I've been having this same issue, but never saw it before upgrading to 5.1.1..I think it has something to do with that update. None of us probably had the problem before?
I regularly have very good battery life and that continues, but there IS one problem since 5.1.1.. on a sprint Note 4.
Once I get down to about 12-15% I get an alert, battery is low, etc.. If I start to do something with the phone, open a browser or download an app, boom it just shuts down completely.
I can reboot the phone, but it shuts down again. When I plug in the power, it says it is at 0% battery so either the battery meter is totally wrong or the battery is damaged?
thoughts?
I've reset the cache several times now, to no sucess