Re: [NTLK] battery reconditioning

From: Marco Mailand (Newton2k1_at_mac.com)
Date: Tue May 07 2002 - 10:15:36 EDT


> >> NiCD cells generally don't recondition successfully after 5 years,
whether
> >> you use them or not.
> Apparently, you can, but even if they're new, they've been sitting on a
> shelf and I read a message no later than yesterday (hmmm, maybe it was on
> the G-Books list) about the chemical process that occurs even if the
battery
> is not used, which will reduce its life expectancy over the course of a
> couple of years. I don't know, I'm merely reporting what I've read...
A few minutes ago I read several data sheets of a different types of NiMH
cell with a much smaller capacity as well as AA cell as are used in the
Newton. There are different values mentioned depending on the manufacturer
but many are comparable. A small hearing aid accu cell with a nominal 350mAh
was stated to have typically 400mAh and a guaranteed lifetime of 6 years at
room temperature (20 deg C in EU) and only 3 years at 45 deg C in so called
buffer operation, meaning low current draw and longtime and continous
recharging. Also mentioned was that the self-discharging increases
considerably at higher temperatures.
The conclusion is that a NiMH accu pack which was laying 5 years on a shelf
might be like new or completely destroyed, depending which temperature it
has seen and how deep it was thus discharged and for how long. Storing the
NiMH accus in a cellar or even fridge and recharging them on a half-year
base is certainly the best and will help to expand the lifetime to a
maximum.

--
With best regards / Viele Gruesse

Marco Mailand http://slsbd.psi.ch/timing http://slsbd.psi.ch/~mmailand https://www.paypal.com/refer/pal=YYD3VUXUVD2YG

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