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HP Forum Archive 08

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The exchange of the built-in NiCd battery of HP-34C.
Message #1 Posted by Hiroshi Ito (JAPAN) on 23 Aug 2002, 10:54 p.m.

I want to examine an exchange because the built-in NiCd battery of HP-34C deteriorates. Does HP-34C become stable when a NiCd battery is changed to the NiMH battery? Generally a NiMH battery outlasts a NiCd battery. But, a NiMH battery becomes useless if HP-34C doesn't become stable. Which of the NiCd battery and NiMH is it the choice whose it is better for HP-34C to choose?

      
Re: The exchange of the built-in NiCd battery of HP-34C.
Message #2 Posted by David Smith on 24 Aug 2002, 4:46 p.m.,
in response to message #1 by Hiroshi Ito (JAPAN)

I have used AA NiMH cells in all my rebuilt HP battery packs (classic, Woodstock, and Spice series) with great success. They take longer to fully charge (in direct proportion to their increased capacity over the regular NiCad batteries). 1800mAH NiMH cells take three times longer to charge than the 600mAH Nicads, but run the machine for three times longer.

            
Re: The exchange of the built-in NiCd battery of HP-34C.
Message #3 Posted by Karl Schneider on 26 Aug 2002, 4:37 a.m.,
in response to message #2 by David Smith

David --

What are you using as replacement 1.2V NiMH AA cells? I have both the "older" Spice pack (with silver metal holder and plastic spacer), and "newer" pack (2 cells in one assembly; cannot be taken apart). Both are dead.

I plan to build new packs using 1.2V NiCad AA "replace-a-cells" from Radio Shack. These are short, flat-ended, and have soldering tabs. RS does not sell similar 1.2V NiMH AA cells -- only the longer ones with posts on the + terminal, dimensionally identical to 1.5V alkaline AA cells, which break the delicate battery springs.

I agree with Mr. Rodriguez -- better to recharge these externally, even the NiCad -- and take no risks.

      
Re: The exchange of the built-in NiCd battery of HP-34C.
Message #4 Posted by Andrés C. Rodríguez (Argentina) on 25 Aug 2002, 11:44 a.m.,
in response to message #1 by Hiroshi Ito (JAPAN)

Since the charging cycles of NiCd and NiMH are similar but not identical, it is advisable to charge the NiMH cells in an external, NiMH specific charger. In such manner, you also reduce some risks of overvoltage which can affect yor calculator in case of bad contacts, etc. And it also will be faster!


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