simple-battery-log

Scripts to log and plot battery energy level on Linux systems.

Bash script fetches battery status at /sys/class/power_supply and writes it to a file. Python script parses the created file and creates a plot like this:

Setup

I have not tested this on any other machine than my Thinkpad laptop. Likely there will be differences in how the battery information is stored on your machine, so you will have to adjust for that. Make sure /sys/class/power_supply/BAT0 exists and energy_now and status are in the same format as the example below.

• Clone the repository: git clone https://github.com/stgloorious/simple-battery-log && cd simple-battery-log
• Create a cronjob so log-battery.sh is executed each minute: crontab -e, then enter * * * * * sh /path/to/log-battery.sh
• This will write to $HOME/BAT0.log each minute. Check if this is the case, make sure you can execute the script manually if not.
• After sufficient time, you can move BAT0.log to the same directory as plot.py. Execute the script ./plot.py and find a plot for every discharge phase recorded in png format in the same directory.

Dependencies

You will need:

• Python 3 with csv, matplotlib and numpy
• Basic linux utilities (bash, date, echo, cron etc.)

Remarks

On my system, the output file BAT0.log looks like this:

1636047661,Discharging,45090000,34660000
1636047721,Discharging,45090000,34610000
1636047781,Discharging,45090000,34520000

Where the first column indicates the current unix time, the second indicates the battery status with the values 'Charging', 'Discharging', or 'Full', followed by the maximum energy of the battery in uWh, followed by the current energy of the battery in uWh. The scripts are designed to work with these kinds of values. In the current version, the maximum energy is ignored.

Tested and developed on Gentoo Linux with Kernel version 5.10.61-gentoo-x86_64