Apple Confirms It Slows Some Older iPhones to Protect Batteries

Apple confirmed in December 2017 that iOS could reduce peak CPU performance on some older iPhones with degraded batteries. Users had noticed benchmark scores dropping after updates, which created suspicion that Apple was deliberately slowing old phones to encourage upgrades.

The technical reason involved lithium-ion battery aging. An old battery can suffer a larger voltage drop under sudden high current demand. If voltage falls too far, the phone may shut down unexpectedly. Apple’s power-management code reduced processor peaks to avoid those crashes.

The controversy was largely about transparency. The engineering trade-off was defensible, but users had not been clearly told that their phone’s performance might change because of battery health. Apple later added battery-health information and offered discounted replacements.