I had the same problem with less then year old Ipod Touch 5gen after installing IOS 7. The battery just wasn't the same anymore, and that's even after turning off backgound processes and location services and all apps killed in the background. Maybe times the device would just shut down in the middle of using it, once turned on to show there is still 30%+ battery life which then would drain down quickly.
I could just pull up Battery Saver app and watch the battery percentage drop by doing nothing.
I took it to Apple store and had the technician watch the battery go from 50% to 20 just wathcing the home screen in full brightness for few minutes. Then turn off the device, turn it back on and batter would show 50% again and then continued to drop until the device just shut down on it's own.
I was told it was a bad battery 😟 Very odd since it was less than 1 year of device and also a month earlier (prior to installing 7.0) all was well. Didn't feel right that a battery could just go bad in 1 year normal use.
To make the story short, since I still had 4 days for the warranty on the device I was given a new device right on the spot running IOS 6.0. It's been 2 weeks and I am still sticking with IOS 6.0 . I am getting 9 hours+ between charges with same regular daily use as before which is what my experiance was prior to IOS 7.
Don't take me wrong, I enjoyed IOS 7 enhancements but if I had to pick between reliable battery performance and ios 7, for NOW I will sit tight on IOS 6 until all these kinks are ironed out of the OS.
I really hope that Apple comes out and figures out what exactly is happening here and fixes it. If I didnt run into this first hand I would think all these people here are just making this stuff up but this is a real issue and Apple have yet to admit it. Hope this gets corrected soon.