Battery consumption: Android System at 56%?

[AC Question]

I recently bought a Huawei P8 which seems like a good phone so far except in its battery consumption. Android System is often at 56% or so which I find very strange because most Android smartphones I've used had Android System somewhere between 6% to 10% max. When I go to sleep with a 100% fully charged battery, I wake up with 65% or 70% left. That's with Wifi, GPS, Bluetooth, mobile data and auto sync all turned off. I even tried using the ultra power saving mode but to no avail. I sent it back to the warranty and they "reinstalled" the software or so they say but Android System is still using up more than 50% (it keeps changing but it's always above 45% or 50% and after a long time of standby when I'm sleeping it hits 86%!). I just got back home from the service center so I still haven't got the chance to test it out and see if anything has improved with their "software fix".
I should also mention that I got to play around with one of the P8 demo units on display at the store and it had Android System at 44%.