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."