Last year, Apple instituted a program to replace out-of-warranty batteries for the iPhone 6 or later for just $29 — a $50 price drop from the usual $79 cost. If you own an iPhone 6 or later and have battery issues, you have until December 31 to take advantage of the lower price to replace your battery. If you own an iPhone 6 or later and have issues with your phone's battery life, now's the time to visit an Apple Store and get your battery replaced.