Apple has discovered a flaw on the batteries of what they are saying is “very small percentage” of iPhone 5's can led to the phone “suddenly experiencing shorter battery life or need to be charged more frequently.” The affected iPhone 5 units were originally sold between September 2012 and January 2013.
For those impacted by the flaw the replacement program will be available at Apple Retail Stores,
Authorized Apple Service Providers, and via AppleCare. To find out if you're eligible, Apple has a serial number checker here.
Apple recommends that all iPhone 5 owners backup their data, turn off Find My iPhone,
and erase all content and settings before visiting their Apple Store or returning the phone to have the battery
system replaced. Apple says it won’t repair phones with other problems
like cracked screens. If you’ve already paid to get your battery fixed
(and you’re eligible for this replacement), Apple is offering refunds.
This iPhone 5 battery replacement program is the second time Apple has had to use the replacement program to fix the iPhone 5 this year. Previously Apple offered to fix units affected by sleep/wake button issues.