That was only a few miles from my work apartment in San Jose. It's better to let the professionals put out a battery fire like that. It says he probably died from the smoke while he was trying to put it out.
From what I understand it has been happening when the bikes are off and being charged. That eliminates controller over-draw. On my batteries that would cause a fuse to blow in the battery. Like if you hooked a 20Amp battery to a 30Amp motor.
I like to have healthy BMs every morning. Eating probiotic stuff with a lot of fiber like kimchi helps the BMs.