The battery in an old laptop often won't show an accurate reading of the life remaining. Calibration is a relatively easy process and will get things back to how they were.

Increase Battery life of Windows 11/10 laptop. Learn how to manually calibrate your laptop battery to improve its life and performance.

Calibrating the battery helps keep the computer in sync with the battery's microprocessors, which are responsible for reporting the battery's charge.

Pawing through the Dell website, he pointed me to a page displaying a muddy picture of a battery that looked different from what was in my computer.

Does your laptop battery say 100% but dies when unplugged? If yes, it may be due to several reasons – like a defective charger, failing battery, etc.