My battery life on iOS 12.1.1 seems to have taken a hit. I’m at 66% after 24 hours with no activity on the device, including background refresh, push, and fetch all turned off. Location services only activated for Find my iPad. What gives?
If you just installed, there was plenty of activity on the iPad. Siri runs a background process to index everything that it is told to search. Generally this settles down after about a day, maybe two.
I just set up my old iPhone 6s from a backup the other day. On the first day after, the battery was at 20% or so by 8 pm after taking it off power at about 6 am, and I never even looked at it until then. The next day it was at 75% at the same time.