Likely you have a faulty battery. My girlfriend had the same thing and they simply gave her another battery.
Your best bet is to:
1) Call apple, tell them the problem and you will get a case number.
2) Make a genius appointment
3) When you arrive let them know about the case number. This will speed things up and hopefully you will walk away with a new battery.
There's also the possiblilty that when you call apple they will send you out a battery. It's more or less up to you and what's convenient for your lifestyle. But in my experience visiting the genius bar, it's always best to have a case number.
Cheers, Tom