On 28 December 2017, Apple responded with "A Message to Our Customers about iPhone Batteries and Performance", a carefully worded clarification and apology. Frequent unexpected shutdowns can make the phone unreliable and unusable. Apple will be able to generate about $1.56 billion in revenue from the estimated 54 million battery replacements, but that will not be enough to offset the potential lost sales.
Apple sought to clarify its long-rumored battery problem and how to fix it in a December 28 message to concerned and outraged customers, acknowledging that "there's been a lot of misunderstanding about this issue".
Apple also says it will cut the price of a battery replacement by $50 to $29.
Getting battery replacement on your old iPhone models can actually make a lot of difference to the overall performance of the device.
Here's what I'd suggest: if you've got anything older than an iPhone 7, get the $29 battery change next time you're anywhere near an Apple Store.
However, Apple announced in a statement that the effort was created to prevent sudden shutdowns caused by aging batteries.
Unbeknownst to iPhone 6, iPhone 6 Plus, and iPhone 6s owners, Apple inserted code into iOS 10.2.1 that deliberately slowed down the processing performance of these phones by linking each phone's processing performance with its battery health. When that happens while the battery is already low - 30 or 40 percent - the iPhone can just shut down.
Further, if you want more information than a simple pass or fail test result or don't feel like asking Apple Support to know your battery's health, there is this third-party app called Coconut battery.
To apologize for the issue, Apple reduced the cost of out-of-warranty iPhone battery replacements to only $29, from the original price of $79.
Conversely, you could also send your iPhone to Apple by mail, though you'll have to foot the bill for shipping.
There's also online tech support from Apple that shows options: Bring it to a store, send it in for fix, and, according to news accounts, owners also can take phones to authorized fix shops, such as Best Buy.
Apple also promised that it will release an update to the iPhone's operating system, iOS, to add features that will give users more visibility of their devices' battery health. The Apple Store has all of the tools and resources required to run a diagnostic test on your phone's battery. As my Genius explained it, you can't get in the queue for a replacement battery until a Genius has signed off on your order - so there's no way to avoid two trips. It's possible that's just a miscommunication between Apple Corporate and individual stores.
The iPhone battery, starting with the iPhone 6, uses a lithium-ion technology.
Now that you're armed with the info needed to measure capacity and even charge cycles, you've got to decide when to get that new battery.