I came here from a google search with the same problem. I have had this phone for about 21 months. It will drain to about 50% remaining, then you can literally watch it drop down by 10 or 15 percent at a time until the phone switches itself off.
It is very inconsistent, sometimes I have it sitting in my pocket all day and literally haven't looked at since taking it off charge that morning and it will die suddenly like I described above, but other times I can be using it constantly for several hours and it will slowly drain in a reasonable way based on usage. I have investigated my apps to ensure they are not running in the background and made sure to only activate gps, wifi and mobile data when I am using them, but it still happens.
What's weird is sometimes I plug it in, and the screen shows that the battery still has about 50% charge, even though I just watched it drop to 0%
These two images are from different days:
I took the
left image as it was dropping down, it went to 0% soon after.
The
right image shows that it dropped off entirely without warning.
It's as if the battery charge isn't being tracked while the screen is off, even though it's still draining. Then when you turn it on, it updates it to reveal that it is very close to dead.
One suggestion I've read is that the phone uses more power to maintain a connection at low signal strength. You can see that power drops off hard when the cellular network signal gets in the red, so this might be part of the problem. In the right hand image you can see the signal has been in the red for some time, and then when the screen briefly comes on, the phone dies.
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