Multiple Layers of Redundancy in Boeing's Measures
First Layer or Improvements:
Measures to Eliminate the Root Cause (prevent internal heating of a cell)
- Adjust the torque appropriately to tighten the nut connecting the electrode
- Improved insulation of cells (wrap with insulation tape)
- Improved insulation at the bottom of the battery case interior
- Improved insulation between cells and between cells and the battery case
- Improved insulation of the upper part of the battery case interior
- Improved insulation of reinforced material of the battery case interior
- Drain holes to address moisture
- Lower the highest charge allowed in the battery monitoring unit and charger
- Stabilize battery charging current
- Improve protective function against over discharge
- More stringent screening of the battery cells after production
- Improve quality control, etc. in the production process
Wrap insulation tape around cell
Prevent loose nuts
Second Layer of Improvements:
Measures to prevent problems from spreading between cells
- Insulation to isolate cells from each other and from the battery case to resist heat
- Make a gas vent inside the battery case
- Insulation around wiring inside the battery case to resist heat
- A tube to join value valve and vent in lower fuselage
Phenol glass laminated panel between cell and case
Third Layer of Improvements Measures in the unlikely event of a battery failure
(a new enclosure to prevent trouble from spreading to the cabin)
- Enclose the battery case
- A tube to join value valve and vent in lower fuselage
Testing the enclosure
