Chosen Solution
Нow to disassemble the case and replace the battery?
If anybody is still interested in this, I recoded my process of replacing the batteries in a Braun Cruzer3: http://spbnick.github.io/2016/06/24/Brau…
Cameron Frye, still trying to find an English version but here is something interesting. http://www.service.braun.com/line/SH/S57… it shows the picture on page 8 how the batteries are changed but in Chinese and was omitted on the English version. Hope it will get you started until we find something in English
I know it is an old thread. For other people coming across: BRAUN cruZer6 beard&head Haar- und Barttrimmer Type 5417 repair_cruzer6_beard_and_head.pdf
Camaron Frye, in english: http://www.service.braun.com/line/SH/S57… it shows in page45 how the batteries are changed.