Reminder: Apple's $29 battery replacement deal ends at the end of December
Last December, Apple admitted that it throttled iPhone models with older batteries. Without slowing down the CPU on these units, certain tasks requiring battery strength that these handsets just didn't have, would result in these phones shutting down and rebooting. To combat this, the company had slipped software into the iOS 10.2.1 update that "dynamically manages the maximum performance of some system components when needed to prevent a shutdown." In other words, the update allowed Apple to throttle these older iPhones with weak batteries, and the company didn't say a word.