Find the report and read its usage history
Generate the HTML with powercfg /batteryreport and use the file path shown by the command. Open the original file in a browser to inspect Installed battery, Recent usage and Battery usage. The local parser extracts capacities, cycles, a capacity ratio and three system fields (report time, computer name and system product); it does not summarize those history tables. The ratio is a reported-capacity snapshot, not a certification or a runtime prediction.
Capacity is a reported estimate
Firmware and the battery-management system estimate capacity. The value can move after calibration, firmware changes, temperature shifts, storage, and cell balancing.
Runtime depends on the workload
A battery can report acceptable capacity and still deliver poor runtime under a bright display, discrete GPU, video calls, background updates, or high-performance mode.
Physical safety overrides the percentage
Swelling, odor, unusual heat, shutdowns, damaged casing, or charger problems require physical attention even when the report looks normal.