How to fix Surface laptop not charging up to 100% (or charges only up to 80%) and there is a heart sign on the charging icon.
The heart sign on the charging/battery icon means it is in smart charging mode. There is no way to manually turn on Smart charging, when it detects the device is plugged in for prolonged periods or used at elevated temperatures, then it will turn on automatically.
Steps to Follow:
1. In order to turn OFF Smart charging, launch Surface App from the Start menu
2. Select Smart Charging > Charge to 100%
Reference Links:
Smart charging on Surface - Microsoft Support