I've heard that some of the Braun batteries are not replaceable because
they are complete with the board that they are attached to. I know of
a service center that might be able to help you out. I've used them
several times to get repairs done on my husbands shavers. They are
honest and very helpful. You might try them. Their link is
www.shavtronics.com. I know what you mean by expensive. But I guess
if you add up all the blades they add up too.
Hope this helps
Watley