When the description says "non-removable battery" it doesn't mean that you can't replace the battery :winktongue:
It does, however, mean that it won't be as easy as popping off the back cover and remove the battery. This feat will require some work on your end.
There are quite a few guides out there explaining just how to go about doing this. You will require the right tools and a lot of patience!
This is one of the many:
http://www.ifixit.com/Guide/Nokia+Lumia+928+Battery+Replacement/40763
May the force be with you
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