Why does my S4 battery drain fast while it is idle (Android OS processes)?

[Bluefield]

S4 draining battery fast in idle (Android OS processes)

To preface, I know this is a common problem that has been documented elsewhere and attributed to all manner of causes eg. faulty battery, rogue apps, GPS, OS bugs etc etc. What I can't find, is a way to deduce which of the infinite possibilities is the actual culprit.
My s4 is running 4.4.2. I go to bed on 100%, wake up to find the battery on single digits, check the battery graph and find during the night it's gone from draining at around 5% an hour to suddenly nose-diving at 20% an hour when not in use.
It doesn't do it all the time, but when I've looked at the stats on GSam, the largest consumption always says Android OS. There's so many processes listed under this heading to make identifying any one reason impossible.
The only app I've heard of that might list the specific reason for the sudden power surge is Wakelock detector, but this doesn't seem to be supported on stock Android.
Is there an app that gives a more precise breakdown? I'm looking for something that identifies what individual process causes the sudden spike in power at the time the battery nose dives on the graph, like a snapshot of the breakdown it shows on the android battery screen, but for a given moment in time, not just the total discharge period. Is there such a thing?
Thanks in advance

 

[Sanjay Chandra]

Re: S4 draining battery fast in idle (Android OS processes)

Hi there,

Location services and Google now are always the culprits. Turn off both. You can expect much better battery life on standby.

 

[Bluefield]

I tried switching both the above off and all seemed ok until yesterday when the same thing happened again; 60% battery level, screen off, not in use, meanwhile something is draining battery at 25% an hour. 3 hours later, battery dead.
I've noticed 2 apps that stay in ram after closing down manually; these being chrome and Facebook. I can understand that would drain a little battery if open in the background, but 25% per hour is the kind of power usage you'd get with screen on, everything open and running.
Incidentally, I noticed the Android battery breakdown lists Wi-Fi as using a few % even though I never have it on.
I now wonder if this is actually an Android problem as it seems to be to do with power management and I never had the same problem with jellybean on my galaxy s2.