[AT&T Galaxy Note 3 General] Rukbat:
People are misunderstanding a few things,

1) 10% battery usage doesn't mean 10% of the battery is being drained per hour by that service, it means that 10% OF THE BATTERY POWER THAT'S BEING USED is being used by that service. IOW, if 3% of your battery power has been used, and Android OS is listed at 10%, Android OS used 0.3% of your total battery power - 10% of the total that was used.

2) Android OS will use battery power no matter what you do - unless you pull he battery out. This is a computer. At the very least it's tight-looping - going around and around looking to see if anything needs to be done. (It's called an event-driven system - it sits there waiting for an event - like you touching the screen - to happen.) It's going to keep running as long as the phone is powered up. (If the power switch is a push button, the phone is running even if it's off - waiting to see if you pushed the power switch.) Computers are dynamic devices - they run constantly, even if they're doing nothing but waiting to do something.

3) From the few Note 3s I've tested, if you turn everything off - airplane mode, let the screen go dark, etc - the battery should last for at least 3-4 days - IF YOU CONDITIONED IT. A battery right out of the box? How long has it been sitting on the warehouse shelf? A week? Nine months? What was the state of charge when you got it? 90%? 2%?

The only way to know what's happening is to condition the battery - 3 full charge cycles (power off, let the phone tell you to remove the charger), then 3 full discharge cycles - don't charge the phone again, not even to plug it into a computer, until the phone tells you to turn it off or recharge it. Use it - make calls, play games, take notes, but don't plug it in. With the supplied charger and the 3.0 cable, charging an almost dead battery should take a couple of hours. And, in the case of the Note 3 ad almost no other phone, you can actually run the phone on the "charger" - it can supply enough current to keep the phone on and charge the battery at the same time (although it'll take longer to reach full charge that way). You should also get a lot more than the typical 18-24 months of full battery use if you condition the battery. (I know, Battery University, and I respect almost everything they say, doesn't go along with that. Tell that to my made in 2002 battery that's still giving me a full charge.)

You'll see plenty of warnings, from carriers, from manufacturers and on forums, to NOT expect full battery life until you've used the battery through a few charges. This is because every battery has been treated differently since it came from the factory. Condition your battery, then take measurements of what's eating how much power, how long a charge lasts, etc. But don't fault the OS for using 10% of your power, if the AMOUNT of power is almost zero. You need power use in Amps (or mA - thousandths of an Amp) to know whether your phone is using more or less current than it should be. The fact that your OS is using 10% of some number you don't know is meaningless. If the OS is using 10% of your entire battery in 1 hour you have a problem. If it's using 10% of the entire battery in a week you have a great phone. Even if it's using 10% of the total power being used in both cases.