Iphone 6s gap in battery 100% to 10% in seconds! more discussion on this topic
Just like 354 other people I have exactly the same issue, when taking the iphone6S off charge it reads 100% (as you would expect). Immediately the phone shuts down and the battery is at zero percent and needs to be recharged again before it can be used. I have checked the battery health and it's at 85% Maximum Capacity and currently supporting normal peak performance. This is obviously a software issue affecting thousands of people. When are Apple going to issue a fix for this?
iPhone 6s, iOS 14