A GNOME shell extension to show the remaining time until fully charged/discharged as well as battery charge in percent in the panel.
Battery remaining: 
Battery charging: 
Battery fully charged: 
Battery time estimating: 
Battery not charging (Threshold reached): 
https://extensions.gnome.org/extension/2929/battery-time-percentage-compact/
This is a fork of https://github.com/mzur/gnome-shell-batime (prior to Version 20: https://github.com/luispabon/gnome-shell-battery-time-and-percentage).