What percentage does the battery need to be to replace at the Apple store?
My battery is at 78% and has bad performance. What percentage does the battery need to be so it can be replaced?
Agreed- 80% or less, get it replaced - iPhone Battery Replacement - Official Apple Support
The out-of-warranty cost will be $49 or $69, depending on the model. However, if you've only had it for less than a year (still within the AppleCare limited warranty), battery replacement is free.
