battery pack that allows you to have the 4batteries in a tight formation and then to extend that as a stick with as many more 4batteries ...

• print 2 pieces of battery_pack_end.stl
• print as many batter_pack_middle.stl as you want
• put m3 nuts into battery_pack_end (4 in each) and tighten with bolts
• put batteries into one battery_pack_end
• put battery_pack_middle over batteries
• add more batteries if you like, and after each set add another battery_pack_middle .. make sure you slide battery_pack_middle to cover end of one and beginning of another set of 4 batteries
• finally add second battery_pack_end
• use the m3 threaded rod and thread it trough all plastic pieces, and tighten on each end with m3 nut

voila, you have your battery pack

NOTE: The SCAD file have original battery dimensions! If your printer is not able to print holes that are accurate (visit stretch plugin in skeinforge) increase battery diameter in order to get holes where batteries will fit.