iPhone 5 battery doesn't last?

Sounds like a wide spread issue with iOS7.1. Just Google it.

There are only 3 reasons for battery drain. 1) Background apps. 2) Aging battery. 3) Short circuit. But if it's #3, your phone will overheat in no time. No way your battery is old so it's not #2. That leaves #1, which goes back to iOS7.1 update. I believe your phone and battery are fine, but Apple screwed up the latest update. Many Android devices have battery drain too due to the inability to deep sleep for some unknown reasons.

Iphone Battery Does Not Last

Smart phones are power hungry. But its like turning a light on -if you want to save power, turn it off.

In the iphone, the way to turn off the things that you don't use is simple:

Go into settings and check for the following:

Bluetooth - turn off when not needed. IOS updates for some reason turn the blue tooth on without your permission

Notification Center - go into the individual apps that you really don't need constant notification from, and turn them off. You can still access manually when needed. You will save a ton of batter space by turning the notification off (I went from barely one day battery to three days with most notifications turned off!)

Apps - Just check the individual aps and make sure there not active unless you need them

Get him to complain about it so they repair it, then give it back to you.