The release continues, saying that “outside the affected batch, a small number of customers reported an unexpected shutdown." Fortunately, the issue isn’t a safety concern, and will likely be sussed out through a new diagnostic feature to be rolled out during next week’s iOS update.
“This feature collects a variety of information in the coming weeks that may help us improve algorithms for managing battery performance and shutdown operations. If such improvements can be achieved, we will deliver them through further software updates,” Apple notes.
The iPhone 6s battery debacle is the second major challenge Apple has faced this month, after the company acknowledged its “touch disease” problem, charging customers a $149 fee to participate in a different replacement program. Still, there are no safety issues to be worried about for iPhone 6s users, unless, of course, you're using a shoddy, counterfeit charger.