Concerned about battery on android

[dsr07mm]

Is it normal to have "Android OS" as highest battery usage ?

Lets be clear here, I'm aware that I have low budget 7" tablet with weak battery but I'm just making sure is this normal anyways.

This happened after 10 hours of sleep, 100 minutes of not touching tablet neither and then 20 minutes reading my emails and checking viber messages. So basically - idling. (No I didnt drop to 47% after that but I did drop around 15%).

After trying to find why is this happening I did reset to factory settings and screen was highest usage by far after 2-3 hours, while wi-fi was on second place and then Android OS with around 5%. After casual emails, conversations on viber and installing some apps (not running all the time) Android OS is again just under Screen with 40% while wifi is still draining only 14-15%.

Is it normal or something is bugged in this Android version ? It should've been 4.4 Kit Kat but in tablet I cant find "Kit Kat" so I will assume that its not.

If its normal please let me know, otherwise I will try and do something.
Asking this here because when I'm searching for screenshots I usually see Android OS at low % number along with Android System and Wifi is always above that.

 

[hang-the-9]

Don't know about your battery life since it varies by device, but I can tell you that every time I checked my Android phones for battery use the screen is always the top user or battery, often by quite a large %. My screen on my LG G3 is at 48%, Androis OS is at 9, Android System is at 7, rest are 5 or less like Chrome, Play services, Facebook, Phone.