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Aha, quality defect with the wiring. That's actually good news for Boeing. It means that the basic design was solid, and they can fix the problem. They'll probably end up adding an extra safety feature to the battery pack, and improve the inspections and testing on the wiring.
The short-term fix focuses on a new containment system for the existing unit, together with added venting ducts for smoke and additional monitors.
Boeing Pushes For FAA Green Light On 787 Plan
Or another way to say it - they're adding a fireplace and chimney around the battery.
Conner’s proposal package is also believed to include longer term options for a revised configuration that would minimize the chances of a battery overheating in the first place, as well as from being destroyed in a thermal runaway. These would include a more significant redesign of the battery itself with the provision of interstitial space and possibly insulation between individual cells, additional voltage and temperature monitors and cooling. The longer-term fix likely would be undertaken through a supplemental type certificate, say regulatory agency sources.
This report just came out today. Doesn't appear that there is any internal cooling process in these batteries. Different chemistry than Tesla battery pack?
New Report Points to Risk With Boeing 787 Battery - The Daily Beast
Aha, quality defect with the wiring. That's actually good news for Boeing. It means that the basic design was solid, and they can fix the problem. They'll probably end up adding an extra safety feature to the battery pack, and improve the inspections and testing on the wiring.
With the root cause of the Boeing 787 battery fire still unclear, one leading battery expert suggested this week that the need for an active cooling system on Dreamliners is even more important.
"This is a step in the right direction," Elton Cairns, a professor of chemical and biomolecular engineering at the University of California Berkeley, said of Boeing’s reported intention to put more space between the battery’s cells. "But it’s not clear that it’s sufficient."
Cairns told Design News that an active cooling system -- particularly one that uses a liquid coolant to draw heat away from the battery pack -- is especially important, given the fact that the failure mechanism in the JAL Boeing 787 fire in January is not fully understood yet. A liquid cooling system -- like the kind used in the Chevy Volt battery pack -- would be more likely to isolate heat and prevent it from passing from cell to cell, he said.
"The battery did catch fire and you don’t want that to happen under any circumstances," Cairns said of the 787 incident. "We know for sure that the thermal management system needs to be changed, even if there was an externally caused short circuit."
Cairns is a well-known expert in the battery community, having designed fuel cells for the Gemini space program, and having served at General Electric Research Laboratory, General Motors Research Laboratory, Argonne National Laboratory, and Lawrence Berkeley National Laboratory
According to numerous news reports, Boeing plans to fix its 787 battery by employing additional spacing between the battery’s eight cells to allow for more effective cooling. Boeing reportedly will also use a more fire-resistant container, add sensors for monitoring cell temperatures, and equip the 787 with the ability to vent smoke to the outside. Venting would require that Boeing cut and reinforce holes in the jet’s carbon fiber skin, according to a report in The Wall Street Journal.
After more than a month of intense study of the January battery fire, Boeing is confident that its engineers know the way to fix the faulty lithium-ion battery packs that grounded the 787 Dreamliner fleet in January. The company is now awaiting approval from the Federal Aviation Administration (FAA) to test the new battery design. “Ever since the fleet was grounded, our team has been working around the clock,” Boeing Co. spokesman Marc Birtel told Design News. "We brought in experts from outside, as well as within the company, to validate our ideas, and that culminated in our proposal to the FAA."
Cairns told Design News that the biggest safety concern is the low density of air at high altitudes. There, he said, it might be more difficult to draw heat away from the battery.
"A much safer solution would be to have a liquid-based thermal management system," he said. "You don’t want the battery to get too cold and you don’t want it to get too hot." A liquid-based cooling system would not be affected by the density of the surrounding air, he added.
The U.S. Federal Aviation Administration has given Boeing’s battery system redesign plan the green light, but only on condition the manufacturer conducts “extensive testing and analysis to demonstrate compliance with the applicable safety regulations and special conditions.
Here's a scan of the other battery in the plane that was not involved in a fire. The cells are also swollen, probably from overcharging.
Before any of these fire issues they were replacing these batteries at an alarming rate.
I'm sorry but this battery should not be getting hot enough to need active cooling, if it is then it's not sized properly and/or it's not the right chemistry. This is not an EV pack that needs to put out a lot of power for a long time, it's a starter battery for the APU, (generator). From the beginning I've thought this could be a charge/discharge issue that wasn't properly controlled by the BMS and/or the charger, and in the latest EVTV episode Jack Rickard points out a possible flaw in the design. The specs show a max operating voltage of 32.2V or 4.025V per cell. If the generator is run for a long period and charging is never completely shut off then 4.025V is above the full resting voltage of the cell, so that means the cell could be consistently over charged every time the APU is running. Over time this could lead to swelling, shorting, and eventually burning of the cell, especially after one cell goes dead and the charger tries to bring the voltage back up by increasing current.