In short, a phone's performance can be throttled if it can no longer cope with power demands. There is the option to turn throttling off, but this will result in more frequent crashes. Neither situation is ideal, so a battery replacement seemed like a smart way forward for me, since it wasn't my main phone and I was willing to take the risks.

According to Apple, iPhone 14 models and earlier are designed to retain 80% of their original capacity at 500 complete charge cycles under ideal conditions, while the batteries in iPhone 15 models can retain 80% of their original capacity at 1,000 complete charge cycles, again under ideal conditions.

Apple is raising the price of battery replacements for its new iPhone 16 Pro and iPhone 16 Pro Max phones to $119, up $20 from the current cost for the iPhone 15 Pro and iPhone 15 Pro Max. The cost to replace an out-of-warranty battery on an entry-level iPhone 16 model will remain $99,