Why does my iPhone 5 battery draining like crazy?

It was on 80% like 20 mins ago and now it's already on 71%. I have all my apps closed. I'm using 3G because it's important. Location services are off. Bluetooth is off. I've tried everything and nothing's improving.

It could be that you have background processes running, but I'm not sure how to fix this on iOS. It's quite likely that your battery just doesn't have the charge capacity it used to - if you use it while it is charging then this could be the problem. If all else fails, you can get batterys of ebay, and you'd have to get it fitted.