I havent read every post in this thread. But i know on the 747-400 there is a thermal cut off switch preventing this from happening. I know nothing about the 787 but does the 787 have a thermal cut off switch (im assuming not)?
pull-up-terrain
To my knowledge, 747-400s have NiCd batteries.
They behave totally different compared to LiIon types.
NiCd have ONE charge current for all cells.
LiIon are more complex, every cell has to be charged seperately and within certain limits. Don't know if their "runaway temperature" is monitored in 787 chargers/controllers.
Regards