I just bought my iphone 15 128gb last august 2024 and it’s already in 93% battery health. Whenever my battery percentage drop to 29% my battery health will also drop 1%. For example, i forgot to charge my phone, the battery health percentage is 94%, because i forgot to charge it, it is currently in 29% battery percentage. When i look up the battery health percentage, it is now 93% Btw, i use 30% - 80% charging tech. Sorry for my english. English is not my first language.