My iPhone 5 (1 year old now) has started having a battery problem since I upgraded to IOS 7. It will shut itself off under these circumstances:

battery is below 40%

I take a number of photos using the Apple Camera app

photos taken in rapid sequence (no flash) or one or two taken with flash





The next thing I know I see the radar symbol and the phone shuts off. If I try to turn it on I get the drained battery icon with the power plug moving into the screen an it turns off.





I then plug it in to turn it on and find that the battery is still around 30%. If I am not near my charger, I can wait about a half hour and power the phone on. I just did that and the battery is at 29%.





What is going on? This is not right. I've never seen this before and have had 2 other iPhones. Any thoughts or ideas appreciated.