I have an iPhone SE which began to discharge rapidly and reboot with "unexpected shutdown, battery unable to deliver peak power" errors (and of course "performance management" was applied). All this, while Battery Health claimed that my battery was at 95% maximum capacity. Apple replaced the battery and the phone stopped rebooting, so the battery was clearly deficient. Why did Battery Health say that it had 95% maximum capacity? Recently my mother complained that her phone had rebooted with an error. I look in Battery Health, and what do you know: Crash and throttling despite Battery Health claiming that the battery is 97% healthy. To make matters worse, my phone (the one with the replacement battery), has dropped from 100% to 94% healthy in the <3 months since the battery was replaced. Why? The phone has barely been used in that time. I can't know whether they gave me a defective battery or if Battery Health just being useless again. So now I'm wondering whether to even recommend a battery replacement to my mother. It seems clear to me that Battery Health doesn't have a clue what is actually going on Oh, and one more thing I should note: on two other iPhones, I have observed the maximum capacity percentage sometimes increasing by as much as 3%. Doesn't exactly fill me with confidence. How did this feature get out of beta, and does the Maximum Capacity reading have any purpose other than giving second hand buyers a false sense of security?