Charge level is not battery health
This page reads the Battery Status API when available. The percentage describes reported current charge, not original capacity, battery wear or cycle count. A worn battery can still report 100%.
Compare charging state before and after connecting a known-working charger, only when the device and port are dry and undamaged. Updates depend on the browser and OS; a delay is not automatically a charging fault.
Unknown time estimates are normal
The API may omit time-to-full or time-to-empty, or return an infinite value when it cannot estimate. Workload and charging conditions change those predictions. Do not treat them as a promise of remaining runtime. Desktop systems can provide a default full/charging state without a physical battery.
If the API is unavailable, check battery information in system settings. The browser cannot recover hidden capacity, voltage or temperature data. For a used phone, compare the native battery-health display, charging behavior and seller's repair history using the purchase checklist.
When browser readings are not enough
Unexpected shutdowns or rapid drain require a longer, controlled comparison of normal use and system battery statistics. A hot, swollen or damaged device should be inspected professionally rather than stress-tested here. The device information page shows other browser-exposed capabilities, with similar limitations.
Battery readings are processed locally. A saved reporting status means the API returned data, not that battery hardware passed an electrical test.