As the old Oral-B Professional Care 500 so had a battery in 4/5 A design with 43mm length and 17mm in diameter, and I still know the plastic holder - There were no bridges to limit the battery diameter 14 mm - I have in "new" but already weak Professional Care 550 unceremoniously out ground with a 17 mm Mounted points as the Dremel the bars and everything else. Since the plastic holder hard plastic is not necessary to the grind so be very careful as the cut where like too much breaks away. The battery fit in now, and the Oral-B is now running again wonderful with even more capacity.
