Open the phone’s Settings app
Search for Battery or Battery Health
Check the battery health percentage or status
On iPhone, go to Settings > Battery > Battery Health & Charging
On Android, use the built-in battery diagnostics if available
Dial the manufacturer’s diagnostic code if supported
Use the phone maker’s support app for battery diagnostics
Check battery usage and charging behavior in Settings
Look for signs of battery wear such as fast draining, overheating, or sudden shutdowns
Use a trusted battery health app if your device supports it
Visit an authorized service center for a professional battery test