acpiconf shows 100%, but laptop switches off

[Ian Smith]

On Sat, 30 Apr 2011, Anton Shterenlikht wrote:
 > On Thu, Apr 28, 2011 at 01:16:41AM +0200, Bartosz Fabianowski wrote:
 > > >Design capacity:        1 mAh
 > > >Last full capacity:     1 mAh
 > > 
 > > Those are obviously bogus values. Your battery quite likely is actually 
 > > dead and provides 20 minutes of run-time only. But since its capacity is 
 > > not being reported properly via ACPI for some reason, FreeBSD has no way 
 > > of knowing that.
 > > 
 > > - Bartosz
 > 
 > Thanks. I wonder whether ACPI is working correctly
 > at all. What other things can I check?

If there were problems with ACPI, you would most likely see some ACPI 
messages in dmesg regarding battery status, or problems showing the EC 
(embedded controller) having trouble communicating with the battery.

This seems more likely a battery failure than a problem with ACPI, both 
from misreporting its capacity and the actual behaviour of the battery 
under load.  The best course would be to replace the battery, preferably 
with a genuine or at least fully compatible one, and see how that goes.

The little chips on the battery that record charge in and out, voltage 
and estimated capacity can get well out of synch with the real situation 
especially when there isn't regular use of the laptop on battery, which 
is why many manufacturers recommend 'conditioning' cycles - where the 
battery is run down to total exhaustion without shutting down (best done 
from eg the BIOS setup screen, where no filesystems are at risk), then 
fully charging the battery - sometimes repeating that twice or thrice.

'Conditioning' can a) raise 'Last full capacity' to a greater fraction 
of the original 'Design capacity' (likely in the range 3,000 - 5,000mAh) 
and b) improve the battery's estimate of capacity and/or time remaining.  

That said, I've not seen a battery misreport 'Design capacity' before, 
nor show silly values (also 1mAh) for 'warn' and 'low' capacities which 
are usually about 2-3% and 1% of full capacity, respectively.  But then, 
what's 1%, or even 100%, of (the misreported) 1mAh remaining capacity?

Only one cell needs to die, either short or high internal resistance, to 
render a battery pack useless, unless you're prepared to open the pack 
to replace single cells.  At 4 years old, I wouldn't bother trying.

It should be useful to compare acpiconf -i0 data with your new battery.

cheers, Ian