Older devices are no stranger to battery issues. As iPhones are charged and discharged, the battery will naturally lose some capacity over time. Apple has recognized that a range of iPhone 5 units with specific serial numbers can suddenly loose their charge.
For those experiencing the problem with their iPhone 5, Apple has offered to replace the battery free of charge. Since a specific range of serial numbers is affected, the company has set up a web page that makes it possible to check your device for eligibility under the replacement program.