Apple watch series 4 battery drain about 15% per hour without any active app
I have an apple watch series 4 and the battery can only last for about 6 hours after a full charge. I went to the apple store to have it diagnosed but nothing was wrong with the watch(at least this is what I was told based on the diagnose result). Also tried send it to the repair center for deep diagnoses but they cannot find any issue with the watch and just sent it back to me. I've tried unpair/repair the watch, set it up as new watch without installing any app on it, turn off background app refresh on the watch, disable wake screen on wrist raise etc. but none of them solve the problem. Apple customer service said there mush be some background app refresh that is draining the battery since nothing with the battery is wrong, but they cannot fix the issue or point out what app it is. The watch is basically useless at this point since I don't want to charge it every 6 hours. Any help is appreciated.
