battery notification

battery-notification.service

[Unit]
Description=battery notification

[Service]
Environment="DISPLAY=:0"
ExecStart=/bin/bash /path/to/battery-notification.sh 20 10
Type=oneshot

[Install]
WantedBy=default.target

battery-notification.sh

#!/bin/bash

app=$(basename "$0" .sh)

[[ $# -eq 2 ]] || {
  echo "usage: $app warning critical" >&2
  exit 1
}

warning=$1
critical=$2

function notify {
  notify-send -c device -i battery "$@"
}

for battery_path in /sys/class/power_supply/BAT*
do
  battery=$(basename "$battery_path")

  capacity=$(< "$battery_path/capacity")

  if [[ $capacity -le $critical ]]
  then
    notify -u critical 'Battery CRITICAL' "Capacity $capacity%"
  elif [[ $capacity -le $warning ]]
  then
    notify -u normal 'Battery WARNING' "Capacity $capacity%"
  else
    echo "OK $battery $capacity"
  fi
done

battery-notification.timer

[Unit]
Description=run battery-notification

[Timer]
OnBootSec=1min
OnUnitActiveSec=1min

[Install]
WantedBy=timers.target