Read http://www.androidauthority.com/ad-suported-android-apps-battery-drain-65716/ and that's the usual I run into. Install one app or turn on GPS, Bluetooth, NFC and more and you barely get a day on standby.
I can't answer why you can't change the battery but maybe this is not the phone you were looking for?
Bob
I bought LG G Pro 5 months ago and I really find that the quality is so much better than 2 years ago 2X...however i find that their service is still far from international standard for their service center. I complain that recently the battery drain out very fast compare to previously even i did not install any new software. I request for a replacement of my battery as the warranty is expiring soon for the battery, they refuse to change and said need to take 2 days to check the set, they just simply reload the software and said the battery got no issue. i bring back the set and the battery still drain faster than previously. Is it too expensive just to let customer to change battery? No standard for such a big company....

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