The rechargeable AAA cells may of course be worn out, or they may not be installed at all. If this is the case, either insert the cells, or you can order new cells as original spare parts. Please contact Harman Helpdesk for your country, or the distributor for your country, for further info about how to buy new cells. Please note that the cells MUST be compatible with charging contact for the minus pole located on the side of the cell. Normal cells will not work. This is clearly mentioned in the owner's manual, and shown with a drawing. If you have purchased new cells with plastic coating along the length of the cell, it may be possible to peel off the coating by cutting gently with a knife, then peeling it off. Only about 1 cm needs to be open to the metal, closest to the flat end, for contact to be possible. Please note that the ear pads on K 912 are removed by simply grabbing the plastic plate that holds the ear pad, and pulling it away from the ear pod. There is one battery in each ear pod. For K 915, never just pull the pad away, since the locking claws are released by being rotated away from their locked position.. Both batteries are under the right-hand pad, and there is a silk-screened instruction on the top of the pod, showing that you must rotate the pad plate just a few mm counter-clockwise to unlock it.