"Without knowing precisely what caused the problem, Boeing developed more insulation between each battery's cells and a fireproof shell for the battery to starve it of oxygen if there is a fire. Each plane carries two batteries, which will each be surrounded by a stainless steel box. Each battery will have a titanium venting tube to a hole in the fuselage to carry flammable electrolytes and smoke overboard if a battery fails."
We should learn what was modified. Algorithms of chargers, circuitry or just the battery case?
This issue is very important. Batteries are essential so need to be safe and reliable.
Will go deeper to look what was changed. We discussed thoroughly the issue in another thread.