How do I install batteries.

Remove the ear cushion from the earcup, twist counter clockwise a quater turn untill u overcome a slight resistance and lift off, underneath u will see 2 batteries one either side of the driver.(i think it is the right one both cushions are removable anyway. The batteries should be NiMH rechargeable not standard AA do not use AA .the batteries recharge when u put the headphones back on the cradle takes about 18 hrs
u can use a external charger which is probably quicker. There is built in overcharging protection so this should not be a problem.

Hi,
The left ear cup is where the batteries are kept. They are to the left and right of the speaker. The ear cushions are secured to the ear cups by means of a quarter turn fastener. To remove an ear cushion, turn it in the direction of the arrow (towards you) until you overcome a slight resistance and lift it off the ear cup.
This info was taken from a users manual for a Senheisser wireless earphone system, model RS-120
Here is the link for this manual:

http://onlineshop.rnib.org.uk/DownloadInstructions.aspx?filename=DD19.doc&status=True&actualFile=DD19%20A4.doc&prodid=3040

Hope this helps...