The Emergency Locator Transmitter (ELT), supplied to Boeing by Honeywell and used in many other aircraft besides the 787, contains a current limiter — a standard feature, like a fuse, that shuts off the current if it gets above a certain level.
Where is the current limiter located? On the ELT circuit board? That would be too far along the current path to be of any use in the case of a pinched battery wire. The current limiter would have to be in the battery pack itself.
Which raises another interesting issue: If the original Honeywell batteries were replaced (and they incorporated said limiter), were they replaced with OEM batteries? Or is there a generic 'equivalent' that may have been substituted?