Lenovo 20Y5S0BU00 User Manual page 50

1. Disable the built-in battery. See "Disable Fast Startup and the built-in battery" on page 37.
2. Turn off the computer and disconnect the computer from ac power and all connected cables.
3. Close the computer display and turn the computer over.
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ThinkPad X1 Extreme Gen 4 / P1 Gen 4 User Guide