Battery drain after updating to iOS 13.2.2

please help ! Since I updated to iOS 13.2.2 My iPhone 6s Plus battery drains so fast and jumps around ! My phone battery health indicator shows that my phone battery health is 85% which is still a good health ! I don’t know what’s really going on ! I fully charge the phone and it goes down from 100% to 20% in 2 hours ! After i restart the phone I find it June to 60% I restart the phone again it jumps to 40% . I did a fresh install to my phone which unsolved nothing! Should I go back to an old iOS ! I’m really so sad and can’t use my phone since the update! Please help me!