Chosen Solution
I got an iPhone 6 which is damaged by water: I have changed the battery, charging port and the display. But I got 3 big problems Touch ID is not working, restoring is just working in recovery mode but not in dfu mode and the third and biggest problem is, the phone is turning off at 30%, tries to restart immediately but fails. When I plug in the charging cable, the phone starts immediately and charges up to 100%. But it turns off at 30 % every time. Is it possible to fix this?
battery is power rail is probably shot. check the components on the battery power rails with a multimeter. clean off board and do ultrasonic cleaning. have bga chip xrays done, if your ocd. I am working on hacking the touch id pairing, but until I succeed, your touch id is shot forever. only the mighty apple men (and women) can fix it
Feel for hot spots on the board while charging the phone. Like he said, there is a good chance the battery is damaged. Cleaning the board with a tooth brush and isopropyl is a cheap alternative to an ultrasonic bath. Remove all of the shields if you have a hot air rework station. Any hot spots would indicate a short in the area, look as closely as possible at the components in that area to find and replace any damage.
