My iPhone 6s shuts down once unplugged from power source even though the battery management system shows 100%
My iPhone 6s shutdown immediately it’s unplugged from power source, but the battery management system still shows 100%
iPhone 6s, iOS 15
Question marked as
Your battery is shot, regardless of what it shows. A 7 year old battery is not going to be at 100% health, it's time to replace the battery.
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 Repair & Replacement - Apple Support
About Lithium Ion Batteries
iPhone battery and performance - Apple Support (IN)