Have you tried recalibration yet? People say it doesn't work but always has worked for me.
1. Kill your battery to zero.
2. Leaving the phone off, charge it to 100%
3. Turn it on with it still at 100% and download the battery calibration app (assuming you're rooted) and press the calibration button. 4.Restart it and pull the charger as soon as the screen shuts off.
5. Use the phone until it dies and shuts itself off.
6. While dead, plug in charger and turn it on. Wait til it hits 100% or keep it plugged in for at least two and a half hours.
7. Unplug it and should be working just fine! If not, it's a hardware issue.
I've had problems with the battery meter with some ROMs, so it could help by doing a full wipe and installing another ROM or the same one.
I hope this helps, cheers!