Batmon is a daemon that monitors the state of laptop batteries.
I have written this because most available tools can't handle multiple batteries.

Also this does not have a GUI, so is pefect for tiling WMs.

Calculate the battery life over all available batteries and make it available via a state file (I use it for i3blocks/i3bar).

Hibernate/suspend the machine when estimated battery life falls under a limit.

Both things need an accumulated time calculated for both batteries. Most tools calculate battery life separate for each battery, this is bullshit and not useful.

The other thing is, I don't want fancy apps with GUI and tray icon. I want a background daemon that can handle the low battery action and share the estimated battery life with apps like i3bar/i3blocks.

Currently, I use a polkit rule to get permission to suspend or hibernate. This is bad and should work with group permissions or something else...

Do not mistake this with http://www.nongnu.org/gap/batmon/index.html. These are different projects with different purpose.