According to Apple, the iPhone’s battery is designed to retain up to 80 percent of its original capacity at 500 complete charge cycles. So if the full charge capacity is less than 80 percent of the design capacity and the recharge cycles exceed 500, your battery is considered worn. Apple has made it easier for end-users to keep track of their iPhone battery performance. If you are running iOS 11.3 or later, it’s pretty easy to find out when your iPhone battery needs to be replaced. You can go to Settings > Battery > Battery Health and check “Maximum Capacity.” Note that this feature applies only to the iPhone 6 and later models.