Here's the 3.5mm and power cord
The cable does not detach from the headphones
Underneath the rings on either side is, well, nothing.
If you look on the right side in this picture, that side should have the USB charger. That was the side I unscrewed and split open (you can kind of see the inside). That side had a square spot that looked like it could house a battery, but nothing was there. I didn't take it far enough apart where I could hold it open and take a picture at the same time. The left side had no screws and I was afraid I would break little plastic tabs that were holding it together.