[Tfug] Li-on battery

[Jeremy D Rogers]

[snip]
>
> But the estimated remaining available time didn't seem to accurately
> reflect what I estimated to be the remaining time, so I decided to
> deep-cycle it once to see if it would correct the problem, after doing
> some searching around the 'net, and reading some forums.  I ran the
> machine until it died, doing memtest86.  Since then, about 3 days ago,
> it won't charge - the charge light always blinks amber - so that's
> likely the 1st and last time I'll ever deliberately deep-cycle a Lion
> battery.  (How I loath Li-on batteries!  How I wish I could choose a
> NiMH battery - they just seem to be a lot more forgiving, and not to
> age a lot more gracefully!)

[snip]

In my experience, deep cycle = badness. I'm no expert, but I think a lot of
the deep-cycle advice out there is carry over from other chemistries like
NiMH that suffered 'memory effect' that would get reset by a deep cycle.
Unfortunately, this doesn't really work on Li-ion. The only thing like that
for Li-ion is resetting the internal calibration that tries to know what %
you have left. If you run it down, that gets reset and is more accurate, but
this does nothing to the actual battery, so I just avoid that. From what I
read, Li-ion dislikes deep cycles, and if you go too low using something
that is not acpi aware like memtest, it might really take a blow to the
chemistry. The other thing is that Li-ion has a finite number of cycle
counts (usually in the neighborhood of 300-400), and these cycles tick away
even if the cycle is only from 100%-90% and back. That's why leaving the
battery in while on AC often wears a battery down even if you don't run on
battery all the time. Some thinkpads win here, because (at least with my
t60) you can set the charge thresholds so it won't start charging until it
gets below 40% and stops charging at 70%. If I run on AC most of the time, I
only use up only about one cycle every 2-3 weeks.
http://www.thinkwiki.org/wiki/Tp_smapi

Which reminds me.. you can tell a lot about your battery on a thinkpad (even
without tp_smapi installed) using "cat /proc/acpi/battery/BAT0/info" and
also about the status using "cat /proc/acpi/battery/BAT0/state". That might
help you determine what is going on.

Sorry, I don't know about freezing and some of the other 'recovery'
techniques out there, but I do know I lost one battery dead by draining it
all the way (possibly even more than you did with memtest).

Good luck,
JDR
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