fizz57
But the changes beg the question: why weren't they done before the aircraft was launched? What do we know now that wasn't known then, except that the batteries do catch fire? If the root cause of the problem really is unknown - and it all comes back to this statement - how do Boeing know that the changes are adequate?
Because the only way Boeing, Thales or GS Yuasa could get a cell to vent and for that vented electrolyte to catch fire was to massively overcharge the battery. So they focused their protection systems on the charging system to ensure that a battery could not be massively overcharged. The blue aluminum box was there to contain vented electrolyte should a cell somehow be overcharged and subsequently vent.
In JL8, what caught fire was the plastic inside the battery and that spread to the plastic connector outside the battery which charred the surrounding area. As B/T/G knew that a battery in thermal runaway could get very hot, IMO they should have originally used high-temperature plastics (as the new design does) and if they had, they might very well have saved themselves a grounding.
In NH692, electrolyte did leak out of the top of the blue box, but I wonder if that didn't happen on landing. One expects the pilots were hustling that bird down and if they landed hard, the vertical load might have splashed the electrolyte across the top and allowed it to spill out.
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cockney steve
I expect Boeing will change the cathode chemistry down the road, but chances are that chemistry change will change the design and/or properties of the battery. And if the battery design or properties of the battery, that will have to be tested and certified.