There's plenty of people reporting a higher than expected battery drain on the Zenfone 8, and while we just have to assume the cost of using an 888 snapdragon, there seems to be an issue with the system itself, causing a high idle battery drain. The phone just never gets into deep doze, no matter how much times it spends turned off. This causes maybe twice the battery drain what it should use while doing nothing. I'm confident in this being an issue with ZenUI itself, since no amount of wakelocks from apps would cause a literal 0 seconds of deep doze, plus I see no wakelocks or strange behaviour from any apps in either the system battery information or GSam Battery Monitor (an app that's always worked well for me in this regard). I'm uploading to snapshots from GSam, one from the Zenfone that I just took after leaving the phone alone for 2 and a half hours, and one from my old s10e for comparison. As you can see, the Zenfone just doens't ever enter deep doze, leading, as of this moment, to a 0.7% per hour battery drain while doing nothing, a drain that's easily twice as high as it should be with a 4000 mah battery (for reference the s10e drains about 0.4-0.5% per hour with an older 3000 mah battery) If we could get a way of fixing this, it'd go a long way to stretch the battery use of the phone.
I have a zenfone 8 and was getting terrible battery life while trying to optimize apps running in the background etc,then i factory reset the phone 5 days ago and let everything run, not restricting any apps from auto starting,turning optiflex on in assistive tool, disabled adaptive battery and background app management,using ultra steady charging,dual band wifi and hyperfusion enabled,setting network to 3g as 4g seems to heavily drain battery,after doing these steps im running 120hz all the time and can easily go through a 16 hour day with moderate to heavy use with a screen on time around 7-8 hour's, don't know what actually helped the battery in my situation but maybe trying these settings might help someone,