Set charging thresholds on Linux laptops to extend battery lifespans
In the course of setting up my new(ish) Linux laptop home server, I started poking around for information on charging thresholds for laptop batteries.
Current wisdom holds that for a laptop connected to AC power 100% of the time, its a good idea to set the battery charge "ceiling" to less than 100% in order to extend the health and lifespan of the battery.
Information about my laptop's battery are found in various files inside /sys/class/power_supply/BAT0, which can be read with a simple cat $FILENAME.
Kernel docs for sys-class-power indicate two files of interest:
charge_control_start_thresholdrepresents a battery percentage level, below which charging will begincharge_control_end_thresholdrepresents a battery percentage level, above which charging will stop
Note: Not mentioned are two other files - charge_start_threshold and charge_stop_threshold - which I believe are left over from the legacy API (and I'm guessing are preserved for backward compatibility). Regardless, changing the settings in charge_control_* are reflected in charge_* and vice-versa.
For my Thinkpad X230 which is connected full-time to AC power, I set a range between 40-50 percent:
echo '40' | sudo tee /sys/class/power_supply/BAT0/charge_control_start_threshold
echo '50' | sudo tee /sys/class/power_supply/BAT0/charge_control_end_threshold
For my Thinkpad T480s which alternates between AC and battery power, I set a range between 70-80 percent:
echo '70' | sudo tee /sys/class/power_supply/BAT0/charge_control_start_threshold
echo '80' | sudo tee /sys/class/power_supply/BAT0/charge_control_end_threshold
I confirmed that these modifications survived a reboot, so there wasn't a need to setup a script to run at boot.
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