Error code 21 iPhone 5

Hello world so i am facing an issue when trying to restore my phone to factory setting. Phone will not charge and it's stuck in dfu mode. Should i get a new battery or am i better off buying a new iPhone 5? Yes i have replaced the battery in the past and thought i was all set. But turns out that it just simply will not charge when i try and plug it in to another source. So New phone or give it one more try with the a new battery from amazon.