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The Natural Philosopher

wrote:
Dave Plowman (News) wrote:
In article ,
Chris Hodges wrote:
LiIons on laptops which are normally plugged in often suffer - my Compaq
now has about 20 minutes life from a nominal 2 hour battery. Toshibas
don't seem so bad though. This isn't technically memory effect, but it
might as well be to most users.
I'm not overly impressed with the life of LiIon under some conditions,
although this may be down to the charger. They have their uses where the
small size/high capacity is vital, but don't like deep discharge as a
regular thing.

In my (limited) experience, the key words in the PP's post are
"normally plugged in". I know someone who always used their laptop on
mains power. When they came to use it on battery after about a year,
it was next to useless. The Lithium polymer battery in my mobile phone
seems to be going quite well after 3 years plus, and it's only ever on
charge when it needs to be.

Probably best to exercise batteries as they were intended to be used.
Attempts to extend their life by leaving them on permanent charge seem
to be counter productive.

Again, I think its down to the age, and quality of the cells and the
charge regulation circuitry.

Lithium cell actually are best stored at half charge, but they vary
markedly in terms of self discharge, internal resistance and peak power
delivery.

The good news is that its an area of rapid devlopment.