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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