Apple has unveiled a battery case it has designed for the iPhone 6 and iPhone 6s, offering protection and up to 25 hours additional talk time.
Apple has steered clear of bigger batteries in the iPhone, chiefly to keep it light and slim, even if it knows that means the device needs charging more frequently.
However, for customers who want a longer battery life, Apple has released the new Smart Battery Case for its latest iPhones.
Similar to its existing iPhone covers, the external surface is made of silicon. But it includes a battery of an unspecified capacity that it claims will offer an extra 25 hours of talk time, 18 hours' extra internet use on LTE, and video playback of up to 20 hours.
If the battery case lives up to Apple's claim, it would more than double an iPhone 6s' battery life of 14 hours talk time on 3G.
The battery itself sits in a raised block on the back of the cover, which otherwise hugs the original form of the iPhone in the same fashion as Apple's standard silicon protectors do.
It's a different approach to the popular but bulkier mophie Juice Pack Air case, which costs $99.95 and £90 in the UK.
Being an Apple-branded accessory, it also has the advantage of tighter integration with iPhone software and other accessories.
As Apple notes, with the Smart Battery Case on, the iPhone Lock screen and Notification Centre will display "the intelligent battery status", telling users exactly how much charge is left.
The battery case also supports Lightning to USB cable connections and works with the iPhone Lightning Dock.
Apple says that online purchases made today should be delivered between December 10 and December 14. In Europe orders will be delivered in one to three days.
While Apple hasn't revealed details about the battery, it has published the conditions under which it tested a preproduction version of the case.
"Testing conducted by Apple in October 2015 using production iPhone 6s units and software paired with preproduction iPhone 6s Smart Battery Case units and production software. Video tests consisted of repeated playback of a 2-hour 23-minute movie purchased from the iTunes Store.
"Internet tests were conducted over 3G, LTE, and Wi-Fi networks using a dedicated web server, browsing snapshot versions of 20 popular web pages and receiving mail once an hour. Talk time tests were conducted by placing a cellular phone call.
"All settings were default except: Wi-Fi was associated with a network for all but the Internet 3G and Internet LTE tests; the Wi-Fi feature Ask to Join Networks and Auto-Brightness were turned off. All battery claims depend on network configuration and many other factors; actual results will vary."