Most rechargeables are glued in place and/or the connections soldered.
That does not mean they can't be replaced, just not normally by the
average consumer. Hence the common label, no user servicable parts
inside on most items these days.
Even common flourescent lights, like the undercounter type, that still
use a transformer and starter, the starter is hidden inside and
considered not serviceable. In other words, the company expects the
purchaser to buy a new fixture, each time the starter goes out.
If you study the contraption a little, you will more than likely
figure out how to get the new battery installed.