Boeing 787 battery/charging system solutions---Good design or not?
Steve Taranovich - March 16, 2013
Improved Battery Design Features
Changes inside the battery will help to reduce the chances of a battery fault developing and help to further isolate any fault that does occur so that it won't cause issues with other parts of the battery.
To better insulate each of the cells in the battery from one another and from the battery box, two kinds of insulation will be added. An electrical insulator is being wrapped around each battery cell to electrically isolate cells from each other and from the battery case, even in the event of a failure. Electrical and thermal insulation installed above, below and between the cells will help keep the heat of the cells from impacting each other.
Wire sleeving and the wiring inside the battery will be upgraded to be more resistant to heat and chafing and new fasteners will attach the metallic bars that connect the eight cells of the battery. These fasteners include a locking mechanism.
Finally, a set of changes is being made to the battery case that contains the battery cells and the battery management unit. Small holes at the bottom will allow moisture to drain away from the battery and larger holes on the sides will allow a failed battery to vent with less impact to other parts of the battery.
New Battery Enclosure
One change proposed by Boeing is to seal the batteries in a steel box, which would contain any smoke and fire.
The battery case will sit in a new enclosure made of stainless steel. This enclosure will isolate the battery from the rest of the equipment in the electronic equipment bays. It also will ensure there can be no fire inside the enclosure, thus adding another layer of protection to the battery system. The enclosure features a direct vent to carry battery vapors outside the airplane.
New titanium fixtures are being installed in the electronics equipment bays to ensure the housing is properly supported.
It looks like the designers have done everything possible to prevent another mishap, while not actually knowing what the root-cause was. So by over-designing almost every aspect of the charging, monitoring and battery system design, we trust that the engineers have a solid design in place that should be robust enough to fly.
Please give us your comments and technical expertise in this area---we would really like to begin a discussion on this issue.
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