787 Dreamliner Lithium Batteries Absolved
By EV World Editorial Staff
Investigators looking into the cause of fires aboard the new Boeing jetliner determine the plane's lithium-ion batteries weren't the cause of the fire. Now they are looking for the real culprit, which isn't good news for airlines or Boeing.
The folks at giant auto parts supplier Yuasa in Japan can breath a bit easier.
Earlier today, aviation investigators have cleared their lithium cobalt-oxide batteries of blame in the several incidents involving battery failures and fires aboard new Boeing 787 Dreamliners, all of which have been grounded by the U.S. Federal Aviation Administration, bending the outcome of investigations into the cause at least one damaging fire. Thankfully, that incident occurred aboard a parked Japan Airlines 787 after a 12-hour trans-Pacific flight from Tokyo to Boston.
However, this doesn't resolve the mystery of why the batteries are malfunctioning. Attention has now shifted to the battery management system or BMS. According to an article posted on Airline Pilots Forum, there have been several incidences of short-circuiting in the same electronics bay, two of which are found in the front and the rear of the aircraft. It was in the rear bay, near the APU battery box in which the Boston fire occurred. It took firefighters 40-minutes to extinguish the fire.
The Dreamliner incorporates many innovations, the most debated being the extensive use of carbon fiber composites that are extremely strong and very, very light, making them ideal of aircraft construction; but it is still a comparatively new material. EV World's technical editor, a specialist in aerospace composites, is working with a major aerospace systems provider on updating their software to better handle the properties of composite materials. The 787 is also the first commercial aircraft to incorporate lithium-ion batteries to this extent: its onboard electrical system generates 1.45 megawatts of electrical power, four times that of the Boeing 777 and enough to power 600 homes. The lithium battery pack, about one-and-a-half times the size of the average automobile starter battery is used to start the aircraft's auxiliary power unit or APU, a small turbine engine used to power the aircraft's electrical system, usually while on the ground.
Ground personnel and caterers at Boston Logan noticed smoke in the cabin during routine servicing of the aircraft prior to its return flight.
With the batteries cleared, potential other instigators multiple, from the BMS to what is described as the 787's "innovative electrical system." Had the high-energy density cobalt-oxide cells been at fault, Boeing could simply have replaced them with those from another manufacturer or chemistry: pilots have suggested NiCAD. Personally, NiMH might be even better, though heavier and somewhat less energy-dense. The longer 787s stay on the ground, the more it hurts the airlines already operating them, as well as those with Dreamliner's on order. [See http://nyc787.blogspot.com/].
And, naturally, the grounding and delays also have a serious economic impact on Boeing and its suppliers, not to mention creating a public relations nightmare for the Seattle plane maker.
As a number of reports have pointed out, the chemistry used in 787 lithium batteries is not the same as those used in cars like the Nissan Leaf and Chevrolet Volt. Both use lower energy density, but more stable, chemistries: LG Chem-produced lithium manganese spinel, in the case of the Volt. While lithium chemistries have several times the energy storage potential of older types like NiMH or NiCAD, which produce lower voltages than Lithium at the individual cell level, lithium has the drawback of requiring careful charge management, hence the need for multiple microprocessors to monitor and manage charge and discharge of the cells. It could be one of the microprocessors that is failing, but it's still too early to tell.
The implications for electric vehicles is clear: will problems on the Dreamliner impact public perception and acceptance of lithium-ion powered electric-drive cars? The sooner the culprit is found in the 787, the better for the all concerned; but more importantly, the more we will know about how to engineer and manufacture an even safer, more reliable vehicle for the future.
Originally published: 28 Jan 2013
|<< PREVIOUS||NEXT >>|
blog comments powered by Disqus