https://wccftech.com/android-pie-update-causing-massive-battery-drain-for-some-galaxy-s8-and-s9-users/

When the Android Pie update first began hitting the airwaves, some users complained of accelerated battery drain after installing the software. At that time, it could be passed off as an isolated incident considering that not a lot of people had received the update. The update has now hit most of the regions and devices, and users are once again, complaining about the same issue. Making things even more interesting is the fact that even some Galaxy S8 users are complaining about the same problem. The Galaxy S8 begin to receive its Android Pie update only recently, and it is yet to roll out in a lot of regions.

According to users on forums such as XDA Developers and Reddit, the battery life of their devices has gone down drastically after the Android Pie update. In some cases, the screen on time has gone down by up to 50%. Some of the standard solutions for the problems such as a factory reset, uninstalling potentially problematic apps and multiple reboots appear to have worked for some users.