One of the reasons is that it slows down is because the battery is actually not able to deliver enough power to run at full speed. My iPhone 6S would randomly shut down when I was using significant power (I.e a CPU hungry app) even at 70+%. When I got to less then 40% almost any app could cause a sudden restart. Apple apparently fixed this problem in a software update by limiting the power the devices draws, which fixes those random restarts for the most part but slows it down significantly.

Fortunately, I could replace my device because that was the case (I went to Apple and they replaced my battery after they did some extended tests because they were aware that a “small number of iPhone suffered from this issue and they tried to find out which ones“). Sure enough, about one or two months later I checked my old serial number and apples website told my that my old phone was eligible to be replaced.

This seems to affect the iPhone 6 and 6s the most. According to geek benchmark my used iPhone 7 is at 80% speed when it has about 50% battery remaining and at pretty much full speed when my battery is fully charged.

I had one of these phones too - it was a bad batch of serial numbers according to Apple. If this happens to you: https://www.apple.com/support/iphone6s-unexpectedshutdown/

I was referring to that (my old serial number did show up as eligible but I had it replaced before that).

Apparently all phones suffer from that problem but the batch we referred to seem to be especially bad. The software update just seems to have mitigated the effects of iPhones which were mostly ok but shut down occasionally (and the effected ones which shut down almost every week when it was at 70% and about once or twice a day at 20-30%).

The slowdown is related to battery health. For some devices, it starts happening after a year; for others it takes longer.

Replacing the battery restores normal performance. You don‘t need to go to an authorised repair shop.

If something like:

"In order to maintain the battery life you are used to, we had to introduce limits on your iPhone. This is because by time batteries unfortunately lose their capacity. Your phone will be just as new if you take it to our stores and get the battery replaced"

would be communicated, it would be nice. In my opinion. btw batteries usually also have a year of warranty, so there really should be a way to check it's performance.

But essentially infeasible. Most of us cannot spare to not have the phone for even a day. Say what you will about our dependence on the devices, but it's a practical problem.

You can do both, show the warning and implement performance limiting. The information would be nice (if not outright essential/ethical)

Any responsible manufacturer would notify users about faulty hardware and not try to hide the problem.

It's not considered faulty, more like degraded over time. So the CPU is throttled when the battery is no longer optimal to preserve battery life?

I rather have shorter battery life with same performance so it's more noticeable that I need to replace the battery.

Apple says that if they don't throttle it then phone can suddenly shut down (battery overheats, fail-safes shut the power so it doesn't explode) under certain circumstances, which is perceived as fault by end user.

I would like to be informed of this "Your battery is starting to fail". Same way as SMART monitoring in disk drives tells you that it degraded too much and will break soon.

Or have a switch.

I don’t think this is about us having a better experience though. It looks like a strategy to sell new devices by making the old ones obsolete.

I hope we see a class action.

> It's not considered faulty, more like degraded over time.

> I rather have shorter battery life with same performance so it's more noticeable that I need to replace the battery.

I agree, but something is odd about this whole situation.

I have an iPhone 6, iPhone 5, iPhone 4, a 2nd generation iPod Touch, and several Android phones.

The iPhone 6 is the first one I've seen randomly turn itself off when the battery level was below 30%, all of the others would run normally even when the battery condition was poor. I could continue using them normally while the battery indicator ticked down to 1%.

While my iPhone 6 no longer randomly turns itself off, it frequently doesn't respond for 15+ seconds when typing a letter on the keyboard or tapping a text field, it's essentially just as unusable as if it had turned itself off.

What makes me suspicious is that I have a 2nd iPhone 6 here at the moment with a similarly aged battery in fairly poor condition. It doesn't randomly turn off, and the performance difference is immediately noticeable, it's actually usable. The only real difference I can identify is that it is still running an older version of iOS.

Batteries degrade over time. I wouldn't classify that as faulty hardware. I would say it's faulty design (battery should be easily replaced) and faulty communication though.

If replacing the battery restores normal performance, can connecting a charger also restore normal performance?

Because iPhones don't really have user serviceable batteries, I wonder if an after market battery charging case would provide more speed with a new battery pack.

No. Plugging it in makes no difference. The only way performance increases is if you increase the charge in the battery, in my experience.

From what I've been able to tell, plugging the phone in helps in some cases but there are a lot of cases where it does not help.

(That's from reading around on the internets. I only have direct knowledge of my own situation, where plugging my phone in did not help but replacing the battery did.)

How do you know when it's time to replace your battery?

My guess is that most of the billion iPhone users have no idea, and they really don't want to invest much time into figuring it out.

Can’t find the post. But this was asked on Reddit the other day and the user got a three paragraph response on how to ‘simply’ monitor battery performance. Also included was optimal charging methods — common sense right? I just want to use my phone without having to worry about if my battery needs to be replaced or not. Just tell me. Like on the Mac that my battery is degraded and should be replaced.

My battery is at 87% of its original capacity and the phone runs at 50% of its original CPU speed.

ETA: Point being, this doesn't appear to actually be limited to batteries that have seriously degraded.

As an iPhone 6 user I downloaded a an app called CPU Dasher X and found that my CPU was being throttled to 600MHz once it fell to around 40% charge. Not great. Now looking at a battery replacement (~£40)

Nobody has explained why this was suddenly needed with the iPhone 6 and above. It's not like the iPhone 5 didn't have a battery.

While average power draw for a given task for mobile chips has stayed similar or declined over the last few years, peak draw has gone through the roof. It's quite plausible that the iPhone 5's SoC just never drew enough power at peak for this to be an issue.

Normally this sort of issue is solved with a capacitor network. It's actually common to get them removed during a "cost optimization" stage because the device will still appear to work. Just with grately reduced reliability.

Any capacitor network will need some power to stay charged waiting for use. If peaks are rare enough, they won't be a reasonable choice.

The root of the issue is that the internal resistance of the battery is too high to supply current under peak load to the device. Anyone creating an electronic device has to perform these calculations and design a power supply that is sufficient. Its basic electrical engineering.

For extremely short duration peaks up to a few microseconds capacitors are a great workaround. They are necessary for pretty much every digital integrated circuit. A billion transistors all switching at the same time on the rising edge of a clock cycle has a massive instantaneous current draw.

> Anyone creating an electronic device has to perform these calculations and design a power supply that is sufficient.

Yes. And it does look like a case of undersized batteries. If I had to guess, I'd say it was because of too strict product design specifications meeting a lower than expected quality in manufacturing.

CPU power peaks usually last for a (large) fraction of a millisecond or more, because that's how the OS scheduler works. Added to that, peaks may not happen for entire minutes or hours. Both of those work against the usefulness of large capacitor banks.

Apple (like other manufacturers) is continually looking for ways to improve performance, whether that be cpu speed or battery life, or other metric. I don't think this has anything special to do with a particular model, only when they decided to deploy this particular feature.

It's extremely suspicious this coincided with a massive battery recall that caused unexpected shutdowns.

I'm not sure if I follow you here, particularly the use of "extremely suspicious", which makes me think that you believe something underhanded is going on. If so, would you just come out and say it? Innuendo doesn't generally promote useful discussion, and it's even harder on an online forum. Was this something you were thinking about when you wrote your initial comment? If that's not the case, please forgive me. I assumed your initial comment was a legitimate question, and answered in good faith.

If they are related (and perhaps they are, I wasn't thinking about the recall when I wrote my comment), do you think it's unreasonable for engineers at Apple to try to prevent unexpected shutdowns? I would think it would be unreasonable not to, once they saw the impact it was having on user experience. And that's besides improving the battery. The amount of engineering that goes on with respect to power and performance management is incredible, and attacking these types of problems from multiple angles is expected, particularly when you're looking to eek out even more performance in something that's already been through years of optimization iterations.

To be explicit I think this was done to limit the scale of the recall. I think the design flaw exists in all the phones not just the subset they identified.

Apple knew the peak draw of their SoC (they designed it). And they knew the capabilities of the battery. Under sizing the battery is exactly what I would call a design flaw.

This certainly seems to be the case from my experience. Same thing they did for previous recalls on MacBooks.

And how many people end up bricking their phone doing so? It’s not easy and I’m sure a lot of average users simply won’t as they’re afraid to even attempt to take it apart.

It's really great that Apple just removed that option eons ago.

but you need an original battery. Just replaced the battery that seems fake. And.. the clock reduced from 1127 to 600 Mhz instead of 1400 what was I'm hoping.

If only you could just pull the old battery out and put a new one in.

I know you think you're joking, but older vehicles typically lose compression as the engine ages, which will reduce performance pretty significantly. And yes, the engine can be rebuilt which replaces the worn-out sealing surfaces that are causing the loss of compression in the first place.

That's not the same thing. They're artificially limiting one component that's perfectly capable of functioning at peak performance to hide the degradation of another.

If your battery starts degrading while still under warranty how would you know other than "hmm... my phone feels slower than usual".

How does this throttling occur? Is it gradual or does it happen in large noticeable steps? My guess is that it's gradual throttling because it's taken this long for people to identify it.

Does the throttling only occur after the phone is out of warranty? Or is Apple hiding a potential warranty repair?

Do you think the ECU doesn't limit the performance as the engine ages to protect it from damage? Of course they do, just swapping the ECU in an old car for a brand new one will restore some performance, because the ECU starts supplying the stock levels of fuel/air mixture, at least until it learns that the engine is not performing as expected and cuts down on performance again.

The ECU isn't intentionally degrading performance, it's balancing the air to fuel to compression ratios for optimal combustion of fuels and reduced emissions. It's a dynamic systems and degradation in performance occurs as a result.

It's not intentionally handicapping the performance to hide the fact that your fuel tank can no longer hold the same volume of fuel.

And Apple is balancing the battery's voltage level with the CPU utilization for optimal reliability of the device.

I agree with everything you said – but will point out that modern cars, if they are not properly maintained will degrade in capability in an effort to prevent further damage. I was bad about getting oil changes and eventually my car had a limited ability to accelerate and a limited top speed until I got the oil change, it seemed to be clearly done by a computer control, rather than mechanical degradation.

All manufacturers face the same design decision - once the battery life declines, do you cut the CPU speed and keep the battery life, or do you keep the performance but the phone now dies halfway through the day. I'd say Apple took the correct approach here - 100% of your customers will notice their devices dying much earlier than expected, most customers won't notice the phone getting a bit slower. My mum never ever would for example, she only uses hers for making phone calls. If the phone app takes 2 seconds longer to open she doesn't care, she cares about having a phone that works all day long though.

I disagree - people do notice their phones gradually slowing down. They just live with it, because there's nothing they can do about it beyond buying a new phone, which is a large purchase best postponed (that is, if they're not on a contract - if they are, the burden is much worse).

This behaviour adds significant stress and annoyance to lives of millions of people. In my book, it's just evil.

As someone who lived with a phone that would run out of battery around 3pm when unplugged at 7am - I would have gladly traded that experience for a slight slowdown of the software. I can't believe that the "significant stress and annoyance" of having a slow phone is any worse than "significant stress and annoyance" of having a phone that just switches off. Slow phone > dead phone.

Fast phone + a powerbank > slow phone > dead phone.

Apple took away the ability to choose the powerbank option.

> If your battery is only reduced by 8% after a couple of years, why does the device have a artificial, significant decrease in performance after just one year?

You call the decrease artificial, but I don't see evidence of that. I'm not sure what your "reduced by 8%" number is -- capacity? -- but in any case, it wouldn't necessarily scale linearly with the amount of CPU throttling needed to make the CPU stable.

Also, I'm not sure where the "significant decrease in performance after just one year" is coming from. The article says performance starts to degrade after a year, which isn't the same thing. The article doesn't even have a cite for that (that I saw), so I wouldn't take that claim seriously yet.

Of course, I'm sure there are batteries out there that are aging prematurely, but that's not the same as a device being designed to degrade after a year. Personally, my iPhone 6 plus began slowing down really noticeably at close to three years old, which is acceptable, IMO.

But I think Apple needs to have iOS alert you that it's slowing your phone down because the battery has degraded. Then you know what to do: * If it's less than the normal service life of the battery (2 years, I guess), you should get a free battery replacement. * If it's later than that you can choose to replace the battery on your own dime. * Or you can choose to get a new phone after all.

By not telling people what's going on, people with a prematurely degraded battery probably won't know to get it replaced under warranty and people with normally aging batteries are more likely to buy a new phone rather than replace their battery.

>> But I think Apple needs to have iOS alert you that it's slowing your phone down because the battery has degraded.

I see so many Mac laptops with the service battery warning on. People won't replace them until they have to, even to the point of the laptop needing to be connected to the wall outlet to run.

It's exactly because they don't magically lose CPU speed because of battery issues; people can adjust to failing batteries if the device remains useful (even for phones with fixed batteries, powerbanks exist).

With iPhones, Apple decided to make the device less useful instead.

Mac laptops actually used to work in a similar way, however I'm not sure if that is still the case.

If you had a dead battery (or no battery), your CPU frequency would be limited because the AC adapter could not supply enough power on it's own

The link is dead, but it was documented on Apple's support site: http://support.apple.com/kb/HT2332

Tesla slightly understates battery capacity from the factory - to give future headroom and the appearance of less battery capacity.

In this case, are they 'guilty' of leaving extra performance/range on the table when the vehicle is new?

Tesla does not leave any headroom. If they did, then the car would appear to be able to charge to its original value for a while -- but it doesn't:

https://electrek.co/2016/11/01/tesla-battery-degradation/

What Tesla does do is pretend that the bottom 20% of the battery doesn't exist. That's because it's very damaging to use it at low charge.