In a statement sent to techcrunch.com, the technology company said it has released updates to older models to combat battery issues.
Our goal is to deliver the best experience for customers, which includes overall performance and prolonging the life of their devices. Lithium-ion batteries become less capable of supplying peak current demands when in cold conditions, have a low battery charge or as they age over time, which can result in the device unexpectedly shutting down to protect its electronic components.
Last year we released a feature for iPhone 6, iPhone 6s and iPhone SE to smooth out the instantaneous peaks only when needed to prevent the device from unexpectedly shutting down during these conditions. We’ve now extended that feature to iPhone 7 with iOS 11.2, and plan to add support for other products in the future.
According to techcrunch writer Matthew Panzarino, older iPhones were shutting down because they were hitting "peaks of processor power."
"As that battery ages, iOS will check its responsiveness and effectiveness actively," said Panzarino. "At a point when it becomes unable to give the processor all the power it needs to hit a peak of power, the requests will be spread out over a few cycles."
Doron Myersdorf, CEO of instant-charging battery startup StoreDot, told CNN the updates that "smooth out" the older devices rearrange the order of incoming commands.
"The inevitable outcome of it will be an inherent slowdown of the average response times by the system," he explained.
Apple said affected devices include iPhone 6, iPhone 6s, iPhone SE, and most recently iPhone 7 with Apple's latest iOS 11.2 update. More models could be affected in the future.