Battery issue in Ubuntu 18.04 LTS [duplicate]
First, read this Ubuntu Help article about Power & battery
If not enough you may want to install TLP
TLP brings you the benefits of advanced power management for Linux without the need to understand every technical detail. TLP comes with a default configuration already optimized for battery life, so you may just install and forget it. Nevertheless, TLP is highly customizable to fulfill your specific requirements.
To install TLP :
sudo apt install tlp tlp-rdw
sudo tlp start
Then customize suspend setting: System Settings -> Power -> Suspend & Power Button.