The iPhone 6S battery replacement is now offered free of charge by Apple, who blames "ambient Air" exposure of its battery components, which resulted in unexpected shutdowns. Apple will also include a diagnostic capability in its iOS 10.2 update next week, which may indicate that the battery flaw issue may have affected more Apple devices than what was previously reported.

The iPhone 6S battery replacement comes after a series of reports by users of unexpected shutdowns of their Apple devices. The tech giant has now pinpointed the problem and the affected devices, identifying iPhone 6S manufactured between September to October 2015 as having battery components exposed to "controlled ambient air."

The battery components were left exposed to outdoor air far longer than necessary before being assembled in a battery pack of the iPhone 6S. This resulted to the battery degrading faster than usual, thereby causing an unexpected shutdown.

Apple also stressed that the iPhone 6S battery replacement stems from a battery flaw and not a "safety" issue. After the Samsung Galaxy Note 7 debacle, the Cupertino giant wants to assure consumers that the iPhone 6S and all other Apple devices are safe.

The iPhone 6S is designed to shut down automatically in cases when the electronics experience low voltage, The Verge reported. For those with iPhone 6S, Apple advises a visit to the local Apple store to verify eligibility for the iPhone 6S battery replacement.

Once verified, a new iPhone 6S battery will be ordered, which will take a week to arrive. Users will be instructed to back-up the phone, turn off Find My iPhone and then drop off the iPhone 6S when the battery arrives, taking an hour or two for the battery to be replaced, Macworld reported. 

However, the problem may be bigger than what Apple previously reported. Last Friday, Dec. 2, Apple posted the iPhone 6S battery replacement announcement on its website, offering a tool where users can check if the serial numbers of their iPhone 6S make them eligible for the offer.

Then on Monday, Dec. 5, the company posted in its Chinese website that a diagnostic capability will be included in its iOS 10.2 software update, rolling out next week. Apple has admitted that there other Apple devices like the iPhone 6 that are having the same battery issue even if their phones are outside of the timeframe provided.

This does not bode well for Apple devices, which were recently plagued with another flaw, known as the "touch disease" where iPhone 6 touchscreens have been unresponsive. Nonetheless, Apple has been offering the best customer service as confirmed with its swift response with the iPhone 6S battery replacement.