Inexplicable Idle Battery Drain

So here's the short version of a very long ongoing story.

My fiancé and I each bought the GS3 back in October of 2012. Since then, she has been the victim of terrible idle battery life. Being more technically minded than she, I have done literally everything I would have done on my own unit to hers. I rooted it to take advantage of apps like Greenify and betterbatterystats. I even heard the app Wakelock Detector was a good way of pairing with Greenify to eliminate Rouge apps and bad wakelocks.

However it is now over a year and two separate batteries later and she is STILL suffering from this idle battery. Today she had a total of 8 minutes of on screen time and her battery died after about 6 hours of being idle. None of the previously mentioned apps have detected any sort of suspicious activity and I've tried factory resetting the phone numerous times.

Can anyone shed any kind of light on just what the heck might be plaguing her device? I've never experienced battery drain as severe as her unit has demonstrated.

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It's been over a year unfortunately. Every time we tried filing for a replacement inquiry Samsung has screwed something up so we never were able to get it exchanged.

Sent from my SAMSUNG-SGH-I747 using xda app-developers app

I gave her my stock battery that came with my GS3 since I was given a Hyperion 4200 mAh external battery. I originally thought it was a faulty battery but my battery is not helping the issue. She's still having terrible battery life. The OP was using my old battery.

Sent from my SAMSUNG-SGH-I747 using xda app-developers app