As a follow up my phone died this morning at around 67% and would not turn back on until I plugged it in again, at which point the battery reported 67% charged. When I got to my office it had gone up to 88%. I then rebooted the phone and it came back up at 8%. 
As my screenshots show there was less than 4 minutes between screenshots and the only thing I did was reboot the phone.
Once the phone is back to 100% I will start taking more screenshots of the battery status page on the phone.
I also have a Xt6150. Here is the problem. I tried this with my phone and my daughters' who has the same one.
If you have battery draining (after 7.1.1 upgrade), your battery will not be calibrated.
here is how you can get you phone working for more than 20hrs at one charge :
Go to recovery mode (vol down, power ) at menu scroll down with vol down to recovery mode. when phone comes back, press power key and tap power up key ) menu will appear, you choose delete cache.
when it reboots, turn power off . put phone on your charger. let it charge( not turned on) until it reaches 100%. Actually it is not 100% it thinks it is. Now turn on your phone again. you may see only 68% or so. That is because turbochargers only charge till 70% then switch to regular mode, but this mode does not work when the phone is off. so you have to charge the remainder 30% when phone is on.
you can plug it back in and charge like this, until it reaches 100%. I personally turn it into airplane mode.
when the other 30% is charged on the phone, (unplug, and check %. if its not yet 100 when you unplug, charge it some more ) it will discharge at regular rate till empty . In my case this is always around 25 hrs or so. with some phone use and browsing.
I also recommend letting it discharge in airplane mode completely before you start re-using the phone.
If you don't, the phone will discharge quicker, and not recalibrate fully. I also recommend swithcing on the battery saver (in the battery status screen)
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You can monitor discharge with the free ampere app( download it) the free one has ads) .
you can see how much your phone charges or discharges. usually, with heavy use, you wil be negative, even while charging. That is why the battery calibration can't fully work if you keep on using your phone while doing this. Be Patient and let it discharge without much load, ( It may take 24 hrs or so , but its worth it). Do this during a weekend or so.
once fully discharged, you can plug your phone in, let it charge offline first, then, restart and recharge the remainder 30%.
That's it your phone battery should be recalibrated.
Note : people recommend to do this procedure maybe every 2-3 months but not more, as it burdens the battery more than it would do good concerning the lifetime of the battery.
Here you see : after 14 hrs in mostly airplane mode (during recalibration process). still 6 hrs left.
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remember : if you start using the phone at great discharge during the recalibration process .. after a while, it will degrade rapidly, because it has not fully recalibrated yet.
