Starting in October, many Nexus 6P users have been experiencing a bug that causes their phone to completely shut down, even though there was 20% or more battery life remaining. At first, it was thought to be a direct result of the recent Android Nougat update, but a combination of factors indicate that this isn't necessarily the case—or, at least, it's not the only problem.
Just this week, a handful of Pixel and Pixel XL owners have started to report the same exact problem, so it seems as though this battery issue is now affecting more than one device. Amidst all of these reports, Google has only issued one statement informing affected users to contact support, so a lot of questions still remain. While we wait on an official resolution, let's take a second to delve deeper into the problem and look for potential root causes.
Current smartphones use lithium ion batteries, which are known to show signs of aging after as little as one year. When batteries age, their capacity for holding a charge diminishes, as does their ability to discharge electrons.
In other words, an older battery doesn't hold as much charge as it once did, and it's not quite as capable of meeting your phone's demand for electricity as it once was.
This could certainly be part of the problem with the Nexus 6P, which was originally released more than a year ago. The issue could simply be that the battery doesn't have quite as much charge as the phone thinks it does, so Android's software-based battery meter could be reporting, say, 15% charge, when there's really only 1% left.
There's some solid evidence to back this up, too. Our research found that most Nexus 6P users who replaced their batteries are no longer experiencing the early-shutdown battery issue, regardless of other factors such as Android version or temperature (more on these below).
But that doesn't explain why the same issue could be occurring on the Pixel and Pixel XL. These phones are hardly even two months old, so battery age can't be the root cause, and there must be more to the problem.
Lithium ion batteries contain a delicate and volatile mixture of chemicals that are designed to store electrons which ultimately power our portable devices. The mixture is so delicate that it has a very narrow window of optimal operating temperatures.
A battery designed to operate at full capacity in temperatures around 80°F will generally yield only 50% power at 0°F. Ever had problems getting your car to turn over on super-cold mornings? Then you've seen this issue in the real world. The same principle applies to almost all battery types, including the lithium ion cells found in Pixel and Nexus devices.
So let's take a step back for a second and think about when Google's battery issue started to appear. The first reports came in during late fall, and the number of affected users seemed to only grow as we got into the winter months.
It's certainly plausible that cold weather can be attributed to at least some of these faulty battery claims. Again, this could be a calibration issue where Android's software-based battery meter isn't accounting for diminished battery capacity due to suboptimal conditions, resulting in the battery icon displaying more remaining charge than the battery itself actually has.
When these battery issues were first reported, Google had just begun rolling out their newest firmware, Android 7.0 Nougat. Logic tells you that's just too much of a coincidence for the two to not be related.
On top of that, Google's staged rollout update system matches the influx of battery issue reports almost perfectly. This could explain why user reports were few and far between at first, but then started to roll in at a rapid pace once Google started sending the update to more users.
However, Pixel devices shipped with Android Nougat pre-installed, yet it took two months before the first set of battery issues were reported. Another knock against the theory that Nougat caused these issues is that Nexus 6P users have reported that rolling their firmware back to Android Marshmallow does not fix the problem.
We have a theory that the Android Nougat update could have contained a software bug that somehow caused physical damage to the battery in the Nexus 6P, which would explain why rolling back to Marshmallow doesn't fix the problem. However, this is just a theory, and after analyzing thermal configurations and other system files in the two software versions, we were unable to find any differences that could have led to battery damage.
All of these potential explanations have inherent flaws. Age of battery can't be the only issue if people with brand new Pixel phones are having the problem. Cold weather can't be the only problem, otherwise we'd see similar reports about devices from other manufacturers. And the Android Nougat update is unlikely to be the sole reason, because if that were the case, users should have been able to fix the problem by rolling back to Android Marshmallow.
The truth, like always, probably lies somewhere in between. If I had to guess, I'd say that some folks are suffering from aging batteries, others are being hamstrung by cold temperatures, Android Nougat might indeed have some sort of battery bug, and confirmation bias is to blame for the recent influx of reports.
Ultimately, only Google has the resources to find the true root of the problem, but we contacted their PR team, and were told that they've just begun investigating the issue, so we don't expect an official resolution soon.