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Date:      Wed, 26 Sep 2012 19:06:09 +1000 (EST)
From:      Ian Smith <smithi@nimnet.asn.au>
To:        Michael Schuh <michael.schuh@gmail.com>
Cc:        FreeBSD Stable <freebsd-stable@freebsd.org>, Brandon Allbery <allbery.b@gmail.com>
Subject:   Re: [SOLVED] Re: battery state - hw.acpi.battery.life goes only down
Message-ID:  <20120926181536.F43208@sola.nimnet.asn.au>
In-Reply-To: <CADwRVEZJFSVFJkwydpJchuvvQoVJKj-=YhRmOPPz=_Kea6iL4A@mail.gmail.com>
References:  <CADwRVEYhb4BqkuOu2rgOLpHBbmm4UaAhsLjLLurMuRs4giL-0A@mail.gmail.com> <CAKFCL4UHVOcaq-9wU2ePbEU=K4gtck%2B8Ro2AEf6nT8D8QJc%2BNQ@mail.gmail.com> <CADwRVEZoa5EH5msXAv069KCG1TQ%2B=S95z5PXaq%2B9V2zuma2j4g@mail.gmail.com> <CAKFCL4WiBtW4aRp-pn7g52F%2BxfaAjFzNvD9Pnthe6bxb51SY9Q@mail.gmail.com> <CADwRVEZJFSVFJkwydpJchuvvQoVJKj-=YhRmOPPz=_Kea6iL4A@mail.gmail.com>

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On Wed, 26 Sep 2012 02:24:14 +0200, Michael Schuh wrote:
 > sorry for the buzz...
 > 
 > 2012/9/26 Brandon Allbery <allbery.b@gmail.com>
 > 
 > > On Tue, Sep 25, 2012 at 8:10 PM, Michael Schuh <michael.schuh@gmail.com>wrote:
 > >
 > >> hmm, may be.
 > >> i didn't thinked about that lithium charging feature.
 > >> you may right with that.
 > >>
 > >
 > >
 > Yes you are right with that point.
 > 
 > > I have watched batteries cycle like that on OS X, Linux, and FreeBSD, and
 > > some versions of Windows; possibly more recent versions try to hide it.
 > >  It's also possible the ACPI BIOS normally hides it but needs some
 > > recalibration step (on Macs, for example, you need to fully charge then
 > > fully discharge then fully charge again to recalibrate it; I think that's
 > > common).
 > >
 > 
 > Yesi agree, this is the most logic explanation in our fantastic world.

Just to confirm what Brandon said, I've watched this behaviour for some 
years on a couple of IBM Thinkpad T23s .. while on AC power the battery 
slowly self-discharges down to about 95% before a charge cycle begins to 
boost it back to 100%.  Mine is now sitting at 98% and will take days to 
get down to 95% and start charging again, if I don't run it on battery.

 > >> but one point, this behaviour is new.
 > >> i made some tests to check if my conkyrc is right and there i haven't
 > >> wait that the battery is gone under 90%
 > >> for checking this. after i could confirm that the conkyrc is
 > >> syntactically correct, the battery reached 100% again.
 > >>
 > >
 > > That sounds like it is normal cycling then.
 > >
 > 
 > No idea why that box didn't showed that behaviour earlier.
 > i am fully sure that i made the same tests before and the charger did jump
 > in much time earlier.
 > may be, i was a bit impatient for now.

May depend on your workload; I don't know conkyrc but use gkrellm to 
show battery state, before that I more often ran acpiconf -i0 to check 
state, which also shows such as Last Full Capacity vs Design Capacity, 
for some indication of how well your battery is holding up over time.

Lithium-Ion batteries really should be cycled semi-regularly anyway; as 
Brandon also mentioned, the occasional complete discharge down to (or 
beyond!) exhaustion (safely done at the BIOS setup screen) followed by a 
full recharge is often recommended to fully recalibrate the battery's 
internal Coulomb Counter, ie the battery's own idea of its percentage 
capacity, reported to ACPI typically via the EC (embedded controller).

This is likely more on-topic (and welcome) on freebsd-mobile@ though, 
unless of course some regression in system software is suspected ..

cheers, Ian



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