A number of Nexus 6P owners have reported an alarming battery problem with their phones as of Android 7.0 being released for the handset, which causes the phone to power down when the battery gauge still shows anywhere from 10 to 60% battery remaining. How widespread the issue is at this point isn't clear, but the main thread on the Google issue tracker has 229 stars. There are also a significant number of threads describing the problem on Google's Product Forums (see: 1, 2, 3, 4, 5, 6).
Owners have linked it to Android 7.0, but even those who have attempted flashing back to Marshmallow report the problem still occurs, though generally at lower indicated remaining battery percentages than on Nougat. This suggests some kind of change in Android 7.0 that is exacerbating what would appear to be an underlying hardware problem. There are some reports that 6P owners with the issue who have their batteries replaced see the problem largely alleviated, again pointing to what seems fundamentally a hardware failure that has been made worse by software.
While Google has assigned the issue in its tracker, it's been given a low priority and there has been no indication of an incoming fix. Those who have attempted to receive warranty service from Huawei have been rebuffed, with the OEM telling them the problem is not with the phone or the battery, but with Google's changes to the software.
Interestingly, it seems the problem is most common in very cold climates. These are where we see reports of phones dying at upwards of 60% battery remaining indicated, which is obviously completely ridiculous. As some on the various threads point out, this could easily be a major safety issue. We have become deeply reliant on our smartphones to help us get around - be it hail an Uber, navigate us to our destination with a map, or simply to call or text a person to let them know where or when we'll be. Such functions have become so critical that suddenly having your phone die unexpectedly could actually place you in danger. Imagine if you were in an unfamiliar place (one without frequent taxis), late at night, trying to hail an Uber in exceptionally cold weather, and then your phone kicked the bucket. What would you do?
This actually happened to one poster on reddit, who was fortunate enough to find a hotel where he or she was able to use a phone to call a friend (whose phone number they knew - how many people know each other's phone numbers these days?) to pick them up. What if your car broke down on a freezing night and you were unable to phone a tow company? Our world and infrastructure, and our very decision-making processes as humans, have started to evolve around the ubiquity of constant connection through our smartphones. Without them, we can be left feeling helpless.
We'll be reaching out to Google about this to see if they have any comment.