Now for my actual post. I have a Droid RAZR XT912 on CM11 the 8/12 nightly, although what I'm posting about has been an issue since I first went to CM11 (from stock.) I've noticed since going to CM11 my battery doesn't seem to last as long as it used to. I started looking into what's causing this and came across some things, however I also noticed something else.
The other day my phone showed it was about 78% charged in CM11 then I rebooted into recovery mode to do a nandroid backup. At first TWRP indicated my battery was 99% charged, which I knew wasn't true. After the backup ran for a few minutes, I noticed it showed about 62% charged (down 16% from what CM11 last said.) After the backup finished and I booted back into CM11, it showed my battery was at around 75% (lower than what CM11 previously showed which is to be expected, but higher than what TWRP showed.)
Later that day I had partially charged my phone a few times, never left it on the charger long enough to get a full charge. At one point my phone showed about a 49% charge in CM11 then I restarted it for one reason or another, and after restarting CM11 showed my battery was only 14% charged. This was just a normal reboot, off then back on, I didn't go into recovery or anything and the reboot only took a few minutes.
So my question is this... does anyone have any idea what would be causing these discrepancies in the battery charge indicator, and how to fix them? It feels like CM11 shows a fuller charge than what the battery really has (which could explain the TWRP difference), and like CM11 thinks it's 100% charged when it's only actually 70-80% charged (which would explain why my battery doesn't seem to last as long as it used to.) This still wouldn't really explain why CM11 went from 49% to 14% after just a reboot though, and this wasn't the first time I've seen big drops in my charge over a short period of time.