It was a "pyrotechnic battery disconnect", i.e., basically a type of switch/active fuse using some type of small explosive charge as part of its operation. Her

It was a "pyrotechnic battery disconnect", i.e., basically a type of switch/active fuse using some type of small explosive charge as part of its operation. Here's the patent for all the gory details: https://patents.google.com/patent/US9221343 https://patents.google.com/patent/US9221343 The fact that this part has a "problem" probably means that it was triggered, e.g., maybe some type of false collision detection, short circuit or other failure which ended up triggering the disconnect.