iPhone batteries degrade with use—over time, they lose their ability to hold a full charge. Apple's batteries are rated to hold 80% of their capacity for up to 500 charge cycles, which lasts roughly 18-24 months for most users. When your battery's chemistry is degraded, it may also cause your iPhone to run more slowly. Use this guide to replace your battery and restore your iPhone to full performance. [ … ] If your battery is swollen, [[What to do with a swollen battery|take appropriate precautions|new_window=true]]. [ … ] and Taptic Engine taptic engine for better access to the battery's adhesive strips. [ … ] guide, [https://www.ifixit.com/Wiki/Battery_Calibration|calibrate] [[Battery Calibration|calibrate]] your newly installed battery: Charge it to 100% and keep charging it for at least two more hours. Then use your iPhone until it shuts off due to low battery. Finally, charge it uninterrupted to 100%.