787 Batteries and Chargers - Part 1

[saptzae]

@RR_NDB

The ground strap shows little thermal damage and its cross section is too small to have carried any significant current in destroying #3.

The ground strap was likely mechanical damaged and partially cut either before the event or by intervention.

Severe damage seen is tertiary. I would not spend time on it.

Important is Primary failure, cause of deterioration leading to shorting cell and Secondary failure, if/why the battery was not protected from charging.

Edit: If ground strap was cut pre-event and could have touched BMU PCB, it possibly could have induced the battery failure.

Edit: Arcing at the pole of #3 due to loose nut, I think it would have welded shut, not burned the pole off.