Why your iPhone battery meter sometimes goes haywire

Posted on Feb 6 2017 - 1:46am by Huzoor Bux


I understand alternate facts. Sometimes my iPhone’s battery meter delivers them.

Fact: I have a 18-month-old Apple iPhone 6. I keep it in god shape, never dropping it, subjecting it to extreme temperatures, or dunking it in bodies of water. I charge it regularly. 

Fact: On a recent weekday afternoon, I picked up my iPhone, which had been sitting on my desk untouched for hours, and noticed it was reporting just 18% battery life. It was officially in the red. I quickly plugged it into a charger and, a moment later, the rating was 43%.

18% to 43% — in seconds.

I think that initial battery meter reading may have been an alternate fact and this iPhone battery problem is more widespread than I realized — or Apple is willing to admit.

For months, I’d been hearing bizarre iPhone battery tales from friends, co-workers and family members. Last year, Apple beat back reports in China and the U.S. before finally admitting that some iPhone 6S device batteries were faulty.

This iPhone battery problem is more widespread than I realized — or Apple is willing to admit.

The problem is that these bizarre battery issues extend back to the still-in-use iPhone 5S and through to the iPhone 6S (but not, as far as I can tell, the iPhone 7 and iPhone 7 Plus, at least not yet). They include battery-percentage free falls, where you can watch your battery life drain from, say, 30% to zero in the space of a few minutes or suddenly shut down with 20-30% battery life remaining. There’s also the perplexing sudden supercharge, like I described at the outset: The battery demands to be charged only to show hearty available battery life as soon as you plug it in.

Even though many people complained to me about bizarre battery hiccups, I was unconvinced until I experienced virtually every one of them myself. 

Apple has a lot of advice for managing iPhone battery life and I followed as much of it as possible:

  • I made sure my iOS was up-to-date.

  • I took a good look at which background apps were eating battery life, especially those with a lot of background refresh activity, and tried, where possible, to curb their use (Mail and Instagram were often near the top of the list for me).

  • I used Low Power Mode.

  • I even followed the advice I found on other sites and recalibrated the battery, letting it run down to zero to and then did a reboot holding the home and power button.

None of these actions, however, prevented the battery life miscalculations from happening again.

And they’re not helping others who have experienced the same bizarre battery life percentage issues.

On the ground

I already knew my own wife had watched her iPhone 5S shut down at 20% and 30%. I started asking friends and co-workers about their experiences. Pretty much anyone I mentioned iPhone battery issues knew what I was talking about or had an experience to share.

While taking an Uber with two co-workers a few weeks ago, I quizzed them about their iPhone batteries (on their iPhone 6 and 6S devices). Both reported unexpected shutdowns at 20%. Then our driver piped up and said he’d has similar issues to the ones I described, even though he only had his phone for a year.

Apple Support forums are full of similar complaints. Going back to the iPhone 5S and iOS 7.1, users recounted rapid battery drains. Those complaints persisted through the iPhone 6 and iPhone 6S and 6S Plus, with some users also complaining that the phone got very hot.

Apple won’t comment about what’s going on with the iPhone’s rechargeable lithium-ion batteries or the iOS software that manages them, and it hasn’t acknowledged any issue beyond unexpected shutdowns on some iPhones.

However, late last year Apple did reveal that a small number of iPhone 6S devices manufactured between September and October 2015 had a battery issue and were eligible for free battery replacement. Then in December, and only on the Chinese version of its support site, Apple announced that there were some phones “outside the affected range” of phones that they knew had a battery defect that were also shutting down. This prompted the company to integrate new battery diagnostic software in an iOS update for all users. That software is out in the field now, gathering data for Apple. Early this year, a report surfaced claiming that Apple might extend the battery-replacement program to iPhone 6 devices.

As I write this, though, Apple has yet to reveal what, if anything, it’s learned about the erratic behavior of some of its iPhone batteries or the software that manages them.

Considering how intermittent and inconsistent these issues are, that’s not that surprising. Plus, there’s the complexity of lithium-ion technology itself.

Inside your phone

Lithium-ion is, essentially, live chemistry inside your phone. Every lithium-ion battery is made of sheets of positive (lithium cobalt oxide) and negative electrodes (carbon), with perforated separators between them, wound in tight, overlapping spirals. During charge, the ions move in the direction of the negative electrode and during discharge, they move in the direction of the positive electrode.

Lithium-ion batteries are lighter and offer far more energy density that their predecessors, nickel-cadmium batteries. They lose roughly 5% of their charging capacity every month, which is a considerable improvement over nickel-cadmium batteries, which could lose 20%. They can also be volatile if not handled and manufactured correctly.

Lithium-ion batteries will last longer if they’re never fully charged or recharged.

A typical iPhone lithium-ion battery should last for approximately 500 cycles. A cycle is a full recharge, which could span over a number of days: You might use 25% of the battery’s power on day one and then 75% the next day. Apple told me last year that it even applies artificial intelligence to improve battery management, so those cycles presumably stretch out even more.

How you drain and recharge the battery also impacts battery life. Lithium-ion batteries will last longer if they’re never fully charged or recharged (this is why, when you buy a battery-powered gadget like a smartphone, it typically ships with about 50% charge, plus or minus 20%). Side reactions in the chemistry increase when you drain the battery to 0% and constantly recharge to 100%.

No matter what, though, the charging capacity of lithium-ion batteries will change over time.

Like a new car that starts depreciating the moment you drive it off the lot, lithium-ion batteries are continuously losing their charging capacity. This can be confusing since, for the life of your phone, the meter is always showing you something between 0% and 100%. This is not a lie — 100% of 10 hours is 10 hours, just at 100% of the 3 hours you might get four years into the life of your phone is still 3 hours. That percentage is relative.

This commonly accepted wisdom about rechargeable batteries still doesn’t explain sudden shutdowns, rapid drains and inaccurate battery life meter reports.

Fuzzy science

Experts, though, told me that battery life and maintenance is an inexact science. Different lithium-ion batteries, for instance, use different chemistries, which can impact recharge cycles. Professor Donald Sadoway, who studies material sciences at MIT, said most lithium-ion batteries are engineered to go thousands of cycles and still retain 80% of their capacity.

Even the way you measure battery life differs from between phones and manufacturers, since there isn’t a way to measure the remaining charge directly. So the readout at the top of your phone could be based on voltage, “by identifying what the voltage is on a battery, you can get a sense of the state of a charge,” said Sadoway.

Others uses what’s known as a “voltage plateau,” and some rely on the more difficult-to-integrate measure of the amount of current flowing: If you know the amount of electrical current served over time, you can calculate how much energy has been used, and this, how much is (probably) left. Professor Sadoway has no idea what chemistry or methodology Apple is using.

The percentage of battery life we see is an estimate.

Other experts I spoke to agreed that the percentage of battery life we see is an estimate. “The only information a phone or laptop can use is the voltage of the battery, but there isn’t necessarily a 1-to-1 correspondence between the cell voltage and the amount of energy remaining inside,” wrote Stanford University PhD chemistry student William Gent to me in an email. 

Temperature, battery degradation and the amount of power being drawn from the battery can all affect that estimate.

“Some more advanced systems may be able to use additional information like this to get a better estimate, but it is always an estimate,” wrote Gent, who owns an iPhone 5S and has experienced rapid discharge, inexplicable battery-meter jumps and sudden shut downs. 

“Also,” wrote Gent, “you can’t just measure the amount of energy taken out and put in each time, since there is a some hard-to-calculate amount of the total energy that you put in that goes into waste heat (due to inefficiencies in the cell itself) and side reactions. Any error in calculating this non-useful energy put into the battery will add up and result in large errors in SOC [state of charge] determination after repeated cycles,” wrote Gent.

Professor Sadoway agrees that there are many reasons why a battery charge meter in the iPhone might be wrong. 

“Suppose the phone is actually measuring correctly, but the conversion to the display is flawed. It could be something silly like that,” added Professor Sadoway.

Testing

During my research, I came across this post, The Ultimate Guide to Solving iPhone Drain, by Scotty Loveless. It offers a nice, step-by-step approach to better, daily iPhone battery performance. I was most intrigued, though, by Loveless’s background. He’s worked as an Apple Store Genius for two years (mostly working on the iPhone 3GS iPhone 4, iPhone 4S and the first wave of iPhone 5 devices). He writes, “The most difficult issue to solve was short iPhone battery life. It was extremely difficult to pinpoint the exact reason why someone had iPhone battery drain.”

I wondered if Loveless, who currently works as an Apple consultant at Appinstructor, could offer some insight and maybe help me troubleshoot my own iPhone battery issues.

Loveless told me he never saw issues like mine while working at the the Genius Bar “unless the battery was failing.”

Results of my iPhone 6 diagnostic tests. No obvious issues.

Battery life does go pretty fast throughout the day.

Battery life does go pretty fast throughout the day.

He still has access to his old iPhone diagnostic tools and showed me how he could run them remotely on my iPhone (side note: I had no idea anyone could do this). I did have to share some details from my phone, including the IMEI number. After a few steps and screens on my phone, Loveless was in and he started running a full set of diagnostic tests.

We ran the tests with my Apple Smart Case on the iPhone 6 and then again with it off. In both instances, the results showed my battery is not failing and has 423 charge cycles remaining out of, according to Loveless, as many as 1,000.

This result is far from conclusive, but it might support the notion that these issues are not related to dying batteries or end-of-life devices.

Recharge

Stanford’s Gent reminded me, though, that as lithium-ion batteries degrade, “Determination gets less accurate, particularly when you get close to 0% SOC. So your phone or laptop may think, based on the voltage of the battery, that it has 30% left, but then the voltage unexpectedly starts dropping rapidly (because the cell is old and somewhat degraded) and the computer realizes that actually the SOC is lower than originally thought.”

This supports my theory that there is actual confusion among the real state of the battery, the hardware’s ability to deliver that information to the operating system and the system’s ability to accurately interpret it.

Research teams around the world are working on next-generation lithium battery technologies including lithium air (which has extremely high-energy density) and lithium sulfur (far cheaper than lithium ion), but like lithium ion, these technologies will also degrade over time, which means measurement challenges will remain. Gent thinks that the work to improve battery measurement may, in the long run, pay bigger dividends. “My guess is that the biggest improvement will come from the battery management side rather than the battery tech.”

The good news, for what it’s worth, is that you’re not crazy. Everyone I spoke to, consumers and experts, acknowledge that there is an issue with iPhone battery readings. 

MIT’s Sadoway told me an iPhone charge physically cannot be both 10% and 40% within the space of a few seconds or minutes. “It wasn’t both. There’s a broken link in that chain somewhere.”



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