How to Restore a Missing Battery Icon in Windows 10
Select Start > Settings > Personalization > Taskbar, and then scroll down to the notification area. Choose Select which icons appear on the taskbar, and then turn on the Power toggle.
How do I recover lost battery icon?
If you don’t see the battery icon in the panel of hidden icons, right-click your taskbar and select “Taskbar Settings.” You can also head to Settings > Personalization > Taskbar instead. Scroll down in the Settings window that appears and click “Turn system icons on or off” under Notification area.