Replacing the battery in your product - QuietComfort® 3 Acoustic Noise Cancelling® headphones
Amazon.com: AOLIKES 750mAh Replacement Battery for Bose QC35 QC45 QuietComfort 35 II Wireless Headphones, Compatible with Sony WF-1000XM3 WF-SP900 Charging Case Battery : Electronics
How to change the battery on the Bose QC25 headphones - YouTube
Battery door is missing - QuietComfort® 15 Acoustic Noise Cancelling® headphones