The battery is in the right cup while the USB-C charging port is on the left, with separate iFixit guides for each and for the ear pads.
What to check before buying
Battery and connector
iFixit places the WH-CH720N battery in the right side and the USB-C charging port in the left. A charging fault may involve either path, so the two guides support a narrower diagnosis.
Worn pads
An ear-pad guide covers replacement when the cushions tear. Pad wear is externally visible and should be priced separately from soldering work on the charging connector.