The questions being:
- What causes the draining of the batteries?
- When does the draining process start?
- Why are the built in provisions to prevent this low state ineffective?
- What systems have to be reengineered to prevent excessive discharging?
and at last
- How can the battery be protected against going fireworks.
Leaving them switched on and ground power dropping off line.
Towing on Battery only for too long.
Fuelling on battery only for too long.
APU switch left in 'On' position (to vent APU core)
In short a lack of education by Boeing to it's students during training.
I for one have only learned about the major problem with this battery (IE don't let it drop below a certain charge state or it's u/s) on pprune. Not Boeing.