Battery
My phone keep shutting down and he has full and little battery
iPhone 11
Question marked as
Batteries degrade over time with usage due to chemical aging, that's just how they work.
You can expect about a 1% drop per month with average use on an iPhone. This is an approximation, that is why it may be plus or minus a few percent on a month to month basis.
Apple recommends replacing it when it reaches 80%. To check your battery health, go to Settings > Battery > Battery Health.
iPhone Battery Replacement.
iPhone Battery Replacement - Apple Support
About Lithium Ion Batteries
iPhone battery and performance - Apple Support (IN)