[arch-general] POWER_SUPPLY_CHARGE_FULL(_DESIGN) semantics

[Matthew J.P Walker]

On 18/08/14 05:00 AM, Chrisitan Burkard wrote:
> First of all: sorry for the last mail. I copy pasted the wrong email.
> Needed to resend it as I sent it with the wrong mail account to the list.
>
> @Curtis: Thanks. The hint to the manpage and the "last_full_capacity"
> property did their job.
>
>
> On 16.08.2014 22:11, Jakub Klinkovský wrote:
>> On 15.08.14 at 12:27, Chrisitan Burkard wrote:
>>> ... Another issue I have is that the POWER_SUPPLY_STATUS shows
>>> 'Unknown' on AC but 'Discharging' on Battery. Do you have any
>>> idea why? My guess is that i3 uses this property to show the
>>> battery/AC state in i3status and because of the 'Unkown' value I
>>> don't get updates on the state there.
>> The values for POWER_SUPPLY_STATUS on my laptop are: - when running
>> on battery, it is always 'Discharging' - when running on AC: -
>> 'Full' for 100% - 'Unknown' for 95%-99% - 'Charging' for <95% Note
>> that my battery is not getting charged if the level is between 95%
>> and 99% when I plug in AC.
>>
>> -- jlk
>>
> You are right. I can confirm this behaviour but with different
> thresholds. Because of the age of the battery a FULL is never reached.
> The battery just has to get really low in order to come to its
> charging status.
>
> I just remembered a thing and would be interested what you think.
>
> Today only arch runs on my notebook but some time ago I was using
> dualboot windows, too. At that time the lenovo energy manager realized
> I mainly use the notebook on AC and switched the maximum battery
> capacity to around 70% (cannot recall the ecact value). I did not
> switch that back to 100% before wiping windows.
>
> -Is it possible that's (partially) the reason for the low CHARGE_FULL
> value compared to the CHARGE_FULL_DESIGN value? Or to put it
> different: Is it possible that the lenovos' windows energy manager
> driver set CHARGE_FULL to a lower value and linux drivers cannot
> overwrite this value?
> -Is there a possibility to change propertys displayed in
> /sys/class/power_supply/BAT0 without reinstalling windows and fixing
> it there?
>
> If you have links or knowledge for me, I would be really glad as I
> didn't find anything on my own.
>
> Best regards,
>
> Christian
>
>

I also get the Unknown value, but I've set the thresholds of my T530 to 
something lower, using TLP [ https://wiki.archlinux.org/index.php/TLP ].
I don't think the value of CHARGE_FULL related because the charging 
thresholds seem to be completely independent, and I've been watching 
mine go down slowly ever since I bough my laptop. Also, reduced capacity 
over time is expected for any battery.

Additionally, TLP lets you change the charging thresholds arbitrarily at 
runtime, and that value doesn't follow.

~Matthew