I've tried calibrating it, to no avail. We have a signal booster, so I'm on full bars constantly, unless I'm out. Also, I've even tried setting my network to only use 2G, and that didn't make a difference either.You can try calibrating your battery. It's simple. Run the app from the play store or just let your phone die completely. Then keep pressing the off button until it no longer shows any notification to plug into charger. Leave your phone off while it's charging until it reaches 100%.
Other issues that cause battery drain is your network constantly swapping between HSDPA and EDGE.
My P1's battery is going strong after 2,5 years but it does need calibrating now and then.
I'm currently back on B119 (to my dismay, lol), just to check that it isn't just B7xx that has been killing my battery. I've tried before with B510, and my battery was a little better, but not by much, and it still drained every 2 seconds when it reached 20%, so we'll see after a few days on JB if my battery is still as bad. Otherwise I'll buy a replacement battery, and ask my husband to replace the damn thing. If he breaks it, he pays for it anyway, lol!

