Thanks for raising this again.
Bose actually sent me a new pair when I reported it had a red light when charging[br]
https://cubicgarden.com/2019/12/29/after-all-that-hunting-for-new-headphones-bose-make-good/
Its similar to the previous ones but all black instead. I did look at taking it apart previously but it seems to have those clips which once opened never go back to their default state, they tend to break under a small amount of pressure.
After the Bose battery goes again, I'm going to study iFix for a on ear bluetooth & lead, multipoint headphones.