Boeing has gotten permission from the U.S. Federal Aviation Administration to test a solution to the battery problem that grounded its worldwide fleet of 787 Dreamliners in January. Tests in two planes could begin in a matter of days, ABC news reported this morning.
Whether it's a solution for the ages or a mere Band-aid is a matter of judgment, or of taste. What is clear, though, is that the solution aims not to prevent battery fires but to live with them. It uses the same lithium-ion cells as before but inserts insulating barriers, which should make it harder for a thermal runaway reaction in one cell from propagating to neighboring cells. The containment vessel will also be strengthened and fitted with a smoke-venting system.
Boeing’s solution reflects some but not all of the suggestions made last month by Elon Musk, the founder of Tesla Motors. That company's pioneering all-electric Tesla Roadster uses lithium-ion batteries based, like Boeing's, on a cobalt-oxide chemistry, perhaps the best on offer in the mid-2000s, when both companies made their key design decisions. No Roadster has had a battery fire, but even so, newer, safer lithium-ion chemistries have pretty much taken over the electric-car industry.
Tesla’s design is safe, Musk contends, because it uses a large number of small cells and separates them properly, with an air gap. Boeing’s solution uses the same eight comparatively large cells as before, though with added insulation.
“When thermal runaway occurs with a big cell, a proportionately larger amount of energy is released and it is very difficult to prevent that energy from then heating up the neighboring cells and causing a domino effect that results in the entire pack catching fire," Musk told Flightglobal back in February.
Airbus, Boeing’s archrival, had also planned to use lithium-ion batteries in its upcoming A350 airliner, but last month it announced that it would revert to the old-fashioned nickel-cadmium battery. That move ensures that the market debut of the plane will not be delayed much. It would be much harder for Boeing to undertake such a fundamental redesign. For one thing, it would have to retrofit all the planes it has already delivered.
Both manufacturers originally wanted lithium-ion not so much because they were lighter than nickel cadmium—a difference that here amounts to about the weight a single, burly passenger—but because they're supposed to be quicker to charge and easier to maintain. It’s fair to say that the latter claim has already been debunked.