Re: Low battery -> power down + clock set back to 1904-01-01
> > I've had the same happen on occasion, and won't of course blame pmud for
> > it :-) Seriously, what seems to happen is the battery is lying about how
> > much charge is left, and runs out during sleep.
>
> This may be the cause, as I got the message after less than 2 hours,
> though the battery usually lasts about 2.5 to 3 hours. Wouldn't it be
> possible to increase this charge limit?
1) battery capacity tends to decrease over time. To see how much capacity
is left, run without pmud (or similar service), remount everything ro and
wait for it to power off.
2) There are ways of resetting the PMU itself (see the Apple technotes)
manually, this may also force a recalibration of the battery capacity
reading.
3) batteries suffer from many (incomplete) discharge/charge cycles
(result: 1)). Occasionally draining the battery to the limit will bring
the capacity back up a bit. I find the PMU (or battery controller) tends
to overshoot, though: the capacity jumps a lot, and next time the battery
may die even before the critical limit is reached and pmud kicks in.
The bottom line: the battery critically low threshold is already set
pretty low (6 minutes time left, or about 3%). If your reported capacity
isn't accurate, that's sometimes too low already. Using a higher threshold
will result in more partial battery drains, shortening battery life as I
understand it.
Michael
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