IPhone 5 battery dying at 30-40 percent?

I received this phone knowing about the battery problem, but it's starting to really get on my nerves. My battery dies at 30-40 percent and will rarely make it under 30. Any solutions besides getting a whole knew battery?

Let the batter run down until the phone turns off, then recharge it immediately. That will allow the phone to measure the battery capacity and it might give a more accurate indication thereafter. But if there's really a battery problem you might need to get the battery replaced.