Default [Q] Tablet turning itself off around 15%

Hey guys, I've been experiencing some issues about my Tab 2's battery. It all started some hours ago.
I was chatting with a friend, then it suddenly turned off. I knew something was wrong, because it wasn't even near 4% yet.
Plugged it to the charger and couldn't turn it on before waiting at least 10 minutes. When I turned it on, I took the cable off and quickly opened an app to show battery stats. Something caught my eye.
With 17%, the battery had almost 3000mV, and that was really weird (I've heard it should be around 3370mV at this percentage).
What should I do? Calibrate my battery is a choice?
Device: Samsung Galaxy Tab 2 7.0 (Wi-Fi)
CyanogenMod version: 11-20140906-NIGHTLY-p3110
Android version: 4.4.4
Kernel version: 3.0.31-CM-g9b3f943
Build number: cm_p3110-userdebug 4.4.4 KTU84Q d4dba7c401 test-keys
Recovery: CWM