A few days back I noticed my phone just shutdown when I had 25-30% battery. It wouldn't switch back on till I charged it again. Since then it has gotten progressively worse, switching off at 40%, 50% and yesterday I noticed it went off at around 60%. I thought it could be the ROM I was using, but that was fine for months. Maybe an app, I tried to figure out what could be causing the issue, but to no avail. Last night I switched to Cyanogenmod but the issue still occurs. Has my battery gone?