Why is my laptop’s battery not charging to 100?

Identify the right kind of cable that is used to connect your laptop to the power outlet.
Re-connect your laptop to the power outlet in case the connection is not securely done.
Restart your laptop to check if this helps resolve the issue of the non-charging battery.
You may also need to inspect the power outlet, and also check the power cord for any visible signs of damage.
Look for any dirt or lint that may be stuck in the power outlet and clean it.
Inspect the laptop’s socket and pins for any signs of corrosion.
If you are using an external power adapter, inspect the adapter for any visible signs of damage.
Use the device manager to check if the power adapter is supported by the system.