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Re: [OM] Ni-Cd Pack features

Subject: Re: [OM] Ni-Cd Pack features
From: Garth Wood <garth@xxxxxxxxxxxxxxx>
Date: Sat, 19 Dec 1998 17:14:22 -0700
At 04:57 PM 12/19/98 +0000, Giles wrote:
>
>My experience supports the negative aspects of Ni-Mh batteries.  I have had 
>experience with two laptop computers with Ni-Mh batteries and the batteries 
>do not even last 2 years, even when the computers are run off mains 900f 
>the time.  Given the incredible cost of these batteries this is not good.  
>An HP engineer told me he recommended removing the battery pack at regular 
>intervals and shorting it with an appropriate resistor - forget the value - 
>to ensure a complete discharge then fully charging the pack and discharging 
>it again - perhaps doing this a couple of times!  This little proceedure 
>was certainly not in the manual!

Hmmmm.  I've had NiMH batteries for my analogue cellular for three years now -- 
same set.  Still working perfectly.  However, I *always* discharge the buggers 
completely -- they have less memory effect than NiCad, but not tons less.

>
>To my mind Ni-Mh have a far worse memory effect than NiCad and then there 
>is the horrendous self-discharge.
>
>The best technology seems to be rechargeable Lithium Ion batteries - 
>negligable self discharge even after a year, high current delivery, NO 
>memory effect at all, higher energy density than Ni-Mh or NiCad and I 
>believe William indicated they function at low temperatures - or was that 
>only the non rechargeable Lithiums?

Non-rechargeable lithiums do put out a fair amount of power at low temps.  
*Rechargeable*, on the other hand, cease functioning below zero degrees Celsius 
(although they recover once you warm 'em up).  My new digital cell uses 
lithium-ions, and it's packed 'er in a couple of times when I got it too cold.  
(Easy to do in Edmonton during the winter -- it's about minus 22 Celsius right 
now, with a wicked wind chill...)

Garth

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