[Debian-eeepc-devel] 701 battery capacity has wrong dimension?

[Patrick Strasser]

Axel Beckert wrote am 2008-10-30 13:09:
> Hi,
> 
> On Thu, Oct 30, 2008 at 12:49:42PM +0100, Patrick Strasser wrote:
>> The ACPI 3.0b specs[1] say in chapter 10.2.2.3 that providing 
>> percentages in the ACPI Battery Status (_BST) is OK as long as the 
>> battery is "primary", that is, not rechargeable. The EeePC has 
>> rechargeable batteries, so this can not apply. Both Battery Status and 
>> Battery Information (_BIF) should report capacities in mAh or mWh.
> 
> Then the fact that it does report in percentage is a bug in the EeePC
> firmware or battery firmware. (I suspect the last.) But it is
> definitely not a bug of the firmware that some software can't cope
> with it.

Agreed.

>> I'm running a EeePC 4G (=701?)
>> with Bios 1101 and Debian stock kernel 2.6.26, and it's not working
>> for me.
> 
> What exactly is "not working" for you? 

Yields values like in the first posting, still percentages instead of 
mAh. The values from the first are with BIOS v1101 and Linux 2.26.6-1

> 1/0/0 root at nemo:pts/0 13:00:42 [~] # acpi -V
>      Battery 0: Full, 100%, rate information unavailable, design capacity 5200 mAh
>   AC Adapter 0: on-line
>      Thermal 0: ok, 30.0 degrees C
>      Cooling 0: Processor 0 of 7

Seems like acpi uses the right algorithm. See ACPI specs 3.0b, chapter 
3.9.3:

At the most basic level, the OS calculates Remaining Battery Percentage 
[%] using the following formula:
Remaining Battery Percentage[%] = Battery Remaining Capacity [mAh/mWh] / 
Last Full Charged Capacity [mAh/mWh] * 100

If both Battery Remaining Capacity and Last Full Charged Capacity have 
the same dimension, Last Full Charged Capacity will have a sane value. 
With Last Full Charged Capacity equal 100%, this will alway yield the 
value of Battery Remaining Capacity.

> I know that there are others (at least one or two of the dozens gnome
> panel apps) which don't display the battery state correctly.

I'll file a bug for those I use.

> Just not all applications can cope with batteries reporting
> in percentage although it is allowed and officially in the standard.

I have not found a passage allowing percentages for rechargable batteries.

Patrick
-- 
Engineers motto: cheap, good, fast: choose any two
Patrick Strasser <patrick dot strasser at student dot tugraz dot at>
Student of Telematik, Techn. University Graz, Austria