If your iPhone 5 can't hold a charge, you may be able to get a new battery for free, starting this Friday, Apple says.

The company has determined that "a very small percentage" of iPhone 5 smartphones may "suddenly" have a shorter battery life or need to be charged more often, Apple acknowledged on its support website.

The affected devices were sold between September 2012 and January 2013.

IPhone owners who have already paid for a replacement battery can contact Apple for a refund, the company says.

Affected devices are identified by their serial numbers, and Apple is providing an online serial number checker to help iPhone owners figure out if their phone has the battery problem.

The company has already started replacing batteries for users in the U.S. and China. Those in Canada and the rest of the world will be able to get a new battery starting Aug. 29 by:

Visiting an Apple authorized service provider.

Making an appointment at an Apple Retail Store.

Contacting Apple Technical Support by phone.

The company asks users to back up their data to iTunes or iCloud and erase it from the device itself before replacing the battery.