Apple Confirms It Slows Some Older iPhones to Protect Batteries

Apple confirmed on December 20, 2017 that iOS implemented “performance management” — dynamic CPU and GPU frequency limiting — on older iPhones with chemically degraded batteries, following a Reddit post by user “TeckFire” in October 2017 claiming that replacing an iPhone 6S battery had restored its performance, and a detailed benchmark analysis published December 9, 2017 by John Poole of Primate Labs (makers of Geekbench). Poole compared Geekbench 4 single-core scores from thousands of iPhone 6S devices running different iOS versions and found a distinctive bimodal distribution in iOS 10.2.1 and later: devices clustered at either the expected ~2500 score range or a lower ~1400-1600 range, with the lower cluster growing larger in iOS versions released in 2017. When Poole tested the same 6S with a fresh battery versus a degraded one, the degraded battery device scored in the lower cluster. Apple’s statement confirmed that iOS 10.2.1 (released January 23, 2017) had introduced performance management for iPhone 6, 6 Plus, 6s, and 6s Plus, and that iOS 11.2 extended it to iPhone 7 and iPhone 7 Plus. The feature had not been disclosed in any iOS release notes, developer documentation, or user-facing settings.

The technical rationale Apple provided was accurate and grounded in lithium-ion battery chemistry. Lithium-ion cells lose capacity over charge cycles through electrolyte decomposition, lithium plating on the anode, and structural changes in the cathode material — processes that increase the battery’s internal resistance. A high-resistance battery can deliver its rated nominal voltage at low current draw but suffers a larger voltage sag under peak current demand. Apple’s A-series SoCs could draw 2-4 amperes during intensive tasks; an aged battery providing insufficient current would cause the voltage to drop below the minimum required for stable processor operation, triggering an unexpected shutdown rather than a graceful low-battery warning. Apple had documented a higher-than-expected rate of unexpected shutdowns on iPhone 6s devices in 2016, which had prompted a battery replacement program for a specific battery production batch. The iOS 10.2.1 performance management was Apple’s systematic solution: dynamically throttling the peak CPU and GPU clocks to reduce maximum current draw to within what the degraded battery could sustain, preventing shutdowns at the cost of measurable performance reductions in CPU-intensive tasks.

Apple’s response to the public disclosure was a December 28, 2017 open letter in which the company denied any intentional planned obsolescence and reduced out-of-warranty iPhone battery replacement pricing from $79 to $29 for all iPhone 6 and later models for the calendar year 2018 (restored to standard pricing January 1, 2019). iOS 11.3 (released March 29, 2018) added a Battery Health section in Settings — showing battery maximum capacity as a percentage of original design capacity and a toggle to disable performance management (with a warning that it increased the risk of unexpected shutdowns). Despite these responses, regulatory and legal consequences followed in multiple jurisdictions: Apple paid a $113 million settlement to 34 US state attorneys general in December 2020; the Italian Autorità Garante della Concorrenza e del Mercato (AGCM) fined Apple €10 million in October 2018 for planned obsolescence; and France’s Directorate General for Competition, Consumer Affairs and Fraud Control (DGCCRF) fined Apple $27 million in February 2020 for failing to inform French consumers of the throttling. Approximately 45 class-action suits were filed against Apple in the US. The controversy changed how Apple communicated about performance management in subsequent devices: iPhones from the XR (October 2018) generation onward received redesigned power management systems with more granular battery state reporting, and Apple incorporated battery health disclosures into standard iOS update notes going forward. The episode also prompted broader industry discussion about the tradeoff between performance, battery longevity, and thermal management — and consumers’ right to understand when software updates change the performance characteristics of hardware they have purchased.