acpiconf shows 100%, but laptop switches off

[Anton Shterenlikht]

On Sun, May 01, 2011 at 03:39:24PM +1000, Ian Smith wrote:
> 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

Many thanks
Anton


-- 
Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
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