A:Answer what do you mean at what percent? If you mean the battery health... when you go to the battery health in your iPhone, it will tell you whether your battery needs to be replaced or not. For me, I actually have my iPhone battery fully charged at 100% before I went to Bestbuy, and they just replaced it in within 1 hour. My battery health is about 70% and when I checked the battery health it said I should replaced the battery