I think the perseverance of NiCd cells in certain applications is
readily understandable in terms of the rate of self discharge. NiCd
cells (until recently) have had much lower self discharge rates than
NiMH cells. NiCD persists for a walkie-talkie or portable drill since
you haven't been able to count on an NiMH powered device to have any
charge left if you haven't used it in 3-6 months.
But that all started to change recently. You may recall the
announcement posted here the other day by Tim Hughes concerning three
new types of NiMH batteries from Sanyo Eneloop. The newest cells
promise 75% power after 3 years sitting on the shelf. That's probably
better than NiCd, maybe even much better.
Also, I note that drill drivers are starting to show up that have
lithium-ion batteries. The last I noticed they were expensive enough
that I wasn't willing to replace my own NiCD powered drill but the next
power tool purchase could be something different.
Chuck Norcutt
On 12/16/2010 12:54 PM, Jan Steinman wrote:
>> From: Moose<olymoose@xxxxxxxxx>
>>
>> On 12/15/2010 11:00 AM, Jan Steinman wrote:
>>> Although it's open on my desktop, I've not looked at the
>>> BatteryUniversity.com site yet, but my understanding of classic
>>> NiCd is that repeated incomplete discharging to about the same
>>> level causes a crystalline precipitate to form at a certain
>>> location related to the discharge depth, therefore causing the
>>> mis-named "memory effect." (It should really be called the
>>> "forget effect." :-)
>>>
>>> Memory effect is not a problem when the cell is repeatedly
>>> discharged to different levels. Classic case: a cop runs a
>>> walkie-talkie for eight hours a day and drops it in the charger
>>> overnight -- bad news for NiCd cell life. But memory effect is
>>> not likely if you're using a flash or motor drive for various
>>> periods of time and then topping off on a charger.
>>
>> "Among rechargeable batteries, nickel-cadmium remains a popular
>> choice for two-way radios,"
>>
>> Since what you say here doesn't agree with what's on that site,
>> perhaps you might read it and resolve the differences.
>
> Yea, I'll have to check that out, because it doesn't go along with my
> experience as a ham-radio operator, my work as a repair tech in a
> two-way communications shop, nor my stint as an RF engineer.
>
> I don't know of any hams who still use NiCd cells in their two-way
> radios, but note that the OEM battery packs you get from Icom for
> older radios still have them. Perhaps its just because NiCd's are
> still cheaper. (New hand-held ham gear is almost all lithium
> powered.)
>
> NiCds do have lower internal resistance than NiMH, which might make
> them preferable in high-current applications -- like photo strobes.
> But that wouldn't explain hand-held radios, which have relatively
> moderate current needs. And if they're so good for hand-helds, why
> don't you ever see them in cell phones? Puzzle.
>
> But such fun has to wait. I have to go pick up a buck to romance our
> four Nubian goats today.
>
> Obligatory camera content: I need to take some photos of our
> zero-mile raw goat milk ice cream... if there's any left...
>
> ---------------- Religions are the great fairy tales of conscience.
> -- George Santayana :::: Jan Steinman, EcoReality Co-op ::::
>
--
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