Battery Problems on the 787 Dreamliner

Battery incidents  occurred on 2 of 50 operational 787 Dreamliners.  One battery smoked while the 787 was in flight, causing the need for an emergency landing.   The second battery actually ignited while the 787 was parked on the ground.

Today Boeing announced that they have FAA approval for a list of design changes that they say should allow the Dreamliners to fly again.

The thing that struck me about the information is that the design changes all seem to address the symptoms of the batteries overheating.  They do not seem to address the reason, or root cause, of the overheating.

The last press release on the Boeing website is dated Feb 7 2013 and states:

"...the NTSB has identified the origin of the event as having been within the battery. The findings discussed today demonstrated a narrowing of the focus of the investigation to short circuiting observed in the battery
..."

The design changes reported by the New York Times Include:

• fiberglass-like insulation between the battery cells [whatever fiberglass-like means.  these sheets can supposedly "keep" a short-circuit (and the heat) from cascading to neighboring cells]
• stainless steel battery case instead of aluminium [withstands overheating battery heat better]
• titanium tubes to help vent smoke to outside the plane [yikes]

The only hint in the article at the search for a root cause is that the National Transportation Safety Board has found that in the Boston episode, a short circuit in one cell caused the battery to overheat and burst into flame on Jan. 7. 

But investigators in Japan have raised the possibility that a battery on another 787 nine days later started smoldering because it might have been hit by a surge of electrical current from another part of the plane.

A few things come to mind.

• The battery design engineers apparently did not consider the possibility of either 1) short circuit in a cell or 2) electical surge to the battery.  Here I think the DFMEA would have been the key tool from our toolbox.
• I can imagine the battery design team(engineers, purchasing, fabrication, etc.) busting their asses coming up with these fixes and thinking "figure out why the cell short circuited!" and "prevent the power surge from reaching the battery!" Was the short circuit caused by a design flaw, or a quality problem?
• When I hear "lithium-ion battery" I think of the many times I also heard "overheated". Remember the laptop that caused the pickup truck to burn up?  Remember the news about cheap lithium-ion nonbrand mobile phone batteries?  Come on!  Shouldn't the overheating concern been HUGE when doing the design and manufacturing development?
• I wonder if there was ever a case of battery or cell short circuiting in development or validation testing.