Help Phone shuts down

[VegasLakers]

If I use the phone for a decent amount of time, it shuts down. I had the phone for a few months and its only happened recently. If I try and access battery use, it shuts down. I thought it was the battery so I bought a new one and the same problems happen? Do I need to reset it or something? Any help is appreciated.

 

[sinisin]

Are you rooted? If you are check out Battery Calibration on the Market. If not, sounds like a warranty issue to me.