Questions about the cooling of the Boeing 787's batteries came up again this week, as Tesla Motors CEO Elon Musk publicly stated that the plane's large pack design is a risky one.
"Unfortunately, the pack architecture supplied to Boeing is inherently unsafe," he wrote in an email to Flightglobal.com. "Large cells without enough space between them to isolate against the cell-to-cell thermal domino effect means it is simply a matter of time before there are more incidents of this nature."
Tesla uses lithium-ion battery packs in its Tesla Roadster and Tesla Model S vehicles. Its design involves 6,000-7,000 small lithium-ion cells. Musk told Flightglobal that the cells are separated in a way that makes them less likely than large cells to suffer from thermal runaway events.
Elon Musk of Tesla and SpaceX: "Unfortunately, the pack architecture supplied to Boeing is inherently unsafe." (Source: revengeoftheelectriccar.com)
Musk has tweeted his desire to help Boeing with its battery problems, which included incidents in two Japan Airlines flights and a United flight this month. On Jan. 18, he wrote, "Maybe already under control, but Tesla and SpaceX are happy to help with the 787 lithium ion batteries." A few days ago, he followed up: "Desire to help Boeing is real & am corresponding w 787 chief engineer." Shanna Hendriks, a spokeswoman for Tesla Motors, confirmed to us that Musk made the comments on his Twitter account and by email to Flightglobal.
Marc Birtel, a Boeing spokesman, would not verify whether his company's chief engineer has been in contact with Musk. "We're engaged with a number of experts both inside and outside the company," he told us, but Boeing is "not identifying them by name publicly."
The issue of battery cooling has been at the forefront of the Boeing story for a week. Donald Sadoway, the John F. Elliott professor of materials chemistry at MIT who is involved in a battery startup with Bill Gates, told us last week that a forced air cooling system and sensors may be needed to monitor and cool the battery in the event of overheating. Elton Cairns, a professor of chemical and biomolecular engineering at the University of California, Berkeley, and a fuel cell designer for NASA's Gemini spaceflights, also suggested that an air- or liquid-cooled system would be necessary.
Even at low temperatures, the Boeing system could still have been at risk, according to Cairns. "When the plane is at altitude, the air is less dense," he told us. "So even if it's cooler, the less dense air may not have adequate heating capacity to provide enough cooling for the battery. If they don't have active cooling, then I question the adequacy of the cooling arrangement."
Boeing uses eight lithium cobalt oxide cells in its battery packs. According to experts, the cobalt oxide chemistry is known to have higher energy densities than other forms of lithium-ion, so it needs an active cooling system.
Boeing representatives told us that they are not aware of an active cooling system for the 787 batteries. "Obviously, there were multiple backups associated with the battery to ensure the system was safe against overcharging and overdischarging," Birtel said. "But there was not a specific cooling system associated with the battery."
Cairns called battery management ICs (to monitor voltage and current) an important part of a safe pack, but he also said energetic batteries often need more than that.
"The electrical system that manages the battery is not a complete battery management system," he said. "In my view, a complete battery management system includes the dispersion of any heat that is generated by the operation of the battery. Just having protective circuits is fine, but it is absolutely insufficient."
Give Boeing some credit for all their latest generation satellites using lithium ion batteries, no active cooling, in service for years, nasty environment. They successfully use lithium ion batteries in environments much tougher than the street. Were the batteries tested? Throwing a half billion dollar satellite up with untested batteries would be unthinkable.
Spot-on, Warren! They sound like the typical arrogant EE refusing to admit they overlooked something. On the flip side of that, Musk is trying his best to kill the potential fear-induced legislation that will surely follow the frenzy of unfounded "lithium is evil" headlines.
Since the batteries were probably not online and sourcing current (let's hope their design doesn't require cells all the time), I would look into their BMS/charging system. That's most likely the root cause here.
The heat developed by these batteries was ignored during design and project management. How can be ignored that 4 batteries have half of surface cooled and by the other 4 (in the middle) less than 1/4 of the lateral surface is cooled.
The case has no openings, the air cooling was not present. The only cooling available was trough the contact between the bottom of the batteries and the case.
Tesla can teach Boeing! They have several years of experience with LI-ION and this should not be ignored by very proud engineers.
Here's a short article from EE Times on the history of the lithium-ion battery chemistry, and its original devloper, John Goodenough of the University of Texas:
It kinda sounds like Boeing engineers were not aware that their Li-ion batteries needed active cooling. You would think the battery supplier would have provided that information or that the issue would have been discovered in testing... Maybe not. Either way, I'm sure Boeing will have the issue resolved very soon.
If I'm not mistaken, these units are intended as a backup power source. If so, they would not be expected to be used significantly during a routine flight. It makes me wonder why these batteries are being completely drained and failing. It seems like this may be a symptom of another problem. Not enough main power?
I am just amazed at all of the irresponsible comments flying around. Tesla in particular is not one to talk. They actually used standard laptop batteries rather than the much more costly space rated batteries in the 787. The Tesla design struck me as total seat of the pants engineering. Me thinks Musk's comments are more CYA than anything.
Obviously something is going on and the folks invloved need to figure it out. Nothing flys on a commercial airliner without a significant amount of history. Lithium batteries have been a subject of conversation in the airline business since the 70's. I'm sure they fully understood what needed to be done.
The NY times article mentions that the batteries have a long history in space applications. I would not be surprised if they did not have a long history in military applications also. The main reason for the use of older technology is precisly that it has a longer history than the next latest thing. The question now seems to be what went wrong.
We need to wait for the results of the investigation.
Encourage the Liaison Engineers to come forward since they are the fixers who return nonconformances to the design intent during the manufacture of aircraft. Most times the fixes are viable, other times they may be over ruled by circumstances but nevertheless there is a paper trail which defines what's going on.
Encourage the Liaison Engineers to come forward since they are the fixers who return nonconformances to the design intent during the manufacture of aircraft. Most times the fixes are viable, other times they may be over ruled by circumstances but nevertheless there is a paper trail which defines what's going on.
For 3D printing to make the jump from rapid prototyping to manufacturing, engineers will need to find easier ways to move products from their CAD screens to their printers.
Gigabit and PoE are two networking technologies moving ahead in tandem as industrial users power remote Ethernet devices such as IP security cameras at 1,000 Mbps over existing CAT5 cable.
New versions of BASF's Ecovio line are both compostable and designed for either injection molding or thermoforming. These combinations are becoming more common for the single-use bioplastics used in food service and food packaging applications, but are still not widely available.
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