mdr-rf985rk has a 3.7 v lithium-ion battery, 610mHa (3x4x0.5cm=2x1.5x1/4") that is wired in. Go to L(left) designated side, remove ear cup and three screws (small phillips/star screwdriver) on the inner facing (note positions). Careful! wires are short, then remove one screw on the green...