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Your old phone was never getting slower. Something else inside it was getting weaker.

As a lithium battery ages, its internal resistance climbs steadily. Ask an old cell for a sudden burst of current, the kind a camera launch or a game demands, and its voltage sags below the level the processor needs, so the phone simply shuts off, sometimes with 30 or 40 percent still showing on the meter. Apple's answer, shipped quietly inside iOS 10.2.1 in January 2017, was to smooth those peaks by holding back maximum processor speed on iPhone 6, 6s and SE models carrying worn batteries. The company said the change cut unexpected shutdowns by more than 80 percent on the iPhone 6s and over 70 percent on the iPhone 6.

Nobody was told any of this. In December 2017 benchmark data collected by Geekbench founder John Poole showed one phone model scoring in two clearly separate clusters depending on battery condition, and Apple confirmed the throttling within days. The apology followed on December 28, along with a cut in out-of-warranty battery replacement from $79 down to $29 for the whole of 2018. Apple is reported to have replaced around 11 million batteries that year against a normal run of one to two million. Regulators in Italy and France both fined the company over the omission, and the whole episode permanently changed how phone makers talk about battery wear in public.

The bill kept arriving for years afterward. The US class action settled for up to $500 million, and checks of about $92.17 per affected iPhone finally reached owners in January 2024. iOS 11.3 also added the Battery Health screen, which is the first time anyone outside Apple could see the number that actually mattered.

Go check yours: Settings, then Battery, then Battery Health and Charging. If maximum capacity has dropped under 80 percent, the phone is not old, the battery is, and a replacement usually costs less than a tenth of a new handset while handing back the original speed. An independent shop will normally finish the swap inside an hour, and a phone that could not survive an afternoon goes back to holding a full day...