manjaro i3 and the eeepc: battery and lightdm

Hello I am an happy user of manjaro i3, I like to install on a asus eeepc 1001 px with a new 6600 mah battery.
On this netbook until now I have used WattOS Microwatt 10 (and Ubuntu based distro) with i3 and I have 9 hours of stand by.
How can I tweak the battery usage in i3?
I am sorry if this question was already posted but I find difficult to find the answer in these forums.
I also find Microwatt use Laptop Mode Tools and Manjaro uses Tlp and Upower.
I also have a problem with Lightdm: I can't change the wallpaper, I try to click on the icon of Lightdm confg from pcmanfm/programs but after writing the root pasword this don't work.
Thanks for your answers

My first advise is to avoid graphical browsers and use a terminal based browser like links as much as possible.

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