I recently changed the battery, and like you, was baffled at first as to where it is located and how to get to it. Check out YouTube where you should find multiple videos on to get the little plastic "tray' out that holds the re-chargeable battery in it. It's a pain to pry out, but a snap to put back in. Be careful to put the new rechargeable battery into the tray facing the right direction - the videos will show you. And NEVER use a NON-rechargeable battery in it. You can damage it. The rechargeable batteries are available at Amazon if you haven't already purchased one. I haven't been able to locate them locally, and the Logitech website is always sold out.