Erratic battery on iPhone 5

Question

I've being experiencing erratic battery behavior since before installing ios7 but it got worst since.
Basically the battery charge drops dramatically (this morning: from 50% to 0 when the phone stopped completely and shut down, in the space of 20 minutes, without me doing anything special) only to be told once I plug the iPhone to electricity that the battery is at 35% of its battery charge.
Any ideas? Anyone have the same problem?

Answer 1

I'm having the same issue, but only since installing ios7.  It's gotten worse today. 
I was fully charged at 1:30p, listened to music until 3:30, and went to 85%. 
Put it in standby, and by 5pm had gone down to 45%. 
By 9pm, I was down to 30%. 
Within a few minutes after 9pm, I got a 20% power warning, and the phone immediately shut down.  When I tried turning it back on, it said I had to plug it into a power source. 
After 10 minutes shut down without charging, I turned it back on, and it said 30% power, then immediately went to 1% and shut down again. 
After a few minutes, again, I turned it back on, and it was at 30%. 
After 5 minutes, it was at 19%.  It went down 1% every few minutes until it got to 8% and shut down again.
I turned it back on at about 10:10pm and it was at 21%.  By 10:50 it was down to 13%.
What in the **** is happening?