So B was aware about battery issues and didnīt communicate this status to FAA since grounding? This is a major topic in finding answers to the system failures. I canīt belive that this comes on top by an insider.
If 150 bat are deep discharged, then the power has gone somewhere. Internal short would destroy the bat and weīd had seen much more incidents and early grounding. So for me it is the surrounding system which is sucking at the bat.