On 2020-09-11, Martin Gregorie  wrote:
> On Fri, 11 Sep 2020 13:10:31 -0400, Dennis Lee Bieber wrote:
>
>> My first was an HP-25, and the third was the HP-28 -- I don't
>> recall if the latter is in storage or self-destructed; the 25 died when
>> I couldn't get new battery packs (it was the only one I owned that
>> could be used at work, as it lost its mind when powered down... Working
>> in a black program is a pain.)
>>
> I discovered how to repair the HP-21 battery packs: split them open and
> replace the pair of AA size NiCd batteries. The inner case is just glued
> to the textured removable base of the battery compartment and easily
> enough removed with a sharp knife.
>
> My latest effort, now that AA NiCds no longer exist, was more complex.
> This time I fitted a pair of Perspex tubes as battery holders that each
> take an AAA Sanyo Eneloop. These give longer runtimes between charges and
> are still recharged by the original mains charger.

Were the replacement cells NiMH chemistry?  For some
applications, (Wahl series 4000 shavers, for example) a NiMH cell
of the same physical size can replace the original NiCD cell, (as
mentioned) the original charger still (at least the old
high-current type) works, and the NiMH provides about 3X the
shaves per charge compared to the original NiCD.

HTH

--
Robert Riches
spamtrap42@jacob21819.net
(Yes, that is one of my email addresses.)

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