Samsung Galaxy S3 Battery Dying Extremely Fast - After 4.3 Update

Question

I have been struggling with this same issue, have killed all unnecessary apps, cleared the cache, performed a factory reset and even tried a new battery, and still have an issue where after a full charge, my battery would drain to around 90% in less than 30 minutes.  Sometimes, even faster.
It seems that nobody has been able to nail down a solution, so I attempted to contact Samsung to see what their suggestions might be. 
The conversation I had with an agent basically sums up like this:
There's nothing they can do because they do not have reports of this issue and request that I send in my phone to be physically examined.
So, Samsung basically told me to send it in and see if they can do anything about it.  I don't have the insurance set up on my account, so I can't hold that in place, and I have no other way to get in touch with people and have a small child, so I can't exactly just mail off my phone for them to examine it.  So, basically, Samsung is avoiding the issue and we still have no true resolution. 
If anyone has any other ideas, fixes, things I can attempt without having to send my phone in for someone to "examine", it would be greatly appreciated.
Please note that I have deleted/uninstalled/cleared cache on many apps, finally completely reset the phone to factory settings and then tried a brand new battery, and the drainage is still extremely significant.

Answer 1

Simple fix. No. Seriously. I had this on mine and the fix worked like a charm.
I appologize in advance that I do not have screenshots, so I'll do my best to step by step describe this as best as possible.  The culprit is your e-mail app (not g-mail --- e-mail).  I don't know the specifics, but it has issues with syncing between Yahoo accounts and Google accounts and it supposedly causes the e-mail client on your phone to run CONSTANTLY to try to sync.  This will drain your battery like crazy. 
No. This process never shows up in the battery useage thingy that they had you check.  It is a background app process and won't show there.  Sorry VZ people, but your normal tech magic has no power here.  This is a known bug with Android 4.3.
You have to disable the sync, but this has the unintended effect of rendering your e-mail app useless since it will no longer get your e-mails for you, even if you manually sync it.  Just download the Yahoo Mail app and you'll be fine. (or whatever other e-mail service you're using).
From your In-Box, touch the menu button to the left of the home button.  The menu comes up with "Sort By", "View As", "Font Size", and "Settings"  -- Touch "Settings"
Under the settings menu, you should see "+Add Account" at the top and "Account Settings" with your e-mail address directly under that.  Go ahead and click that.  It should bring up another menu with your e-mail address and a green check mark beside it.  Touch your e-mail address to open its settings.
The top option is "Sync Settings" - that is the one that we want... click it.   You should see "Sync E-mail" at the top and below it, it will say "Master sync has been turned off" and there should be a green check in the box to the right.  Touch the green checkmark to fix the issue. The green check should be on and it should now say "Sync turned off."
You've now fixed the problem and disabled your e-mail app from sucking your battery.  Not sure why it sets up like that, but with the Master Sync turned off, your e-mail app will try endlessly to sync with the other services via master sync and it will never be able to.... so it keeps running and running and running.  Sucks.
Now that you're fixed, just get a service specific e-mail app and be happy with a phone that doesn't die in an hour!!!!
Keep in mind that you will still need to monitor things like Wifi being on when you're not connected to Wifi, GPS, and screen brightness.  Those will drain it quickly too.
I used to be able to unplug my phone @ 100% and litterally watch it drop without even unlocking it.  Now, I can use it casually/semi-hard all day at work and still go home with 40-50% of a battery.
Best of luck!
Adam