How to fix my iPhone 4 battery?

My iPhone is like 5 months old and the battery sucks. It dies very quick. It will die on like 50% an then when I plug it in it will be on 50%. When the phone dies on 10%. It will take about an hour for it to turn back on. I don't know what I should do but I need the battery to be fixed

The fact that it is only charging by 50% would point to the charger. Get a new charger and see if that takes care of the problem. If not, you will need a new battery. However, smart phones are not known for battery life.

Change your battery and charger and it should be alright and wait for it to charge up to 100% and then plug it out. Put it back for charging after the power has come down to 0% and switches off. If you are out then buy a portable charger as it looks good and acts as a phone cover and when your battery has drained out u simply need to turn it on and charge it and it doesn't cost much but worth every penny as it helps me out too. Glad I could help you out.