iOS 12.1 Extends Battery-Related Performance Management Feature to iPhone 8, iPhone 8 Plus, and iPhone X

Apple on Tuesday released iOS 12.1 following six weeks of beta testing. As mentioned in the release notes, the software update extends Apple's performance management feature to the iPhone 8, iPhone 8 Plus, and iPhone X.

iphone x battery
From the release notes:

Adds a performance management feature to prevent the device from unexpectedly shutting down, including the option to disable this feature if an unexpected shutdown occurs, for iPhone X, iPhone 8 and iPhone 8 Plus.

Apple has reflected this change on its iPhone Battery and Performance website, noting that performance management "may be less noticeable" on those iPhone models due to their "more advanced hardware and software design."

The performance management system was first enabled in iOS 10.2.1, but it was limited to the iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPhone SE, iPhone 7, and iPhone 7 Plus until yesterday's release of iOS 12.1.

Last December, Apple did mention that the design of the iPhone 8, iPhone 8 Plus, and iPhone X allows for a "different" performance management system that "more precisely" prevents unexpected shutdowns, but prior to iOS 12.1, no performance management feature of this kind had been enabled on the trio of iPhones:

iPhone 8 and later use a more advanced hardware and software design that provides a more accurate estimation of both power needs and the battery's power capability to maximize overall system performance. This allows a different performance management system that more precisely allows iOS to anticipate and avoid an unexpected shutdown. As a result, the impacts of performance management may be less noticeable on iPhone 8 and later. Over time, the rechargeable batteries in all iPhone models will diminish in their capacity and peak performance and will eventually need to be replaced.

Why is Apple slowing down some iPhone models if necessary?

From our January 2018 article What to Know About Apple Slowing Down iPhones to Prevent Unexpected Shutdowns:

iPhones, like many other consumer electronics, are powered by lithium-ion batteries, which have a limited lifespan. As the battery in your iPhone ages, its ability to hold a charge slowly diminishes.

A chemically aging battery can also have increased impedance, reducing its ability to provide a sudden burst of power when demanded by other components in an iPhone, such as the CPU and GPU. A battery's impedance will also temporarily increase when it has a low charge and/or in cold temperatures.

A battery with a high enough impedance may be unable to provide power quickly enough to the iPhone when needed, and Apple safeguards components against the drop in voltage by shutting down the device.

Apple recognized that iPhones unexpectedly shutting down on users is not a good experience, and starting with iOS 10.2.1, it quietly implemented a power management feature to prevent these shutdowns. The update was released in January 2017, and a month later, Apple said it saw a major reduction in shutdowns.

The performance management feature can be disabled if desired in the Settings app, under the Battery Health menu. At this time, the feature does not appear to extend to the new iPhone XS, iPhone XS Max, or iPhone XR.

Top Rated Comments

1144557 Avatar
42 months ago
I'd be fine with it if the battery lasted more than a single year before needing it. In fairness it's probably only a small group where the battery is bad enough to need throttling but even so, for the price of the phone the batteries should have better longevity.
Blame battery tech not Apple. Apple didn't invent lithium-ion batteries. They simply chemically degrade over time due to charge and discharge cycles. No devices (not just smartphones) are immune from battery degradation. Same reason your cordless dustbuster/stick vac battery wont hold a charge after a certain amount of time; it has nothing to do with the device the battery is in but number or charge/discharge cycles.

Seems like a problem that could have been solved if Apple bothered to ship their phones with an appropriately sized battery...
Huh? What does battery capacity have to do with number recharge cycles and chemical degradation of a lithium-ion battery? ALL batteries degrade over time.


"The lithium-ion battery works on ion movement between the positive and negative electrodes. In theory such a mechanism should work forever, but cycling, elevated temperature and aging decrease the performance over time. Manufacturers take a conservative approach and specify the life of Li-ion in most consumer products as being between 300 and 500 discharge/charge cycles."

Temperature 40% charge 100% charge
0°C 98% (after 1 year) 94% (after 1 year)
25°C 96% (after 1 year) 80% (after 1 year)
40°C 85% (after 1 year) 65% (after 1 year)
60°C 75% (after 1 year) 60% (after 3 months)

So charge cycles and ambient temperature make a HUGE difference in life of a battery. And since no one keeps their devices at 0°C (freezing point) and factoring most charge the battery to 100% each time, a 20% degradation after 1 year per the chart is proven by science. It's not simply "Apple said"
Score: 19 Votes (Like | Disagree)
NexusUser Avatar
42 months ago
Seems like a problem that could have been solved if Apple bothered to ship their phones with an appropriately sized battery...
Score: 16 Votes (Like | Disagree)
neliason Avatar
42 months ago
Apple’s management of batteries across devices is odd. Why doesn’t iPad have a low power mode? More importantly why doesn’t iPad have a battery health report? These are important features for all devices and not just the one’s Apple decides to surreptitiously tinker with.
Score: 13 Votes (Like | Disagree)
gnipgnop Avatar
42 months ago
Why doesn’t iPad have a low power mode?.
Because the overall size of the battery plays a role in whether or not it can supply the proper voltage under certain conditions. The iPad battery does not have the same constraints as the smaller iPhone batteries.
Score: 11 Votes (Like | Disagree)
BulkSlash Avatar
42 months ago
Totally fine with me. Better than a phone becoming unusable, but of course they've should've been disclosing it and allowing users to toggle it on and off from the beginning.
I'd be fine with it if the battery lasted more than a single year before needing it. In fairness it's probably only a small group where the battery is bad enough to need throttling but even so, for the price of the phone the batteries should have better longevity.
Score: 9 Votes (Like | Disagree)
Nicksd84 Avatar
42 months ago
Totally fine with me. Better than a phone becoming unusable, but of course they've should've been disclosing it and allowing users to toggle it on and off from the beginning.
Score: 8 Votes (Like | Disagree)

Popular Stories

iPhone 14 Mock pill and hole thumb

ProMotion Now Expected to Remain Exclusive to iPhone 14 Pro Models, Not Expand to Entire Lineup

Sunday January 16, 2022 8:56 am PST by
Continuing the tradition set with the iPhone 13 Pro, only the highest-end iPhone 14 models will feature Apple's ProMotion display technology, according to a respected display analyst. Ross Young, who on multiple occasions has detailed accurate information about Apple's future products, said in a tweet that ProMotion will not be expanded to the entire iPhone 14 lineup and will remain...
safari icon blue banner

Safari Bug Allows Websites to Track Your Recent Browsing Activity in Real Time [Updated]

Sunday January 16, 2022 3:37 pm PST by
A bug in WebKit's implementation of a JavaScript API called IndexedDB can reveal your recent browsing history and even your identity, according to a blog post shared on Friday by browser fingerprinting service FingerprintJS. In a nutshell, the bug allows any website that uses IndexedDB to access the names of IndexedDB databases generated by other websites during a user's browsing session....
ipad air 4 video

New iPad Air Rumored to Launch This Spring With A15 Chip, 5G, Center Stage Camera, and More

Saturday January 15, 2022 8:05 pm PST by
Apple is planning to release a fifth-generation iPad Air with similar features as the sixth-generation iPad mini, including an A15 Bionic chip, 12-megapixel Ultra Wide front camera with Center Stage support, 5G for cellular models, and Quad-LED True Tone flash, according to Japanese blog Mac Otakara. Citing reliables sources in China, the report claims that the new iPad Air could be...
Unlikely Products 2022 Feature

Six Rumored Apple Products You're Unlikely to See This Year

Saturday January 15, 2022 2:06 pm PST by
Much has been said about what consumers could see from Apple in 2022, but the company is also working on a handful of rumored products that aren't expected to be unveiled for at least another 12 months, and in some cases a lot longer. Of course, that's assuming they get released at all. Apple works on many potential products some of which ultimately never see the light of day. With that in...
AirPods Pro Gen 3 Mock Feature Red

AirPods Pro 2 Could Start a New Accessory Ecosystem

Friday January 14, 2022 2:34 am PST by
Apple's second-generation AirPods Pro could arrive alongside a new series of accessories, recent leaked images suggest. Alleged leaked photos of the next-generation AirPods Pro obtained by MacRumors showed a charging case with a metal loop on the side for attaching a strap. Apple has not used this design for any of its other AirPod models and it is unclear why it would be added in this...
netflix2

Netflix Again Raises Prices for All Plans, 4K Streaming Now $20 Per Month

Friday January 14, 2022 12:46 pm PST by
Netflix today updated the prices for its streaming plans, and all of its offerings are now more expensive. The Basic plan is now priced at $9.99 per month, the Standard plan is priced at $15.49 per month, and the Premium plan is priced at $19.99 per month. The Basic plan is $1 more expensive, up from $8.99 per month. This plan allows users to watch on just one screen at a time, and it limits ...
tesla carplay solution

Developer Showcases Apple CarPlay Workaround for Teslas

Monday January 17, 2022 7:24 am PST by
A Tesla Model 3 owner has resorted to a workaround to implement Apple CarPlay in his vehicle, amid no sign of official support from Tesla (via Tesla North). Apple CarPlay and Apple Music support are among the most-requested Tesla features, but with no indication that Tesla is willing to implement Apple CarPlay in its vehicles, Polish developer Michał Gapiński took matters into his own...
top stories 20220115

Top Stories: iPhone 14 Pro Rumors, iCloud Private Relay Controversy, iOS 15.2.1 Released, and More

Saturday January 15, 2022 6:00 am PST by
Hole-punch? Pill? Hole-punch and pill? Rumors about what the front camera system on the iPhone 14 Pro will look like are evolving rapidly, and it now appears we might be getting a novel but potentially controversial design later this year. Other major stories this week included some confusion and controversy about iCloud Private Relay being disabled for some T-Mobile customers, increasing...