Based on a discussion in comments we found out the problem and how to solve it:
Your problem is that on an old Android phone with a weak battery you have set-up a limit of 75% to start energy saving mode. This settings was synced via Google Cloud to your new phone and on the new phone there is no UI for changing the energy saver limit back to a more reasonable limit.
What you can do is check the system settings for a the 75% value:
In an adb shell
execute:
settings list system
settings list secure
settings list global
For each command check the output if there is an setting with value 75
and a name that indicates something with energy or power.
In your case the matching setting value was low_power_trigger_level
from settings global
namespace.
This setting can be changed to 25
% by the command
adb shell settings put global low_power_trigger_level 25