Why won't my iphone 5c work unless its charging?

As soon as i unplug it, it only lasts about 1 min & then it turns off so i have to plug it back to use it. I've already tried hard powering ( holding down the home & power button) & also letting it charge for hours so it not that… What should I do?

Battery is probably dead take it to the dealer where you bought it

If its under warranty return it