I was looking for a solution to manager power settings on Ubuntu with i3wm [1].

Battery Life
============

For an optimal batterly life, I choose tlp [2]:
  
  Popularity: https://qa.debian.org/popcon.php?package=tlp

Install with:

  $ sudo apt install tlp tlp-rdw

Then enable the service:

  $ sudo systemctl enable tlp
  $ sudo systemctl start tlp


Suspend timing
==============

A simple bash script on managing the power options should do the work.
Create the file ~/.config/i3/scripts/power_manage.sh:

  #!/bin/bash
  
  # Check if system is on AC power
  POWER_STATUS=$(cat /sys/class/power_supply/AC/online)
  
  if [ "$POWER_STATUS" -eq 1 ]; then
      # On AC power: Longer timeout
      
      # Display: standby, suspend, off - in seconds, 0 for disabling
      xset dpms 600 1200 1800
  
      # Disable sleep/suspend/hibernate
      systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target
  
  else
      # On Battery: Shorter timeout to save power
      
      # Display: standby, suspend, off - in seconds, 0 for disabling
      xset dpms 300 600 900

      # Reenable sleep/suspend/hibernate
      systemctl unmask sleep.target suspend.target hibernate.target hybrid-sleep.target
  fi


Then enable execution of ~/.config/i3/scripts/power_manage.sh:

  $ chmod +x ~/.config/i3/scripts/power_manage.sh

Finally, add execution of script on ~/.config/i3/config:

  # Monitor for power status changes every 30 seconds (using watch command)
  exec --no-startup-id watch -n 30 ~/.config/i3/power_manage.sh

Reload the i3 config:

  $ i3-msg restart


Reference:
  [1] https://i3wm.org/
  [2] https://linrunner.de/tlp/