Stylus battery reported as having 1% charge even though fully charged

[Sebastian Arnhold <sebastian.arnhold387@xxxxxxxxx>]

Dear developers,

when using GNOME 42.3 on Wayland on my ASUS ExpertBook B5 Flip, it 
reports my stylus battery to be stuck at 1% all the time, independent of 
its actual charging status. This is also independent from the stylus I 
use, as I've tried with two different ones.

The battery device registers as ELAN9008:00 04F3:2E12 in GNOME energy 
settings.

The GNOME developers helped me track the bug down to upower, as upower 
itself shows the charging status to be stuck at 1%. The upower 
developers then sent me here.

My kernel version is 5.18 on an x86_64 architecture on Fedora 36. My 
upower version is 0.99.19.

Observed behaviour: Kernel reports 1% after pen is switched on and 
touches the touchscreen for the first time. upower reports this to GNOME 
which then throws a "Battery low"-warning message.
Expected behaviour: Kernel reporting the correct charging percentage 
from the pen to upower, or 0% if charging status cannot be determined. 
The latter would be a workaround since 0% seems to be ignored by GNOME.

Can you help me to resolve this bug?

Thanks in advance!
Sebastian


Attachment 1 - Output of upower -d BEFORE pen switched on and touched 
screen:

Device: 
/org/freedesktop/UPower/devices/battery_hid_0018o04F3o2E12x0001_battery
  native-path:          hid-0018:04F3:2E12.0001-battery
  model:                ELAN9008:00 04F3:2E12
  power supply:         no
  updated:              Do 01 Jan 1970 01:00:00 CET (1658223097 seconds 
ago)
  has history:          yes
  has statistics:       yes
  keyboard
    present:             yes
    rechargeable:        yes
    state:               unknown
    warning-level:       none
    percentage:          0%
    icon-name:          'battery-missing-symbolic'


Attachment 2: Output of upower -d AFTER pen switched on and touched 
screen (resulting in "battery low" message in GNOME):

Device: 
/org/freedesktop/UPower/devices/battery_hid_0018o04F3o2E12x0001_battery
  native-path:          hid-0018:04F3:2E12.0001-battery
  model:                ELAN9008:00 04F3:2E12
  power supply:         no
  updated:              Di 19 Jul 2022 11:33:19 CEST (5 seconds ago)
  has history:          yes
  has statistics:       yes
  keyboard
    present:             yes
    rechargeable:        yes
    state:               discharging
    warning-level:       critical
    percentage:          1%
    icon-name:          'battery-caution-symbolic'