Warn & hibernate on low battery

battery-warn.service

# put this in ~/.config/systemd/user/battery-warn.service
# and adjust the line in exec-start

[Unit]
Description=Battery warning

[Service]
Type=oneshot
Environment="DISPLAY=:0" "XAUTHORITY=/home/bit/.Xauthority"
ExecStart=/home/.../battery.sh

battery-warn.timer

# put this in ~/.config/systemd/user/battery-warn.timer
# then enable the timer with 
# systemctl --user enable battery-warn.timer

[Unit]
Description=Battery warning timer

[Timer]
OnCalendar=minutely
Persistent=true
Unit=battery-warn.service

[Install]
WantedBy=timers.target

battery.sh

#!/bin/sh

# thresholds
notify="15"
warn="11"
shutoff="10"

# calculate charge
count=$(acpi -b | wc -l)
sum=$(acpi -b | egrep -o '[0-9]{1,3}%' | tr -d '%' | xargs -I% echo -n '+%')
charge=$(( sum / count ))

discharging() {
 acpi -b | grep 'Discharging' > /dev/null
 return $?
}

exitoncharge() {
  if ! discharging; then exit 0; fi
}

countdown() {
  notify-send "Battery low! Will shutdown in 30s." -u critical
  sleep 10
  exitoncharge
  notify-send "Battery low! Will shutdown in 20s." -u critical
  sleep 10
  exitoncharge
  notify-send "SHUTDOWN IN 10s" -u critical
  sleep 5
  exitoncharge
  notify-send "SHUTDOWN IN 5s" -u critical
  sleep 5
  exitoncharge
  systemctl hibernate
}


exitoncharge

if [ $charge -le $shutoff ]; then
  countdown
elif [ $charge -le $warn ]; then
  notify-send "Battery: $charge%" -u critical
elif [ $charge -le $notify ]; then
  notify-send "Battery: $charge%"
fi