Open the Phone app and dial `*#*#4636#*#*` if supported
Go to `Settings`
Tap `Battery`
Check `Battery usage` or `Battery health` if available
Open the device manufacturer app or support app
Use Samsung Members, Xiaomi Security, OnePlus Diagnostics, or similar built-in tools
Check `Device care` or `Battery and device care` on Samsung
Use a battery health app from the Play Store
Look for battery capacity, charge cycles, and estimated health
Check `Settings` > `About phone` > `Battery information` if available
Use ADB or third-party diagnostic tools for detailed battery stats
Observe battery drain, overheating, and charging speed as signs of battery condition