Pub User
Details seem to be under wraps at the moment (why?) but I believe the 'fix' incorporates the following: a software change to the charging system, re-designed cells with better quality-control, re-configured battery internals (cell arrangement), insulation between cells, more comprehensive monitoring of cell condition and monitoring of insulation condition.
In other words: Fiddle with everything (including a few things that have been ruled out already) and hope something works.
All of that was Boeing's solution, and I believe the FAA then insisted on an improvement in the containment device, just in case..
Which is just the FAA's way of saying "We don't trust your fixes 100%. So we're putting in this extra layer of protection."
The 'why under wraps' has a lot to do with the public's perception of safety. The 'put it in a heavy box and let it burn' won't sound too safe to the flying public. Even though it may be. In the final analysis, putting the battery in a box and reducing the failure effects from a threat to the aircraft to a maintenance headache may put more pressure on Boeing to find the root cause of the problem. Once the FAA signs off on this, they can't go back.But customer airlines can bring pressure for a solution to bear.