Wrong current/voltage plugged into charging port

@dripordrown

you will have to disassemble your phone. you can use these guides ZTE ZMAX or something like this video Then check your motherboard for any damaged component (PMIC,capacitors or resistors). Usually with an overvoltage you will have obviously damaged components. Here comes the real problem, schematics are not readily available. So, there will be a lot of guessing etc. to determine what needs to be replaced. It is possible that this is a damaged battery (replacing it will rule it out/in).

You can of course post some good pictures of your motherboard etc. with your question so we can see what you see. somebody may see and recognize any damaged components. iFixitでの質問に画像を追加する方法