A:Answer This was found on head-fi.org. The 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 CPU-type board (note position of LED lights) under which is a black plastic covered battery pack with two additional silver screws. Either remove battery or cut the red (+) and black (-) wires close to it. Now remove the outer facing with the logo by prying out plastic snaps with flat screwdriver. Feed the red/black wires into outer area via the holes at the perimeter of the chassis. Replace all screws. Find similar battery (which I am unable to locate at present) or wire in an AA or AAA battery holder, fixed at the outside face with tape, etc. Soldering is, of course, best; metallic epoxy might work; and use nickel metal hydrate rechargeable batteries which should perform OK.
