What is wrong with the battery of my iPhone 5?

I have an iPhone 5 since two months and suddenly the battery drains quickly. I have to charge it at least twice a day and when I lock my phone, the battery still drains. At night it still drains so I can't use my alarm. Just within half an hour it gets from 60% to 48%. I still have warranty though.

Make sure you close any unwanted open applications. To close apps, you need to double click on the button below the screen and then click on the little red circle logo on the corner of each app.

Turn off Wi-Fi/Bluetooth when you're not using it as these drain the battery fast.

To preserve full life of a rechargeable battery its better if you let the device drain completely before doing a full charge.

You may have to replace the battery.

http://comparefroggy.tumblr.com/post/56876301264/whats-the-best-phone-in-the-market

Just replace it! It may be poor in quality, a bad phone battery is quite dangerous

You are running apps that continue to run in the background and use up the battery. Things like alarm clocks and such are often in this category. There's nothing wrong with the phone, you're just leaving too many apps running on it. Close the apps and the battery life will return to normal. You may have to sacrifice things like alarm apps, though.

If you turn the phone completely off (press and hold the button on top, then swipe the red button to shut the phone down), it will use essentially no battery power at all. Of course, then, your alarm apps and such won't work, either.

In other words, you can't have all sorts of apps running all the time AND have a battery that lasts for a long time. It has to be one or the other.

By the way, it is not necessary to drain the battery completely before recharging it. Doing so allows the phone to figure out how long the battery lasts, but it has no effect on the life expectancy of the battery.