[ltp] Battery recalibration (was: T470 multi-battery, discharging order)

[Axel Braun]

Hi,

Am Mittwoch, 30. März 2022, 16:22:43 CEST schrieb Kevin Locke:
> > 
> > +++ Recommendations
> > * Install acpi_call kernel module for ThinkPad battery recalibration
> > 
> > I was not aware that Battery recalibration und Linux works, and I dont
> > have a acpi_call kernel module (running kernel 5.16.15)
> > 
> > Does anyone know how to get this working?
> 
> I believe battery recalibration simply discharges the battery then
> recharges it.[1]  To do so without disconnecting AC power, tlp can use
> Linux-native force-discharge added in b55d416d48f5[2] (5.17-rc1),
> acpi_call[3][4] (via tpacpi-bat[5], if installed), or tp_smapi[6] for
> older models, which it tries in that order.

I have enabled acpi_call and tp_smapi for openSUSE Tumbleweed (and Leap as 
well, just FYI - you can install them with opi from home:DocB:ThinkPad) and 
tested on a T520 and a X1 Extreme 

> On a T470 with kernel 5.16.15 you'd likely want to install tpacpi-bat
> with the acpi_call kernel module, as described in Diego's reply, then
> run `tpacpi-bat -g FD 1` to force-discharge battery 1.  However, if
> you can upgrade to Linux 5.17, no additional software or modules are
> required and the process should be as simple as:
> 
> if charge thresholds are being used, clear them during recalibration:
>     echo 0 >/sys/class/power_supply/BAT0/charge_control_start_threshold
>     echo 100 >/sys/class/power_supply/BAT0/charge_control_end_threshold
> echo force-discharge >/sys/class/power_supply/BAT0/charge_behaviour
> # Wait until battery is fully discharged
> # Wait until battery is fully recharged
> # Restore change thresholds as desired

While this worked well for the T520, the result on the X1E was in so far 
disappointing as at the end of the discharge process the Laptop just switched 
off, despite power was connected. Obviously the charge_control_start_threshold 
should be above 0.
 
> Of course, if you have physical access to the machine, you could
> recalibrate without software by simply disconnecting AC power,
> discharging the battery, then reconnecting.

Sure, tried that as well. Nice to see that one can gain some percent of 
capacity back. Although I was of the impression that driving down a LiIon 
battery to Zero is not something that LiIon likes....

Cheers
Axel