Chosen Solution
Is there an inside battery that I might have to replace even though it is always plugged in?
Yes - Inside the sealed case is a glued & soldered & welded you-can’t-get-me-out Li-on battery. How old is it ? Mine is old and has become “brush-as-fast-as-you-can”. If you can get it apart, yes, you could replace the battery. However, most of them wear out & leak where the gear shaft meets the brush. If yours is the charge-by-wire type, I advise users to store it BRUSH DOWN, to avoid leakage. If it is the charging-stand type, always give it a vigorous shaking after each use. I’d wait for Santa to bring a new one ;>)
