in stock were 1000mAh.

    I guess it's probably safer anyway that someone like me didn't do it ;)

    Thanks all again.
  9. Han

    Han Guest

    no. most NiCd chargers can't correctly charce NiMh cells.

    Ta for that, probably a good thing I did go the NiMh route then.

  10. Poxy

    Poxy Guest

    Actually, model toy shops would most likely have the high-performance NiMH
    batteries that he wants.

    I'm curious though, do these drill packs still use temperature sensing for
    charge cutoff? Or do they use delta V with temperature as a safety backup?
    If they still use temperature, would the temperature change of a NiMH pack
    be close enough to that of NiCads?
  11. No, NiMH have an exothermic charging process and generate a lot more
    heat (and internal pressure) during and at the end of charging, totally
    different to NiCd.

    Only the expensive drills have any sort of proper charging design. The
    cheap $15-$50 Bunnings drills have no cutout at all.

    Dave :)
  12. Guest

    Have a look at the next (December) issue of Silicon Chip - this exact
    topic is covered in a feature and also a charger controller to stop you
    coooking the batteries in the future.

    Ross Tester
  13. jasen

    jasen Guest

    NiCd charging is endothermic, so the increase when they fill up and go
    endothermic is more pronounced.

    it could work.

  14. jasen

    jasen Guest

    On 2006-11-08, I

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