"Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
news:higt7s$4vr$1@news.eternal-september.org...
> Lithium batteries have a finite number of charge-discharge cycles; the
> number varies but is typically in the mid-hundreds.
>
> You do not have to worry about "memory effect" that was an issue with NiCD
> batteries. In fact, practices that were used with NiCads are actually
> harmful to Lithium batteries.
>
Agreed. I still cringe when salesmen tell me to charge the battery for at
least 24 hours the first time you charge it. Fortunately the charge circuit
won't actually let you.
> If the laptop is plugged in all the time, remove the battery. Being
> continuously installed in a laptop that is always plugged in will destroy
> the battery over a period of 6 to 24 months. The culprit is a combination
> of exposure to high temperatures and over charging, but over a decade of
> user experience makes it clear that removing the battery is the best thing
> to do on the vast majority of laptop models. [Note, the battery does need
> to be "exercised" every 60 or 90 days.]
>
Information is surprisingly scant here (especially from the battery
manufacturers). My personal belief is that it is purely the heat aspect
that destroys the batteries. If the charge circuit is correctly designed it
should not be possible to overcharge the battery. Li-ion batteries are
destroyed by even moderate amounts of heat. This may be because the boiling
point of the electrolyte is just 34 °C and raising the temperature to
anywhere near this level will almost certainly stress the cell structure.
The available information in the aerospace industry is that the batteries
should be fully cycled every 45 days. However, the lack of information
means that I can no more *prove* that figure is correct than Barry's is
wrong. Having said that, I have several examples of batteries that are now
over 15 years old and still have almost their full capacity that have not
been regularly so charged and discharged (and I doubt that one has ever been
charged and discharged more than a dozen times).
Since the life of a laptop is rarely that long (or anywhere close), the
prevailing wisdom is to remove the battery when on AC and regularly
charge/discharge it.
> I've never heard of your freezing trick. I would not recommend that for a
> lithium battery, indeed actually freezing the battery (below 32 degrees F)
> will possibly damage it. Some laptops have battery calibration software,
> either in Windows, the BIOS or on a utility program, I'd say that most
> don't. Some laptops will "recalibrate" the battery if you do a full
> charge-discharge cycle, also, but only some laptops, not all.
>
The one piece of information that is known is that batteries should never be
placed or stored in a freezer. One discredited source did claim that
batteries should be stored in fridge when not in use (and repeated in many
other places). Quite why batteries should not be stored in a freezer is not
clear as the electrolyte doesn't freeze until cooled to -116 °C.
>
> Father Justin wrote:
>> Normally I rely on the power of the Holy Spirit. However when the Holy
>> Spirit is on vacation I rely on a Lithium Ion battery to power my laptop.
>> Do they eventually stop charging? Back in the days of NiCd and NiMH,
>> batteries would be able to charge and discharge X number of times.
>> Is this still true for LiION? One time I received a usenet tip to reset
>> a setting in the laptop's bios, and freeze the battery that wouldn't hold
>> a charge. After the battery was frozen for 24 hours, it was brought to
>> room temperature, charged and seemed to work fine - including holding a
>> charge again. Does that old school trick still work?
>>