The Smart Battery Case -- priced at $99 -- comes in either white or charcoal gray, and according to Apple, will increase talk time to up to 25 hours, browsing time to as many as 18 hours on an LTE network, and adds an unspecified amount of additional time for audio and video playback.
Apple currently claims that the iPhone 6S will handle up to 14 hours of talk time on a slower 3G network, up to 10 hours of Internet usage on LTE, and as many as 11 hours of high-definition video play.
The secondary battery is packaged into a bulge on the back of the case, making it resemble Lon Chaney's Hunchback of Notre Dame.
When the iPhone is connected to an electrical outlet, it charges both the internal and external batteries simultaneously.
iPhone battery cases are not new -- although this is the first from Apple itself -- with options available from such third-party vendors as Morphie, Otterbox and LifeProof. Most of those cases, however, double the overall profile of the iPhone.
They're also less expensive in some instances -- not a shock to long-time Apple product buyers -- with Morphie's juice pack reserve running $60, for instance. Otterbox's Resurgence Power Case, on the other hand, is the same price as Apple's new offering, but claims more talk time.
The Smart Battery Case can be ordered from Apple's online store, with delivery as soon as Dec. 10. In-store pickup is also available in many locations.