For those with poor battery on 10.3.1
I found that using an SD card made my system use shoot through the roof ( even when it was formatted properly, it was as if the phone would continue to keep nuking it and reformatting ) and after relieving all efforts to try and rectify my battery problem, taking out the SD card has got me back to 1 percent drain per hour even on 4g. Something to try if you are having some problems and no amount of resetting and killing apps in backgrounds helped. Hopefully this helps some of you out there.
On a second note, is there a reason the sd card is causing this? is there a fix i haven't seen yet?