iOS 11.4 battery drain

Hello there.

I am an owner of an iPhone 6s plus and i had installed iOS 10 since last month and honestly i was very happy with it. No problems at all.

I decided to move forward and update the iOS to 11.4. Since then the battery consumption changed a lot. I have my phone charged every few hours and honestly and I can't figure out what's happening. With iOS 10 I had a day battery life.

Is there something I did wrong? Does anyone encounters the same problem? According to the device, my battery health is 84%

Note that the update was made from the device itself