the black pieces that came out...was that the delrininsulator that seperates the center pin from touching the outer ring? If so that will make a short as well. You say you have another top cap...is the black insulator ring still in that one?
Also, make sure ur spring is not bent and touching anything else but the bottom of the batteries....
Hope it works out for you, Im sure Rob or Imeo will sell you just an isulator ring if thats all thats wrong w it....
Good to see you on this thread. They both broke after i took it apart to see if that was an issue.. they just crumbled in my hand. I used the proper tools to take them apart also. the spring is fine.