People are still having issues with the non replacable batteries not charging and not everyone has had success with getting their units replaced.
Fact is you don't need to charge Keystone 3's battery, it will drain out after a couple of days. Plug it in a USB cable when you use it instead. Keystone 3's batteries are a joke.
That's what I did till I dropped it.
BUT, you then always have the worry of the battery dead shorting as some lithium batteries will do when dead and then the unit will not work at all.
Have had that with some rarely used test equipment. Once you pulled the battery you could power it with the AC adapter.
-Dave