STILL A FAN OF THE PHONE....FOR ME THE BATTERY BACKUP WAS GOOD IN PIE FOR A LONG TIME(I GUESS MIUI 10.1.3) BUT  JUST A WEEK BEFORE THE RELEASE OF MIUI 10.2.2 THE PROBLEM STARTED...THE BATTERY  BACKUP STARTED GETTING REDUCED I WONT SAY IT REDUCED SO MUCH THAT YOU CANT USE THE PHONE BUT A NOTICABLE CHANGE IS THERE...ACTUALLY I HAD FACED THE SAME PROBLEM FOR SOMETIME(ONLY A LITTLE TIME 2,3 DAYS) IN ONE OF THE  PREVIOUS ROM (THE ROM JUST BEFORE THE RELEASE OF PIE(MIUI 10 WITHOUT PIE)) BUT IT AUTOMATICALLY GOT  FIXED (BEFORE THE UPDATE ITSELF..AFTER THE UPDATE TOO BATTERY BACKUP WAS GOOD) ... ANYHOW HOPING THAT DEVOLOPERS WILL FIX THIS PROBLEM SOONER.. ITS BEEN ALMOST A MONTH...