I just wanted to say thanks for this thread. I too have experienced the somewhat random "plummet" phenomena that seems to be related to the throttling of the LTE signal on our devices. My plummets have mostly occurred in the overnight hours (nothing like starting your day with your phones battery DEAD) I have also confirmed that the two solutions recently posted on this thread DO actually solve the plummet problem (changing the band setting from Automatic [which we all know will always use LTE] to HSPA+ or WCDMA) But I submit that this problem is also solved by the "original" solution of adding a HSPA+ APN. (and its also less complex/tedious to implement) I have run with these settings for the last three days with no problems essentially creating an APN called ATT HSPA.: (hat tip to post number 1 and listed as #3 @ this link:
http://androidforums.com/nexus-4/691559-fixing-t-mms-keeping-hspa.html) The only time I feel I actually need LTE is when I need to use my device as a wifi hotspot; or when I am in certain rural areas where it seems that LTE coverage is actually better than 3G...I just throttle back to using the default APN in those cases.
I also wanted to throw this is there as well...since the "plummet" for myself and other users have actually occurred when on wifi (or from what I can determine, when the device is on wifi or on wifi with mobile data turned off) I'd like to share a hack for a rooted phone that will force connect mobile when the device needs to send or receive MMS. Taken from this link:
Auto connect data on sending/receiving MMS on Pg 4 | Galaxy Nexus > XDA
For completeness sake...I have an ATT stock rooted 4.1.2 GS3 and used this method to do so:
How to Root AT&T Galaxy S3 SGH-i747 on Android 4.1.2 Jelly Bean Firmware I use an app Power Toggles...
https://forums.androidcentral.com/e...tails?id=com.painless.pc&hl=en&token=1gwz-Zoz mobile data is turned off and wifi turned on when I'm home and mobile data is on with wifi off when I'm away from home. I have wifi set to Always keep on while sleeping and have a static IP assigned to the device.
I consider what is below as pretty good battery life...4 hours of listening to music, Pandora/KiesCast/Native Music Player and almost 3 hours of screen time. The quick 20 minute charge was when I was running Maps/GPS for a short trip yesterday. Mobile data, when on, was using the wap.cingular APN listed above.
I will post follow-ups re: my battery life. I have a vested interest of making this work...I've only had my GS3 for a year...and don't want to throw money at a new device at this time. Again...thank you for this thread.