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  • Topic: Ni-CD battery replacement with Ni-MH

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    • November 17, 2020 10:24 PM EST
      • Farmington, New Mexico
         
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      Ni-CD battery replacement with Ni-MH

      Ok .... I need someone thats a lot more savvy at this then I am......

       

      Here's the deal... I have a Dremel battery powered tool.   Its got a 7.2Vdc removable clip in battery pack...   6 ea 1.2 V AA Ni-CD cells rated at 700mh.  To recharge,  the snap in battery pack is put into a charger base, that plugs into a standard wall outlet ( 110 AC  US ).   This pack is dying ( won't hold a charge, short run time etc.)  Time to replace it.

       

      I can get Ni-MN AA cells with 1500mh rating w/tabs to replace the batteries,  not difficult.

       

      But...  Will the charger work to re-charge the new NI-MN pack as is?  If it can great.... IF NOT,  Then how would I go about re-charging the new pack?   Or should I just go back to some higher mh NI-CDs?  And would the charger handle the added load?

       

      Thanks ahead of time...

      Dave

      ____________________________________

      New Mexico­ Northern ­Railroad
      D&RGW ­315 Crew ­member, Fireman
      RRR #4
      Board Memb­er, Durang­o Railroad­ Historica­l Society

    • November 17, 2020 11:44 PM EST
      • Elverta, CA
         
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      Dave,

       

      The charger will work, but its insufficient; as NiCd chargers are not as sensitive as required to detect the peak of NiMH technology. Not to mention its likely anemic as in provides less than the desired current for a 1500mAh battery to properly charge. That said, your existing charger is likely a trickle only device...

       

      I assume 700mAh Ni-Cd is not available? Larger capacity cells would likely work, but again they will charge at a lower than specified rate.

       

      Perhaps purchasing a new charger that is capable of charging modern battery technologies would work for you, they can be had very reasonably IMO.

       

      Michael

      This post was edited by Michael Glavin at November 17, 2020 11:56 PM EST
    • November 18, 2020 12:08 AM EST
      • Gig Harbor, WA
         
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      That's a pretty old tool if it is using ni-cads.  Maybe its time for a tool tool.  You can get a small Dremel 7700 kit for about $45.00 that comes with Li-ion batteries and a charger. Just a thought.

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      Paul Burch

      Sierra Cascade & Pacific RR

    • November 18, 2020 12:08 AM EST
      • Gig Harbor, WA
         
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      That's a pretty old tool if it is using ni-cads.  Maybe its time for a tool tool.  You can get a small Dremel 7700 kit for about $45.00 that comes with Li-ion batteries and a charger. Just a thought.

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      Paul Burch

      Sierra Cascade & Pacific RR

    • November 18, 2020 8:44 AM EST
      • Farmington, New Mexico
         
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      @Paul.... Thanks for the reply.........   It is a 7700 03  model.   Ni-CDs.....  Replacement packs are listed as NI-CD 700mh...   

       

      @ Michael...  So a Replacement build of 1000mh battery pack would recharge with the plugged  into charger, only it would take longer to re-charge... Correct?  This is a encased Snap in pack.....  I have a high end charger for loose batteries.

       

      Your thoughts?

       

      ____________________________________

      New Mexico­ Northern ­Railroad
      D&RGW ­315 Crew ­member, Fireman
      RRR #4
      Board Memb­er, Durang­o Railroad­ Historica­l Society

    • November 18, 2020 10:09 AM EST
      • Elverta, CA
         
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      Dave

       

      If it were I, I'd use the 1000mAh cells mentioned and trickle charge the battery as usual with an occasional topping charge with a NiMH peak charger. Are you able to ascertain the charge value of the existing wall wart/charger power supply? Looks like current NiMH cells can trickle charge at less than 0.1C of rated capacity. Does your charger support NiMH peak charging?

       

      NiMH cells benefit from an initial charge regimen coined as a form charge. Basically peak charge and discharge fully for at least three complete cycles, each discharge will garner higher discharge current totals until such time you realize the rated capacity of said cells.

       

      Michael

      This post was edited by Michael Glavin at November 18, 2020 10:18 AM EST
    • November 23, 2020 8:36 PM EST
      • Farmington, New Mexico
         
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      @ Michael...  The charger that the pack drops into is rated  

      INPUT: AC 120V 60Hz   6W

      OUTPUT: DC 9V   0.20A

       

      This Dremel pack charger will not take loose cells, only the battery pack....

       

      I'm leaning to using 1000mh NiCd replacement cells w/tabs.   Should do the job, just  take longer to charge to 1000mh cells?

      Stop me if this is wrong thinking.

       

      Dave

       

      ____________________________________

      New Mexico­ Northern ­Railroad
      D&RGW ­315 Crew ­member, Fireman
      RRR #4
      Board Memb­er, Durang­o Railroad­ Historica­l Society

    • November 25, 2020 9:42 AM EST
      • Elverta, CA
         
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      Dave,

       

      Yes, I'd go with the 1000mAh Ni-Cd cells. The charger @ .20A will be fine. I'd limit charge cycles to 24 hours or so. That said if possible an occasional topping charge with a peak charger is highly recommended IMO.

       

      Michael

       

    • November 25, 2020 10:21 AM EST
      • Farmington, New Mexico
         
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      1000mh NiCd it is.....

      Thanks  Guys...      I can always count on LSC to keep me from looking too stupid.....

      Dave

       

      ____________________________________

      New Mexico­ Northern ­Railroad
      D&RGW ­315 Crew ­member, Fireman
      RRR #4
      Board Memb­er, Durang­o Railroad­ Historica­l Society

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