To see the health of your ThinkPad battery, and to protect its health in the long term, KDE and GNOME desktop environments allow you to graphically control charging start/stop values. But if you’re on a window manager like me, or on a desktop environment which doesn’t allow graphically changing these values, Linux offers built-in control commands to achieve those optimal charging start/end thresholds.

Battery Monitoring

To see Battery stats like, charge cycles, current voltage, charge end and start thresholds:

upower -i $(upower -e | grep BAT)

This command summarizes all the battery related stats in a single place.

The above command will summarize all the related info. But sometimes, it doesn’t show the most recent info related to charge_control_start_threshold and charge_control_end_threshold. These can be used to control how much ThinkPad battery should charge, and when it should restart charging when battery percentage falls below the certain threshold.

To see when battery should stop charging:

cat /sys/class/power_supply/BAT0/charge_control_end_threshold

If it shows 100, it means your battery will stop taking further current after this charge level is achieved. It’s a default value, which doesn’t protect your battery from high voltage when most of the time your ThinkPad remains plugged in.

To see when battery should restart charging:

cat /sys/class/power_supply/BAT0/charge_control_start_threshold

If it shows 0, it typically means the charge start threshold feature is disabled.

Charge Control

If you use your ThinkPad plugged-in most of the time, you should lower those charge end/start values to protect your battery being ruined from high voltages in the long run.

The suitable percentage to charge your battery is 80%, which provides you with enough juice in case of power outage or outdoor use, but also the voltage remains significantly lower to ruin your battery over the long run of time.

Let’s create a systemd service to control battery charging thresholds:

sudo nvim /etc/systemd/system/thinkpad_battery_control.service

Add the following lines to thinkpad_battery_control.service file:

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[Unit]
Description=Set battery charge threshold

[Service]
Type=oneshot
ExecStart=/bin/sh -c 'echo 80 > /sys/class/power_supply/BAT0/charge_control_end_threshold && echo 70 > /sys/class/power_supply/BAT0/charge_control_start_threshold'

[Install]
WantedBy=multi-user.target

To enable and start this service:

sudo systemctl enable --now thinkpad_battery_control.service

Now your thinkpad_battery_control.service is enabled, with charge_control_end_threshold set at 80 and charge_control_start_threshold set at 70. It means your battery will stop charging at 80% and its charge level falls below 70%, it will restart charging the battery. This service will run only on boot-up once, and then will remain inactive until next reboot.

If you check your battery stats with upower command, it will show the old values for charging start/end thresholds, to make sure the new values are set, use the cat command with full path to the sysfs as shown above in the Battery Monitoring section.

Fully Charge Your Battery for Emergencies

If for an emergency, you need your laptop to be fully juiced up, you can temporarily bypass the charge end threshold:

echo 100 | sudo tee /sys/class/power_supply/BAT0/charge_control_end_threshold

It will temporarily change the charge_control_end_threshold value to 100 percent.

Then to immediately start charging instead of waiting for it to fall below 75 percent (It will never fall below 75% as long as you’re plugged-in).

echo 0 | sudo tee /sys/class/power_supply/BAT0/charge_control_start_threshold

When an emergency situation is over, you can simply run the think_battery_control.service again:

sudo systemctl restart thinkpad_battery_control.service

OR just reboot, and on login the systemd service will run again on its own, and set the appropriate values accordingly.