The degraded performance is latching. After a brownout occurs, it will stay on until you get the battery changed or turn it back on. I.e. it’s not based on any

The degraded performance is latching. After a brownout occurs, it will stay on until you get the battery changed or turn it back on. I.e. it’s not based on any fixed percentages. The fact that people can put third-party batteries in and also that different batches of batteries will age differently means that this is probably the best solution. More info here: https://support.apple.com/en-gb/HT208387 https://support.apple.com/en-gb/HT208387 “This iPhone has experienced an unexpected shutdown because the battery was unable to deliver the necessary peak power. Performance management has been applied to help prevent this from happening again. Disable…” As for not (easily) allowing third party replacements, as someone who designs products: why should I (or Apple) have to support third party items? Why should I use engineering resources debugging why a third party touchscreen doesn’t work with my new firmware (this happened to Apple)? Also, as someone who buys second-hand electronics I don’t want a third-party battery in the phone, or at least I want to be able to tell if there is one in order to reject the phone. I like my house in a non-burned-down state thank you very much. And you just know that the average punter with a third-party battery is still going to blame Apple when their phone bursts in to flames from an eBay battery. Now, I believe there should be laws to dictate reasonable repair costs and, more importantly, number of years of support to ensure electronics live a long life.