Apple has determined that a ‘very small number of iPhone 6s devices may unexpectedly shut down.’ The problem affects a limited range of serial numbers manufactured between September and October, 2015. If you’ve experienced unexpected shutdowns, contact an Apple Store, authorized service provider, or technical support. If your iPhone qualifies Apple will replace the battery free of charge. If, however, your iPhone needs other repairs that would impair the replacement of the battery, like a cracked screen, those repairs must be completed for the standard applicable fees before the battery is replaced. In addition, if you paid to have your battery replaced before the replacement program began, you can request a refund from Apple.
This is the second repair program announced in the recent past. Less than a week ago, Apple instituted an iPhone 6 Plus repair program for phones that lose touch sensitivity. That program carries a $149 repair fee because Apple says the problem is caused, at least in part, by dropping the phone repeatedly on a hard surface.