digest from https://bbs.archlinux.org/viewtopic.php?id=62286 ,run in cron mode , to check if it is low battery and then suspend

suspend.sh

#!/bin/bash

battery='-';
bat_dir="/proc/acpi/battery/BAT0";

if [ -d "$bat_dir" ]; then
        remaining="$(awk '/remaining capacity/ {print $3}' <${bat_dir}/state)"
        total="$(awk '/last full capacity/ {print $4}' <${bat_dir}/info)"
        battery_level="$((remaining *100 /total))"
        battery="${battery_level}"
fi

if (( "${battery}" <= 5 )); then
        /usr/sbin/pm-suspend
fi

echo "${battery}"