Chosen Solution
How do i change the battery?
You must desolder it. There is now a partial teardown guide that includes how to access the battery. Bose QuietComfort 35 PARTIAL Teardown I’m not sure what type of battery to replace it with though.
I found a battery. https://www.ebay.co.uk/itm/3-7V-500-mAh-… It’s the wrong shape, but I made a small hole for the wires in the side of the battery compartment, and I hotglued it just outside the compartment. Unfortunately the battery light still stays on even when the headset is off. I think there must be something in the firmware which turns on when a battery reaches end of life, and I don’t know how to reset that despite installing the new battery. However, the headset turns on now and seems to charge correctly. I’m going to see if I can reset the firmware somehow.
