Apple says its testing involved charging and draining the batteries 1,000 times under specific conditions and a suite of tests reflecting common uses. As for how the estimate doubled without any physical or software changes, the company attributes the upgrade to continual improvements to its battery components and iOS power management.
For older iPhones, the original estimate of retaining 80 percent capacity after 500 charge cycles still stands at least for now. Apple said it’s looking into whether older models’ estimates need to be updated.
