Apple builds tools into iPhones that let owners check battery health and, on newer models, cycle count, giving a clear picture of how much a battery has degraded. This matters both for existing owners deciding whether a battery needs replacing and for anyone buying a used iPhone, since a heavily cycled or degraded battery can mean reduced performance and shorter time between charges.

To check battery health, users open Settings, tap Battery, then Battery Health (called Battery Health & Charging on some older models like the iPhone 13), which shows a Maximum Capacity percentage. Apple designs batteries to retain up to 80% of original capacity, based on 1,000 full charge cycles for the iPhone 15 and later, or 500 cycles for older models; dropping below 80% may trigger performance management warnings. Cycle count is viewable directly in Settings on the iPhone 15 and newer, while older models require third-party tools such as coconutBattery. Enabling Optimised Battery Charging, and setting a charge limit on iPhone 15 or later, can help slow battery degradation over time.