# Boeing 787 & Li-Ion batteries vs recent fires



## moldyoldy (Jan 8, 2013)

This is not good for several reasons:

http://online.wsj.com/article/SB10001424127887323482504578227621155767836.html?KEYWORDS=Boeing

while at an exercise club at about 0640 this morning on Ch-355 on DirectTV, there was a long exchange about Li-Ion batteries replacing the usual electrical generation from bleed-air on Boeing 787s. Not only has the 787 had various fires, but systems have shut down in flight with no warning. All TBD.


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## Nite (Jan 17, 2013)

[h=1]U.S., others ground Boeing Dreamliner indefinitely[/h]http://www.reuters.com/article/2013/01/17/us-boeing-dreamliner-idUSBRE90F1N820130117




[h=1]Batteries blamed in Boeing 787 grounding are widely used[/h]http://www.reuters.com/article/2013/01/17/us-boeing-dreamliner-faa-battery-idUSBRE90G06320130117


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## VidPro (Jan 17, 2013)

from http://www.nytimes.com/2013/01/18/b...e-ground-boeing-787s.html?pagewanted=all&_r=0
this artical, It has a Picture of this Power unit
http://www.nytimes.com/imagepages/2013/01/17/business/DREAM2.html
Different view found on google images (google images search dreamliner battery or dreamliner auxiliary power)
http://images.smh.com.au/2013/01/16/3956405/Art-Dreamliner-Battery-20130116122831682810-620x349.jpg


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## cognitivefun (Jan 17, 2013)

the A380 which has been flying for a few years now also has a lot of lithium ion batteries...


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## moldyoldy (Jan 17, 2013)

http://www.huffingtonpost.com/2013/01/16/787-grounded-faa-orders-a_n_2490941.html

"Mike Sinnett, chief engineer on the 787, said last week that the plane's batteries have operated through a combined 1.3 million hours and never had an internal fault. He said they were built with multiple protections to ensure that failures "don't put the airplane at risk". 
The lithium-ion design was chosen because it's the only type of battery that can take a large charge in a short amount of time."

No wonder those batteries are having problems!


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## TedTheLed (Jan 17, 2013)

Why?

I'll bet on charging without removing them from the circuit, so a parasitic load causes them to charge at too high a voltage..


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## mattheww50 (Jan 17, 2013)

moldyoldy said:


> http://www.huffingtonpost.com/2013/01/16/787-grounded-faa-orders-a_n_2490941.html
> 
> "Mike Sinnett, chief engineer on the 787, said last week that the plane's batteries have operated through a combined 1.3 million hours and never had an internal fault. He said they were built with multiple protections to ensure that failures "don't put the airplane at risk".
> The lithium-ion design was chosen because it's the only type of battery that can take a large charge in a short amount of time."
> ...



This is really UNTRUE. It is certainly not the only type of battery that can take a large charge in a short amount of time. The real reason to use Li-Ion batteries is that for the same capacity, the Li-Ion battery set is about 40 pounds lighter than the NiCd's usually used for this application. 

In the Airline business weight savings=money savings. How much is 40 pounds worth each year? About $3000 at current Jet-A prices.

And as we all know, NiCd's can take immense abuse, and very rapid charging at the expense of battery life.


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## Illum (Jan 17, 2013)

Older passenger aircrafts uses NiCd chemistry to store power from either the APU for the turbine from engine bleed,, is it possible [or even remotely plausible] that the 787's li-ion batteries are being maintained by an NiCd algorithm?


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## Steve K (Jan 17, 2013)

My personal theory is that there are two ways to use an airplane.. the first is the way the designers think people/airlines will use it, and the second is the way that people/airlines will actually use it! 

My guess is that the batteries are getting used much harder than Boeing design and test engineers anticipated.

The example of this principle that sticks with me is the F-18 Hornet. It was designed with the ability to fly at high angle of attack, which was a big change from current aircraft. The pilots liked it so much that they spent much more time at high angles of attack. The downside of this is that the big vortices generated off the leading edge extensions beat the heck out of the rudders, causing cracks at the rudder bases. The fix was to add some ugly brackets at the rudder base, and some uglier strakes on the leading edge extensions. These can be seen on the F-18C/D models, but are eliminated on the F-18E/F models. 
for reference, here's a shot of that strake on the leading edge:
http://www.flickr.com/photos/kurtsj00/5003952301/in/set-72157624827485299
The adjacent photos will help put it in context.

Anyway... I'm hoping that Boeing gets this under control soon. Maybe a switch to a less volatile lithium formulation? Tweak the software to be a bit more gentle with the charging and discharging?? Cross your fingers!


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## moldyoldy (Jan 18, 2013)

The verdict is not in, but the suspicions are very strong: excessive charge rate in to these Li-Ion batteries.

http://kstp.com/news/stories/S2901852.shtml?cat=1

"In the case of the 787 in Boston, the battery in the plane's auxiliary power unit had recently received a large demand on its power and was in the process of charging when the fire ignited, a source familiar with the investigation of the 787 fire in Boston told The Associated Press."

Evidently the Cessna Citation also had similar problems with Li-Ion batteries.


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## jerry i h (Jan 20, 2013)

*LiCo on Boeing 787*

Here is a photo of the fried LiCo:
http://www.technologyreview.com/new...eamliners-use-batteries-prone-to-overheating/ 

Here is photo before "spontaneous combustion": 
http://www.foxnews.com/science/2013...-responsible-for-boeing-dreamliner-grounding/ 

Comments? I realize the technical details are buried in a Boeing spec book somewhere. I also read that Yuasa made Boeing's lithiums. More info?


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## TedTheLed (Jan 20, 2013)

"An investigator in Japan, where a 787 made an emergency landing earlier this week, said the charred insides of the plane's lithium ion battery show the battery received voltage in excess of its design limits.
** *
The similarity of the burned battery from the All Nippon Airways flight to the burned battery in a Japan Airlines 787 that caught fire Jan. 7 while the jet was parked at Boston's Logan International Airport suggests a common cause, Japan transport ministry investigator Hideyo Kosugi said.
** *
"If we compare data from the latest case here and that in the U.S., we can pretty much figure out what happened," Kosugi said."

That about covers it, I'd say... :shrug:


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## ElectronGuru (Jan 20, 2013)

TedTheLed said:


> the charred insides of the plane's lithium ion battery show the battery received voltage in excess of its design limits.



Since the charging system checks out, it almost sounds like the battery packs were wired up at a lower voltage. But it can't be that simple...


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## shadowjk (Jan 21, 2013)

Single cell short out due to foreign object damage, which the pack survives without catching fire, but effectively drops the pack voltage by 3.7/4.2V?


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## TinderBox (UK) (Jan 21, 2013)

heard on the news this morning that overcharging had been ruled out!

Will these cells have been charged using a ballanced charger so charge level imbalance would not happen.

John.


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## jerry i h (Jan 21, 2013)

According to this Reuter's story, Dreamliner probe widens after excess battery voltage ruled out

Now, would it be wrong to say that among a large number of LiCo's after a decent amount of usage, even if a 'good' batch properly manufactured and properly designed recharging circuits, that a small % will fail anyway?


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## Al_D (Jan 26, 2013)

*Battery Fire NTSB Briefing - JAL 787*

For all you pilots, avionics techs, battery fiends, and just plain interested.

http://www.youtube.com/watch?v=83BT8NL_9EU


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## moldyoldy (Jan 26, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Thank you for that link! NTSB Chairman Deborah Hersman was very calm, collected and very much in control of the presentation. That was a masterful presentation, both from the aspect of a well-grounded presentation as well as from the political aspect of how to present a high-level in-process engineering root cause analysis to a technical public with Q&A allowed! Ms. Hersman very neatly avoided many of the pitfalls that so many corporate chairmen have fallen in to during Q&A (hence Q&A is usually not allowed). There is a lot of political and technical pressure on her and the NTSB in this very visible investigation of the Boeing 787 battery system. As importantly, Ms Hersman very clearly separated the responsibilities of the FAA from the NTSB. 

Some observations about the information given: The cells were flattened, almost like a pocket plate NiCd cell, yet were a jelly roll construction. How much flattening occured after the jelly roll was wrapped? The information provided in this presentation omitted a report from a Boeing designer that the JAL Boston 787 battery underwent heavy current surges in/out of the battery just prior to the fire. However such information was dealt with by the repeated comment that the NTSB is attempting to understand what was being measured, how and where (& when). The photos provided by Ms. Hersman did show that the system intended to monitor the batteries seems to have suffered the most damage, although it was not clear where that circuitry was located in relationship to the cells.


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## Al_D (Jan 26, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

I'm pretty sure what will end up happening is that Boeing will deflect to the manufacturer of the pack. If Boeing was only a commercial company I would say they were in serious trouble. A fleet grounding is as severe as it gets (hopefully).


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## TedTheLed (Jan 27, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

I hope this long paste is ok.
if not here is the link:

1/27/2013 @ 10:25AM 
MIT Professor: Battery Fix Could Ground 787 Until 2014

http://www.forbes.com/sites/peterco...ssor-battery-fix-could-ground-787-until-2014/

Copyright content removed, a brief sample is OK, but copying the whole article is not - Norm


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## jerry i h (Jan 29, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Here is very cool CAD drawing of the battery cluster, including the internal construction of the Li-ion cells. 
Here is a very interesting picture showing the battery pack cover. Most press photos cut-off the covers at the bottom of the photo. I did not realize that it covers the whole box, making a neat and tidy hermetically sealed box. 
Question for the Boeing engineering staff: OK, the heat that builds up during recharge, escapes from the sealed box...how??


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## IMSabbel (Jan 29, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Cause you know, nobody ever had that unique thought ever before, and surely nobody included the heat parameter in the countless FEM calculations that had this box tested for vibration load, thermal stress, air pressure cycling, current densities and so on that are the basic requirement to get anything certifed to fly on a plane.


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## TedTheLed (Jan 29, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Hey, something wasn't done right. It may well be the non-spacing of the batteries was a factor. Even I leave half an inch between lead acid batteries in my solar bank..
Those batteries sure are packed in and sealed tight, not even a fan in sight, if there were space to blow between cells..


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## SemiMan (Jan 29, 2013)

TedTheLed said:


> Why?
> 
> I'll bet on charging without removing them from the circuit, so a parasitic load causes them to charge at too high a voltage..




This is mainly an issue of Lead-Acid batteries where polarization causes the charge voltage to be higher than the operational voltage of the battery which can lead to the battery being continuously charged if there is a parasitic load. That generally leads to a shortened life for the battery, not a sudden failure.

With lithium, you are going to be 4.2V and under. If the parasitic load draws the battery under that voltage, then the battery is discharged and leaving a voltage on it would not cause any sudden failures.

Semiman


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## SemiMan (Jan 29, 2013)

Looking at the linked pictures, it looks like there is some space between the sets of batteries. Does it look that way to others or am I misinterpreting the pictures?


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## Steve K (Jan 29, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



jerry i h said:


> ...
> Question for the Boeing engineering staff: OK, the heat that builds up during recharge, escapes from the sealed box...how??



seems like a fair enough question...
A common method for cooling avionics is to have cooling air ducted through the avionics package via a port in the rack that the avionics device is mounted to. This is normally at the rear of the device. I don't see anything in the pictures that suggests cooling air. 

Some hybrid cars use liquid coolant in their battery packs. I haven't noticed anything in the photos that suggest liquid coolant either (and I can't recall ever seeing liquid coolant on an aircraft, other than radiators for reciprocating engines).

A quick perusal of the web comes up with various tech folks asking the same question about how the thermal regulation was implemented on the battery packs. I feel confident in two things, however:
1. the Boeing lawyers have carefully instructed the relevant personnel to keep their mouths shut.... and
2. the relevant personnel are being kept busy in labs and meetings to find out what the heck went wrong, and probably haven't had the luxury of sleep since this whole thing started.
(don't ask me why I have this insight, though.. "I can neither confirm nor deny")


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## Steve K (Jan 29, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



TedTheLed said:


> Hey, something wasn't done right. It may well be the non-spacing of the batteries was a factor. Even I leave half an inch between lead acid batteries in my solar bank..
> Those batteries sure are packed in and sealed tight, not even a fan in sight, if there were space to blow between cells..



The spacing doesn't appear much different than the nicad batteries in the satellite power system I used to work with.
little picture: http://farm5.staticflickr.com/4025/4436489635_6063868596_d.jpg
big picture:http://farm5.staticflickr.com/4025/4436489635_08d90267c2_o_d.jpg
The photo of the module is in the upper left hand corner, and you can see the three batteries composed of rectangular nicad cells roughly in the lower center.

There was no coolant; neither liquid or gas. The batteries were mounted on a thermal plate, and there were louvers that permitted the energy to radiate into space as needed. There were also plenty of temperature sensors on the batteries that would reduce charging current as they reached full charge and warmed up.


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## BVH (Jan 29, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Not that it matters and probably just being picky but the last inch or so of the termination of the two sets of bulkhead connector wires into the connector just looks sloppy as compared to typically military hardware.


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## Norm (Jan 30, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Boeing Knew About The 787 Dreamliner’s Battery Problems Before It Caught Fire

Norm


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## jerry i h (Jan 30, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



Norm said:


> Boeing Knew About The 787 Dreamliner’s Battery Problems Before It Caught Fire
> 
> Norm



Oy...


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## Steve K (Jan 30, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

It's worthwhile to read the New York Times article that Norm's link references.. lots more detail there:
http://www.nytimes.com/2013/01/30/b...of-battery-ills-before-the-fires.html?hp&_r=0

I think it's a bit misleading for the headline to say that Boeing knew about "the battery problem". Boeing knew that some batteries had been replaced....
"Officials at All Nippon Airways, the jets’ biggest operator, said in an interview on Tuesday that it replaced 10 of the batteries in the months before fire in one plane and smoke in another led regulators around the world to ground the jets. The airline said it told Boeing of the replacements as they occurred."

Not a lot of info on why the batteries were replaced.... 
"In five of the 10 replacements, All Nippon said that the main battery had showed an unexpectedly low charge."
and.. 
"The airline also revealed that in three instances, the main battery had failed to start normally and had had to be replaced, along with the charger. In other cases, one battery showed an error reading and another, used to start the auxiliary power unit, failed."

Later in the article, Boeing suggests that there is a problem with the charging of the battery:
"Boeing officials said the need to replace the batteries also suggested that safeguards were activated to prevent overheating and keep the drained batteries from being recharged. Company officials said the batteries can drain too deeply if left on without being connected to power sources. Trying to recharge such batteries could generate excessive heat, so safety mechanisms lock out any attempts to do that. "

That's all that I could see that addressed the cause of the battery issues. 

If the previous history with the batteries was a problem with keeping them charged, then that doesn't seem to indicate an immediate safety concern. However... I can see a scenario where problems with battery charge regulation could easily also produce overcharge instead of undercharge. Should be interesting to see where the investigation goes next.


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## TedTheLed (Jan 30, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

.


Steve K said:


> The spacing doesn't appear much different than the nicad batteries in the satellite power system I used to work with.
> little picture: http://farm5.staticflickr.com/4025/4436489635_6063868596_d.jpg
> big picture:http://farm5.staticflickr.com/4025/4436489635_08d90267c2_o_d.jpg
> The photo of the module is in the upper left hand corner, and you can see the three batteries composed of rectangular nicad cells roughly in the lower center.
> ...











.and satellites still use Nicads, I understand , because they are so tough..
..just want to note space is a bit cooler than the tarmac..


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## Steve K (Jan 30, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



TedTheLed said:


> .
> .and satellites still use Nicads, I understand , because they are so tough..
> ..just want to note space is a bit cooler than the tarmac..



well, the modules that I'm referencing were being built in the early 90's (yes, I'm getting old!), so that's one factor. We were exploring the use of nickle-hydride batteries for the next generation. The whole design was based on the airlock battery charger from Skylab, and it was a very dated design even when I was working with it. It was favored because all of it's quirks were well established and there wouldn't be any surprises or risks. The satellite people really didn't like risks.

Space can be hot or cold, depending on whether you are in the sun and/or have any protection from the sun. Spacecraft are usually well designed with this in mind, though. 

Having worked on military aircraft in southwest Arizona for three years, I have more knowledge of tarmac temperatures than I want!  There's nothing like working on an airplane that's been sitting in the sun with the temperature around 124F. Our aircraft didn't have batteries, but the Harriers next to us did. No idea what problems they might have had with their batteries.


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## TedTheLed (Jan 31, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Interesting. Of course, you're right about the sun warming things in space..
And talk about not taking risks, sounds like the building code here; you can't join two pieces of any material that haven't been joined for fifty years already, and you can't use a fastener that isn't approved. Everything, every shape, depth, material, length, overhang, setback, tilt, proximity, size, is specified, so it kind of stultifies creativity, and improvement..


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## gadget_lover (Jan 31, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Batteries in planes should have a high priority, yet for some reason they are sometimes treated like car batteries.

My brother was delayed because the battery was dead in the Cessna that he was supposed to fly cross country. He was part of a flying club, and one of the club employees jump started it for him. He flew it to an airport 2 hours away, and had to have it jumped again to take off. Really! 10,000 feet above the Arizona desert and no way to start the engine if it dies, or to use the radio if you go down. 

I suspect that the airline mechanics have not been given any special training about the possible dangers of high capacity li-ion battery packs. If they don't know about thermal run-away then they might ignore batteries that have an obvious charging problem.

I would be compelled to discover why my battery pack was misbehaving before trusting my safety to them. When my hybrid car threw an error code on vacation, I had it investigated before driving home. That was the prudent thing to do, even though it uses NiMH and the worst that could happen would be that I'd have to pull over and call a tow truck. 

As technology improves we can't count on idiot lights and fuses, we still need to understand what dangers are hidden in the black boxes that we rely on.

Daniel


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## RNDDUDE (Jan 31, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Stacked cells + passive cooling only + wildly varying ambient temperatures around the battery = very poor thermal management of the battery. Hard to believe they violated SO MANY Li-Ion design basics in the packaging.


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## Steve K (Jan 31, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

I was poking around the web looking for application guides for lithium batteries. Didn't find a lot, but did come across Yuasa's site with some pics of their lithium products. 
http://www.gs-yuasa.com/us/products/index.html

You have to scroll about 2/3 of the way down the page to see their lithium batteries. The photos of lithium battery packs don't suggest any cooling. I suppose that they could be air cooled, though. They say they supply cells for aircraft and satellite, which does suggest that they know how to make a very high quality battery cell.


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## Steve K (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

another tidbit of info: Elon Musk has been in contact, he says, with Boeing's 787 chief engineer regarding the battery pack. The article says:
""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." "
http://www.designnews.com/document....84,industry_aero,aid_258307&dfpLayout=article

That last portion of the article is the most interesting, I think...
"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." "


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## TedTheLed (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Stunning...

...and no overheat sensors?

Maybe they oversold the lower heat output of lion vs. Nimh (I think one third the heat output was mentioned) to Boeing..?


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## jerry i h (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

From an article in FlightGlobal :



> Mike Sinnett, Boeing's 787 chief project engineer, explained the careful design philosophy employed for the 787's battery system, the first to serve as a starter for an auxiliary power unit and emergency power back-up in a commercial aircraft.
> 
> 
> "I design a cell to not fail and then assume it will and the ask the next 'what-if' questions," Sinnett said. "And then I design the batteries that if there is a failure of one cell it won't propagate to another. And then I assume that I am wrong and that it will propagate to antoher and then I design the enclosure and the redundancy of the equipment to assume that all the cells are involved and the airplane needs to be able to play through that."



ummm...those of you engineers, sounds like one of those non-answer answers you give at a dog-and-pony shows where you get an uncomfortable or inconvenient question?
In any event, Elon Musk's Dragon9 space shuttle that docked with the ISS has similar battery packs; you don't suppose the answer is that simple? Here and also in the Tesla EVs, he chose to use consumer grade individual 18650 Li-ions from Panasonic, so if one cell blows (and they will), it won't take the whole battery pack with it.


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## Steve K (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

I can only assume that Boeing's lawyers didn't carefully explain the need for ambiguous answers that the plaintiff's attourneys can't use to their advantage...

We'd need to know the full context of that quote from Sinnett, but it's hard to see how those cells can't propogate a failure from one to the next. Clearly the battery housing wasn't containing the smoke from the failed battery, although I don't recall any evidence that flames were coming out (or did I forget that??).

A good FMEA (Failure Modes and Effects Analysis) is critical for anything, and especially for things related to safety, so it's good to see someone acknowledge that a designer has to assume that anything can fail and eventually will. I'd also like to see him address the issue of the thermal control of the battery; how cooling is provided, what sort of temp sensors are implemented and how it affects the charging algorithm, etc. It would also be nice to see how they tested each of these. Due to liability, I don't expect them to start publishing it all on the web, but I hope that one of the investigators from the NTSB, FAA, or NASA is asking for it.


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## jerry i h (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



Steve K said:


> I can only assume that Boeing's lawyers didn't carefully explain the need for ambiguous answers that the plaintiff's attourneys can't use to their advantage...



I mean...


anyway, wait just a doggone second:


> ...I design a cell...


Is he claiming to be an expert in battery chemistry who has done this before, gave custom specs to GS-Yuasa, and that they made the li-ion cell to his specs? It seems more likely that he simply chose an off-the-shelf model and went from there. I found a similar rectangular Li-ion rechargeable in the McMaster-Carr catalog (dang, it is at work so I cannot give relevant specs; that will have to wait for Monday) for like $40.


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## gadget_lover (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

I find it interesting that my cell phone ( an HTC EVO running the Android OS) has heat sensors for the battery and (evidently) stop charging when the battery heats up too much. It shows an alert when it overheats.

I base my interpretation of the charging logic on the fact that when the phone is in it's cradle on my dashboard acting as a GPS in 100 degree summer heat it overheats. It does not fully charge during my drive home when this happens.

It's so simple to add a heat sensor, I can't imagine not having one in a large battery pack charging at altitude.

Daniel


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## mattheww50 (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



gadget_lover said:


> Batteries in planes should have a high priority, yet for some reason they are sometimes treated like car batteries.
> 
> My brother was delayed because the battery was dead in the Cessna that he was supposed to fly cross country. He was part of a flying club, and one of the club employees jump started it for him. He flew it to an airport 2 hours away, and had to have it jumped again to take off. Really! 10,000 feet above the Arizona desert and no way to start the engine if it dies, or to use the radio if you go down.
> 
> Daniel



Two points. Aircraft engines have very low compression ratio's (makes them much easier to turn over). Unless the engine seizes, it will continue to turn over even after it dies. However an inflight engine failure that isn't the result of a catastrophe, or flying into conditions that the aircraft isn't approved for, is a very rare event. Even if the engine does die, there is enough wind moving over the prop to keep the engine turning. For example the Pilots handbook for a Cessna 177RG (200hp O360), says maintain 75 kt IAS, fuel selector to both, ingition to both, mixture full rich, aux fuel pump on, and if the engine is going to start at all, that is all it likely to take. Most light aircraft with fixed landing gear will operate very happily with no functioning electrical system and a dead battery. Don't recommend it, but been there, and done that. (It was a matter of ferrying the aircraft to someplace where we could get the electrical system repaired).


Depends upon the Cessna, (many have O360 engines or smaller). The O360 can be easily started with your bare hands. Takes two people, one in the cockpit, and one to flip the prop. I know this from having had to do it twice on a 180hp O360. Again not recommended, but it certainly can be done.


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## moldyoldy (Feb 1, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



mattheww50 said:


> Two points. Aircraft engines have very low compression ratio's (makes them much easier to turn over). Unless the engine seizes, it will continue to turn over even after it dies. However an inflight engine failure that isn't the result of a catastrophe, or flying into conditions that the aircraft isn't approved for, is a very rare event. Even if the engine does die, there is enough wind moving over the prop to keep the engine turning. For example the Pilots handbook for a Cessna 177RG (200hp O360), says maintain 75 kt IAS, fuel selector to both, ingition to both, mixture full rich, aux fuel pump on, and if the engine is going to start at all, that is all it likely to take. Most light aircraft with fixed landing gear will operate very happily with no functioning electrical system and a dead battery. Don't recommend it, but been there, and done that. (It was a matter of ferrying the aircraft to someplace where we could get the electrical system repaired).
> 
> 
> Depends upon the Cessna, (many have O360 engines or smaller). The O360 can be easily started with your bare hands. Takes two people, one in the cockpit, and one to flip the prop. I know this from having had to do it twice on a 180hp O360. Again not recommended, but it certainly can be done.



Correct, although exceptions exist. I was taught light A/C flying in a Cessna 173 with the geared-up prop as built for Caterpillar, complete with Caterpillar yellow paint. The airline pilot owner did not like to push the climb rate because if the motor cut out, only the battery would start the engine and that was not especially reliable under many flight conditions - which was the subject of the only time he took over the controls from me since I choose too steep of a climbout from takeoff for his preference.

Back on the Boeing 787 batteries: Based on public statements, although the overall battery pack evidently is closely monitored, I am unable to determine what monitoring is provided for at the individual cell level. I suspect that only the macro characteristics of a stack of cells are controlled/monitored/recorded. Are there any reports of individual cell monitoring? In a system like that, the system is probably not self-healing with the ability to cut a "bad" cell or stack of cells out of the circuit because of some undesirable use characteristic. That leaves a rather large gap of knowledge of battery performance during normal flight usage, thus leading to unpleasant discoveries.


----------



## LEDAdd1ct (Feb 2, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

If there is one thing I don't want on a long flight, it is an "unpleasant discovery."

Also, "vent with flame." I don't want that either.


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## jerry i h (Feb 4, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

In the McMaster catalog, I found this interesting thing: *Lightweight Quick-Charging Lithium Batteries*

It looks similar to the 787 cells, but of course this might just be coincidence. Anyone know what's inside? I am hoping that it has plates, since it might be fun to have a similar cell (yes, I saw the price, charger not included). It has 12.8 volts, so I suspect just a 3x2 or 3x3 cluster of smaller, consumer, cylindrical cells Li-ions. Since there is a 2 x voltage version with about half the amp-hours of the 12.8v model, I am pretty sure that it is 6 x 1 or 6 x 2 pack. Just wondering.


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## moldyoldy (Feb 4, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



jerry i h said:


> In the McMaster catalog, I found this interesting thing: *Lightweight Quick-Charging Lithium Batteries*
> 
> It looks similar to the 787 cells, but of course this might just be coincidence. Anyone know what's inside? I am hoping that it has plates, since it might be fun to have a similar cell (yes, I saw the price, charger not included). It has 12.8 volts, so I suspect just a 3x2 or 3x3 cluster of smaller, consumer, cylindrical cells Li-ions. Since there is a 2 x voltage version with about half the amp-hours of the 12.8v model, I am pretty sure that it is 6 x 1 or 6 x 2 pack. Just wondering.



I suspect that the ad writers for that catalog entry were writing open loop:
- I am not aware of a _lithium_ cell, not Li-Ion or any derivative, that can be recharged.
- "can be recharged thousands of times". Really? 
- "Chargers automatically switch between a fast charge and maintaining the charge level.". "maintaining the charge level"? on a rechargeable Lithium cell? sounds like the ad writers were copying the manual for a normal lead-acid or gelled battery.
- 20 hr discharge rate - the ampere rates are all less than 1 amp. and what UPS will run 20hrs?
- "they're a good choice for uninterruptible power supplies (UPS)". nope, not for any UPS that I know of.

Even if I overlook the obvious errors in description, no way these cells are even close to what Boeing was using in the 787.


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## moldyoldy (Feb 6, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Crew-only Boeing 787 flight approved by FAA. no passengers. This flight is not a battery test flight. 

http://www.nytimes.com/2013/02/07/business/faa-to-allow-a-787-flight-with-crew-only.html?hp&_r=0

Per the article, engineers are studying changes to the electrical system. NTSB is trying to figure out how the battery weaknesses were not found during testing. Boeing engineers are evidently attempting to retain the Li-Ion batteries with workarounds for thermal runaway and containment, although another Boeing team is investigating alternative technologies:


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## jerry i h (Feb 7, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

Uh-oh...

U.S. Officials Fault F.A.A. for Missing 787 Battery Risk

seems that the Boeing engineers did not bother to tell the FAA that LiCo rechargeables have a bad habit of venting-with-flames, and that this can spread to the next cell that it is duct-taped to 

I wonder if the 787 will ever fly again...


----------



## Steve K (Feb 8, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*

I'm still trying to figure out why no one had Yuasa review the design of the battery pack/assembly, or maybe why Yuasa didn't say "hey guys, don't pack the cells so close and add some cooling air". It's a fairly safe guess that Boeing subcontracted that battery assemblies out to a supplier. The supplier was probably already building stuff for aviation, and perhaps didn't have experience with large lithiums as a result (or maybe no experience with lithiums?). I can only hope that this supplier had some battery experience and understood some of the risks, but.... ??? 

Ideally, the supplier was already providing the battery systems to Boeing for other aircraft, and the big challenge was the change to lithium technology. My experience with working on nicad batteries on satellites was that our team worked very closely with our battery cell supplier, as well as our team members having lots of experience in satellites and spacecraft (going back to the Mercury & Gemini capsules). Did the supplier drop the ball and not seek the guidance of Yuasa, or did Yuasa not understand the demands of an aviation application? ...or did Boeing just throw together a specification, send out a bunch of Request For Quotes, and pick the cheapest bid?? Uugghh.... so many ways for things to have gone wrong!

Well, I'm also waiting to hear about why the flight test program didn't uncover this problem before it got into the customer's hands. There are always things that slip by the validation testing, but this seems fairly significant. What was it that Boeing didn't understand about how the customer uses the aircraft? It is important that they figure this out before they decide on the fix for the battery issue, or they'll never know if the eventual proposed fix is really adequate.


----------



## Steve K (Feb 8, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



jerry i h said:


> In the McMaster catalog, I found this interesting thing: *Lightweight Quick-Charging Lithium Batteries*
> 
> It looks similar to the 787 cells, but of course this might just be coincidence. Anyone know what's inside? I am hoping that it has plates, since it might be fun to have a similar cell (yes, I saw the price, charger not included). It has 12.8 volts, so I suspect just a 3x2 or 3x3 cluster of smaller, consumer, cylindrical cells Li-ions. Since there is a 2 x voltage version with about half the amp-hours of the 12.8v model, I am pretty sure that it is 6 x 1 or 6 x 2 pack. Just wondering.



In an earlier post, I provided a link to the Yuasa site. If you scroll about 2/3 down the page, you can see a photo of the lithium-ion cells that they make for aerospace and satellite applications:
http://www.gs-yuasa.com/us/products/index.html


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## moldyoldy (Feb 8, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



Steve K said:


> In an earlier post, I provided a link to the Yuasa site. If you scroll about 2/3 down the page, you can see a photo of the lithium-ion cells that they make for aerospace and satellite applications:
> http://www.gs-yuasa.com/us/products/index.html



Interesting! Thanks for the link! I observe that nearly all of the listed cells are essentially oblong.

Having had to deal with military NiCd cells (pocket-plate), and having disassembled a number of Ni-Cd and NiMh battery cells in my design work (not Li-Ion), I worry about the deposited material thickness tolerance of these Li-Ion cells in the assembly process - which evidently use the jelly-roll style wrap. 

My worry concerns the possible thickness variation of the layered materials in the completed oblong cell. ie: the primary strength sheet on which the materials are deposited is subject to the difference in wrapping tension between the relatively straight portion and then being wrapped 180 deg around the end of the cell. Doing that automatically or consistently on an oblong cell is much more difficult than with a round cell. Seems as though that wrapping process would lead to thinner or thicker chemical layers. In a lower capacity cell that is not subject to high stress from fast charging, variations in that oblong wrapping process probably would not be troublesome. However these are high-rate cells. Even in conventional cylindrical cells, the conversion of the chemicals during charge/discharge is not even throughout the cell, thus leading to hot spots. 

According to reports, the Boeing 787 Li-Ion cell design inherently subjects the cells to high stresses from fast charge/discharge. One of the Boeing engineers reported that the 787 at Logan AP had just gone thru high discharge/charge process. I wonder if the other events were close in time to heavy discharge/charge events?


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## moldyoldy (Feb 8, 2013)

*Re: Battery Fire NTSB Briefing - JAL 787*



TedTheLed said:


> Interesting. Of course, you're right about the sun warming things in space..
> And talk about not taking risks, sounds like the building code here; you can't join two pieces of any material that haven't been joined for fifty years already, and you can't use a fastener that isn't approved. Everything, every shape, depth, material, length, overhang, setback, tilt, proximity, size, is specified, so it kind of stultifies creativity, and improvement..



yes, the deep space probes are even more risk averse. For many years, the highest density uP used in the deep space program was the Intel 8080, or even the 8008. The primary difficulty was the density of the uP and ability to rad-hard the uP to deep space conditions - which was a non-survivable radiation level for humans due to no significant radiation shielding on the probe. The uP design had to tolerate a zap "upset" from the ocassional sub-atomic particle hits. Plus which if the chips had not been qualified for a 20 year functioning lifetime, they could not be used. That eliminated nearly all of the later uPs and uCs because of internal circuit density or heat generation. Internal heat sinks had no air to circulate. hence dissipation of heat was thru the chassis or a heat pipe to the outside. I found that out when my first design effort out of the military used the 4004 and we upgraded to the 4040. The lead designer had talked to Intel about the 8008 and 8080 and came back with the verdict that we would not progress beyond the 4040.

Coming back on topic, I am surprised that Boeing not only used Li-Ion cells, but pushed them to their limits. and that the FAA approved the design. As another poster wrote - so many of the guidelines we use were violated.


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## LEDninja (Feb 8, 2013)

NTSB investigators found that at the time of the battery failure, the voltage of the lithium-ion battery dropped from 32 volts to 28 volts, indicating that one of the eight battery cells had failed. 
http://www.businessinsider.com/update-on-dreamliner-battery-failure-probe-2013-2

Photos From The Dreamliner Investigation Reveal Major Damage To The Jet's Battery
http://www.businessinsider.com/photos-of-burned-dreamliner-batteries-2013-2
You have to click on the link on the bottom of the page to get to the National Transportation Safety Board photos.

- They ruled out the idea that the short circuit started outside the battery.
- And that mechanical damage was to blame: All impact damage happened after the fire started, some of it the result of firefighting efforts.
- A CT scan of the battery in question showed cells on one half of the battery were especially misshapen afterward.
- The probe narrowed its focus to cell number six, where the most damage had occurred.


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## SemiMan (Feb 8, 2013)

Well since everyone is making their own theories, I am going to put mine out there ..... and yes there is as much likelihood I am wrong as anyone else!

Some facts:

- It is almost guaranteed that each and every cells is monitored and balanced properly during charging.
- The charge/discharge control probably was working properly
- Of course there are temp sensors (on the outside of the battery cells, so short will not be detected perhaps till too late)
- During testing, they DID test the effects of a short in one battery and found it did not propagate to other cells (FAA supposedly was there for these tests)



Sooooooo, I am going to present a theory 


What if when they tested the shorting of a single battery the other batteries were not at an elevated temperature? Perhaps that is why they did not see the propagation to other cells but in the real world failures, the other cells were already at an elevated temperature?


Just guessing of course.


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## moldyoldy (Feb 8, 2013)

LEDninja said:


> NTSB investigators found that at the time of the battery failure, the voltage of the lithium-ion battery dropped from 32 volts to 28 volts, indicating that one of the eight battery cells had failed.
> http://www.businessinsider.com/update-on-dreamliner-battery-failure-probe-2013-2
> 
> Photos From The Dreamliner Investigation Reveal Major Damage To The Jet's Battery
> ...



The key comment is above: The overall battery voltage dropped by some 4 volts, which meant that a Li-Ion cell failed. Was that cell instantly disconnected and bypassed? or did that Li-Ion cell go in to reverse voltage in the series stack of cells? If that Li-Ion cell voltage was reversed, most CPF members know what would happen next. and evidently did.


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## SemiMan (Feb 8, 2013)

moldyoldy said:


> The key comment is above: The overall battery voltage dropped by some 4 volts, which meant that a Li-Ion cell failed. Was that cell instantly disconnected and bypassed? or did that Li-Ion cell go in to reverse voltage in the series stack of cells? If that Li-Ion cell voltage was reversed, most CPF members know what would happen next. and evidently did.




They indicated no specific concerns with the battery management mechanism so it is reasonable to believe that the drop from 32 to 28 was detected and acted upon. It was noted that was the point of failure, so that may be the point where the failed battery started to flame, but no guarantees.


This reminds me of the Avestor batteries that AT&T put into remote telco boxes and which started to explode after Avestor went under. They had fairly sophisticated battery management but it wasn't enough.


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## alpg88 (Feb 8, 2013)

I'm still surprised my sonata hybrid 270v gel li ion pack did not catch on fire, when the car was flooded by sandy, the battery was submerged in salt water.


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## SemiMan (Feb 10, 2013)

In the big scheme of things, salt water is not that conductive.

Given it's automotive, all the electronics would be conformally coated and/or potted and many of the connectors may be water proof and/or water resistant. The salt water beyond parasitic load on the batteries would not hurt them one little bit. I would only be concerned about electronics damage or impact and the potential for erroneous battery management in the future. A wash down with fresh clean water (preferably distilled) would likely fix any issues.


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## moldyoldy (Feb 10, 2013)

according to the latest Der Spiegel issue (Heft SP-2013-7, Seite 15), the EASA (European Agency for Flight Safety) based in Köln Germany refused to independently certify the Boeing 787 Li-Ion batteries. The EASA wrote in an internal memo that these batteries were lacking in maturity <<essentially little history of safe flight usage>>. Instead the EASA went along with the FAA special certification methods which certified the Boeing 787 in August 2011. The reason was that these Li-Ion batteries represented a potential fire danger and very little flight experience with such batteries existed. Evidently the EASA was not informed by the FAA of two events: 

In 2011 the Li-Ion batteries on a private Cessna jet caught fire. Because of the investigation by Gulfstream in to that incident, Gulfstream made the decision choose a different battery technology for their business jet G650. 

In 2006, a Li-Ion battery intended for the Boeing 787 caught fire and ignited a fire in the vendor's lab! 

Aua!


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## Steve K (Feb 12, 2013)

The Chicago Tribune has informed me that the NTSB is investigating whether dendrites might have caused the failed cell to short circuit. ...
http://www.chicagotribune.com/busin...ry-failure-ntsb-says-20130212,0,5221372.story

from the article: "As part of our continuing investigation, we are looking at whether dendrites may or may not have been a factor," Kelly Nantel, director of public affairs for the NTSB, told Reuters in an email.

I'm not even sure if this could be considered news, since this seems like one of several causes that should be investigated. 

The NTSB web page for the overall investigation is fun to review, but doesn't say anything about dendrites:
http://www.ntsb.gov/investigations/2013/boeing_787/boeing_787.html

The bottom of this web page has links to the NTSB's presentations, which have some great photos of new and failed batteries.


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## moldyoldy (Feb 15, 2013)

fyi: Although the US NTSB has not rendered a verdict on the Boeing 787 incidents involving Li-Ion batteries, Airbus abandoned the Li-Ion battery chemistry for it's A350 program and switched to Ni-Cd battery chemistry. Airbus indicated that it would continue investigation in to the Li-Ion chemistry.

http://money.cnn.com/2013/02/15/news/airbus-dreamliner-battery/index.html?hpt=hp_t3


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## Steve K (Feb 15, 2013)

I just saw that news article too. Nicad is certainly a well understood technology, but I would have thought that aerospace had tried NiMH or nickel-hydride cells by now. Can't blame Airbus for having second thoughts about lithium ion batteries, regardless of their own validation testing.

edit: the Chicago Tribune has a few more details:
http://www.chicagotribune.com/busin...on-batteries-in-a350-20130215,0,1599789.story


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## BVH (Feb 15, 2013)

They could have considered LiFeP04 chemistry also and reaped the weight benefits without the explosive and fire issues.


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## moldyoldy (Feb 15, 2013)

BVH said:


> They could have considered LiFeP04 chemistry also and reaped the weight benefits without the explosive and fire issues.



That poses an interesting question: I agree that a cell using the LiFePO4 chemistry is lighter, but what about the other characteristics as compared to the NiCd and NiMH chemistry? ie: energy density and ability to deliver high amperages or absorb fast charging. NiCd is well known for high-current applications, hence long use in the military (aviation) and later civilian aviation. 

Lithium primary cells were used in A/C emergency beacons because of the low self-discharge and long life. Unfortunately those Lithium cells also caused more than a few fires. The last event I remember from active service was sending out a chopper to a light aircraft that was forced to land on a glacier snow field. The Lithium cell caught fire. At least his radio using more conventional batteries was still functional.


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## moldyoldy (Mar 4, 2013)

bump - been a while. Seems as though Boeing sidestepped at least one basic problem with Li-Ion cells. No comment found as to why the control circuitry did not shut down a bad cell.

from: http://www.nytimes.com/2013/02/28/business/boeing-shows-dreamliner-battery-plan-to-japan.html?_r=0

"Boeing has proposed separating the battery cells with insulation to keep heat from spreading from one to another. It also would build a fireproof container around the batteries and add tubes to vent smoke or hazardous gases out of the plane."

and: http://abcnews.go.com/Business/wireStory/boeing-ready-move-787-fix-faa-approves-18650056

"Boeing's fix has been described as a long-term solution aimed at making sure that short-circuiting in one battery cell can't spread to another."

and: http://www.cnn.com/2013/02/20/travel/boeing-dreamliner-fix/index.html?iref=allsearch


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## alpg88 (Mar 5, 2013)

dBoeing 787 Dreamliner’s failed battery was wired incorrectly, Japan says.


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## moldyoldy (Mar 6, 2013)

alpg88 said:


> dBoeing 787 Dreamliner’s failed battery was wired incorrectly, Japan says.



Thanks for that link! In another link on that page, there was this curious statement:

"Japanese investigators, however, have maintained that there is still not enough evidence to show that the batteries themselves are the cause of fires, and that a shock could have caused them to overheat." 

Huh? a "shock" causes a Li-Ion cell to overheat? No comment as to what kind of a shock. however nothing I recall from CPF indicates that a sudden temperature change or physical impact shock has caused any problems with flashlight Li-Ion cells. or?


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## moldyoldy (Mar 6, 2013)

BVH said:


> They could have considered LiFeP04 chemistry also and reaped the weight benefits without the explosive and fire issues.



I am still curious about a comparison between LiFePo4 chemistry and Ni-Cd as to high current draw capabilities. Ni-Cd chemistry has been well proven in aviation for high-current draw such as in engine starting, initiating equipment before engine starts, etc. and flashaholics know that LiFePo4 also provides higher current capabilities than Li-Ion cells. But I have never read about a comparison between those two chemistries.


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## alpg88 (Mar 6, 2013)

moldyoldy said:


> Thanks for that link! In another link on that page, there was this curious statement:
> 
> "Japanese investigators, however, have maintained that there is still not enough evidence to show that the batteries themselves are the cause of fires, and that a shock could have caused them to overheat."
> 
> Huh? a "shock" causes a Li-Ion cell to overheat? No comment as to what kind of a shock. however nothing I recall from CPF indicates that a sudden temperature change or physical impact shock has caused any problems with flashlight Li-Ion cells. or?


 may be they meant not physical shock, but electrical, too much charging current, or some cells got more current than others, thus overheated, .. just my speculation. 
similar to charging fireman scba units, with air, fill with air slowly, and they will last long time, do the slam charge, and sometimes tanks develop cracks


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## alpg88 (Mar 6, 2013)

moldyoldy said:


> I am still curious about a comparison between LiFePo4 chemistry and Ni-Cd as to high current draw capabilities. Ni-Cd chemistry has been well proven in aviation for high-current draw such as in engine starting, initiating equipment before engine starts, etc. and flashaholics know that LiFePo4 also provides higher current capabilities than Li-Ion cells. But I have never read about a comparison between those two chemistries.


power tools use LiFePo4, i have used drils with nicd and LiFePo4, they work just fine, however when i opened LiFePo4 pack after i used it for a year or so, shrink wrap had signs of cells getting hot, i took apart dozens of nicd, packs, never seen nicd have similar signs. however even with signs of cells getting hot enough to melt wrap, they still work just like the first day.


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## Steve K (Mar 6, 2013)

moldyoldy said:


> Huh? a "shock" causes a Li-Ion cell to overheat? No comment as to what kind of a shock. however nothing I recall from CPF indicates that a sudden temperature change or physical impact shock has caused any problems with flashlight Li-Ion cells. or?



I thought it was a known issue with Li-ion that a mechanical shock could cause overheating (not that I know of a reference off the top of my head). My assumption is that it had something to do with damaging the separator material between the plates. My fuzzy memory wants to say this is not uncommon in RC planes that periodically have unplanned returns to earth.

here's a reference...
http://www.electrochem.org/dl/interface/sum/sum12/sum12_p037_044.pdf
"Physical damage (puncture, crush, vibration, or shock) has the possibility of creating internal short circuit within the cell or creating short circuit within a battery pack to cause current flow in unintended and unanticipated manner. Internal short circuit is one of the most difficult failures to defend against and is discussed below."


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## moldyoldy (Mar 6, 2013)

I certainly agree that any flying device that experiences "unplanned returns to earth" will usually suffer damage to just about any component. ditto for cars in crashes. Nevertheless, the Boeing 787 Li-Ion battery problem was in a presumably undamaged aircraft. In photos of the damaged areas in the 787s, I have not been able to discern whether the battery package was in a low pressure compartment or fully exposed to outside temps & pressure. There are at least 3 pressure areas on the larger passenger A/C.

===================================================
The link above provided by *Steve K* is a most excellent link, highly worthwhile read for any flashaholic using any of the Lithium chemistries to peruse and reflect about! and the source authors seem well qualified to discuss the subject. ie: E.Peter Roth is a retired consultant to Sandia Labs on Li-Ion cells. Surely the Boeing engineers at least skimmed the following documents?

There are more than a few quotable quotes from the above linked Doughty & Roth study on Li-Ion battery safety (highlighting is mine). Talk about "understatements"!

"When 
discussing battery safety, it is important to
understand *that batteries contain both the
oxidizer (cathode) and fuel (anode) in a
sealed container.* (*This is rarely done—other
examples are high explosives and rocket
propellant.)* Under normal operation, the fuel
and oxidizer convert the chemical energy
to electrical energy with minimal heat and
negligible gas. If allowed to react chemically
in an electrochemical cell, the fuel and
oxidizer convert the chemical energy directly
into heat and gas. Once started, chemical
reaction will likely proceed to completion
because of the intimate contact of fuel and
oxidizer"

"Overcharge
can also generate heat within the cell due to
other oxidative chemical reactions that can
trigger thermal runaway"

=========================================================
More on some E. Peter Roth investigations:

http://www.osti.gov/bridge/purl.cover.jsp?purl=/766568-NYNjEL/.../766568.pdf

-------------------------------------------------------------------------

E. Peter Roth is also a consultant to the US Gov regarding battery abuse testing:

http://www.transportation.anl.gov/b...ery testing roundtable/sandia_batlab_roth.pdf

The above link has many photos of fires from batteries.

One quotable quote *from the section on field failures*:

*"PTC, CID, shutdown separators, electronic controls are not effective"*

Wow! That blows a hole in some of my thinking! If the reader scans down to the section on Accelerating Rate Calorimetry (ARC), LiFePO4 has the lowest temp rate increase of all chemistries! That confirms my thinking about reducing any ICR-type cells in my usage and transitioning to IMR cells regardless of capacity differences.

========================================================

so back to the Boeing 787: In the _perfect_ world of anticipating all possible events short of a crash, the circuit designers and packaging designers could have prevented the known events. Hence some team took at least one short cut (sic) assuming that such a series of events would not happen. and therein lies the problem - linear thinking. Most catastrophic failures are a chain of events that are decidely non-linear!

FWIW, In my work with UL certification, in particular with explosion proof design and certification, the rule was that the UL examiners could choose _any_ _three_ failure points in the system being tested in a methane atmosphere so composed to facilitate any ignition source - meaning literally blow up. The examiners could short out any component they wished, or cut any gasket they wished. Hence "intrinsically safe" circuitry was about the only lower-cost method that could be relied on. Otherwise the physical and electrical design was quite challenging for the electrical and mechanical engineers.

This is a good discussion in it's own right!


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## jerry i h (Mar 6, 2013)

moldyoldy said:


> ...why the control circuitry did not shut down a bad cell...


I looked carefully at the photos of the battery pack, and they seem to be all simply wired in series, w/o any sort of wiring so that each cell can be monitored independently. 

*FAA likely to OK Boeing battery testing in days - sources *:sick2:

I find it disturbing that Boeing's solution is to simply reduce the ancillary damage if a Li-ion vents with flame: separators, super-duper-fireproof-box, a tube to vent the flames. As one researcher at a Japanese university said, does this not set up a possible flame-thrower scenario, when the 787's Li-ion pack is on fire and re-fueling is taking place?

My question to you engineers: what in the blue blazes are the Boeing engineers smoking? How can they possibly solve a problem, when they do not know what caused the failure in the first place?


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## moldyoldy (Mar 6, 2013)

+1. I also saw only a series connection of the cells. and the various voltage readings published were only the combined battery pack reading, nothing from individual cells. The control circuitry seems to have suffered significant damage itself. The only recorded current data evidently was that a high amperage discharge and charge occured just before the fire - which seems to be disputed by later comments. 

Worse still, the NTSB has NOT rendered it's verdict as to the 787 battery fire at Logan airport. NTSB Chairman Deborah Hersman said in her original public presentation that the NTSB would search until it found the combination of events that caused the Boston Logan airport 787 to flame. So far all the NTSB resolved was that there was a short in one of the cells. Ms. Hersman was very careful to state that the NTSB only investigates the cause of the accident. The FAA authorizes/certifies an aircraft to fly.

However Boeing is exercising very significant pressure on it's engineers and also on the FAA to put the 787 back in to the air at least in a test mode. 

Although there are many design aspects of Boeing A/C that I prefer, I have to admit that Airbus made the better decision for the battery pack for it's 350 series and shelved a Li-Ion battery design to the back burner. The Li-Ion chemistry is still an immature technology!


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## jerry i h (Mar 7, 2013)

moldyoldy said:


> ...The Li-Ion chemistry is still an immature technology!


Beg to differ: being insufficiently developed is not the problem. The problem is that some goofball engineers want to take advantage of high energy density, but refuse to consider that a small % will spontaneously vent with flame, no matter what you do.


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## Steve K (Mar 7, 2013)

jerry i h said:


> My question to you engineers: what in the blue blazes are the Boeing engineers smoking? How can they possibly solve a problem, when they do not know what caused the failure in the first place?



what are they smoking? 787's, apparently... (a small joke... sorry)

I think the change to increase cell separation in the battery is a good thing, but until they figure out why the failures occurred, they won't know if the change is effective or not. I assume that this is just a measure to buy time until they manage to duplicate the problem and find the root cause. 

Personally, I'm anxiously awaiting news on how this problem managed to go undetected during all of the validation tests.


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## inetdog (Mar 7, 2013)

jerry i h said:


> I looked carefully at the photos of the battery pack, and they seem to be all simply wired in series, w/o any sort of wiring so that each cell can be monitored independently.



There were something between 16 and 30 wires in the small gauge wiring harness that sits on top of the battery array. You may not have noticed them or they may already have been removed in the photo you looked at. They constitute redundant voltage monitoring lead which probably double as balancing current wires. However there does not (for reasons of design current of 600+ amps) appear to be any contactors between cells, only one and a parallel backup for the whole series string. This serves as low voltage cutoff, overcurrent protection and last ditch overcharge protection if the charger fails to shut down when requested. 
There was exactly one Hall Effect current sensor on the opposite lead from the contactor. 
No per-cell temperature measurement, just two thermistors. 

The first event seen was a sudden 1 volt drop in series string voltage while the battery was being charged at 45 amps. The charger and BMU did not consider this significant enough to stop charging! The voltage dropped from 32 down to 28 over the next 30 seconds, coming back up to 32 at the end. (At that time were the rest of the cells in the string being overvolted, beyond the ability of the BMS to compensate?) 

The per cell voltages (and the overall temperature??) were NOT being recorded.


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## inetdog (Mar 7, 2013)

jerry i h said:


> Beg to differ: being insufficiently developed is not the problem. The problem is that some goofball engineers want to take advantage of high energy density, but refuse to consider that a small % will spontaneously vent with flame, no matter what you do.



At the time the electrical design was committed (~2005) there was not nearly as much long term performance info on LiFePO4 as there is now.


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## jerry i h (Mar 7, 2013)

From this link:
*NTSB still seeking root cause of Boeing 787 fire*



> ...For example, a system designed to vent smoke from the plane during a battery fire failed to function because it lacked power after the battery caught fire. The system's auxiliary power unit (APU), a gas-driven engine in the tail of the plane, also was shut off at the time, and the battery is used to start that system.
> "As a result, smoke generated by the APU battery could not be effectively redirected outside the cabin and aft (electrical equipment) bay," located in the fuselage behind the right wing of the 787.
> Boeing had said that the venting system failed because the plane was on the ground and lacked cabin pressure to use in expelling fumes from the cabin.
> ...
> ...



OK, anyone care to explain?


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## alpg88 (Mar 7, 2013)

if you had voltmeter to a cell\pack, it would show you its voltage, if you short the cell\pack, reading would be 0. remove short, voltage will recover. but being in a pack single cell short would not make your dmm see 0 for entire pack, it has to be either shorting entire pack, or open circuit. but since i never seen the pack in question, and have no idea how it is wired, i can only speculate. and so pbly the rest of us. ntsb can't figure it having access to cells and entire plane, doubt we could. but it is fun to guess thou


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## mattheww50 (Mar 7, 2013)

The reason you won't see contactors between cells is that it is a fact of life that at rated current, you can expect a loss of about .5 volts per contactor in use, and to handle the DC current required to spin up the APU, you need contactors rated in the hundreds of amps. Contactors that large are not exactly light weight either. My guess is the extra 7 contactors would eat up most if not all of the weight savings of Li-Ion versus NiCd batteries. It also introduces 7 new single point failures in the design.


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## moldyoldy (Mar 7, 2013)

jerry i h said:


> From this link:
> *NTSB still seeking root cause of Boeing 787 fire*
> 
> 
> ...



The best quote from the above link:

"The report also suggests that the NTSB is looking at whether the FAA, and its designees who work at Boeing, had the technical knowledge to critically question test data used to show the failure rate for the battery was acceptably low."

IOW, to my view, the NTSB is challenging the FAA competence to certify the battery system - quite a statement!


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## jerry i h (Mar 8, 2013)

This is an interesting article, describing the (unsuccessful) efforts at putting out a lithium fire in the 787's lithium-cobalt battery pack with conventional fire extinguishers and water.


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## moldyoldy (Mar 8, 2013)

The link above from jerry_i_h provides an impressive series of statements from those present at the scene! The fire department personnel evidently did not understand that Halon means nothing to Li-Ion cells which contain internally all of the components to burn until the materials are exhausted. See the statements in links above from Doughty and Roth. In a server room, if the Halon extinguishers are tripped/dumped, the room is uninhabitable for a while, and supposedly the electrical fire is extinguished. The unaffected servers themselves may continue operation.


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## moldyoldy (Mar 8, 2013)

Not to diverge too far from the Boeing 787, but here is an example of a modern vehicle design functioning only with batteries from Mercedes:

from the world of cars. Mercedes is about to release it's Mercedes SLS AMG electric drive. In this article in German, it is described as an effort to achieve performance. period. Mercedes designed this car as an example of advancement thru technology.

www.spiegel.de/auto/aktuell/mercede...egeltuerer-mit-vier-e-maschinen-a-886392.html

Not incidentally, the automobile has an electric motor drive on each wheel for a total of 751 HP and 1000 NM torque. Top speed is nominally listed as 250KMH. The cost is 416.5K Euro. The Mercedes development head sees no problem that the actual range of travel on battery is incidental, the listed range is 250KM. Quote: "the limiting factor is not the capacity of the battery, but the stomach of the passengers". However in "comfort mode", the driving characteristic is more like a small hatchback.

For the purposes of CPF, some details about the Li-Ion battery power pack were provided: The battery pack weighs 548 KG. There are 12 blocks of 72 cells in each block. The total battery capacity is 60 KWH. <<No statement as to how these cells were connected, probably in some series/parallel combo>> I wonder if Mercedes designed the battery pack with a view to the electrical/mechanical fragility of the Li-Ion cell technology.

It seems that Elon Musk of Tesla worked with the Mercedes bosses since 2007 to convince them of his design methods for a battery driven vehicle. Evidently Mercedes owns part of Tesla Motors. Now if only Boeing had been paying attention...


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## moldyoldy (Mar 9, 2013)

It seems that officialdom (FAA) has finally recognized that Li-Ion batteries are very touchy and easily cause problems. and that after Boeing used a newly designed Li-Ion battery pack for critical flight systems in the Boeing 787 - which were predictably sensitive and caught fire. Boeing was not paying attention to teh Tesla car that used laptop 18650 cells in special configuration, thus capitalizing on the production experience of a common cell size. Pilots are used to problems in flight and check/verify any situation, before making a decision to continue the flight or abort to the nearest airfield that can support their A/C. It seems that the speed of that behaviour will need to be adjusted for the Boeing 787. or at least until Boeing comes up with a believable fix, not just a fire containment patch job.

Ref link: 
http://www.cnn.com/2013/03/07/travel/ntsb-dreamliner-report/index.html?hpt=hp_bn10

Best quote from the link:
"The batteries -- one in the front of the plane, one in the rear -- power the aircraft's main and auxiliary power units, flight control electronics and emergency lighting system.

But in general, the FAA says, lithium ion batteries are significantly more susceptible to internal failures that can result in thermal runaways, or self-sustaining increases in temperature and pressure. Both overcharging and overdischarging can cause problems, and lithium battery fires are more difficult to extinguish than other batteries, experts say."

Aua!


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## EZO (Mar 9, 2013)

There is an interesting article on CNET today about Elon Musk's SpaceX Mars presentation at SXSW. However, the article went into Musk's recent dispute with the New York Times poor review of the Tesla S. It seems the reporter who wrote the review complaining of poor cold temperature battery performance claiming the battery "died" on him prematurely was completely clueless about the fact that the Tesla S maintains highly detailed logs of battery performance showing that he was apparently FOS.

In any event, there was an interesting quote from the article I thought might be of interest to this thread.

_"Although it is known as a car company, Tesla may more accurately be called a battery technology company that happens to build cars. As such, Musk, who is Tesla's chief product officer, as well as its CEO, has a fair bit of knowledge about batteries. In the wake of a series of well-publicized problems plaguing the lithium-ion batteries on board Boeing 787 Dreamliners, Musk offered to help the aviation giant address those issues. Today, he explained his thoughts -- that the planes' battery cells were too big, but didn't have enough space between them to avoid a "thermal cascade" spreading between them. Ideally, he said, 787s should feature smaller batteries with smaller gaps between the cells. He did note that Boeing had rebuffed his offers to help."_


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## moldyoldy (Mar 11, 2013)

Ref a poster above who mentioned that LiFePO4 were not market ready when Boeing made it's unfortunate decision to develop it's own Li-Ion cells, and not incidentally in a much larger format than Elon Musk recommends. here is a modern Electric Auto developed in Thuringen in Germany called the Colibri (Hummingbird). A one seater with 100+ KM range. more importantly it uses the LiFePO4 battery system. 

An English presentation is here:

http://www.topspeed.com/cars/others/2012-innovative-mobility-colibri-ar136904.html

A more extensive article in German about Electric cars, including the Colibri is here:

http://www.welt.de/motor/article114325882/Neuer-Elektro-Schock-in-der-Autobranche.html

The above article comments that the Germans are focusing on development of pure electric cars only for city driving. The battery technology simply is not sufficiently mature for longer-haul drives.

WRT EZO's post above, I am inclined to agree with Elon Musk's contention that many smaller cells in a series/parallel configuration is easier to control compared with fewer much larger cells - when dealing with the volatility of Li-Ion technology. Boeing took what appears to be the standard route with very few very large Li-Ion cells in the 787 and used them for critical systems on board - and is paying the price for that bad leap of faith that "bigger is better"... Most technologists would advise taking a much more cautious path in using the latest technology.


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## markr6 (Mar 11, 2013)

Not to get too far off topic, but I just read an article in Popular Science about the new ALVIN research sub. They're updating it and possibly replacing the lead-acid batteries with lithium-ions if they "pass safety tests to prove that they won't catch fire"

Just like 8 miles above sea level, 4 miles BELOW sea level is not a good place to run into problems!


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## moldyoldy (Mar 13, 2013)

again not to diverge too much from the Boeing 787 problems, but those problems are a Li-Ion battery application problem, A recent article in the German Zeit (Time) is indicative of the many problems with attempting to commercially employ Li-Ion battery packs. 

http://www.zeit.de/auto/2013-03/elektroauto-winter-test

The cold temperature testing by BMW and Opel of their Ampera, i3 and i8 data may be useful to this forum. At -40C, the Li-Ion battery pack was useless. at least warming to -25C was required. and that took took an hour of plugged in conditioning before the battery pack was warm enough (-25C). At that temp, the Ampera would start, but still run the IC engine in order to keep the battery pack warm enough. On the dash of one test vehicle, there is an indicator that reads "Combustion engine is running for temperature reasons". Only at -10C were the batteries warm enough to run w/o the IC engine. the operating range was down to maybe 130KM. Worse still, the thin tubes containing the coolant required to cool the battery cells at operating temps were thin enough to worry about them freezing in cold temps which is why the coolant was rated to -40C. Cracked or plugged tubes would be equally damaging for the batteries. 

Audi stopped development of their A2 because of the cost of the batteries and protections. Only the A8 e-tron will be produced in maybe a quantity of 100, and for 150K - 200K Euro. . 

The primary problem is that Li-Ion cells heat up excessively w/o active cooling at what appears to be useful levels of discharge/charge current in Autos, etc. and conversely, Li-Ion cells have to be warmed before they are usable at low temps. For all practical purposes, the energy efficiency of using a Li-Ion battery pack in a vehicle is decreased because of all the energy-robbing protections required by the Li-Ion battery chemistry at it's present stage of development. that observation was also found in the written comments after the article.

Hmmm, so what did Boeing do? packed large sized Li-Ion cells in like sardines with essentially no cooling, and had their B787s grounded. and now Boeing is proposing ceramic plates between cells to avoid cell-to-cell heating? They did not learn their lesson! As I wrote before, Li-Ion technology is not only immature, but I suspect that it is sufficiently troublesome that it will be eventually replaced by another chemistry.


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## Steve K (Mar 13, 2013)

I'm not sure that cold temperatures are going to be an issue for a commercial airliner like the 787, considering that the battery is contained in an area of the plane that isn't allowed to get very cold. The latest news I've seen is what's in this article:
http://www.flightglobal.com/news/articles/faa-approves-boeings-787-battery-solution-383364/

It does describe the ceramic spacers, somewhat improved spacing between cells, fire-proof container, and smoke venting system. No mention of a cooling system, as far I can see.
"Boeing's proposal involves three layers of protection to prevent overheating in the lithium-ion batteries that power the 787's auxiliary power unit: improved separation between the battery cells, installing ceramic-plated spacers between each of the cells and the addition of a containment and venting system so smoke cannot enter the passenger cabin."

I'm still wondering why they aren't using cooling air to help control the battery temperature. It's a standard method for cooling avionics, so the infrastructure is already there. There are housings that allow the circuitry to be sealed, and just duct cooling air along fins on the outside of the enclosure, so this could be done for the battery pack too.

One of my other questions has been "what changes are they making to the validation method in order to catch the failures that the original validation tests missed?". The article does touch on the subject of better testing:
"Boeing Commercial Airplanes president and chief executive Ray Conner says the airframer has a "great deal of confidence" in its solution. "Working with internal and external experts in battery technology, we have proposed a comprehensive set of solutions designed to significantly minimise the potential for battery failure while ensuring that no battery event affects the continued safe operation of the airplane," he says.
Boeing says the test plans for its proposed solution were written based on the FAA's standards as well as guidelines published by the advisory committee, Radio Technical Commission on Aeronautics. These guidelines were not available when the original 787 battery certification plan was developed, says Boeing."


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## PapaLumen (Mar 13, 2013)

Looks like they working hard on it... http://www.flightglobal.com/news/ar...oeings-787-battery-certification-plan-383364/


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## moldyoldy (Mar 13, 2013)

fyi: the link contains the usual info that the FAA allowed Boeing to proceed with testing. 

http://finance.yahoo.com/news/boeing-tests-prompt-analysts-upgrades-170933043.html

However buried in the article is this paragraph (Emphasis mine):

"Last week, the National Transportation Safety Board, the top U.S. safety investigator, said it would hold _*public hearings* _next month to examine Boeing's proposed fix for the battery system, and _*about lithium-ion technology in general.*_"

That is quite an agenda. I wonder how far the NTSB Chair will allow the discussion to go? Ms. Hersmann has presented herself very competently, and the NTSB certainly has a lot of control, at least after the fact, over the transportation industry, but questioning a battery technology in general? hmmmmmmmmmmmmmmmm


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## gadget_lover (Mar 14, 2013)

Sometimes it is appropriate to look at the general technology. It's logical that some tech may not really be a good idea for every circumstance. There is a really neat molten sodium–sulfur battery that would be great for powering cars. If I remember the 1980's magazine article, the liquid sulfur could even be exchanged in minutes at a gas station, providing an "instant recharge". The 600 degree (F) operating temperature and extreme corrosive nature of the mixture made it impractical for use on public streets. 

When they look at the state of the art for Li-Ion they will (if they are smart) identify the chemistry and construction that would be appropriate for planes, cars, etc.
I suspect that they will find several that DO work.

Daniel


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## moldyoldy (Mar 14, 2013)

I read on a couple websites today (dated the last day or two) that not only is the battery housing being redesigned, but the cells themselves are being modified, and evidently that includes "rewiring" of the battery box. The wording of the press commentary leaves me wondering whether some journalists are being creative with what they have heard from ??? or not. If I take the somewhat nebulous wording at face value, I wonder if Boeing is finally installing individual cell monitoring - which, based on released information released to the press, was not done. ie: only the total battery voltage was monitored/recorded, nothing at the cell level.


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## inetdog (Mar 14, 2013)

moldyoldy said:


> ie: only the total battery voltage was monitored/recorded, nothing at the cell level.


It is open to interpretation. The individual cell voltages were being measured by the two Battery Management Unit (BMU) boards that together make up the Battery Management System (BMS). The BMS would bypass charge current around a cell for over voltage and send an alarm to the Battery Charger Unit (...) for under voltage so that the load would be shut off. And it might open the contactor in series with one battery lead in addition. 
But none of the cell voltages were stored in the BMS inside the battery, nor were they reported digitally to the charger which in turn generated alarms and sent data to the Flight Data Recorder. Likewise the only temperature sensors were one for under temperature to signal the charger to stop charging and one for over temperature to also cut off charging and maybe current to loads. But their position was such that they measured the average temperature inside the battery box or the temperature of one inter-cell connector. Nothing which would respond quickly to an overheating single cell. The connection to the Battery DC bus was routed through the charger.


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## moldyoldy (Mar 14, 2013)

Good info! As I recall, the NTSB report stated that the BMS system suffered extensive damage in the Logan AP case. I wonder if the entire battery could be disconnected via a contactor? if so, where did that power come from? the other battery up front? Are there other battery packs besides these two Li-Ion battery packs on a Boeing 787?


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## inetdog (Mar 14, 2013)

moldyoldy said:


> Good info! As I recall, the NTSB report stated that *the BMS system suffered extensive damage *in the Logan AP case. I wonder if the entire battery could be *disconnected via a contactor? if so, where did that power come from?* the other battery up front? Are there other battery packs besides these two Li-Ion battery packs on a Boeing 787?


The contactor to disconnect the battery under the control of the BMS is inside the case, interrupts only one battery lead, and is NORMALLY CLOSED when not powered. 
The BMS in question was inside the battery case itself. Need I say more? 

Well I will anyway. The data and control cable between the battery pack and the charger also suffered significant damage, probably as a result of high current, mostly in the shield. Not clear where the current came from, except that at some point the case of one of the cells near but not at one end of the stack shorted to the case.


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## moldyoldy (Mar 15, 2013)

Finally some actual photos/diagrams showing the changes made in the Boeing 787 battery pack:

http://www.aviationweek.com/Article.aspx?id=/article-xml/awx_03_14_2013_p0-559485.xml


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## Steve K (Mar 15, 2013)

thanks for the link to the Aviation Week article!

Maybe it's sufficient to contain the inevitable fires, but I'd feel better if they could duplicate the failure.


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## moldyoldy (Mar 15, 2013)

part way thru that Aviation Week article, VP and 787 Chief Project Engineer Mike Sinnett referred to over/under charging as being the probable cause of the incidents. So they changed the charger parameters, including "softening" the charging waveform. Maybe the charger algorithm changes did address the original root cause? I am waiting for the NTSB final report.


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## inetdog (Mar 15, 2013)

moldyoldy said:


> part way thru that Aviation Week article, VP and 787 Chief Project Engineer Mike Sinnett referred to over/under charging as being the probable cause of the incidents. So they changed the charger parameters, including "softening" the charging waveform. Maybe the charger algorithm changes did address the original root cause? I am waiting for the NTSB final report.



The smoking gun, IMHO, is the structural changes seen in the cells of the "good" main battery of the BOS aircraft. They might be attributable to a combination of charging waveform, overcharge and undercharge, of a chronic natures. But no conclusive explanation for that has been put forward yet, no mechanism identified. 
A internal short circuit in a cell can certainly come about without overcharging being the root cause. Unless you redefine overcharging as any charging method that causes these structural changes. If you never charge the battery at all, you will not have a fire problem.


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## jerry i h (Mar 18, 2013)

inetdog said:


> ..A internal short circuit in a cell can certainly come about without overcharging being the root cause...


Hallelujah. Where that one of the Boeing engineers understand that. As far as I can tell, Li-ions will, a small % of the time, spontaneously vent with flame, no matter what you do. Boeing, rather than choose a different, safer technology, are stubbornly staying with the same solution, but add doo-dads that reduce the side effects when it will inevitably happen again. The link above is way cool, but I am not convinced.


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## AnAppleSnail (Mar 18, 2013)

Ooh, Electrical Isolation Tape To Separate Cells. I use that on my skateboard...

I think Boeing wants to knock this problem out. I've been there. Something _almost_ works, and surely this next tweak will fix it. Best luck to them... But I'm glad I was in a 737 last time I flew long distance. Li-Ions can indeed be safely managed, but it takes ground-up design to isolate, alleviate, and prevent escalation during failure.


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## Brigadier (Mar 18, 2013)

I wonder how Li-Mn chemistry would fair in that environment....


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## inetdog (Mar 18, 2013)

AnAppleSnail said:


> but it takes ground-up design to isolate, alleviate, and prevent escalation during failure.


The Tesla, in addition to using smaller cells (~6800 18650 size), uses liquid cooling. If there is any power left in the battery, it is able to run the A/C to supply additional cooling if required.


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## Steve K (Mar 19, 2013)

there's an article in Electronic Design News (EDN) magazine that discusses the 787 electrical power system in some detail, as well the anticipated battery failure modes, the changes made to the battery, etc. It's more detailed that what I'd seen before.

http://www.edn.com/electronics-blog...charging-system-solutions-Good-design-or-not-


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## jerry i h (Mar 19, 2013)

Great link: primer on the electrical system of the 787.


> As design engineers, you and I know that the solution is to prevent failure, not contain smoke and fire after the fact...It’s difficult to zero in on a solution when investigators have not determined the root cause of a problem.


I noticed with great curiosity on page 4 that the 777 uses a NiCd battery pack but at 24 volts. I calculated that a 32v one would be about 35# more, about one carry-one and golf bag full of clubs. I was about to question the wisdom of this decision to use LiCos, when I noticed that the 787 is pulling 150 amps. They probably chose LiCo cells, because they had no other choice, and shoved a square peg into a round hole. In fact, even today, I am not sure that there is a practical replacement lithium chemistry.


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## mattheww50 (Mar 19, 2013)

Actually the initial current to spin up the APU is closer to 1000 amps, and yes, that does tend to limit the battery choices. NiCd's have extremely low internal resistance and in aircraft applications that kind of
initial current draw for starting ~1000hp Gas turnbine engines is the norm.


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## inetdog (Mar 19, 2013)

mattheww50 said:


> Actually the initial current to spin up the APU is closer to 1000 amps, and yes, that does tend to limit the battery choices. NiCd's have extremely low internal resistance and in aircraft applications that kind of
> initial current draw for starting ~1000hp Gas turnbine engines is the norm.


We have some figures from the NTSB Accident Investigations - NTSB - National Transportation Safety Board specific to the 787: Boeings initial design spec for the system called for availability of 3 consecutive starts of 18kW watts each for 45 seconds, with a minimum battery voltage of 20V. 
For the maximum battery voltage of 32 volts, this would be 562 amps, if we try to get the same power at 20 volts, it would be 900A. 
But their actual tests of the APU as installed on the BOS aircraft showed a probable maximum current at 32 volts for one start of only 332A. (They reported kW, not amps.) 

On the other hand, the Yuasa spec on the battery calls for an absolute maximum draw of 5C or 75 x 5 = 375 A. 

How to reconcile these numbers? NTSB did not attempt to. 

[full credit for this data collection and analysis goes to PickyPerkins at pprune.]


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## BVH (Mar 19, 2013)

jerry i h said:


> ................... I was about to question the wisdom of this decision to use LiCos, when I noticed that the 787 is pulling 150 amps. They probably chose LiCo cells, because they had no other choice, and shoved a square peg into a round hole. In fact, even today, I am not sure that there is a practical replacement lithium chemistry.



I would think the LiFePo4 chemistry batteries would also offer high Amperage rates at a not-too-much weight penalty.


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## Steve K (Apr 5, 2013)

No big news, but Ray LaHood, Sec of Transportation, says Boeing's test plan is good:

http://www.chicagotribune.com/busin...-787-fix-a-good-plan-20130405,0,2794793.story

Reuters
10:40 a.m. CDT, April 5, 2013


Boeing Co. has a "good plan" to fix the battery problem that has grounded its 787 Dreamliner jets since January, U.S. Transportation Secretary Ray LaHood said on Friday.

LaHood said he wants to ensure that the Dreamliner is safe before allowing the planes back in the air, and that no decision had been made on commercial flights.

"They're doing the tests now, and we've agreed with the tests that they're doing. And when they complete the tests, they'll give us the information and we'll make a decision," LaHood said at the U.S. Export-Import Bank's annual conference in Washington.


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## moldyoldy (Apr 8, 2013)

It seems that Boeing completed tests on the new battery system. These tests include an intentionally failed battery. I wonder how they induced the failure since the NTSB has not released a failure progression analysis. Commercial flights are expected by EOM.

http://www.aviationweek.com/Article.aspx?id=/article-xml/awx_04_05_2013_p0-565960.xml


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## Chauncey Gardiner (Apr 9, 2013)

Just got off the phone with a friend. Tomorrow he leaves for Japan, 11 hour flight to South Korea, (hopefully the crazy to the North won't fire a nuke) then a one hour flight to Japan. He will be there retro-fitting the 787 for Two weeks. Then he's off to Germany to work on another 787 for another two weeks. Then he'll be flying to Huston for the work on his third 787. He said he's scheduled to return on the 21st on May. Mike is 56 years old. He will be working 12 hours a day for the next 41 days. :shakehead

~ Chance


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## Steve K (Apr 22, 2013)

A very interesting examination of the battery failure reports in Electronic Design magazine...

http://electronicdesign.com/blog/dreamliner-battery-fire-solutions-and-concerns


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## Freax (Apr 24, 2013)

mattheww50 said:


> Actually the initial current to spin up the APU is closer to 1000 amps, and yes, that does tend to limit the battery choices. NiCd's have extremely low internal resistance and in aircraft applications that kind of
> initial current draw for starting ~1000hp Gas turnbine engines is the norm.



Sounds to me like Boeing needs to be informed about NiZn.

I wonder how many amps a large stack of F-Size NiZn's would put out. :naughty::bow:


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## BVH (Jun 2, 2013)

A minor glitch with new, improved battery?

"........ a sensor problem was found in one of the exchanged batteries for a Japan Airlines Boeing 787 jet. NHK TV says the problem emerged Sunday in a sensor that detects overheating in the modified version of the lithium-ion batteries used in the aircraft. The sensor problem did not endanger safety......"

ww.foxnews.com/world/2013/06/02/report-says-problem-found-in-japan-airlines-boeing-787-jet-but-no-risk-to/?test=latestnews#ixzz2V4SoEJ4B


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## inetdog (Jun 3, 2013)

At least the glitch was just improper installation of a pressure sensor. (I assume pressure inside the firebox and not pressure in a cell?)


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## alpg88 (Jun 4, 2013)

Freax said:


> Sounds to me like Boeing needs to be informed about NiZn.



not really. nizn proved to be of inconsistent quality and a short life, there is a thread here about it. 

nizn is probably the worst choise of cells to use in real world, at this time. but sure they look good on paper.


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## BVH (Jul 12, 2013)

http://www.foxnews.com/world/2013/0...s-after-fire-on-parked-plane/?test=latestnews

Hope it's something different and benign this time.


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## Steve K (Jul 12, 2013)

oh dear... I heard about this on the radio this afternoon (July 12), and read a bit at the Chicago Tribune web site. The indications seem to be that this isn't related to the battery. I think it's too early to say. I will say that this can't help Boeing any, and their stock price has dropped accordingly. Ugh.


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## LEDninja (Jul 16, 2013)

The London fire is in the rear of the plane. Not near the battery compartments. One is behind the main wing. The other is under the cockpit.


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## BVH (Jul 16, 2013)

That's good news. Read something yesterday, certainly not definitive yet, that it might be the Emergency Locator Transmitter and maybe its' Lithium operating batteries. Article says it's located in the vicinity of the fire.


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