Couldn't really find any tutorials for disassembly of shavers from this century (almost, not quite, kidding) for Braun, Panasonic or Norelco, but some earlier techniques:
Braun Series 7
Panasonic
May not be applicable for today's modern shavers (although the old Braun S7 is still kicking), but obviously anything can be taken apart. The trick being, of course, reassembling in working order. And I don't believe the factory provides any mail-in refurb/battery replacement options, at least among the Big 3. But an interesting question/experiment nonetheless.
After watching both videos I’m NOT going to replace the battery in any of my shavers. Besides not being very handy, if I get five years of use out of a shaver it’s probably time to replace it. I got five years of use from my previous Panasonic ES8103s shaver and I replaced it when the battery wouldn’t maintain a charge for an entire week. After five years there may be new features that may improve the quality of the shave or it may just be time to buy a new shaver because it’s about when I get tired of the old shaver.