There are so many things that it could be. I doubt any aircraft has ever produced as much electricity. An airplane is a "floating ground". This many trons running through a machine provides huge opportunities for errors.

Everybody was a hoping for a simple smoking gun. They will find the answer, but when they do, it will probably be a single line of bad code, a single electronic component sourced from a dodgy supplier (China), or something poorly grounded, or grounded in a slightly different place than it should have been.

Almost all the world's lithium comes from China. Maybe somebody added a little "filler" to make a little more for little cost? Maybe a single grounding wire or ground plane has higher resistance than it should? Maybe a single component in the charging and monitoring system reacts poorly to temperature change?

Oh yeah, isn't carbon fiber a good conductor of electricity? Maybe a carbon panel is discharging static electricity into one part of the system, throwing off voltage readings?

Too many possibilities. Good luck to them.

What we know
 

Hi,

USMCProbe:

"Too many possiblities"

We may think on EMI/EMC (groundind and shielding, etc.). I agree.

So far we know:

1) Both batteries went to thermal runaway WHEN FULLY CHARGED.
2) Cell overvoltage (IIRC > 4.025 V) may trigger the runaway to the cell.
3) A single cell runway promotes the runaway of the others.
4) The battery terminals didn´t exceed 32V
5) Recorded data (if) was not available after BOS case.
6) Batteries (main and APU) are rarely used (delivering power)
7) Bus spikes are not an issue. The batteries are not (most of time) "electricaly isolated from the bus"
8) The main battery DIODE MODULE failure could explain ANA case. We may expect the investigators checked it. Takes few seconds to test it.
9) Both incidents have in common the batteries.
10) The cells are serially charged. Evident from the pictures showing the connections to the cells.
(i would decide for a safer PARALLEL CHARGER)

So, we need more info.

Fault Tolerance and Graceful Degradation
 

Hi

The battery System in both incidents didn´t exhibit the MANDATORY "Fault Tolerance and Graceful Degradation" characteristic.

FAA (and all) expected a much better behavior from TWO battery Systems.

In TAK the plane (due crew prompt action) showed the MANDATORY feature.

In BOS ABSOLUTELY NOT!

The grounding was a natural consequence.

The landing in TAK (ANA) involved a warning on ECAM. Plus, smell.

SOPS in re: emergency landing would be an interesting discussion. It is a separate issue from the failure of the Battery....

It is in fact the most important issue. WHY? Because nothing about ANA should have caused the a/c to land, the system functioned within FAA RULES.

Likewise UAL, technically even JAL..... Says alot about the rulemaking, imo.

And, the 'legality' of the rules....It is a good foundation for Boeing's theory of defense regarding damages. If they demonstrate the rules were observed, the grounding becomes an unnecessary burden.....

Charger information
 

RR NDB,
Thanks for your welcome and reply.

The more I think about it, the more curious I am about the information provided by NTSB on the charger vs. the information provided for the battery (BOS). For the battery, everything -- photos, cat scans, physical access for reporters. For the charger, all I have heard is a general "no problem found".

And if the data collected by the charger has been lost, is that a design problem also?

Thanks to all the participants here. I've learned a lot.

bjm

Cockpit indications?
 

I have read all the posts - in this thread and in the other 787 threads, but it has never been mentioned, which exact failure indications were present in the cockpits in the 2 cases.

In the ANA case it was reported that, "the crew received indications of battery problems, at the same time a burning smell developed on board."
OK, but which problems were displayed? Overheat? Fault? Or?
And which indications were there in the JAL case? Same as in the ANA case?
I suppose that this info is on the FDR tapes, but not published yet - but anybody knows?

Which warnings/cautions are there in the B787 cockpit regarding battery issues?
And what actions does the SOP call for?

(I have seen 3 different types of battery failure indication variations in my career: battery fault - meaning charging current outside limits (A340), battery discharge (B767) and battery overheat (F27).)

Hi,

Grebllaw123d @ (#265)

There is a major difference in the 787 electric architeture in respect to the batteries.

In ANA case i would expect:

1) A battery fault warning indicating a failure.
2) A second one indicating battery temperature.
3) A third possible indicating smoke in EEbay

Interestingly to mention DC bus certainly NEVER SUFFERED any influence. (the battery is always OFFLINE if gennies (redundant) are working normally.

The approach to keep the battery "disconnected" brings advantages.

RR_NDB

Is this technically correct? Not having my flight manual at hand for the 777 but I thought the battery was online (so to speak) but just not carrying any load. I know the 777 is a different fish than the 787 but I am wondering why Boeing would have treated the basic battery logic any differently.

I know that offline might be defined as not carrying any load but I am speaking to the physical connection in this case e.g., the hot battery bus.

Re http://www.pprune.org/tech-log/50569...ml#post7662369

Just a simple question. How cold does it get in those battery bays? The diagram you show indicates that the cathode can break down and short circuit not a lot below zero.
The aircraft has flown a long way at high altitude and then parks at Logan in January (not the warmest spot). Could cold temperatures in the electronic bays cause a problem?

Both E/E compartments on 787 are pressurized and air conditioned.

If the aircraft parks in Anchorage in the winter time for a prolonged period, well that's another story.

Room for improvement
 

Hi,

bjm_bi:

It ´s of great interest the tracking of new technologies during the teething period. Considering the low cost for data recording the designers could put the recording chips NOT IN THE SAME BATTERY CHAMBER. This could delay the analysis of WHAT and WHY.

The partition of building blocks should take into account all factors.

Battery connection to DC bus
 

Hi,

Uncle Fred:

In an earlier post i commented on that. The scarce info we have so far points to a "switching" (automatic and immediate) of the battery (main) to the DC bus through a Diode. Doing that the designers could guarantee the bus will receive energy from the (charged) battery when this is required (when bus voltage starts to drop due any reason). As TURIN mentioned this happens automatically (when battery switch is ON).

I will comment further on that in few minutes.

Critical batteries
 

Hi,

Ian W and hetfield,

All this factors allow us to say we are dealing with critical parts. And they are not showing are "av. friendly". :mad: just the opposite.

When abused (electrically or environment) became furious. :E

RR_NDB

Good vector. I somehow missed Turin's post. Your and his points are well made--the battery is more or less isolated from providing power unless needed.

That is what I thought you said the first time but I just wanted to make sure that for some odd reason that the 787 did not depart from decades of precedence as to how the busses are powered and when.

I am still mulling over a point you raised on one of the threads (this one perhaps) regarding that unless the aircraft is completely unpowered (no external power for example) or else a serious in-flight degradation of the power supplies occurs, that the battery may never undergo a complete (or near complete) discharge and re-charge cycle. There simply would be no need for it.

There is something about that point that makes one wonder if it in any way relates to the matter at hand. I am afraid I cannot answer that but someone needs to...

From what I remember, the system will ground it self automatically to cycle, it is supposed to ground on full charge as well, to never have a full charge...

Isnt the system run through the batteries on a constant flow? (even simply to provide a clean source?)

Lyman.
I am not sure what you are saying here. That the ANA crew overreacted? That the grounding is unnecessary? Didn't you repost the FAA rules specifically excluding the leaking of elecrolyte and preventing thermal runaway? The crew had strong reasons to believe their battery was on fire, which it was.

From Flight Global's web site an interesting article titled:

Elon Musk: Boeing 787 battery fundamentally unsafe
by Zach Rosenberg

Elon Musk: Boeing 787 battery fundamentally unsafe

Radken
 

Maybe this is aleady mentioned in this thread.... but isn't one of the very real negatives about these LiI batts that they can simply, without any predictability, installed or uninstalled, new or old, suffer an internal short, and instantly dump huge current with resultant explosive arcing---- which will always ignite the flammables inside as well as adjacent cells? Isn't this how the cargo of Li batts brought down that Everglades DC9 about 20 years or so ago?

Isn't shaky batt technology, potential arcing, ignition, uncontained fire, et al, an unnecessarily nasty threat to colocate in the same area with flight critical electronics and thousands of wire pairs all ready to fuse together for the slightest of excuses? IMHO 'twas mostly the bean counters who have created this situation. Engineers would never have thought this up on their own unless forced to do so? Right?

Really agree with this statement by Elon Musk as linked in Airman1900's post.
"They [Boeing] believe they have this under control, although I think there is a fundamental safety issue with the architecture of a pack with large cells," writes Musk in an email. "It is much harder to maintain an even temperature in a large cell, as the distance from the center of the cell to the edge is much greater, which increases the risk of thermal runaway."
The shorted cell in the NTSB briefing appears to show exactly this effect, short along the centerline of the battery plates. That is where the temperature sensing devices belong in each battery cell.

radken
I believe you have muddied up the details of the Everglades (Valujet) DC-9 crash.
There was a skid of loose oxygen generating canisters that was implicated in that onboard fire.