I am quite sure that all the battery packs for the Metz 45 series are the same. The rechargable pack is optional and Metz doesn't want user to take it apart. The one in the figure 4b is one that uses standard AA alkaline batteries. It's normal for the price of the Metz battery pack to be quite high. I think one can carefully disassemble the pack and replace the batteries with new NiMH cells.