The diagram suggests the case isn't (must not be?) earthed. Anyone read Japanese? Seem a little unusual ?

Lyman:
I would expect the venting system would be designed for a more controlled release.

In the case of JA804A (NH), electrolyte that reached the bottom of the EE bay was vented out of the plane (via either the outflow valve or a drain valve - I am not sure which). This is the brown streak visible on the underside of the fuselage.

The airflow cooled the material before it could do any real damage to the CFRP of the fuselage. This would also be the case with a controlled vent directly from the battery container.

Kiskaloo,

I would expect that, certainly. How quickly the pressure descent is ennabled would have serious repercussions: Not too quickly, the cells would rupture and make the problem worse, (far worse?). Too slowly, the pressure would build, risking the cabling penetrations and their integrity.

Malfunction? Disastrous. The EE Bay could be shredded in toto by the resulting release of highly pressurized gases and flaming fire... To involve the fuselage structure? There is no way to extinguish a structural fire involving CFRP....

Who shall design/build this system, Secure a Plane? Thales?

Who will test it? Will there be destructive testing? How long will it take? Is there a better choice of Battery instead?

Kiskaloo...forgive the nature of my post if it is too strong. BOEING have asked and answered these questions long ago. In that sense, you may consider them rhetorical in nature.

But since BOEING will not share their answers, perhaps a discussion, here?

vented NiCad battery
 

All main,apu or emergency batteries (NiCad) on Airbus and ATR aircraft are vented outboard due to gaseous fumes produced by the battery during charging.

For the record no-hoper, I think Boeing is entertaining a vent for products of combustion, NOT charging "off gasses".

stand to be corrected

Case is grounded by a/c cable
 

Hi,

cwwaters

Actually grounding wire was fused by high current coming from battery. I posted the equivalent circuit of this (very probable) fact. There is information posted earlier on that.

I guess the seat of the battery (MAIN) is also grounded.

Where is the valve* of the battery case? The battery case was sealed?
 

Hi,

Kiskaloo:

:ok:

no-hoper:

:ok: A battery "breaths" and venting is normally used. The case of the 787 battery was designed, i suspect, with some assumptions like:

Cell will not heat

Venting is not required

And also there is a VERY STRANGE POINT :suspect: (to be confirmed):

Each cell has it´s own valve (hole near plus terminal as posted earlier).

Where is the valve of the battery case?

(*) By valve i mean a hole where breathing of cells can pass through. A pressure gas passage.

My take on the design of the Stainless enclosure is that the top was not "sealed"

There were too few fasteners, (screws) and the top was "unhemmed", (not doubled). Nor did I see any remnant of gasketure. Nor fasteners bearing down from the top....

The penetrations likewise seemed unsealed, though there appeared to be "grommets" to prevent abrasive wear...

The case appeared to communicate (pressure wise) with the EE bay as a whole, any sealing attempt would have made pressurization of the Battery enclosure separate from, and more difficult, than pressurizing both at once.

??
 

Hi RR_NDB,

First of all thank you for all your interesting posts!

You wrote in post#27:

Each cell has it´s own valve (hole near plus terminal as posted earlier).
By valve i mean a hole where breathing of cells can pass through. A pressure gas passage.

I am not sure there is a vent at all for the following 2 reasons, and I am referring to the info given by the manufacturer in this link.
http://www.s399157097.onlinehome.us/...s/LVP10-65.pdf

It is stated that the cell has a Sealed Structure. I suppose that it means that all gases (normally!) will be held within the structure of the cell, just like on a AA battery, so no need for a vent?

On the picture "Cell construction" there is a white circular "thing" just below the plus terminal labelled "Rupture plate".
I suppose that this plate will blow out, if some serious failure has occured within the battery in order to relieve excess pressure.

My view is supported by the info given in post#772 in the thread Battery and chargers, where the JTSB states that "the safety valves 7 and 2 open".
Safety valve = Rupture plate?

Or maybe you are referring to another hole in the cell.

Where is the safety valve* of the battery case? The battery case was sealed?
 

Hi,

grebllaw123d:

You are right! The chemistry in these cells doesn´t require venting. At least in normal conditions. but if the cell has this safety exit, why not the battery was not designed with it? Or something less "sealed" (Lyman: My take on the design of the Stainless enclosure is that the top was not "sealed").

What concerns me is:

Cells heat and we don´t see in the battery case means to provide an expansion (and inverse movement when cooling down)

The venting i mentioned (your observation is correct) is not on the meaning of traditional batteries.

Better expressing: Why not battery case has not a similar mechanism. Certainly would be safer a "venting" (rupture mechanism) than an explosion of a battery inside an EEbay. Electrolytes certainly would create a serious risk for a plane with this structure.

No, i was expressing erroneously. Thank you for precise observation!

Edited the title.

Hiya Mac.....

There is no dedicated vent tube to the exterior. (From the Battery enclosure).

To me, that signals that any venting or discharge is reliant on gravity, pressure differential, and a strategically located scupper (venturi).

All very passive and not in tune with flaming electrolyte migrating about the decking of the EE Bay.

The Bay is pressurized, and conditioned, the Battery needs warmth to function, though not too much....

The enclosure must not be tightly sealed, one would think it must have the same pressure as the rest of the volume of the E/E Bay?

I agree with the white expansive plug, and posit that it faces inward, away from the enclosure sides, where it might conflict with its own migration out of its hole.

I am speechless that Boeing have come up with these "fixes", each and every one requiring substantial design and engineering, not to mention approval, (Self approval perhaps not in the mix this time :ok:).

The whole set-up presents as a too passive design/fail chain.

I am likewise surprised that there does not appear to be sufficient caution to protect the composite structure from burning fluids, and hot gases. The fuselage is flammable...

The lack of an active pressure/venting system being the giveaway....

Guam B2
 

This "fire" from the two incidents seems will burn much longer than the 40 hours + the B2 in Guam had.

Question: Is the same composite?

Bold mine

:mad:

Mac...

Yes, the construction is of Carbon Fiber Reinforced Plastic. (CFRP). This material is not allowed in the areas of the aircraft that contain passengers, and/or crew. It is flammable, and burns with toxic byproducts.

Two Phase (Resin/Matrix) materials are not new. I started working with them in 1953, when I was building model aircraft, and my father came home from the lab with beakers of evil smelling brown amber liquid, and a lavender coloured "paste". Mixed together, the reaction created heat and a rapidly hardened polymer glob that was seemingly indestructible.

I used it for motor mounts, filleting wing/fuselage, and anything else I could sculpt quickly. I have used it on boats, autos, and flown Bede and Rutan aircraft, made of composite construction.

It makes the Dreamliner an historic benchmark in efficiency, its light weight and remarkable strength signal a revolution in air travel, and fuel efficiency.

It has a downside. As amicus has posted, it is chemically complex, and burns with a long list of products not conducive to mammalian respiration.

My concern when I first saw the NTSB image of the technician in the EE Bay was how much, if any, involvement there was of resin in the fire. Once ignited, it is very difficult to extinguish, and since it is structural, there are concerns. I have had some difficulty finding the outcome of the injured firefighter, my hope is that he was equipped with a breathing system, and had adequate heat protection.

The wrecked B2 burned for two days.

Battery Circuit Design
 

I am trying to take the discussion on a different route here. Having worked on several Boeing and Airbus aircraft including A380, there is a point worth noting. If Boeing is making a new aircraft and require a new battery circuit design, looks like, they just call the guy who designed the previous aircraft DC circuit. He pulls out his old drawing and makes a few changes and presto we have a new design. I am not saying that is exactly the way it was done here, but when I compare B747 to B777 thro to B787, it would appear so.
Airbus designs are no different. The battery circuit design is the same on A300 to A310 to A330 to A340 to A380. For A350 schematics are not yet in the public domain but it will not be very different. But the design is more clever on this side of the pond.

So why am I bringing this point here? You should wonder how Airbus has managed to quickly switch back to Ni-Cad for A350, when the heat is on LI. With Boeing when the aircraft became bigger or system demand increased, the battery size also increased and we have now a massive 70AH battery that can supply 150A peak load. It is just 50AH battery on larger B777. They have just failed to consider other options when the demand increased. failed to think out of the box.
Look at Airbus design. From A300 to A310 to A330 to A340, they have 3 batteries that can be switched as the load demands and each one of them is smaller in size in comparison. Each battery has it's own control, which disconnects that unit in case of a defect. So when they designed the A380, they used 4 batteries, again switched in parallel if the load demands. For A350, I am sure they had 3 small LI battery which they can quickly change to Ni-cad at the blink of an eye. Clever design and config.

Why Boeing is not thinking of splitting the battery into 3 or 4 units? That way the heat build up and the danger to the air-frame is minimal. I know this will be time critical for certification etc.
Think about it, instead of trying to create a meteor shower in the sky with a burning LI battery. ( I am neither American nor an European - so don't think that this is start of spat who is superior across the pond).

Your post has important points
 

Hi,

Hi-Tech

This STRATEGICAL ERROR is going to cost Billions of dollars to Boeing. And we are talking of a MERE battery. A device with a VERY SIMPLE TRANSFER FUNCTION: You store energy (you charge it) and it give you back the energy (after losing some % in the process). Is ABSOLUTELY DANGEROUS (IN ALL ASPECTS) to have only one option.

Last night i did look the data sheet of the SiC modules 787 uses as switches (one that may explain the "miswiring" reported). Sandia AFAIK funded by US taxpayers made an R&D for these devices used also in F35. Even this modules has competitors. (i will send you the data sheet by email. I lost the internet link but downloaded the .pdf) and are costly. (thousands dollars) Are "simple" switches. Seems the R&D of 787 suffered many difficulties (many delays, etc.) and they put the plane in commercial operation assuming risks (certainly estimated) and now they are completing the R&D by the hard way (field retrofit). :{:{:{

The config you mentioned in EADS planes certainly is more "flexible" due two things:

1) You mentioned
2) Requires less electricity from batteries

In 787 the required redundancy (did you see the newairplane site?) required the "150 Amps" and the weight optimization probably was the decision making big factor. (together the pressure on Boeing to use the NEW WONDERFUL cells)

But the use of just one BAD battery (MAIN) was a serious TECHNICAL AND ORGANIZATIONAL error. It would be too risky and Boeing is receiving the bill. :{

Did you see my first and second version of a possible (quick) fix:

2 similar batteries in parallel (same cells better separation, larger case)
Both PCB´s in separate chamber
Same (revised) BMS
Same charger (One for both batteries, "switched")
Improved sensing to shut off (battery) when one cell "starts" to fail
1 BDM per battery (MAIN)
Sturdier and vented (to outside) case.
Located nearby current positions (cable lenght optimization)
Total 4 batteries (2 MAIN, 2 APU)

Result: Better dependability, fault tolerant, graceful degradation, less fire risk, planes flying sooner (probable) and safer also because (batteries) could be derated.

Weight penalty: Aprox. "1 pax"

The mentioned posted approach could be expedite

Problem is much more serious than just a battery burning. An "electric" plane (we can say that on the 787) made using flammable parts is a new issue.

I did study EMI/EMC (ESD, grounding, etc.) and always think on issues in non metallic planes. The extensive use of solid state switching devices is another concern.


To be continued by editing.

Not a "vent" in the traditional sense. The EE Bay is pressurized, so the jettison tube needs to be controlled. The Battery enclosure is in no need of "ventilation" save in the instance of a thermal runaway within. There would need to be a backflow preventer (check valve) that prohibited loss of pressure in normal ops.

Sensors of temperature and pressure would activate the dump duct only in an emergency. The outflow would need to be managed to prevent any sudden changes in pressure, when the contents are being evacuated. An external shield would be necessary to protect the CFRP fuselage from heat and corrosives. The staining of the Main battery dump scupper (ANA) shows why this is required.

The battery enclosure would have to be of sufficient strength to resist crumpling in the interior as the pressure dropped within. If the case crushed the connectors or hots, the situation could get very intense.

Not a "new" issue, really. Engineers have studied CFRP behaviour in burning for decades. What is new is installing a volatile new type of battery in proximity to CFRP structures... There will have been mountains of data generated in the 787 development that address this issue. Part of NTSB's concern in the certification process will be this marriage of possible fire and flammable structures. It is inconceivable this issue was not addressed, and then satisfied.

In the development of this project, there is one consideration that must be observed. Critical Path. Everything that moves along with this path is collateral, to the point where it must be decided which direction to go. Past a certain "jumping off" point, it makes no sense to continue a collateral and replaceable scheme, eg NiCad.

This point can be in design or any time up to the inexorable progress of the path critical... Dance with the one you brought to the dance.

"This technology suits the demands of the airframe"...At that point, the NiCad alternative is terminated, in design, development, engineering, and production.

Airbus will still have a time of it. None of these systems can be made modular past this committed decision point.

The LiIon system is deeply integrated into 787's electrical distribution complex (sic!).....

Daft question, WHY NOT ?

AIUI the charger/monitor is a self-contained unit in a box....it interfaces with the aircraft systems and with the battery it controls

The battery, IMHO should ONLY interface the control box(charger-monitor) It's a bit of a stretch to say that this is met by the contactor/relay within the battery, being switched by the controller. However

The battery and controller together form (or should) an integrated, self-contained electricity storage and supply system.
Physical space should be the only problem,if the storage-device (battery) and it's associated controller are designed to be compatible to each other and the power-requirements (aircraft) they are hooked into.

What am I missing?

cockney steve

We should find out this morning, after BOEING meets with Huerta, of FAA.

:ok:

Why?
 

Hi,

Why?

Isn't the APU controller powered by the APU Battery? If the BATT fails, the controller shuts off the APU, and itself......


No?