Have the Samsung Galaxy II, it's a little more than a year old.
Within the last 10 days or so, it's started acting up. With ample battery life (>70%), the phone will occasionally shut down and show 0% battery life. This only happens when I'm working in an app or browsing the web. If i'm away from a power source, the phone is useless.
I went to see the Samsung rep at Best Buy and he updated my phone and checked to make sure I didn't have a wonky app that was causing the problem. Still have the problem.
Do I need a new battery? Is the phone kaput?