Is there somethings wrong with my Samsung Rant?

I charge the phone last night so its been charging for like about 10 hours. but after i took the charger out for about 30 mins, the battery goes down really fast. why is my phone does that? it did that yesterday too when i first for the phone =/





please help.Is there somethings wrong with my Samsung Rant?
take it to sprint and see if you can get a new rant.. you might want to wright down all your contact cuz you might loose them