Boeing Dreamliner Investigation Focuses on Combusting Batteries

A week after the Federal Aviation Administration initiated a grounding of the Boeing 787 that spread worldwide, there is still no indication of when the Dreamliner fleet may return to the skies. After some initial hope that the airplane could begin flying again over the weekend, investigators in the U.S. and Japan continue to focus on the pair of cooked lithium-ion batteries that led to the first grounding of an American commercial airplane fleet since 1979.

The National Transportation Safety Board is examining the 63-pound lithium-ion battery from the 787 that caught fire in Boston on January 7, along with stored data from the airplane, and currently believes the battery did not suffer an overcharging. Japanese investigators came to a similar conclusion after looking at the 787 that made an emergency landing last week in Japan.

At a press conference today, NTSB Chairman Deborah Hersman emphasized the seriousness of the two events affecting the 787.

“This is an unprecedented event,” Hersman said, “and this is a very serious air-safety concern.”

Hersman said the NTSB is concerned that there were two separate battery failure events involved in such a new aircraft. The NTSB is working with Boeing, Japanese investigators along with other investigators from around the world to try and determine why the battery failures occurred.

The NTSB has two shifts of investigators working in both the U.S. and Japan. Hersman confirmed the battery involved in the 787 that caught fire in Boston did show evidence of a short circuit in one of the eight cells that make up the battery. No information was given about how long the investigation may take or what may need to be done to the grounded 787 fleet before it can return to flight.

“If we find that there are any vulnerabilities, we will make recommendations” Hersman said.

The lithium-ion batteries used in the 787 are relatively new batteries made of relatively large cells compared to those used in most consumer devices. The history of lithium-ion batteries has many thinking the problem might not be a “teething problem” with the airplane, but instead an issue with the batteries.

Unlike the well-proven, and relatively small bundles of battery cells used in consumer devices or even the Tesla electric car known as “18650s,” the batteries in the 787 made by GS Yuasa of Japan are produced in low numbers and are not used in many applications. And as the focus on the battery continues, one lithium-ion expert says the large batteries used by Boeing simply increase the potential for failure

“As the size of the cell increases, the chance of something happening increases because you have an increased amount of material being exposed” says Dr. K.M. Abraham. “[Lithium-ion batteries] are not as forgiving as far as design and construction are concerned. If you have quality control issues, it can be very bad.”

Dr. Abraham is a battery consultant and professor at Northeastern University in Boston and has been researching lithium-ion batteries since 1976. The large 32 volt battery like those found in the 787 is made up of eight 3.7 volt cells.

Lithium-ion batteries are extremely power dense, delivering a lot of electricity from a relatively compact package. To do this they need extremely thin sheets of the plastic material to separate the cathodes and anodes inside the battery. Dr. Abraham says the design and construction of a battery is critical so that these separators are not damaged during manufacturing or during a battery’s use.
 
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