Whew, I doubt the battery is bad or at least you are unlucky. FYI, when you go to the Apple store bring along your charging cable and charger. There's an article on MR that indicates some charging cables are susceptible to corrosion or outright fail to work. If that's the case you may not be getting a proper connection.
According to the article, Apple is aware of the problem and if a lightning cable fails it's replaced free of charge.