Lithium ion batteries suspect in 787 fire

[TonyWilliams]

Wow. I knew LiMn2O4 was safer, but I had not seen these numbers. They suggest that Tesla and RAV4 EV drivers have to put a lot of faith in the quality of Tesla's battery and temperature management system. Has its record with the Tesla Roadster been clean with respect to Li-ion fires?

I'm not aware of any Roadster battery issues, except bricking !!!

 

[surfingslovak]

John Voelcker wrote a good and timely article on this: Boeing 787 Batteries Same As Those In Electric Cars? Umm, NO

 

[dgpcolorado]

Exactly what are these batteries used for? To back up the power generation from the engines? That comes from bleed air? Or is it to start the APU?

The 787 uses "fly-by-wire" controls, rather than hydraulics (or cables and push rods going farther back in aircraft design). I believe that the batteries are used to back up the various control systems in case of generator failure.

Fly-by-wire is lighter than traditional mechanically linked controls but it takes some redundancy to have enough backups in case of an electrical system failure. As someone used to mechanical flight controls, fly-by-wire makes me uncomfortable! So I guess that dates me as an old guy.

 

[TonyWilliams]

Exactly what are these batteries used for? To back up the power generation from the engines? That comes from bleed air? Or is it to start the APU?

The 787 uses "fly-by-wire" controls, rather than hydraulics (or cables and push rods going farther back in aircraft design). I believe that the batteries are used to back up the various control systems in case of generator failure.

Fly-by-wire is lighter than traditional mechanically linked controls but it takes some redundancy to have enough backups in case of an electrical system failure. As someone used to mechanical flight controls, fly-by-wire makes me uncomfortable! So I guess that dates me as an old guy.

Fly-by-wire has been used in commercial transport (Airbus) for decades. Boeing goes to the next step, and largely (maybe entirely?) eliminates hydraulics, even for the brakes.

Bold stuff in a very conservative business. It sounds like the electric components are fine, and "just" an issue associated with the battery components (which can include wiring).

 

[LTLFTcomposite]

Bold stuff in a very conservative business.

Interesting to note from that article that the first foray into Li Ion batteries in jetliners would be with the riskier chemistry.

 

[evnow]

Technology
Lithium Cobalt Oxide cathode material: Provides the best combination of high reliability, high
energy storage,and long life.

Hmmm ... this is the laptop battery.

 

[Herm]

I believe LiFePO4 was getting started (A123?) around 2005, about when this system was getting certified. How long will it take them to certify a different chemistry?.. years?

 

[surfingslovak]

I believe LiFePO4 was getting started (A123?) around 2005, about when this system was getting certified. How long will it take them to certify a different chemistry?.. years?

Great point. On a related note, how long will it take Toyota to replace their NiMH batteries in the Prius with LiFePO4? I think the benefits are clear, and yet it's seemingly not enough to affect change. In the case of the Dreamliner, it was likely a tradeoff between cost, weight and the perceived risk. They probably expected that the BMS will keep the cells safe and happy. I bet that there were people at Nissan thinking something along the same lines, when they decided against an active temperature management system for their batteries. None of these decisions was perfect, obviously, and they all signal varying risk tolerance level. If nothing else, at least battery fires are not a concern with the LEAF.

 

[TonyWilliams]

If nothing else, at least battery fires are not a concern with the LEAF.

Yes, I think I prefer the "safe" LEAF batteries, but not enough to not buy a Tesla (or drive my Rav4). Fortunately, I don't think they will blow up, short of a major impact.

 

[mkjayakumar]

A large OEM like GM or Ford has just too much at stake and too much to lose to take a risk like that. Only a struggling small start-up like Tesla, which is an extremely risky venture to begin with, on the perilous edge of survival, can afford to take an enormous risk like that."

Somehow this last statement in that writeup makes me think the facts are selectively chosen to create a FUD against Tesla. In a technical article that supposedly talks about battery chemistry and their relative merits, the adjectives such as 'struggling', 'small start-up', 'extremely risky', 'perilous edge of survival', 'enormous risk' - all suggest that the author has an axe to grind against Tesla. While the narrowly focused technical facts may be accurate, the larger picture painted might be grossly exaggerated.

 

[TonyWilliams]

A large OEM like GM or Ford has just too much at stake and too much to lose to take a risk like that. Only a struggling small start-up like Tesla, which is an extremely risky venture to begin with, on the perilous edge of survival, can afford to take an enormous risk like that."

Somehow this last statement in that writeup makes me think the facts are selectively chosen to create a FUD against Tesla. In a technical article that supposedly talks about battery chemistry and their relative merits, the adjectives such as 'struggling', 'small start-up', 'extremely risky', 'perilous edge of survival', 'enormous risk' - all suggest that the author has an axe to grind against Tesla. While the narrowly focused technical facts may be accurate, the larger picture painted might be grossly exaggerated.

The quote is from 2009 or 2010, I think. Yes, Tesla was struggling then.

 

[surfingslovak]

The quote is from 2009 or 2010, I think. Yes, Tesla was struggling then.

Right, they are doing much better today. Instead of manually assembling an ultra-low-volume car from Lotus gliders at a former a GM dealership in Menlo Park, they have a state-of-the-art factory in Fremont churnig out very desirable cars based on their original design. It's a tough industry, but they seem to be on a path to success now.

 

[TomT]

Perhaps Boeing needs a battery TMS too:

http://arstechnica.com/business/2013/01/boeings-dreamliner-batteries-inherently-unsafe-and-yours-may-be-too/" onclick="window.open(this.href);return false;

 

[LTLFTcomposite]

They help start up the plane's onboard power plant, which generates 5 megawatts of electricity

Holy moly.

The batteries selected for the Dreamliner "were very large scale—65 amp-hour batteries which is very, very large,"

Without stating the voltage, does that statement in itself indicate the batteries are all that large? A car battery has more amp hours that that doesn't it?

"They are very high power batteries, and they charge them to 90 percent (of capacity) in about 70 minutes. That's a very fast charge for any lithium battery of this size. And that's a problem when there isn't a cooling system incorporated."

No TMS? They took a page from the LEAF playbook.
They probably just need to set the charge timer to 80%.

 

[surfingslovak]

But there are also much safer choices for the cathode material in large lithium batteries that can reduce the risk of explosive combustion. Allen hopes that the Dreamliner issues will lead to wider adoption of safer battery technology.

"They are available and becoming more popular," Allen said. "Lithium nickel manganese oxide cathodes are safer, and iron phosphate ones are much safer because they don't actually release oxygen when you arc it or when it's damaged."

Great article, thanks for posting. Love the glowing endorsement of LMO and LiFEPO batteries.

No TMS? They took a page from the LEAF playbook.
They probably just need to set the charge timer to 80%.

LOL, yeah. (Unless you were serious).

 

[TomT]

DC aircraft systems used to be 28 volts but I suspect that the 787 uses something much higher to reduce wiring size and losses... In any event, it is a smaller battery than that of the Leaf...

Without stating the voltage, does that statement in itself indicate the batteries are all that large? A car battery has more amp hours that that doesn't it?

 

[surfingslovak]

DC aircraft systems used to be 28 volts but I suspect that the 787 uses something much higher to reduce wiring size and losses... In any event, it is a smaller battery than that of the Leaf...

Without stating the voltage, does that statement in itself indicate the batteries are all that large? A car battery has more amp hours that that doesn't it?

I wonder if they were referring to cell capacity. 65 amp-hour would be giant, even in the automotive world. The LEAF has 33 amp-hour cells with 3.75V nominal voltage. This is very comparable to the cobalt oxide chemistry, which has only marginally higher cell voltages.

EDIT: Looks like this thread is getting some notoriety. I believe Boeing has IT and electronic design functions in Artesia.

 

[LTLFTcomposite]

I'm having a hard time picturing how they get this resolved in any reasonable amount of time. What are the odds we hear is taken care of with a software update? If they have to switch to something different, wouldn't that take many months if not years to test and get certified?

Presumably they are still building planes as fast as they can and will park them on the assumption that a fix is forthcoming. That will only work for so long though.

 

[surfingslovak]

I'm having a hard time picturing how they get this resolved in any reasonable amount of time.

Agreed. I'm not an aviation expert, but I worked on software used to track maintenance work and part replacements by commercial carriers and defense contractors. My impression was that everything is highly regulated, and there is quite a bit of process involved. Even if Boeing left the current battery design untouched and applied minimal changes, such as lower maximum SOC to 70% or 80% in addition to throttling the charge current, it could take a while to get these changes tested and approved.

Here is a post from someone, who used to work at Boeing:

For battery choice, that likely meant going with the most energy-dense battery design possible, and managing the risk of fire through careful planning and procedures.

 

[TonyWilliams]

I haven't honestly been following the 787 fire issue very closely, mostly because I think the root cause will be design arrogance or management override of good design, or maybe both.

But, in aviation, they aren't going to get anything accomplished AND approved by FAA quickly.

As to the size of the batteries, the dune buggy I'm working on has 180 amp/hour LiFePO4 cells at 3.305v nominal multiplied by 138 cells, 82kWh nominal. We can pump those up to 3.6v. The cells themselves aren't that big:

Capacity: 180Ah
Height: 275 mm
Length/Depth: 71 mm
Width: 182 mm .... or 7.17" W x 2.80" L x 10.94" H
Weight: 5.6kg (12.35 lbs)
Bolt Size: M8
Voltage nominal: 3.2V
Charge voltage cut-off: 3.6V
Discharging cut-off: 2.5V
Life Cycle (0.3c Charging-Discharging, 80%DOD): 2000
Maximum Discharging Current (10 sec.): 1000 Amps
Chemistry: LiFePO4