Upon the release of
iOS 10.1.1 in late-2016, reports surfaced of battery usage issues with the update. There were also reports of device instability from some users on
iPhone 6 and
iPhone 6S models, including situations where the device would unexpectedly shut down once its battery capacity reached 30% (with one user having described the battery percentage as unexpectedly jumping down to 1% before doing so, but still appearing as 30% after the device was plugged in and rebooted). Apple confirmed in December 2016 that some iPhone 6S models manufactured in September and October 2015 had suffered from a battery manufacturing defect. The company stated that this defect was not a safety concern, but that it could diminish capacity, and cause shutdowns to "protect [the device's] electronic components". In regards to other instances of shutdowns, Apple stated that it would include an "additional diagnostics capability" in the next iOS update so that it could "improve algorithms for managing battery performance and shutdown operations" in future versions. With the release of iOS 10.2.1 in February 2017, Apple stated that it had reduced unexpected shutdowns on
iPhone 6S by "more than 80%", and by "over 70%" on
iPhone 6. Apple also reported that these issues were separate from the aforementioned defects in the 6S. In December 2017, the developers of the
benchmarking tool
Geekbench issued a report which showed a pattern of performance degradation on iPhone 6 models upgraded past 10.2.1, and
iPhone 7 models upgraded past
iOS 11.2. There had been
anecdotal evidence in the past that Apple had intentionally degraded the performance of older iPhone models on newer versions of iOS as a form of
planned obsolescence, to encourage sales of newer models. In response to these reports, Apple issued a statement to
CNET, confirming that it had implemented software performance controls based on battery health on older iPhone devices, in order to preserve system stability and prevent unexpected shutdowns. The company stated that its goal was to "deliver the best experience for customers, which includes overall performance and prolonging the life of their devices", and explained that "
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". Soon after, Apple issued a formal apology, admitting that it initially believed that the issues were caused by iOS bugs and "normal, temporary" performance decreases following an update, but that "continued chemical aging" of batteries in older iPhone devices was also a factor. Apple stated that replacing the device's battery would restore full performance, and also announced that it would offer a US$50 discount (from $79 to $29) on battery replacements for iPhone 6 and 6S from January through December 2018, and that it would include more prominent battery health information in later versions of iOS. In January 2019, Apple CEO Tim Cook stated in a shareholder letter that over 11 million battery replacements had been made under the discount program. The company stated that it had never, nor would ever "do anything to intentionally shorten the life of any Apple product, or degrade the user experience to drive customer upgrades." Beginning with the
iPhone 11, Apple introduced a new performance management system intended to "reduce performance impacts from battery aging". Unlike the previous system, this is always active in response to the battery's current capabilities, and there is no "peak performance" state. ==Reception==