Forwarding you to

macOS Mojave battery drain - Apple Community

Spoke to Apple, I was skeptical when told it may take 24 to 48 hours for the OS to reorganize the file structure. Also suggested resetting the battery/memory by powering your Mac off then hold the left shift, control, option and power buttons down, then release the first three at the same time. I did that, not sure it contributed to the solution but on day three of the upgrade my Mac has rerturned to normal all on its own.