asus-charge-control

Set your recent ASUS notebook's maximum charge level on Linux.

Recent ASUS notebooks come with a Windows application to set the maximum battery charge level, in order to reduce stress on the battery and prolong its lifespan. On Linux kernels >= version 5.4, the asus_nb_wmi kernel module exposes a sysfs object to manage this setting.

Getting or setting the charge end threshold is rather verbose:

$ cat /sys/class/power_supply/BAT0/charge_control_end_threshold
100

$ echo 80 | sudo tee /sys/class/power_supply/BAT0/charge_control_end_threshold
80

asus-charge-control offers a quicker way.

Installation

asus-charge-control should work with any device running a recent kernel (>= 5.4) with the asus_nb_wmi module loaded. Use lsmod | grep asus_nb_wmi to check; if you see a line like asus_nb_wmi 32768 0, then the module is running.

It has been tested with the following ASUS notebooks:

• ASUS VivoBook 15 X512DA

A Python version >= 3.7 is necessary to run this script. Most Linux distributions come with the right version. To verify that Python is installed on Debian/Ubuntu-based distributions, use apt:

sudo apt install python3

As root privileges are necessary to set the charge end threshold, asus-charge-control should be installed as a global package:

sudo pip install --system asus-charge-control

DANGER: Normally, Python packages should not be installed with sudo, as they may execute arbitrary code. I encourage you to read setup.py before installation.

Usage

You can get the current charge end threshold by calling asuscharge from the command line:

$ asuscharge
Current charge end threshold: 100%

Setting the charge end threshold requires root privileges:

$ sudo asuscharge 80
Successfully set charge end threshold to 80%

Note: The charge end threshold resets back to 100% when the system is rebooted.

You can use a cron job to set the charge end threshold automatically on boot. To do so, find the path of the asuscharge command like so:

$ which asuscharge
/usr/local/bin/asuscharge

Modify the root user's crontab file:

sudo crontab -e

Add the following line to the end of the file:

@reboot /usr/local/bin/asuscharge MAX

Replace MAX with the charge end threshold you would like, then save and close the file.

Development

You can use the asuscharge package in your own applications. The package offers a ChargeThresholdController object, with a settable end_threshold property. It also offers three methods to check if the user's platform supports the charge end threshold feature: supported_platform(), supported_kernel(), and module_loaded().

Version history

• 1.0.2 (2020-12-28)

  • (fix) MAX wasn't properly range checked for a value between 60-100.
  • (feature) added --force to set a threshold value beneath 60.

• 1.0.1 (2020-12-06)

  • (fix) supported_kernel() returned an incorrect value for Linux kernel versions > 5.9.

• 1.0.0 (2020-12-04)

  • Initial release.