Great quote from the article:
As one user asked on Mozilla’s the mozilla.dev.platform Google Group, “Can anyone point to a real website using the Battery API for a legitimate purpose?”
The answer for Mozilla seems to have been “no”, or at least “not enough”, and as of version 52, its Firefox browser will be saying good riddance to the Battery Status API.
Originally shared by Naked Security
This Battery Status ‘super cookie’ tracks you online and, unlike a normal cookie, you can’t delete it!