iPhone Performance and Battery Age

Last week, we ran a post titled iPhone 6s running slow? Consider replacing your battery.

In response to the referenced reddit thread, Geekbench founder John Poole did some testing. If the battery/performance issue is of interest, this is a fascinating read.



  • Meaux

    Doing this without informing users (and giving them a chance to downgrade OSes), is very user hostile. As the article mentioned, it only encourages belief like forced obsolescence even if that isn’t the intent.

    • Horse shit.

      Your phone shutting off without warning is user hostile.

      Anything that avoids that is useful to the user.

      • Meaux

        Then tell the user why it’s doing it. It’s not so hard. Using a slowed down device was a horrible experience.

        • David Stewart

          There are countless performance and optimizations decisions like this in any OS. Should the user be asked about each one every time a decision is made? Would the average user even understand the issues enough to make this sort of decision?

          • Meaux

            Except you go from a device running 10.x that works perfectly fine and maybe has an unexpected shutdown once a month to a phone that is running 11.x and is horrible to use all of the time. I’ll take the uncommon catastrophic failure over constant terribleness. Judging by people’s complains, it seems like I am not alone.

          • One shut down this month, four or five next month, one a day the month after, several times per day shortly after that.

          • Meaux

            “Replace your battery” pop-up.

          • And shut down multiple times per day?

            No thanks.

          • Meaux

            I didn’t have multiple shutdowns a day or even a month.

          • You should thank the capping algorithm for that.

          • rick gregory

            Ohhh drama! iOS 11 runs fine on my 6S plus even with a degraded battery. But let’s #kermitflail and declare it’s unusable.

          • Meaux

            Look at the charts on the link. It’s clear it’s not isolated.

        • Those are literally the options: draw less power or have the phone die.

          • Meaux

            You can inform and give the user the option (low performance mode). You can allow the customer to deprecate the OS (I refuse to upgrade my corporate phone for this reason). You can provide a battery replacement warning. You can fix the power meter calibration for old batteries (the issue was unexpected shutdowns when the power meter was at 40%). Prior to the OS, people got used to full speed and the amount of the day that their phone lasted and could work around that. You can’t adjust to a super slow phone.

          • rick gregory

            I do agree that they should give something like macOS ‘service battery’ warning on iOS. But if they do that I do NOT want to hear people whining about the battery needing servicing… though you know we will hear precisely that.

          • Meaux

            How many people complain about the macOS warning?

          • rick gregory

            Come on… you KNOW people will complain. “Android doesn’t do this, iPhone sucks!!!”

            The macOS warning is unobtrusive. And people seem to understand that old batteries wear out on laptops but for some reason throw hissy fits when they have to deal with it on iPhones.

          • Meaux

            Some people will complain, but all complaints are not equal. There’s random pissing and moaning in message boards and the stuff that gets coverage far an wide on tech sites.

          • Ah! I see. No, you don’t understand what was happening here. It wasn’t that the battery was low enough to die. It’s that a surge in drain was enough to cause it to not deliver enough power to keep the device alive.

            In other words: At 40%, it still had almost half its runtime left. It just needed to be turned back on, at which point it would run until there was another surge in demand.

            Luckily, all recent iPhones have scalable CPUs, and rarely run at full speed anyway. The only good fix is literally to suppress those major demands. That’s not to say the device shouldn’t warn the user (I think it should), but that throttling mechanism on the surge absolutely has to remain if you don’t want the phone to shut down.

            I went through this very process last week with my wife’s iPhone.

          • rick gregory

            See my new comment.

  • rick gregory

    And he doesn’t get it, but apparently wants some attention.

    I’ll use my 6S Plus as an example. It’s new battery capacity is about 2500mah. So a 50% charge on that is 1250mah. The OS can compute out how long that will last based on the tasks the first 50% took up and can determine whether the CPU might need to be throttled. Perhaps iOS does this at a given charge level or perhaps it does it when the predicted time left to 0% is some value.

    However, my 2 year old 6S Plus now has a max battery capacity of about 1700mah. It starts at about 70% of charge even when it’s full to its degraded capacity. Now, 50% charge is really 35% of the new capacity. Yes, I have 50% charge but I don’t have 1500mah left, I have 850mah.

    So, iOS is apparently saying “well, instead of running the CPU at max clock rate even when doing things like just looking at Facebook, I’ll move the clock down to try to conserver battery.”

    The linked post talks about this as Low Power Mode but that is NOT what LPM does. Low Power Mode shuts off background activities etc to conserve battery. It’s much more than clocking the CPU down and In fact it’s mostly saving power by not checking notification updates from all of your apps every minute or so.

    Now… should iOS tell you “hey, your battery is getting worn down, you should consider replacing it” via some indicator? Perhaps. macOS does. But then we’d see a firestorm from people like Meaux who would complain that Samsung phones don’t show this!!

    • Meaux

      Wait, giving you information that you need to replace the battery is bad? Before replacing it, my 6 was unusable. I would have preferred half the life but full performance because the worse performance made the most basic tasks slow and frustrating. And I have no clue what a Samsung phone does or does not show. I don’t have any.

      • rick gregory

        I despair of society when it’s so obvious people either cannot or do not read. I did NOT say that it would be bad. Read again. Nor did I say YOU would. I said ‘people like’ because of your first comment here.

      • bdkennedy

        My concern about this situation is that the iPhone 6 has become almost unusuable, while my iPhone 4S is still going and hasn’t had to have it’s battery replaced.

        • Sigivald

          Possibly just bad luck?

          Or, equally, the 4S has such an old OS that it doesn’t even try to do that?

          (Have you checked detailed battery info on the 4S?)

        • rick gregory

          Your 4S likely is not running iOS 11 or even 10. The throttling based on wear seems to be a 10.x thing.

          Also, what does ‘unusable’ mean? And, well, how much has each phone been used?

          there’s an app called ‘battery life’ on the App Store that can check wear and seems to be relatively accurate. Might want to check that on the 6. Regardless, a 3 year old battery on a device that’s been used a lot is going to show wear.

    • Yeah, LPM is not equivalent at all.

      • LPM shuts down a bunch of services and caps the max CPU rate in an effort to conserve battery.
      • Kid Gloves (not sure what else to call it) caps the max CPU rate (less aggressively, I believe) in an effort to not draw enough power to cause the battery to fail to deliver (and the device to crash).

      (I don’t think I’m contradicting you, just summarizing/agreeing.)

      • rick gregory

        It doesn’t even cap. On mine at least it varies the clock rate base in part on charge. 100% charge? my clock rate is at max. Less than that? It starts decreasing it. There may well be other variables as you note.

        • Yeah, I’m aware they vary the clock speed. The theory is that devices with a bad battery won’t hit full speed. Like my iPhone SE, which can rev up to 1.85 GHz, might only rev up to 1.2 GHz with a bad battery. (Or worse, even, that’s just a number.)

          This doesn’t matter much since the phone is usually chugging at 120 MHz or something equally ridiculously slow. Why use the battery when you don’t have to?

          It’s like KITT’s turbo boost no longer being quite so fast. He’s still a fast car and a good friend, right? He can still put down his roof to pick up girls. He can still chase down other vehicles on the road. He just can’t make that jump over the river anymore, and this analogy really fell apart somewhere… 🙂

      • Dawn

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  • Sigivald

    Unrelatedly – you might wanna post about it – Apple just yesterday, IIRC, released an AirPort/TimeCapsule patch for the KRACK vulnerability.

    Which was a pleasant surprise; I was half certain that since it had taken so long they’d just effectively EOL’d the product line and were never gonna.

  • rick gregory

    What a lot of people aren’t understanding is that iOS DOES NOT throttle you back to one speed and leave it there. It dynamically moves the clock rate up and down depending on what’s happening including what the battery charge is. There’s NO reason to have the CPU running at max rate when the phone isn’t being used or is just redrawing the screen as I read a web page.

  • f1rehead

    I can definitely confirm this. I had my battery replaced last week and was amazed at the speed increase. It’s like an entirely new phone. I didn’t notice that it had been getting slower but it’s much faster now.

  • Lovely. The new iPhone 6 I bought that I bought barely a year and a half ago performs like utter shit. And it’s not like it gets heavy use—majority of the time it sits on my desk plugged in. What a joke.