Before Running any tunning, the average estimated lifetime of my battery was about 3 hours (below image). Through this post we learn how to extend it to almost 4 and a half hours. It's more than 50 percent increase!

Note: I'm currently using a lenovo G50 laptop with Quad-Core AMD CPU equiped with a 4-cell battery and running i3-wm, a lightweight tilling window manager (no Gnome/KDE craps for me) on ArchLinux. So depending on your hardware and programs you have running and your daily usage pattern, the results may vary for you.

First, run powertop to find out which devices/processes are draining power the most. In The Overview Tab you can actually see what processes/devices are draining how much power and By applying the Good option in Tunables Tab, powertop automatically tunes them. you can do this manually for every item in Tunable tab or just use the --auto-tune option.

$ sudo powertop --auto-tune

That single command will probably add a noticeable extra minutes to your battery life. But there are still other ways to improve it more. Let's Go to powertop's Overview Tab again:

Power est.  Usage        Events/s    Category    Description
  5.18 W    0.4 pkts/s               Device      Network interface: wlp2s0 (wl)
  3.80 W    100.0%                   Device      Display backlight
  1.26 W    165.5 ms/s   123.3       Process     /usr/share/atom/atom --type=zygote --no-sandbox
  675 mW    95.9 ms/s    5.3         Process     atom
  660 mW    94.0%                    Device      USB device: USB2.0-CRW (Generic)
  262 mW    27.0 ms/s    90.1        Process     /usr/share/atom/atom --executed-from=/home/bijan --pid=1109
  247 mW    27.2 ms/s    70.4        Process     /usr/lib/xorg-server/Xorg :0 -seat seat0 -auth /run/lightdm/root/:0 -nolisten tc
  103 mW    2.0 ms/s     109.7        kWork      od_dbs_timer

According to above, after my wireless interface (which i use), the display backlight, USB CD-RW and my Ethernet interface are the most draining power sources. The last two I never/rarely use.

Turning Off unnecessary devices

Since I never/rarely use my CD-RW and I never connect to Internet through wired connection, so it seems logical to me to disable them. to find my CD-RW device power location, I used powertop Tunable Tab:

# Disable CR-RW
$ echo 0 | s tee /sys/bus/usb/devices/1-1.3/power/autosuspend_delay_ms
$ echo auto | s tee /sys/bus/usb/devices/1-1.3/power/control

To disable my Ethernet device, first I have to find it's device number:

# Find Ethernet domain:bus:slot number
$ lspci | grep -i ethernet
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 10)

# Find relative device on /sys/devices
$ find /sys/devices -name "*03:00.0"
/sys/devices/pci0000:00/0000:00:02.4/0000:03:00.0

# Turn off device
echo 1 | s tee /sys/devices/pci0000:00/0000:00:02.4/0000:03:00.0/remove

Backlight

To reduce the brightness LED backlight, I set a brightness value (between 0 and 255):

# Brightness
basedir="/sys/class/backlight/"
handler=$basedir$(ls $basedir)"/"

chmod 666 $handler/brightness
echo 100 > handler/brightness

Running as a Service

To execute the above commands at boot up, I created a shell script and run that as a service.

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#!/bin/bash
# /usr/local/bin/powertop_tuning.sh

# Auto-tune powertop
powertop --auto-tune

# Disable CR-RW
echo 0 | s tee /sys/bus/usb/devices/1-1.3/power/autosuspend_delay_ms
echo auto | s tee /sys/bus/usb/devices/1-1.3/power/control

# Disable Ethernet
echo 1 | s tee /sys/devices/pci0000:00/0000:00:02.4/0000:03:00.0/remove

# Brightness
chmod 666 /sys/class/backlight/radeon_bl0/brightness
echo 80 > /sys/class/backlight/radeon_bl0/brightness

And to create proper systemd service:

# /etc/systemd/system/powertop_tuning.service
[Unit]
Description="PowerTop Tuning config"
ConditionPathExists=/usr/local/bin/powertop_tuning.sh

[Service]
Type=oneshot
RemainAfterExit=yes
KillMode=none
ExecStart=/usr/local/bin/powertop_tuning.sh
ExecStop=exit

[Install]
WantedBy=multi-user.target

So, to make powertop_tuning service run automatically, just enable the service:

$ sudo systemctl enable powertop_tuning.service

Conclusion

The result is very satisfactory. In daily usage, my battery life went up from about 3 hours to almost 4 and a half hours.

Disclaimer: The tests and battery benchmark did not placed in a controlled environment but it seems logical to expect similar effects.