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B787 Grounding: Tech/ops Thread Part 2  
User currently offline777ER From New Zealand, joined Dec 2003, 12341 posts, RR: 18
Posted (1 year 9 months 3 weeks 3 days 3 hours ago) and read 14539 times:
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Link to the first thread: Tech/Ops Discussion Of The 787 Grounding (by CM Jan 22 2013 in Tech Ops)

114 replies: All unread, showing first 25:
 
User currently offlinekanban From United States of America, joined Jan 2008, 3875 posts, RR: 27
Reply 1, posted (1 year 9 months 3 weeks 2 days 19 hours ago) and read 14326 times:
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We've tried to keep this thread limited to facts and data limited to the 787 and it's specific battery. Wild speculations, 'similar to' scenarios, and blame game posts are not welcome.

User currently onlineRickNRoll From Afghanistan, joined Jan 2012, 900 posts, RR: 0
Reply 2, posted (1 year 9 months 3 weeks 2 days 13 hours ago) and read 14101 times:

Is there any truth to this claim.

ound this blog topic on the battery fire in Boston. Can anyone confirm the technical details?


The NTSB interim report into the Japan Airlines 787 battery fire in Boston in January says a second smaller lithium ion battery located above the large battery showed signs of failure before it was physically removed from the belly of the Dreamliner by an airport fire crew.

The implication is that had this main rear lithium-ion battery fire broken out while the JAL flight was making its flight from Narita to Boston there would have been a second stacked lithium ion fire in the same location directly under the rear passenger cabin just behind the trailing edge of the wing.

This smaller battery that was installed on a rack above the battery that burned was also supplied by Japanese manufacturer GS Yuasa, and was intended to provide emergency power for the jet’s flight controls for 10 minutes or more “when no other electrical power is available.”

The NTSB investigators found the exterior of this battery had been “lightly scorched” by the fire below and noted its case had openings at the corners.

The firefighters suppressed the fire before it could spread to that second battery.


http://blogs.crikey.com.au/planetalk...7-was-at-risk-of-2nd-battery-fire/

That is, that there is another, smaller lithium battery that was at risk of catching fire from the main battery catching fire.
Also, it appears that there was fire that had escaped containment. There was debate over weather this was due to the fire fighters, or if it had happened before the fire fighters arrived on the scene.


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 3, posted (1 year 9 months 3 weeks 2 days 12 hours ago) and read 14075 times:
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There was truth that a second battery was "lightly scorched", but I am not sure that means it is true it would have subsequently caught fire itself.

I'm guessing this second battery is the one in the copper-colored box with the Honeywell label. Have to say that it looks completely undamaged in the NTSB picture of the APU battery location.


Quoting RickNRoll (Reply 2):
Also, it appears that there was fire that had escaped containment. There was debate over weather this was due to the fire fighters, or if it had happened before the fire fighters arrived on the scene.

That the firefighters reported flames were visible escaping the box when they arrived in the EE bay should have been clear enough evidence.

[Edited 2013-03-09 16:00:36]

User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 4, posted (1 year 9 months 3 weeks 2 days 11 hours ago) and read 14051 times:

Quoting RickNRoll (Reply 2):
a second smaller lithium ion battery located above the large battery showed signs of failure before it was physically removed from the belly of the Dreamliner by an airport fire crew.
Quoting Stitch (Reply 3):
I'm guessing this second battery is the one in the copper-colored box with the Honeywell label. Have to say that it looks completely undamaged in the NTSB picture of the APU battery location.

How could this "smaller lithium ion battery" appear in the NTSB photograph of the APU battery location in the airplane if the fire crew had removed it from the airplane?


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 5, posted (1 year 9 months 3 weeks 2 days 11 hours ago) and read 14042 times:
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Quoting hivue (Reply 4):
How could this "smaller lithium ion battery" appear in the NTSB photograph of the APU battery location in the airplane if the fire crew had removed it from the airplane?

I don't believe they did. To my knowledge, they only removed the APU battery.


User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 6, posted (1 year 9 months 3 weeks 2 days 9 hours ago) and read 13983 times:

Oh, OK. I guess that blogger could use an editor. Will have to check the report to see if what he says is correct.

User currently offlineBoeingVista From Australia, joined Jan 2009, 1585 posts, RR: 3
Reply 7, posted (1 year 9 months 3 weeks 2 days 7 hours ago) and read 13928 times:

Quoting Stitch (Reply 3):
There was truth that a second battery was "lightly scorched", but I am not sure that means it is true it would have subsequently caught fire itself.

I dont think that people have looked at the below document that shows anothe 20 odd picyures of the fire scene.

Take a look at the pictures from page 10, the 10 minute avionics backup battery is clearly marked and does sit directly above the APU battery in a non fully sealed container, as it is on a rack directly above the burning APU battery it was receiving flame, heat and expelled electrolyte onto its bottom like it was on a hotplate, this cannot be good. More certification issues.

Also browse the pictures from page 10 down and read the fire-fighters report, the fire was not on its way out and imagine how much further damage could have been caused before it burnt itself out.

http://www.ntsb.gov/investigations/2...ket_documents/787_docket_doc19.pdf



BV
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 8, posted (1 year 9 months 3 weeks 2 days 5 hours ago) and read 13883 times:

Quoting BoeingVista (Reply 7):

All of the fire/smoke/spillover problems can be solved with containment. What happened didn't happen in the million or so hours of testing by Yuasa and Boeing. The cause of the fire itself is so elusive that the NTSB still doesn't have root cause for either fire...and that's the real problem with these batteries.

Without knowing why they went runaway, you can't fix it. I still hold with my initial reaction; shoehorn an interim battery using already certified chemistry, (NiCd), and get flying. It looks like there's lots of room in there for a longer battery pack to fit on the current batter rails, (if it needed to be longer). I'd be shocked if the 787 charging system couldn't be set for a NiCd pack.

So far, it's impossible to tell exactly what Boeing and the feds are doing, (I'd love to be a fly on the walls), but I'd bail on the current chemistry pronto, and to tell the truth, I'd bail on Li-ion chemistry altogether. No matter how benign the chemistry, (LiFePo4, for example), it's still LITHIUM and that stuff blows up planes, right...? (insert smiley here)



What the...?
User currently online747classic From Netherlands, joined Aug 2009, 2233 posts, RR: 14
Reply 9, posted (1 year 9 months 3 weeks 2 days 1 hour ago) and read 13782 times:

I have some more (technical ) questions :

- How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

- Are all Litium-ion batteries affected by the Boeing solution for lifting of the 787 grounding (containment and extra ventilation) ?

- Is battery re-location also included in the Boeing proposed fix ?

- What is(are) exactly the function(s) of each battery ?

To start things up :

- AFAIK the Main and Avionics batteries are installed as the (last) electrical back-up for flight critical systems if all other electrical sources (engine, APU and RAT generators) have failed or after a total electrical grid failure.

- The APU battery is only used for APU starting and is needed for ETOPS certification, to deliver two extra serviceable APU generators, after an APU in flight start, if needed in a non-standard electrical procedure.
AFAIK the APU battery can't be used to augment the main battery in case of an electrical emergency.



Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 10, posted (1 year 9 months 3 weeks 1 day 18 hours ago) and read 13630 times:

Quoting JoeCanuck (Reply 8):
shoehorn an interim battery using already certified chemistry, (NiCd), and get flying. It looks like there's lots of room in there for a longer battery pack to fit on the current batter rails, (if it needed to be longer). I'd be shocked if the 787 charging system couldn't be set for a NiCd pack.

But there remains the major issue of whether any NiCad solution that could possibly be made to fit could also meet the 787's power requirements. In the Boeing video cited in other posts in other threads Mike Sinnett says Li-Ion was not chosen to save weight (i.e., for its size) but because of power requirements.



Quoting 747classic (Reply 9):
The APU battery is only used for APU starting

The APU controller is powered by the APU battery. If a the APU battery tanks the APU shuts down.

Quoting 747classic (Reply 9):
or after a total electrical grid failure

If there is no electrical grid at all available it's unlikely that batteries are going to be of any use.


User currently offlinercair1 From United States of America, joined Oct 2009, 1357 posts, RR: 52
Reply 11, posted (1 year 9 months 3 weeks 1 day 18 hours ago) and read 13613 times:
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Quoting 747classic (Reply 9):
How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

I don't know precisely - but multiple posts have mentioned that Li-Ion batteries are used throughout many aircraft both from Boeing and AirBus - and presumably others as well. Most of those batteries are quite small and back up individual items - like exit signs and the such.
The uniqueness of the 787 is the use of a large, high capacity Li-Ion for Main Ship and APU batteries. The AB350 was intended to do this as well, but AB has stated they will launch with NiCads and consider upgrade to Li-Ion later.

Quoting 747classic (Reply 9):
Are all Litium-ion batteries affected by the Boeing solution for lifting of the 787 grounding (containment and extra ventilation) ?

I don't think so. If that were the case, many other a/c would be impacted.

Quoting 747classic (Reply 9):
Is battery re-location also included in the Boeing proposed fix ?

I don't think so - but that is not authoritative. Has Boeing's proposal been released to the public?

Quoting 747classic (Reply 9):
What is(are) exactly the function(s) of each battery ?
Quoting 747classic (Reply 9):
To start things up :

I think you have it correct - with one minor comment.. I believe the main battery is intended to be an interim source while alternative sources come up. It is not considered one of the non-time limited extra sources. That is why the APU battery is there - to start the APU. The non-time limited sources include the main engine generators, the APU generators and the RAT.



rcair1
User currently offlinekanban From United States of America, joined Jan 2008, 3875 posts, RR: 27
Reply 12, posted (1 year 9 months 3 weeks 1 day 18 hours ago) and read 13607 times:
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Quoting rcair1 (Reply 11):
The AB350 was intended to do this as well, but AB has stated they will launch with NiCads and consider upgrade to Li-Ion later.

Read somewhere they will stay with Li-Ion on the first three test vehicles and change to NiCad on unit 4.. allowing them to meet first flight and test projections avoiding a 787 type delay. Evidently there needs to be software changes with the battery change.


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 13, posted (1 year 9 months 3 weeks 1 day 17 hours ago) and read 13598 times:
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Quoting BoeingVista (Reply 7):
I dont think that people have looked at the below document that shows anothe 20 odd pictures of the fire scene.

Thank you for that. The bottom is indeed where the scorching happened.



Quoting 747classic (Reply 9):
- How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

Ship's Battery, APU Battery, Avionics Battery (not sure if there is just one in the aft EE bay or also one in the forward EE bay, as well). Li-Ion batteries also power emergency cabin lighting.



Quoting 747classic (Reply 9):
- Are all Litium-ion batteries affected by the Boeing solution for lifting of the 787 grounding (containment and extra ventilation) ?

No. The ones that power the emergency lighting are not considered a risk. The Avionics battery also seems to not be considered a risk.



Quoting 747classic (Reply 9):
- Is battery re-location also included in the Boeing proposed fix?

I am guessing no, but to my knowledge most of the particulars of Boeing's proposed fix have not been made public.

Quoting 747classic (Reply 9):
- What is(are) exactly the function(s) of each battery?

The Ship's Battery assists the APU battery during APU start. It also provides power to the Captain's instrument panel in the event of a loss of generator power (engine; APU; RAT).

The APU battery can start the APU on it's own, but normally is used in conjunction with the Ship's Battery for this function.

The Avionics battery is a new one to me, but it sounds like it's the terminal emergency power source for flight deck instruments.


User currently onlineRickNRoll From Afghanistan, joined Jan 2012, 900 posts, RR: 0
Reply 14, posted (1 year 9 months 3 weeks 1 day 17 hours ago) and read 13566 times:

Quoting hivue (Reply 10):
The APU controller is powered by the APU battery. If a the APU battery tanks the APU shuts down.

Is that correct? What that means is that you can't MEL the APU battery, if you need to have the APU available for ETOPS, doesn't it? The APU could be started with one engine still going, but it can't run at all without the APU battery being functional.


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 15, posted (1 year 9 months 3 weeks 1 day 16 hours ago) and read 13555 times:
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Quoting RickNRoll (Reply 14):
What that means is that you can't MEL the APU battery, if you need to have the APU available for ETOPS, doesn't it?

You can dispatch with the APU battery (or an APU, for that matter) inoperative, but it limits you to ETOPS-180 (you must be within 180 minutes of landing at a suitable airport).

As it has been explained to me, this is the case for other Boeing Commercial Aircraft families, as well.

[Edited 2013-03-10 12:44:12]

User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 16, posted (1 year 9 months 3 weeks 1 day 16 hours ago) and read 13551 times:

Quoting hivue (Reply 10):
But there remains the major issue of whether any NiCad solution that could possibly be made to fit could also meet the 787's power requirements. In the Boeing video cited in other posts in other threads Mike Sinnett says Li-Ion was not chosen to save weight (i.e., for its size) but because of power requirements.

Increasing capacity just means increasing the number of cells. Then, the limitations are size and weight.

The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.

I'm having a heck of a time digging up the physical dimensions of the 777 battery pack, but individual cells don't really care how they're stacked so a pack could probably be built that would fit on the 787 battery rails, but probably stick out further, or be a bit taller.

Anyway, the gist of my position is that I can't wrap my head around why they don't stage the process, using an interim, alternate battery chemistry temporarily. Maybe certifying even a NiCd pack, (since it would have to be a unique pack, regardless of the chemistry being certified), would take as much time as getting the already certified pack fixed.

I don't claim to be an expert in batteries and there are a lot of smart boffins at Boeing working on this. I'm basically trying to understand what the heck is going through their minds, (because inquiring minds want to know), and I want to see that darned plane back in the air, (which I'm pretty sure is their goal as well).

At the same time, I like to solve problems so I don't mind speculating and offering solutions to the ether, which won't make a bit of difference in the long run, but keeps my neurons active.



What the...?
User currently offlinePITingres From United States of America, joined Dec 2007, 1163 posts, RR: 13
Reply 17, posted (1 year 9 months 3 weeks 1 day 16 hours ago) and read 13547 times:

Quoting hivue (Reply 10):
The APU controller is powered by the APU battery. If a the APU battery tanks the APU shuts down.

This apparently did happen on the ground, with no other power sources available (other than the Main battery). I too would like to know whether this is always the case if there are other power sources available: ground power, engine power, RAT, etc. I find it hard to believe that the APU can't be run at all in any circumstances without a functional APU battery.

It does seem a bit odd to have the APU controller requiring the APU battery when the APU itself is running, but no other power source is online. I have to wonder if the APU shutdown on JA829 was due to the way the airplane power was configured at that moment, or if it was a design oversight. I skimmed the NTSB report but I don't recall seeing any information on that point.



Fly, you fools! Fly!
User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 18, posted (1 year 9 months 3 weeks 1 day 16 hours ago) and read 13548 times:
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Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity.

Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.


Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.

Per the same Boeing presentation, the 787 battery uses 8 cells while the 777 battery uses 20 cells. That might impact the size and weight (the 777 battery weighs 48.5kg compared to 28.6kg for the 787).



Quoting PITingres (Reply 17):
I find it hard to believe that the APU can't be run at all in any circumstances without a functional APU battery.

This is evidently the case for all Boeing Commercial Airplane families.

[Edited 2013-03-10 12:51:55]

User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 19, posted (1 year 9 months 3 weeks 1 day 15 hours ago) and read 13492 times:

Quoting RickNRoll (Reply 14):
Is that correct?
Quoting PITingres (Reply 17):
I have to wonder if the APU shutdown on JA829 was due to the way the airplane power was configured at that moment, or if it was a design oversight. I skimmed the NTSB report but I don't recall seeing any information on that point.

See footnote 6 of page 1 of the report:
"The APU battery provides power to start an APU during ground and flight operations. The APU controller (discussed in section 1.6.5) monitors the parameters that are needed to operate the APU. The APU controller is powered by the APU battery bus, which receives its power from the APU battery. If the APU battery fails, then the APU battery bus will no longer receive power, and the APU will shut down."

Quoting JoeCanuck (Reply 16):
Increasing capacity just means increasing the number of cells. Then, the limitations are size and weight.
Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

I think that when they mention power requirements for the 787 they're talking about how many amps can be delivered, but I don't think it has to do with airplane power up but with emergency backup situations. I suspect that the electric brakes pull a lot of amps.


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 20, posted (1 year 9 months 3 weeks 1 day 13 hours ago) and read 13419 times:
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Quoting hivue (Reply 19):
I think that when they mention power requirements for the 787 they're talking about how many amps can be delivered, but I don't think it has to do with airplane power up but with emergency backup situations.

The slide specifically noted this was current provided at airplane power-up.


User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 21, posted (1 year 9 months 3 weeks 1 day 10 hours ago) and read 13329 times:

Quoting Stitch (Reply 20):
The slide specifically noted this was current provided at airplane power-up.

Thanks. I should look at the video presentation again.

If the 787 actually needs 150A for routine processes it looks like the 777 can do on 16A then there may be no hope at all for a non-Li-Ion solution.


User currently onlinemjoelnir From Iceland, joined Feb 2013, 1594 posts, RR: 3
Reply 22, posted (1 year 9 months 3 weeks 1 day 10 hours ago) and read 13313 times:

Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

You are comparing apples with bananas.

A is the current, A/h is the capacity.
The 787 has a battery of 65 A/h capacity and the 777 has a battery of 50 A/h capacity.

The 16 A draw of the 777 should be the draw (current) on the main battery.
Regarding the APU: if the draw for the APU start on the 787 would be 150 A and on the 777 16 A, than the APU on the 787 should be 10 times the size of the APU on the 777.
I think you should rethink your argument.


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 23, posted (1 year 9 months 3 weeks 1 day 9 hours ago) and read 13289 times:
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Quoting mjoelnir (Reply 22):
You are comparing apples with bananas.

No, Boeing is, since it's their slide.

Quoting mjoelnir (Reply 22):
I think you should rethink your argument.

I think you should take it up with Boeing, since it's their slide.



[Edited 2013-03-10 19:57:14]

User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 24, posted (1 year 9 months 3 weeks 1 day 8 hours ago) and read 13272 times:

NiCd's are famous for being able to handle high power draws. The capacity and current draw may have little to do with each other directly, except for duration of power delivery. Generally speaking, they are considered more reliable in high draw conditions than Li-ions...though I'm betting the 787 batteries aren't your standard power drill units.

It's only recently that power tools, (which tend to have a very high amperage draw), began switching to Li-ion batteries. It would take 44 of my Makita power tool batteries to equal the capacity and voltage of the 787 batteries.

I suspect that the 777 NiCd pack could handle a much higher draw than 16Amps. That's just what the 777 batteries are required to provide, not necessarily the maximum current they can supply 24v.
I'm guessing the 777 pack is made up of packs that resemble flashlight batteries, in series and parallel to provide the voltage and capacity.

IF the NiCd's could handle the higher draw, then the capacity and voltage would both have to be increased to match the 787 requirements and that would mean a battery of at least 150 lbs and probably 50% larger than the 777 batteries.

Even going with lead acid batteries might be possible. The gel battery in my motorcycle, (coincidentally a Yuasa), is 12v and 20 amp/hr. It's completely sealed, quite robust and designed for high current draws and random charging. 9 batteries like this with maybe 25 amp/hr capacity would give 36v and 75 Amp/hr total capacity in a package about 12"x12"x18"...but it would be one heavy sucker...probably in the 200 lb range.

I seriously doubt the charging system of the 787 couldn't be reprogrammed to handle either option. These batteries are not nearly as sensitive to charge and discharge variances as Li-ions. You could practically charge them with jumper cables from the baggage carts.

Bullet proof containment is probably the only way they can possibly get the Li-ion packs recertified and even then, they'll be a tough sell. I have a very difficult time believing they aren't working on a permanent solution using different chemistry, even if they stay within the Li-ion family. Cessna has chosen LiFePo4 for the CJ-4, which I think is a very good choice.

The end solution is the easy part....they'll have lots of time to come up with that. It's the interim solution which gets the planes back in the air that's the tough part.

If only they could come up with a root cause for the fires...then they could actually have something concrete to fix. It's the uncertainty and unpredictability that are the real buggers.



What the...?
User currently offlinekalvado From United States of America, joined Feb 2006, 497 posts, RR: 0
Reply 25, posted (1 year 9 months 3 weeks 1 day 8 hours ago) and read 13511 times:

Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.
Quoting JoeCanuck (Reply 24):
I suspect that the 777 NiCd pack could handle a much higher draw than 16Amps. That's just what the 777 batteries are required to provide, not necessarily the maximum current they can supply 24v.

This makes me wonder - 777 battery should last for about 3 hours - capacity of 50 Ah/16 A draw.. 3 hours of what? Over the ocean flight with all engine and APU generators inop, and RAT not deployed? Or 3 hours of ground operation?
It doesn't make sense to me - first scenario is too harsh; and why would 3 hours worth of power be needed?
Possibly there is some other operation mode with much higher current draw not mentioned on a chart, and 16 A is to keep essential instruments and controls in flight?


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 26, posted (1 year 9 months 3 weeks 1 day 6 hours ago) and read 13480 times:

Quoting kalvado (Reply 25):
This makes me wonder

Just guessing but I suspect they did some intentional overkill on the battery. They had to use enough cells to get 24v out of 1.2v cells. They may very well have figured that they have the room on the big beast of a plane that they might as well get some extra capacity. It was also early in the ETOPS era so too much was better than not enough.



What the...?
User currently onlinemjoelnir From Iceland, joined Feb 2013, 1594 posts, RR: 3
Reply 27, posted (1 year 9 months 3 weeks ago) and read 12966 times:

Quoting Stitch (Reply 23):
I think you should take it up with Boeing, since it's their slide.

I do not have to take it up with Boeing, it is your argument in this discussion.

If you look at the advertisement slide of Boeing you presented, it is misleading.

It seems to compare the batteries, but it does not say anything about the maximum current you can draw of the batteries.


The number of 150 A is for the start up of B 787 and the 16 A for the start up of the B 777.
It is plainly misleading to set it up this way.
It has nothing to do with the maximum current both batteries can provide, so it does not say anything about the possibility of using the B 777 battery in the B 787.

As an example a typical automotive lead acid battery of 12 V 65 Ah will provide you with a minimum cold start capability of around 600 A current down to -18°C. 16 A even at 32 V would hardly start even the smallest car.
A typical Ni/Cad D size can provide about 35 A maximum current.

Both the Ni/Cad 50 Ah of the 777 and the Lithium/ion 65 A/h of the 787 are used as a single battery to start the APU.


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 28, posted (1 year 9 months 3 weeks ago) and read 12932 times:
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Quoting mjoelnir (Reply 27):
I do not have to take it up with Boeing, it is your argument in this discussion.

I didn't offer an argument, I asked a question:

Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

Rather than answer that question, you went with a tangential argument unrelated to my question.


User currently onlinemjoelnir From Iceland, joined Feb 2013, 1594 posts, RR: 3
Reply 29, posted (1 year 9 months 2 weeks 6 days 23 hours ago) and read 12924 times:

Quoting Stitch (Reply 28):

So about what is your question?

The question could be can the Ni/cad provide the 150 A?
The question could be is 150 A to much for the lithium/ion?
Can the lithium/ion battery provide 150 A a long enough time'
Is an 65 A/h battery not far too small to provide 150 A if in another application a 50 A/h battery used to provide 16 A?

I can imagine a lot of questions.

But you started of with: the 787 battery can provide 150 A while the 777 battery provides 16 A.
So you compare what batteries CAN provide, and I am reasonable sure that the 50 A/h Ni/Cad battery of the B 777 CAN provide more than a current of 16 A.


User currently offlineCARST From Germany, joined Jul 2006, 837 posts, RR: 2
Reply 30, posted (1 year 9 months 2 weeks 6 days 21 hours ago) and read 12854 times:

Quoting Stitch (Reply 18):
Per the same Boeing presentation, the 787 battery uses 8 cells while the 777 battery uses 20 cells. That might impact the size and weight (the 777 battery weighs 48.5kg compared to 28.6kg for the 787).
Quoting JoeCanuck (Reply 16):

The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.
Quoting JoeCanuck (Reply 24):
IF the NiCd's could handle the higher draw, then the capacity and voltage would both have to be increased to match the 787 requirements and that would mean a battery of at least 150 lbs and probably 50% larger than the 777 batteries.

But what could really be Boeings problem? You can not tell me that an 30-50% weight increase resulting in a battery weighing something around 70kg would really be a problem? That are 40kg more, so what? If it would help to lift the grounding why not certify a NiCd battery?

I think there has to be another reason...

Some people said that NiCd batteries have a slightly varying power output what could destroy components which are not made for this varying power inputs. LIon batteries have a more stable power output, could this be the reason? Did they probably use many components on the 787 that would not accept the varying power of a NiCd battery? (Please note that this should not be a speculation, this is a question to the technical more knowledged people here.)


User currently offlineJHwk From United States of America, joined Jan 2013, 247 posts, RR: 0
Reply 31, posted (1 year 9 months 2 weeks 6 days 20 hours ago) and read 12822 times:

Quoting mjoelnir (Reply 29):

You could do a NiCd battery that would serve the purpose. It would be about 3x the weight and 2x the size based on total watt-hours for the system. You would also need 25-75% extra capacity to account for the differences in charge and discharge characteristics, depending on the total discharge time and regulatory requirements to get the battery back to full strength. This could realistically place it at about 4x weight and 3x volume for comparable performance.

Quoting CARST (Reply 31):
If it would help to lift the grounding why not certify a NiCd battery?

It wouldn't make the process faster. You need a brand new design for the battery management system and charger, and you need to make sure that design is fully vetted and compatible with the 787's power systems.

The reliability of the existing battery is going to need to be addressed, and changes of some sort are likely. Two months after the incidents though, we on a.net still don't really have any idea on the root cause(s). A manufacturing defect in the batteries would have been the easiest to address.

I have no idea of Thales did mimic testing of the flight charge/discharge characteristics to age batteries consistent with real flight conditions (and not just assumed conditions), but hopefully there is enough data in non-failed BMS units that you could do simulation across a large number of units over the course of a month or two and autopsy the cells afterwards to determine if any dendrites have formed, why the premature failures are happening, and if there is something that was unexpected in the behavior.


User currently offlineCALTECH From Poland, joined May 2007, 2322 posts, RR: 26
Reply 32, posted (1 year 9 months 2 weeks 6 days 19 hours ago) and read 12775 times:

Quoting JoeCanuck (Reply 8):
Without knowing why they went runaway, you can't fix it. I still hold with my initial reaction; shoehorn an interim battery using already certified chemistry, (NiCd), and get flying. It looks like there's lots of room in there for a longer battery pack to fit on the current batter rails, (if it needed to be longer). I'd be shocked if the 787 charging system couldn't be set for a NiCd pack.

Posted this long ago in another thread which quickly became overrun with so-called 'experts' who knew everything such as the electrolyte makeup. This is not my opinion, but taken from internal messages which for obvious reasons can not be re-posted. A so called Ni-Cad battery solution for the 787 as we are told, would be about 3 times the weight and size of a 777 Ni-Cad battery. The 787 charging system could not be set for Ni-Cads as it is. There is a voltage at which, if the Lion battery drops below this voltage, that the battery and shuts off and can only be brought back to life with specialized GSE. To go to Ni-Cads would need certification of the entire battery and charging system. From what we hear, it is not in the works to go Ni-Cad for now.

Quoting 747classic (Reply 9):
- How many Litium-ion batteries are in total installed in the 787 ? Three (3) are known to me up to now.

4 sets of Li-ion batteries on the 787, Main aircraft and APU batteries- 1 each, 2 total. Flight Control Bus Batteries 2 total. Battery packs for wireless emergency light units supposedly 30 total, size of laptop batteries. DFDR box battery, 1 for each of 2 boxes. Believe this is the total.

Other emergency batteries that were formerly Ni-Cd – EPAS door assist, fuel spar shutoff valves, etc. – have been replaced on the 787 with capacitors.

Quoting hivue (Reply 10):
But there remains the major issue of whether any NiCad solution that could possibly be made to fit could also meet the 787's power requirements. In the Boeing video cited in other posts in other threads Mike Sinnett says Li-Ion was not chosen to save weight (i.e., for its size) but because of power requirements.

Power output of a much smaller and lighter battery Li-Ion versus Ni-Cad.

Quoting JoeCanuck (Reply 16):
The 787 battery is nominal 30v, 65Amp/hr, (with a normal operating range of between 20v and 30v) and the 777 battery is 28v, 50Amp/hr capacity. You basically have to add 30% more cells, (which means 30% larger size as well), to get the same capacity as the 787 batter...but I have no idea about the size and weight.

We have been told long ago that a comparable Ni-Cad battery would be 3 times the size, and weight, of a 777 battery.

Quoting Stitch (Reply 18):
Is the current provided at airplane power-up an issue? Per a Boeing presentation, the 787 battery can provide 150A while the 777 battery provides 16A.

Looking at some battery check outs of a 777 battery, a discharge current of 47 Amps is used with a test box.

Quoting JoeCanuck (Reply 16):
I'm having a heck of a time digging up the physical dimensions of the 777 battery pack, but individual cells don't really care how they're stacked so a pack could probably be built that would fit on the 787 battery rails, but probably stick out further, or be a bit taller.

As reported toi us, the 777 is twice as tall with approx the same footprint of the 787 battery. Twice as heavy too.

Quoting hivue (Reply 19):
I suspect that the electric brakes pull a lot of amps.

Essential electrical power provided by 787 main ship battery does not supply power for cabin pressure, wing and engine anti-ice, or any other pneumatic system. Rather, most of the battery power (a full 50 Ah of the total nominal 65 Ah) must be conserved for the electric/electronic brakes.

Quoting CARST (Reply 31):
Some people said that NiCd batteries have a slightly varying power output what could destroy components which are not made for this varying power inputs. LIon batteries have a more stable power output, could this be the reason?

Yes.

787 main ship battery (65 Ah nominal) has the capacity to provide essential power for only 5-15 minutes (depending on condition of battery), which is intended to allow time for pilots either (a) to re-start engine(s) or (b) to deploy RAT.

"According to the manufacturer, there is no going back to a Ni-Cd battery on the 787, as it would weigh 3 times as much as a 777 main/APU battery in order to be able to meet the 787’s massive electrical demand." This was stated a while ago.



UNITED We Stand
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 33, posted (1 year 9 months 2 weeks 6 days 17 hours ago) and read 12722 times:

Quoting CARST (Reply 31):

I think there has to be another reason...

The reason could be as simple as the certification process. Even using a certified chemistry, the charging system and application usage is different so it may actually take years to certify a NiCd battery pack.

The 787 battery has been certified for the plane, (having gone through years of the various tests), and the battery can supply the power required by the 787 for all tested scenarios.

The only glitch, (and it is kind of a biggie), is the failure mode where the thing self immolates. My guess is that they assumed that they would find a root cause and be able to eliminate it, showing one and all that the problem is solved.

Now, after months of testing by a plethora of agencies and labs, they still can't find a root cause...and that's the real problem with getting the batteries recertified. That may be why Boeing is going with the safety box route.

What is very easy to forget is that any battery can burn or explode under the right conditions. Boeing has to create their safety box in such a way that those conditions either cannot or are very unlikely to occur...AND.....if they do occur, no harm will come to the plane.

A safety box with each cell physically isolated from the others in its own fireproof chamber so one runaway won't light up the entire pack. A more robust case that can withstand a bomb, much less a burning battery. (The current case actually held up remarkably well considering it is little more than a tin box). As well, I'd add some active cooling to each cell chamber, possibly using Peltier elements...much like one of those nifty 12v camping coolers...or maybe its own air conditioning unit.

If you think about it, that's not much different than the fuel tanks. In the wings, you carry around thousands of gallons of a very volatile liquid, and it's kept from catching fire simply by containment.

So after scratching my head, the only reason I can think of for so doggedly sticking with these batteries, (which doesn't mean it's the right one...I may just have a limited imagination), is the problem of certifying an interim solution. I suspect any temporary one would have to be certified just as rigorously as the permanent solution, since you never know how long it will take for the final fix to go into service.



What the...?
User currently onlinemjoelnir From Iceland, joined Feb 2013, 1594 posts, RR: 3
Reply 34, posted (1 year 9 months 2 weeks 6 days 16 hours ago) and read 12655 times:

What exactly do people imagine happens when for example the Japanese or Chinese authorities will not accept a lithium ion solution even if the FAA does. The bigger part of the coming B 787 fleet will be registered somewhere outside the USA.
The FAA told Cessna to replace the lithium/ion battery with a lead acid or Ni/Cad battery in the Citation C14.
That was about 15 month ago after one battery fire. The FAA decided that the lithium ion battery made the air-plane an unsafe product. The aircraft were grounded until the batteries were replaced.
The battery were replaced (they surely had to exchange charges and computer programs) and it started flying again.
So that is something that seems to be possible to do.
I know that the B 787 is far more complex than any business jet, but Boeing has also many more engineers to throw at such a problem than Cessna.

I know that a new containment is a faster solution than a battery change, but I am afraid of the influence on ETOPS for the B 787.

I do not see why a chemistry change to a different kind of lithium/ion battery should be faster in certification than moving to the trusted and in multiple forms certified Ni/Cad, a solution the certifying authorities have long experiences with.

I thing that all the talk about it being impossible to move to Ni/Cad is hype, apart from leading to a hefty weight penalty.
If there are real technical reasons name them.
A battery is a battery if you need more voltage put more cells in series, if you need more capacity, place more series of cells in parallel, if you need a constant voltage for a bus over the discharge of the battery, go to higher battery voltage and regulate it down. All this solutions of course add weight.
But what does this weight increase really matters if it gets the B 787 in the air and again?

I am afraid that dithering will lead to an extended grounding of the B 787, what at least I would not like to see.


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 35, posted (1 year 9 months 2 weeks 6 days 15 hours ago) and read 12628 times:
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The FAA has given Boeing permission to move forward with their proposed fix.

Quote:
The Federal Aviation Administration (FAA) today approved the Boeing Commercial Airplane Company's certification plan for the redesigned 787 battery system, after thoroughly reviewing Boeing's proposed modifications and the company's plan to demonstrate that the system will meet FAA requirements...

...The FAA will approve the redesign only if the company successfully completes all required tests and analysis to demonstrate the new design complies with FAA requirements. The FAA's January 16, 2013 airworthiness directive, which required operators to temporarily cease 787 operations, is still in effect, and the FAA is continuing its comprehensive review of the 787 design, production and manufacturing process.


User currently offlineKaiarahi From Canada, joined Jul 2009, 3072 posts, RR: 37
Reply 36, posted (1 year 9 months 2 weeks 6 days 15 hours ago) and read 12622 times:

FAA Press Release:

The Federal Aviation Administration (FAA) today approved the Boeing Commercial Airplane Company’s certification plan for the redesigned 787 battery system, after thoroughly reviewing Boeing’s proposed modifications and the company’s plan to demonstrate that the system will meet FAA requirements. The certification plan is the first step in the process to evaluate the 787’s return to flight and requires Boeing to conduct extensive testing and analysis to demonstrate compliance with the applicable safety regulations and special conditions.

.....

The battery system improvements include a redesign of the internal battery components to minimize initiation of a short circuit within the battery, better insulation of the cells and the addition of a new containment and venting system.

.....

The certification plan requires a series of tests which must be passed before the 787 could return to service. The plan establishes specific pass/fail criteria, defines the parameters that should be measured, prescribes the test methodology and specifies the test setup and design. FAA engineers will be present for the testing and will be closely involved in all aspects of the process.

The FAA also has approved limited test flights for two aircraft. These aircraft will have the prototype versions of the new containment system installed. The purpose of the flight tests will be to validate the aircraft instrumentation for the battery and battery enclosure testing in addition to product improvements for other systems.


[Edited 2013-03-12 14:40:54]


Empty vessels make the most noise.
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 37, posted (1 year 9 months 2 weeks 6 days 15 hours ago) and read 12625 times:

Quoting mjoelnir (Reply 37):
The battery were replaced (they surely had to exchange charges and computer programs) and it started flying again.
So that is something that seems to be possible to do.

The cj-4 batteries are a different chemistry than the ones in the 787, but they are Li-ion. They chose to go with LiFePo4.



What the...?
User currently offlinercair1 From United States of America, joined Oct 2009, 1357 posts, RR: 52
Reply 38, posted (1 year 9 months 2 weeks 6 days 14 hours ago) and read 12602 times:
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Quoting Kaiarahi (Reply 39):
The battery system improvements include a redesign of the internal battery components to minimize initiation of a short circuit within the battery, better insulation of the cells and the addition of a new containment and venting system.

There are 3 things being done here - 2 are clear.

One frustrates me because I'm unclear if precise precise usage of the term cell and battery is being observed.

Specifically, the
'redesign of the internal battery components to minimize...'

I think this refers to the battery - as a whole, the device installed in the aircraft - not the cells. In other words -changes to the structure connecting the cells together and holding the cells. But it could be that it means there are some modifications to the internals of the cells themselves.

Does anybody have an authoritative source on this distinction. Are the cells being changed internally, or not.

That would be interesting because it would signify that some detail about the failure mode inside the cells was understood.

And please - do not turn this into the civ thread - I'm seeing way to much of that here already.



rcair1
User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 39, posted (1 year 9 months 2 weeks 6 days 13 hours ago) and read 12555 times:

Quoting rcair1 (Reply 41):
Are the cells being changed internally, or not.

This quote from Conner suggests no:

"” Enhanced production and testing includes more stringent screening of battery cells prior to battery assembly. Operating improvements focus on tightening the system’s voltage range."

More like only selecting 3 stars ping pong balls as opposed to using 1 star balls - all come from the same batch, just select the one that meet more stringent requirements.

But I'm no authoritative.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineKaiarahi From Canada, joined Jul 2009, 3072 posts, RR: 37
Reply 40, posted (1 year 9 months 2 weeks 6 days 13 hours ago) and read 12541 times:

Quoting rcair1 (Reply 41):
One frustrates me because I'm unclear if precise precise usage of the term cell and battery is being observed.

Specifically, the
'redesign of the internal battery components to minimize...'

I think this refers to the battery - as a whole, the device installed in the aircraft - not the cells. In other words -changes to the structure connecting the cells together and holding the cells. But it could be that it means there are some modifications to the internals of the cells themselves.

I have no authoritative source.

However, NTSB/JTSB examination and testing has included the cells, connecting bars, BMU, BCU, and APU controller. The BCU and APU controller were "cleared" in NTSB releases. Both are outside the battery case. The cell and connecting bar degradation on the failed batteries has been examined and described in detail in NTSB releases. However, very little has been said about BMU testing, despite several weeks spent by NTSB and JTSB staff at Kanto (the BMU manufacturer). The BMU is inside the battery case.

Given that the FAA surely (at least by now) appreciates the difference between "battery" and "cell", I would tend to interpret "internal battery components" as anything inside the battery case, including the BMU and the cells themselves.



Empty vessels make the most noise.
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 41, posted (1 year 9 months 2 weeks 6 days 12 hours ago) and read 12484 times:

Quoting rcair1 (Reply 41):

It sounds to me like 'cell' refers to each of the 8 battery power units. It looks like they plan to insulate between the cells to prevent one runaway from taking down the whole battery pack. I think for the cells themselves, the answer is to get even pickier with quality control.

All of these changes make good sense. I wonder how much testing will be enough? I imagine they will be bench testing the hell out of those cells as well as flight testing.



What the...?
User currently offlinebellancacf From United States of America, joined May 2011, 155 posts, RR: 0
Reply 42, posted (1 year 9 months 2 weeks 5 days 15 hours ago) and read 12175 times:

I'm interested in the mechanics of putting a vent to the outside in the battery compartment. (Into both compartments, I assume.) Is this commonly done, putting a valved vent through the skin? Is there anything new that will have to be developed? Is there anything new and unusual when doing it through CFRP? Is this CFRP work something that can be done by airline maintenance out in the field, or will planes have to be brought back to Boeing for the work? (And just how do you cut a hole in the skin, anyway? I assume that it requires more than just a hole saw.) How is the valve to be controlled? Are battery compartments air-tight, or will they have to be reinforced?

Inquiring minds want to know ...  


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 43, posted (1 year 9 months 2 weeks 5 days 15 hours ago) and read 12165 times:

Quoting bellancacf (Reply 42):
Is this commonly done, putting a valved vent through the skin?

Yes, the lower lobe have these vents to dump air overboard. They are dumpling air all the time. Re-routing the air over the battery and dumping it to an existing vent or a new one would be most logical. As for the hot exhaust from any potential battery fire, they may have to bond on a metal sheet near the area of the vent to prevent damage to the skin.

Quoting bellancacf (Reply 42):
Is this CFRP work something that can be done by airline maintenance out in the field, or will planes have to be brought back to Boeing for the work? (

Probably can be done in the field. They can probably do it when they install the supporting brackets for the new containment box.

Cutting into CFRP require a little more care than regular aluminum, but it can be done and Boeing has already demonstrated it with composite repair demo for the 787.

Quoting bellancacf (Reply 42):
I assume that it requires more than just a hole saw.

Maybe a hole saw and a holding fixture.



bt

[Edited 2013-03-13 13:52:03]


Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinecornutt From United States of America, joined Jan 2013, 338 posts, RR: 1
Reply 44, posted (1 year 9 months 2 weeks 5 days 11 hours ago) and read 12023 times:

Quoting bikerthai (Reply 43):
Cutting into CFRP require a little more care than regular aluminum, but it can be done and Boeing has already demonstrated it with composite repair demo for the 787.

My understanding is that the main thing you have to do is seal or bond the cut edges so it doesn't de-laminiate there in the future. They do this sort of thing with race cars all the time.


User currently offlinedynamicsguy From Australia, joined Jul 2008, 887 posts, RR: 9
Reply 45, posted (1 year 9 months 2 weeks 5 days ago) and read 11800 times:

I'm surprised this hasn't been mentioned yet. Boeing will be webcasting a technical briefing on the battery changes. Thursday 6pm US Pacific time, 9pm eastern. Link here

User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 46, posted (1 year 9 months 2 weeks 4 days 23 hours ago) and read 11747 times:

Quoting cornutt (Reply 44):
My understanding is that the main thing you have to do is seal or bond the cut edges so it doesn't de-laminiate there in the future. They do this sort of thing with race cars all the time.

This works fine for race care because the life cycle of the frame is limited and it does not have the delta pressure as seen by an airplane fuselage. For a hole in the 787, even if you use the sharpest cutting tool, you will always expect cracks and micro delamination at the cut edges. Sealing will prevent moisture from getting into the crack (and freeze causing additional delamination). However, most likely they will put some sort of bolted and/or bonded doubler around the cutout so any crack growth would be arrested by the bolt clamp-up.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineKaiarahi From Canada, joined Jul 2009, 3072 posts, RR: 37
Reply 47, posted (1 year 9 months 2 weeks 4 days 20 hours ago) and read 11684 times:

Tom and/or CM explained the process in one of the civav threads. Unfortunately, they've both left.

I wonder if they'd even need new vent holes, or if the existing ones could be adapted.

Edit: Found it - Reply 136 in the previous Tech/Ops thread. Titanium doubler plates.

[Edited 2013-03-14 08:41:32]


Empty vessels make the most noise.
User currently offlineHumanitarian From United States of America, joined Jan 2012, 106 posts, RR: 0
Reply 48, posted (1 year 9 months 2 weeks 4 days 20 hours ago) and read 11669 times:

Installing the vent should be routine for an experienced sheet-metal mechanic trained in CFRP. Speaking generally: drill a hole, install a doubler with sealant and then rivet. From what I have read the batteries will be a simple change out using the existing footprint and hardware. They should be able to finish this mod in one shift. BTW, I thought they were going to tap into an existing vent?

These planes will be in the air sooner then people think assuming the tests go well which I suspect they will. I would not be surprised to learn that Boeing has already tested their modified battery to fail on the ground and found it passed. They would have shown that data to the FAA and which agreed to the test flights as the final step.

While the political leaders at the USDoT dithered over this whole fiasco, there was nothing preventing Boeing from performing tests on the proposed modifications. They do not need FAA permission for any tests as long as flights were not involved and don't forget they have been building the new battery boxes for at least a month in anticipation of that approval.


User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 49, posted (1 year 9 months 2 weeks 4 days 19 hours ago) and read 11652 times:

Quoting dynamicsguy (Reply 45):
Boeing will be webcasting a technical briefing on the battery changes.

And from Tokyo.    I guess that makes PR/marketing sense as JAL and ANA are the most affected airlines and Yuasa is the battery cell manufacturer.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 50, posted (1 year 9 months 2 weeks 4 days 17 hours ago) and read 11549 times:

Quoting Kaiarahi (Reply 47):
I wonder if they'd even need new vent holes, or if the existing ones could be adapted.

If I was designing . . . it would depend on if there is an existing vent near by. Trying to route a tube (titanium?) to and existing hole may be more complicated than it's worth.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 51, posted (1 year 9 months 2 weeks 4 days 16 hours ago) and read 11516 times:

I'm wondering, too, if the LiIon battery pack for emergency flight control power is being moved from its current location directly on top of the APU battery. This came up in the NTSB report, and it would seem to be a poor location when the APU battery catches fire    IIRC, in Boston, it got scorched but didn't catch fire...   


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 52, posted (1 year 9 months 2 weeks 4 days 16 hours ago) and read 11636 times:

Quoting KELPkid (Reply 51):
it would seem to be a poor location when the APU battery catches fire

Not if the new containment strategy works like it's supposed to.


User currently offlineAircellist From Canada, joined Oct 2004, 1735 posts, RR: 8
Reply 53, posted (1 year 9 months 2 weeks 4 days 16 hours ago) and read 11636 times:

Quoting Kaiarahi (Reply 47):
Tom and/or CM explained the process in one of the civav threads. Unfortunately, they've both left.

I hope we'll see them soon, once this trouble with the 787 is over...


User currently offlinetaru From United States of America, joined Sep 2011, 2 posts, RR: 0
Reply 54, posted (1 year 9 months 2 weeks 4 days 12 hours ago) and read 11508 times:
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Webcast link:

http://787updates.newairplane.com/Certification/Webcast

And the slide show to go with the webcast is already available:

http://787updates.newairplane.com/Bo...-solution-presentation-English.pdf


User currently offlineJHwk From United States of America, joined Jan 2013, 247 posts, RR: 0
Reply 55, posted (1 year 9 months 2 weeks 3 days 21 hours ago) and read 11230 times:

Interesting solutions. Curious on two things though:
-How do they deal with heat rejection from the battery?
Cessna has finned heat sinks on their box, but it looks like this will have no conductive heat transfer from the cells to the enclosure thanks to the insulation, and then you have the second layer of heat transfer from the stainless steel pressure cooker to the EE bay. It would appear to need a substantial temperature gradient.

-This statement from their press release:

Quote:
Through another test, the team demonstrated that fire cannot occur within the new enclosure. Its design eliminates oxygen, making the containment unit self-inerting. Inerting is a step above fire detection and extinguishing as it prevents a fire from ever occurring.

Isn't the problem with LiIon the fact that it has its own oxidizer?


User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 56, posted (1 year 9 months 2 weeks 3 days 20 hours ago) and read 11176 times:

Quoting JHwk (Reply 55):
Isn't the problem with LiIon the fact that it has its own oxidizer?

I'm curious about that as well. Mike Sinnett said that "fire" is impossible in the enhanced enclosure, but I wonder if highly energetic oxidation in the broad sense is also impossible. Boeing may only be counting "flame" as "fire." Wikipedia says that some oxidizers besides oxygen can produce flame, but perhaps there are not many?


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 57, posted (1 year 9 months 2 weeks 3 days 19 hours ago) and read 11187 times:
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Quoting JHwk (Reply 55):
Isn't the problem with LiIon the fact that it has its own oxidizer?

It is a misconception that a Li-Ion cell burns because it produces it's own oxygen (a misconception I myself shared, so I am throwing no stones here.   ).

Independent testing have identified that no significant amount of oxygen is found in cell vent gases. Any internal production of oxygen will affect cell internal reactivity, cell internal temperature, and cell case temperature, but plays no measurable role in the flammability of vent gases.

Boeing's new design is self-inerting, so external oxygen cannot get into it. And with no internal oxygen being generated, that seems to knock one side out of the Fire Triangle - and a fire needs all three sides to happen.

[Edited 2013-03-15 09:59:06]

User currently offlineRevelation From United States of America, joined Feb 2005, 12970 posts, RR: 25
Reply 58, posted (1 year 9 months 2 weeks 3 days 18 hours ago) and read 11154 times:

Quoting Humanitarian (Reply 48):
These planes will be in the air sooner then people think assuming the tests go well which I suspect they will. I would not be surprised to learn that Boeing has already tested their modified battery to fail on the ground and found it passed. They would have shown that data to the FAA and which agreed to the test flights as the final step.


You win the prize - this is exactly what we are being told today.

Quoting Stitch (Reply 57):
It is a misconception that a Li-Ion cell burns because it produces it's own oxygen (a misconception I myself shared, so I am throwing no stones here. ).

In http://seattletimes.com/html/busines...0561865_787batterybriefingxml.html we read:

Quote:

He said that the electrolyte inside the battery — a flammable liquid that releases oxygen if it burns — “does not release sufficient oxygen to materially contribute to combustion.”

Sinnett could have saved a.net members a lot of typing if he had put that out there earlier!  
Quoting Stitch (Reply 57):

Boeing's new design is self-inerting, so external oxygen cannot get into it.

We read:

Quote:

The venting system, including a tube from the battery box to the outside of the plane, draws out the air and ensures that there isn’t enough oxygen, he said.

This is all hard for me to visualize, given my admitted low aptitude for mechanical things. What "draws out the air", a pump, or a natural difference in pressure? Is there then a vacuum inside the containment space, or is it filled with an inert agent? How does all this jive with the holes drilled in the box (inner or outer?) to let moisture out?



Inspiration, move me brightly!
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 59, posted (1 year 9 months 2 weeks 3 days 18 hours ago) and read 11112 times:

Quoting Revelation (Reply 58):
Sinnett could have saved a.net members a lot of typing if he had put that out there earlier!

Next time I run into him at the Teryaki place down the hill I'll mention that to him.

Quoting Revelation (Reply 58):
This is all hard for me to visualize, given my admitted low aptitude for mechanical things. What "draws out the air", a pump, or a natural difference in pressure? Is there then a vacuum inside the containment space, or is it filled with an inert agent? How does all this jive with the holes drilled in the box (inner or outer?) to let moisture out?

From the sounds of the description on the news conference there is very little oxygen in the containment box and no ability for more to get in. With a battery failure the increase in pressure inside the container would rupture the disc to the outside of the airplane and force the oxygen out of the airplane as well as the gases vented by the battery. Works both inflight and on the ground.


Excellent presentation if you have an hour and a half to listen to it. It answers a lot of questions posed here as well as on the other "topic that will run forever". Its nice to see an engineer (Mike Sinnett) be able to field questions with valid non PR answers for almost an hour--excellent speaker.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 60, posted (1 year 9 months 2 weeks 3 days 17 hours ago) and read 11100 times:

Quoting 7BOEING7 (Reply 59):
With a battery failure the increase in pressure inside the containe

This is what I also understand. Which means when the cell heats up, the delta pressure would have to be high enough to break the disc: Higher than the 41,000 minus 6000 ft altitude pressure difference otherwise the disk would rupture every time they hit cruise.

Quoting 7BOEING7 (Reply 59):

Excellent presentation if you have an hour and a half to listen to it

  

Always good to hear an Engineer present the information as opposed to a sales guy.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 61, posted (1 year 9 months 2 weeks 3 days 16 hours ago) and read 11044 times:

Quoting bikerthai (Reply 60):
the 41,000 minus 6000 ft altitude pressure difference

Isn't that around 10 or 11 psi?


User currently offlineRevelation From United States of America, joined Feb 2005, 12970 posts, RR: 25
Reply 62, posted (1 year 9 months 2 weeks 3 days 15 hours ago) and read 11007 times:

Quoting 7BOEING7 (Reply 59):
Next time I run into him at the Teryaki place down the hill I'll mention that to him.

I appreciate that, but I imagine he has more important things on his mind!  
Quoting 7BOEING7 (Reply 59):
With a battery failure the increase in pressure inside the container would rupture the disc to the outside of the airplane and force the oxygen out of the airplane as well as the gases vented by the battery. Works both inflight and on the ground.
Quoting 7BOEING7 (Reply 59):
Excellent presentation if you have an hour and a half to listen to it. It answers a lot of questions posed here as well as on the other "topic that will run forever". Its nice to see an engineer (Mike Sinnett) be able to field questions with valid non PR answers for almost an hour--excellent speaker.

The reports in the press aren't mentioning such a disc, so I'll have to watch the presentation. They do use the words "draw the air out" which is what made me think of something pulling the air out of the containment box. It sounds more like the solution will be for the increase in pressure to simply force the air out, but then it really doesn't matter if there's any O2 in the box, no?

I could see the pressure venting is workable, but would think you would want a one-way valve in line, or is this what the 'disc' is doing? That way once the initial pressure is passed, no more O2 would get in and sustain the fire. Or is the consumption of the battery cell so rapid that there's nothing left to burn once the pressure drops, so it's ok if the vent remains open?

Thank goodness software came along, because if I had to figure this stuff out for a living, I'd probably starve...



Inspiration, move me brightly!
User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 63, posted (1 year 9 months 2 weeks 3 days 14 hours ago) and read 10984 times:

Quoting hivue (Reply 61):
Isn't that around 10 or 11 psi?

Looks like 11 psi at 6000 ft altitude and 2.7 at 40,000 ft altitude. Delta P would then be about 8.3 psi.

Quoting Revelation (Reply 62):
but would think you would want a one-way valve in line, or is this what the 'disc' is doing?

From a reliability stand point, the rupture point of the disk is more easily controlled (like a fuse pin on the engine mount - specially if you want a specific delta P at which you want to vent). A mechanical one way valve may have moving parts that require maintenance. You surely don't want a powered valve because that add complexity to the change.

bt

[Edited 2013-03-15 14:55:39]


Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 64, posted (1 year 9 months 2 weeks 3 days 8 hours ago) and read 10808 times:

Quoting bikerthai (Reply 63):
A mechanical one way valve may have moving parts that require maintenance. You surely don't want a powered valve because that add complexity to the change.

I don't know what kind of pressures could develop in a worse case battery failure in the new sealed up containment, but I suspect that the pressure release device is not a part that you would want to have any chance of failing.


User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 65, posted (1 year 9 months 2 weeks 2 days 11 hours ago) and read 10513 times:

Quoting hivue (Reply 64):
I don't know what kind of pressures could develop in a worse case battery failure in the new sealed up containment,
Quoting bikerthai (Reply 63):
Looks like 11 psi at 6000 ft altitude and 2.7 at 40,000 ft altitude. Delta P would then be about 8.3 psi.

I don't think the worst case comes into play since the disk in the vent tube will rupture and release pressure long before 8 cells fail. I presume they would set the disk in the vent tube to rupture at some safe margine over Delta P, say 15 psi. so that it can't happen in normal flight operations. Mike Sinett said in his presentation that they tested the new containment vessel and it ruptured at 3 times the maximum design pressure. So based on this the pressures would'nt go above 15 psi or whatever number they choose for disk rupture and therefore the containment vessel should be good for around 40 to 50 psi before rupture. Once the disk ruptures the pressure can't increase since it's being released. So I don't think the worst case comes into play since the disk will rupture and release pressure long before 8 cells fail. You would think that they would want to start venting if one cell failed, not just to reduce pressure but to get rid of the smoke,hot gases and electrolite and the heat build up because their vessel (1/8 inch ss) is not built like a heat sink.

One thing we know for sure this is probably the most engineered 2 to 3 cubic foot box on the planet. Sinett said they had 500 engineers and many experts from around the world and put in 200,000 hours working on these issues.

One question I have is why does Cessna Citation's new Li-ion battery containment look so different from Boeings. From photos it appears that there is about a 5/8 inch thick steel plate on top with heat sink fins, or is their design approach totally different, in that its built as a pressure vessel for complete containment that does'nt vent.


User currently offlineprebennorholm From Denmark, joined Mar 2000, 6545 posts, RR: 54
Reply 66, posted (1 year 9 months 2 weeks 2 days 10 hours ago) and read 10500 times:

We haven't heard much about the valves involved in this new pressure box. We can only guess.

I have a feeling that it may be rather complicated. It is one thing to open to the atmosphere in case of a pressure buildup. But under normal operation the batteries shall be vented, if for nothing else, then for cooling.

We don't even know whether the batteries will be kept at cabin pressure during flight. I would assume that they will.

Venting cabin air at 11 psi into an FL400 pressure of 2.7 psi will have a cooling effect which would cover the batteries with snow from moisture exhaled by the pax. And it would cool the batteries to very low temperatures. Or special heating of air is needed.

Assuming that the batteries will be at cabin pressure at normal ops, and the battery box will be vented, then it calls for some special valves. Also assuming that battery air never again shall produce smell in the cabin, then it shall have its own regulated outflow valve to the exterior.

A one way inflow valve is needed for any venting. And if the rupture disc breaks due to a battery runaway failure, then the inflow valve must automatically close completely. Otherwise it becomes a serious leak of cabin pressure.

We know that inflow to venting will stop in case of broken rupture disc because Boeing says no oxygen will be present to feed a fire. Any continued inflow for venting would feed plenty of oxygen.

I would like to see a diagram of the whole design. I have a feeling that it is a lot more complicated than just a steel box, a rupture disc, and an exhaust tube to the outside.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlinePITingres From United States of America, joined Dec 2007, 1163 posts, RR: 13
Reply 67, posted (1 year 9 months 2 weeks 2 days 7 hours ago) and read 10461 times:

I could probably convince myself that no valving is needed at all. Just leave the vent tube open, perhaps with some sort of positive closure that is normally open (to prevent backflow during descent if the battery goes poof), and I'm not sure you really need that either given the small amount of airspace involved.

If that box is sealed, as it appears to be, it's not going to be air-cooled. If cooling is needed they are probably going for conduction cooling.

I'll have to go back and take another look at the video.



Fly, you fools! Fly!
User currently offlinefrancoflier From France, joined Oct 2001, 3849 posts, RR: 11
Reply 68, posted (1 year 9 months 2 weeks 1 day 20 hours ago) and read 10328 times:

Quoting PITingres (Reply 67):

If that box is sealed, as it appears to be, it's not going to be air-cooled. If cooling is needed they are probably going for conduction cooling.

That is my main question as well.
On the battery side, the focus seemed to be on better cooling of the battery, or at least the individual cells.
On the containment side, the solution is to encase the whole battery in a sealed box with no airflow...

These seem contradictory. Unless, like you say, the battery case is snug against the battery box and enough conductive heating is achieved this way.

I'm also supposing a battery change is going to be a much less popular task on the 787 from then on. On the video I've seen, the battery containment box had at least 40 bolts!

The containment ability is impressive though. It can basically contain a small explosion... I expect to see no 787 catching fire from a battery anytime soon.



Looks like I picked the wrong week to quit posting...
User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 69, posted (1 year 9 months 2 weeks 1 day 18 hours ago) and read 10251 times:

Quoting prebennorholm (Reply 66):
We haven't heard much about the valves involved in this new pressure box. We can only guess.

What valves are those? There is a disc that ruptures in the event of a sufficient build-up of pressure in the containment vessel following battery failure. When the disc ruptures the contents of the vessel are vented overboard.

BTW I'm willing to bet that in the event of rupture, the disc will not be eligible to be MEL'd under any circumstances.  


User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 70, posted (1 year 9 months 2 weeks 1 day 13 hours ago) and read 10174 times:

Quoting prebennorholm (Reply 66):
I would like to see a diagram of the whole design. I have a feeling that it is a lot more complicated than just a steel box, a rupture disc, and an exhaust tube to the outside.

I think a lot of your questions can be answered if you go to http://www.boeingblogs.com/randy. There is a good picture of the new battery arrangment. From what I can make out the blue battery case is now placed inside this totally sealed (from the electric bay) 1/8 inch thick stainless steel containment vessel that is vented to outside the aircraft. We presume there is a pressure rupture disk in this vent tube and are not aware of any other valving into the containment vessel.

Quoting PITingres (Reply 67):
If that box is sealed, as it appears to be, it's not going to be air-cooled. If cooling is needed they are probably going for conduction cooling.

Yes, I was wandering about the cooling question as well. Origionally they packed the 8 cells in like sardines and you would wonder how they cooled. Now with their new arrangement of wrapping the cells with insulating tape and ceramic separators between cells and case etc. you would think they would also take this oppoptunity to sligthly increase the air space between cells if operating temperatures were an issue. I would expect their new battery case would be slightly larger than the old one to fit in all this new stuff. Getting back to the overall cooling question now, from the photo in the link provided you will note there is about a 4 to 6 inch airspace separating the blue battery case from the new containment vessel. Perhaps this is enough for normal cooling during charging and discharging. I presume surplus heat from the normal battery function would be transferred from the battery case to the above metioned airspace to the containment vessel and into the EE bay. I'm sure they would have done a lot of testing with heat sensors to find out before proposing this new system.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 71, posted (1 year 9 months 2 weeks 22 hours ago) and read 9965 times:

Quoting Revelation (Reply 62):
so it's ok if the vent remains open?

You don't want the battery enclosed space to be continuously open to the out side air as the constant change in pressure will result in unwanted moisture ingested into the chamber via the vent.

Quoting twiga (Reply 65):
From photos it appears that there is about a 5/8 inch thick steel plate on top with heat sink fins, or is their design approach totally different, in that its built as a pressure vessel for complete containment that does'nt vent.

Looks like there is not large vent visible for the vessel. But my guess is the containment box is not completely sealed at the fastener line. So in theory, there can be small leaks through the fay surface between the main box and the bottom battery tray.

Quoting prebennorholm (Reply 66):
We don't even know whether the batteries will be kept at cabin pressure during flight. I would assume that they will.

I would agree, where the box is located, it would be not optimal engineering to have inside the containment vessel at outside atmospheric pressure while the lower lobe is at 6000 ft altitude.

Quoting prebennorholm (Reply 66):
Venting cabin air at 11 psi into an FL400 pressure of 2.7 psi will have a cooling effect which would cover the batteries with snow from moisture exhaled by the pax.

If you are referring to continuous venting during normal operation, then the ice/moisture condensation would more likely occur when the airplane lands at a humid airport with the air entrained from the outside. During operation, most likely that any moisture condensation will occur at the containment box.

If you are assuming that the venting only occurs during disc rupture, then the moisture and ice forming is irrelevant because they will have to replace the battery anyway.

Quoting PITingres (Reply 67):
Just leave the vent tube open, perhaps with some sort of positive closure that is normally open (to prevent backflow during descent if the battery goes poof), and I'm not sure you really need that either given the small amount of airspace involved.

See prebennorholm's comment. leaving the tube open causes all sorts of environmental issue.

Quoting francoflier (Reply 68):

I'm also supposing a battery change is going to be a much less popular task on the 787 from then on. On the video I've seen, the battery containment box had at least 40 bolts!

Yes, I see the 40 bolt holes. However it seems that the 40 bolts are to mount the containment vessel to the tray on which the battery sits. If you look closely, you may see sign that the top of the box is a separate piece. Hopefully, the top has fewer fasteners. Where the battery is currently located you don't want to reach around the back of the containment box to get at the 20 of those 40 fasteners if you don't have to.

In terms of cooling of the containment vessel during regular operation, I'm pretty sure there is some airflow going though the area. They talked about all EE rack have air provided for equipment cooling. So even if they don't pump air directly to the containment box, their should be sufficient circulation in the area to keep such a large heat sink cool during normal operation. Remember, that the battery is only getting maintenance charge during operation. So there shouldn't be too much heat. During a battery failure, hopefully the containment vessel would have enough mass to absorb the heat until the chamber completely vents.



bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinekanban From United States of America, joined Jan 2008, 3875 posts, RR: 27
Reply 72, posted (1 year 9 months 2 weeks 20 hours ago) and read 9937 times:
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Boeing tooling is designing a removal tool that consists of two plates, a mass of gears, 20 sockets, and is driven by a standard Li-ion home depot portable driver... the only problem encountered is the tool weighs 200 lbs.      
(the smilies indicate humor)


User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 73, posted (1 year 9 months 2 weeks 15 hours ago) and read 9819 times:

Quoting kanban (Reply 72):
Boeing tooling is designing a removal tool that consists of two plates, a mass of gears, 20 sockets, and is driven by a standard Li-ion home depot portable driver...

The FAA might take issue with that. What if a maintenance crew accidentally left behind an unauthorized 18 or 20 v DeWalt LiIon battery pack in the E&E bay?  



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 74, posted (1 year 9 months 2 weeks 9 hours ago) and read 9668 times:

Quoting JHwk (Reply 55):
Isn't the problem with LiIon the fact that it has its own oxidizer?
Quoting hivue (Reply 56):
I'm curious about that as well. Mike Sinnett said that "fire" is impossible in the enhanced enclosure, but I wonder if highly energetic oxidation in the broad sense is also impossible. Boeing may only be counting "flame" as "fire." Wikipedia says that some oxidizers besides oxygen can produce flame, but perhaps there are not many?
Quoting Stitch (Reply 57):
Boeing's new design is self-inerting, so external oxygen cannot get into it. And with no internal oxygen being generated, that seems to knock one side out of the Fire Triangle - and a fire needs all three sides to happen.

I just found the following article http://blogs.wsj.com/japanrealtime/2013/.../thermal-runaway-on-787 and I must say that I am now confused. I also origionally thought that Li-ion batteries had their own oxidizers and that was an issue regardless of external oxygen. What I gather from reading this article is in Mike Sinnett's view there are basically two levels of thermal runnaway.
a) Short circuits causing cell venting (each cell has a built in small pressure relief valve on top) which releases pressure, heat and electrolyte gasses - and this can propogate from one cell to the next. And apparently this is what happend at Boston and in Japan. The only reason for a small fire in Boston was because the battery container lid came partly off and exposed the cells to external O2 from the air.
b)Quoting Sinnett " What we worry about from a thermal runaway perspective is an event that has so much energy, so much heat, and so much flame that it would put the airplane at risk. We know very clearly that this was not the case in the Logan event or the Takamatsu event,” he said referring to the incidents where the two events occurred. The first in Boston’s Logan Airport and the second the led to an emergency landing at Takamatsu Airport in southwestern Japan.

Mr. Sinnett said that all of their testing and analysis has concluded the only way a thermal runaway could occur is through overcharging. Boeing’s original designs have four layers of protection against overcharging. A review of data stored on the flight data recorder showed that the system had been “properly charged.”

So is he saying there could be a condition b) his definition of thermal runaway not the presses as in a) and it could not happen because of the 4 layers of protection from overcharging (2 inthe BMU and 2 in the charger). This raises two questions.

1) Does this mean overcharging can excite the chemistry in the cells to the point where they can self oxidize and catch fire without external O2? It appears simple short circuits as in a) won't do this.

2) If condition b} is possible have they designed their containment vessel for this or are they just relying on the 4 levels of protection agaist overcharging.

Perhaps I'm reading something into this that I shouldn't be. I viewed his presentation and his definitions on thermal runaway were a little confusing.


User currently offlinekanban From United States of America, joined Jan 2008, 3875 posts, RR: 27
Reply 75, posted (1 year 9 months 2 weeks 8 hours ago) and read 9635 times:
Support Airliners.net - become a First Class Member!

Quoting twiga (Reply 74):
1) Does this mean overcharging can excite the chemistry in the cells to the point where they can self oxidize and catch fire without external O2?

As I read the available information, there is very little O2 available in the electrolyte and battery materials. This was confusing since there are other Li-ion chemistries that can produce O2. The new containment further reduces the chance of external O2 mixing with any vapors to near zero. hence there may be heat but no fire. The new dividers will reduce heat transference between cells leading to other cells failing. .


User currently offlinerwessel From United States of America, joined Jan 2007, 2422 posts, RR: 2
Reply 76, posted (1 year 9 months 2 weeks 2 hours ago) and read 9544 times:
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Quoting prebennorholm (Reply 66):
A one way inflow valve is needed for any venting. And if the rupture disc breaks due to a battery runaway failure, then the inflow valve must automatically close completely. Otherwise it becomes a serious leak of cabin pressure.

One additional small hole in the fuselage won't make any difference - the (vastly larger) outflow valves will just close down a tiny bit to maintain the same total outflow from the fuselage, thus maintaining the same cabin pressure.

Quoting twiga (Reply 74):
I just found the following article http://blogs.wsj.com/japanrealtime/2013/.../thermal-runaway-on-787 and I must say that I am now confused. I also origionally thought that Li-ion batteries had their own oxidizers and that was an issue regardless of external oxygen. What I gather from reading this article is in Mike Sinnett's view there are basically two levels of thermal runnaway.

People seem to confusing oxidizer and oxygen in these threads. Basically in certain types of chemical reactions (redox reactions), you have one input, the reducing agent, which donates one or more electrons to the oxidising agent. Oxygen is a very common oxidizer, but hardly the only one, in fact there are vast numbers. Nor is oxygen always an oxidizer in chemical reactions (in fact Flourine will oxidise oxygen, making oxygen the reducing agent).

But the point is that you can have a redox reaction without any oxygen - and I assume at least some of that is going on here.


User currently offlinejustloveplanes From United States of America, joined Jul 2004, 1065 posts, RR: 1
Reply 77, posted (1 year 9 months 1 week 6 days 14 hours ago) and read 9434 times:

Quoting twiga (Reply 65):
You would think that they would want to start venting if one cell failed, not just to reduce pressure but to get rid of the smoke,hot gases and electrolite and the heat build up because their vessel (1/8 inch ss) is not built like a heat sink.



yes, and there doesn't seem to be redundant vent lines. A manifold output with multiple rupture discs is an trivial cost increase and I think warranted given the history of the incident. Boeing probably feels since the steel case can take max pressure, then a failed rupture disc (extremely unlikely btw, but still, a single point of failure) won't result in a release anyway.

Quoting twiga (Reply 65):
One question I have is why does Cessna Citation's new Li-ion battery containment look so different from Boeings. From photos it appears that there is about a 5/8 inch thick steel plate on top with heat sink fins, or is their design approach totally different, in that its built as a pressure vessel for complete containment that does'nt vent.

If this is true, then it is a different and less complex, though most likely heavier, approach.

One item of interest in the design is the removal of oxygen to make the unit self-inerting. They don't seem to mention how. Is this a nitrogen charge?

[Edited 2013-03-19 14:44:44]

User currently offlinehivue From United States of America, joined Feb 2013, 1114 posts, RR: 0
Reply 78, posted (1 year 9 months 1 week 6 days 14 hours ago) and read 9412 times:

Quoting justloveplanes (Reply 77):
One item of interest in the design is the removal of oxygen to make the unit self-inerting. They don't seem to mention how. Is this a nitrogen charge?

My understanding is that the system is "inerted" in the sense that it has been engieneered to make it so that there never is sufficient oxygen present, either prior to or after any battery failure, to allow a fire to get going.


User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 79, posted (1 year 9 months 1 week 6 days 14 hours ago) and read 9439 times:

Quoting justloveplanes (Reply 77):
One item of interest in the design is the removal of oxygen to make the unit self-inerting. They don't seem to mention how. Is this a nitrogen charge?

If you're talking about the Boeing design, I believe its "basically" self-inerting--the amount of oxygen available within the containment vessel is minimal and what doesn't get used up in the initial reaction is blown out the vent.


User currently offlinemham001 From United States of America, joined Feb 2005, 3731 posts, RR: 3
Reply 80, posted (1 year 9 months 1 week 6 days 12 hours ago) and read 9362 times:

Quoting mjoelnir (Reply 22):
A is the current, A/h is the capacity.
The 787 has a battery of 65 A/h capacity and the 777 has a battery of 50 A/h capacity.

For true capacities, you need to note the voltages as well.


User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 81, posted (1 year 9 months 1 week 6 days 4 hours ago) and read 9265 times:

Quoting bikerthai (Reply 71):
Looks like there is not large vent visible for the vessel. But my guess is the containment box is not completely sealed at the fastener line. So in theory, there can be small leaks through the fay surface between the main box and the bottom battery tray.

You might be right but can't really tell from the photo, but then again there might be a vent tube behind that we can't see. The problem with vent holes is the introduction of O2 and a fire, smoke and gases if a cell goes. It seems robust enough to contain everything eventhough it might weigh a ton for a battery half the size of the 787's. Just don't have enough info to go on.

Quoting justloveplanes (Reply 77):
Quoting twiga (Reply 65):You would think that they would want to start venting if one cell failed, not just to reduce pressure but to get rid of the smoke,hot gases and electrolite and the heat build up because their vessel (1/8 inch ss) is not built like a heat sink.

yes, and there doesn't seem to be redundant vent lines. A manifold output with multiple rupture discs is an trivial cost increase and I think warranted given the history of the incident. Boeing probably feels since the steel case can take max pressure, then a failed rupture disc (extremely unlikely btw, but still, a single point of failure) won't result in a release anyway.

I think they want to keep it as simple as possible. I don't know how reliable these rupture discs are and what there accuracy is +/- 1 to 2 psi or +/- 5 psi. But I can see where you are coming from if everything else worked and this didn't then what . We don't know the details of their vessel but perhaps they have a flange disc/ safety valve bolted to the vessel set at some value well below bursting threshold for the vessel but sufficiently above the rupture value for the inline venting disc. As a last resort better to vent in the bay than have a bomb go off. But then again as you mentioned perhaps they designed the vessel for max extreme pressure so all this other complication is not required.

The design of this system is quite complex. For example we have the threshold pressure for the rupture disc Delta P + some margine so the valve does'nt rupture everytime the airplane goes up and down. Hopefully the heat and pressure from a one cell failure is sufficient to overcome the threashold pressure Delta P + X to rupture the disc and exhaust everything. If they have done a good job on insulating the cells perhaps the common failure will only involve one cell and not a runaway into the other ones. The sizing (volume) of the air space between the battery case and the new containment vessel, the heat energy from an exothermic chemical reaction all probably have something to do with designing and controlling pressures. I'm sure Boyles Law and thermodynamics come into play here. The point I'm trying to make is you really want the disc to rupture with the failure of one cell otherwise the aircraft mechanics will be faced with opening a pressurized container (some 40 bolts) with some pretty awfull pressurized stuff in it. Ignoring what I said in my first post above I think the new vessel would have more than enough heat sink capabilities to deal with the heat energy from only one cell failing without venting. It has about 3 times the surface area and is made of much thicker material than the old blue battery case. Would you believe it that according to NTSB's material lab report 13-013 pg 3 and 4 (from the 450 page doc on their website) the lid of the blue box was made of an aluminum aloy 0.032 in thick (1/32 inch) and the sides were 0.063 in or 1/16 in thick, pretty flimsy with virtually no heat sink capabilities. The top was fastened on with 8 - flat head screws, three of which tore out from pressure and swelling. Now it looks like they have some 40 - 3/8 bolts holding things together so things have come along ways.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 82, posted (1 year 9 months 1 week 5 days 17 hours ago) and read 9104 times:

Quoting twiga (Reply 81):
As a last resort better to vent in the bay than have a bomb go off

Looking at the design, the containment will probably not rupture. I see the weak link at the bulk-head connector for wire pass thru. If anything blows it would be the wire bundle and you'll get your pressure relief valve.

Quoting twiga (Reply 81):
I don't know how reliable these rupture discs are and what there

Probably at least as reliable as the shear bolt that they used to mount the engines. You know the bots that are supposed to shear off if the engine ever dig into the ground?

Quoting twiga (Reply 81):
But then again as you mentioned perhaps they designed the vessel for max extreme pressure so all this other complication is not required.

From back of the napkin calculation, the pressure box will probably withstand at a minimum of 11 psi delta. This is about the pressure difference you are going to see if the disc rupture at 40,000 ft. Now, will a failed cell cause the temperature to go high enough to get a 11 psi delta across the box? Some one else will have to do the calculation. I was never good with thermodynamics.



bt

[Edited 2013-03-20 11:50:11]


Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 83, posted (1 year 9 months 1 week 5 days 10 hours ago) and read 8992 times:

Quoting kanban (Reply 75):
Quoting twiga (Reply 74):1) Does this mean overcharging can excite the chemistry in the cells to the point where they can self oxidize and catch fire without external O2?
As I read the available information, there is very little O2 available in the electrolyte and battery materials. This was confusing since there are other Li-ion chemistries that can produce O2. The new containment further reduces the chance of external O2 mixing with any vapors to near zero. hence there may be heat but no fire. The new dividers will reduce heat transference between cells leading to other cells failing. .

This is what I originally thought as well. But Sinnett made this big deal about overcharging and 4 levels of protection to stop thermal runaway from happening and in the same sentenece he describes it as an event that has so much heat, energy and flame. According to him the events in Boston and Japan were not thermal runaway events. So this got me thinking that perhaps the exothermic reaction caused by overcharging and not by simple cell short could excite the exothermic reaction to some higher level where extra heat and flame could result without external O2. Perhaps I did'nt explain this clearly the first time. Perhaps things have been taken out of context. But what everyone seems to be saying is there isn't enough oxidizer in the cells to create flame without external O2.

I agree the new containment which has about 2 cu ft of air around the battery will have at 20% O2 only 0.4 cu ft of O2 and this will go poof in less than a 1/2 second and it will be inerted.

Quoting rwessel (Reply 76):
Quoting twiga (Reply 74):I just found the following article http://blogs.wsj.com/japanrealtime/2013/.../thermal-runaway-on-787 People seem to confusing oxidizer and oxygen in these threads. Basically in certain types of chemical reactions (redox reactions), you have one input, the reducing agent, which donates one or more electrons to the oxidising agent. Oxygen is a very common oxidizer, but hardly the only one, in fact there are vast numbers. Nor is oxygen always an oxidizer in chemical reactions (in fact Flourine will oxidise oxygen, making oxygen the reducing agent).

But the point is that you can have a redox reaction without any oxygen - and I assume at least some of that is going on here.

The chemistry is beyond me, you are probably right there is not enough oxidizer to make any meaningful difference to their sealed containment vessel.


User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 84, posted (1 year 9 months 1 week 5 days 8 hours ago) and read 8963 times:

Quoting bikerthai (Reply 82):
Looking at the design, the containment will probably not rupture. I see the weak link at the bulk-head connector for wire pass thru. If anything blows it would be the wire bundle and you'll get your pressure relief valve.

Ah so finally we get something for free - the mechanics would like it since it would be removed for them when they do the change out.

Quoting bikerthai (Reply 82):
Probably at least as reliable as the shear bolt that they used to mount the engines. You know the bots that are supposed to shear off if the engine ever dig into the ground?

So it sounds like we are talking about a design rupture pressure more like design P +/- 5 psi and not P +/- 1 psi.

Quoting bikerthai (Reply 82):
From back of the napkin calculation, the pressure box will probably withstand at a minimum of 11 psi delta. This is about the pressure difference you are going to see if the disc rupture at 40,000 ft. Now, will a failed cell cause the temperature to go high enough to get a 11 psi delta across the box? Some one else will have to do the calculation. I was never good with thermodynamics.

Nor was I. When I took it we talked about entropy and steam engines.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 85, posted (1 year 9 months 1 week 4 days 23 hours ago) and read 8860 times:

Quoting twiga (Reply 83):
According to him the events in Boston and Japan were not thermal runaway events

This was where Sinnet and the reporters were having a "back and forth". From what I understood, Sinnet was defining a run-away event from the "big battery box" stand point when saying whether there was thermal run-away. You can read between the line that he may have admit that there may have been thermal run-away at the cell stand point but did not go there.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineContnlEliteCMH From United States of America, joined Mar 2005, 1465 posts, RR: 44
Reply 86, posted (1 year 9 months 1 week 4 days 12 hours ago) and read 8696 times:

Quoting twiga (Reply 83):
But Sinnett made this big deal about overcharging and 4 levels of protection to stop thermal runaway from happening and in the same sentenece he describes it as an event that has so much heat, energy and flame. According to him the events in Boston and Japan were not thermal runaway events.

This description of his words does him a disservice. He said the following:

(1) He was concerned about events at an airplane level. At that level, there was no event that endangered continued safe flight and landing.

(2) He admitted that there was a venting event in at least one of the battery cells. He even confessed that to some this may constitute a runaway, but at an airplane level, he repeated that there was nothing that endangered continued safe flight and landing.

(3) He said definitively that there was no fire in the Japan incident and that in the Logan incident there was no fire inside the box. The combustion event that occured at Logan was not inside the box; it was wire insulation outside the box.

Quoting twiga (Reply 83):
So this got me thinking that perhaps the exothermic reaction caused by overcharging and not by simple cell short could excite the exothermic reaction to some higher level where extra heat and flame could result without external O2.

Sinnet addressed this.

Quoting twiga (Reply 83):
Perhaps I did'nt explain this clearly the first time. Perhaps things have been taken out of context. But what everyone seems to be saying is there isn't enough oxidizer in the cells to create flame without external O2.

Sinnet specifically addressed this too. Testing showed that there were three distinct fuel-oxidizer regimes within the box when they induce an event inside the box. The first is "too lean": too little fuel concentration for the oxidizer present; the second was flash combustion in which flammability ratios were sufficient for combustion; the third was post-combustion, which was "too rich": too much fuel for the oxidizer present. He even quoted a specific time figure during which combustion occurred and it was a fraction of a second. After that event, the box was "too rich": too much fuel and virtually no oxidizer at all because (a) the oxygen consumed by the flame is gone and (b) the cells don't vent oxygen in sufficient quantity to sustain combustion.

I was very impressed by this presentation. Listening to the questions from the reporters in the room affirmed my opinion that reporters are among the most ignorant of all people in society. The first reporter's questions clearly denoted that she did not/could not comprehend what Sinnet was saying. This is true of most people, incidentally. As Mike said, he's a scientist and an engineer. The implication of this is that he thinks very detailed thoughts about very detailed topics, and those details require precise language and numbers to properly understand and communicate. He did a good job staying away from numbers -- nearly all people are functionally innumerate anyway -- and he communicated only as much detail as was necessary to convey the message. Even that went over the heads of most of the people in the room, as evidenced by the questions.

Mike's overarching point in all of this was that their design philosophy for safety is to make events improbable and then to imbue sufficient redundancy to the airplane so that a single event cannot prevent continued safe flight and landing. All of us who want to understand Boeing's proposed fix to this problem must view it in this context because (a) that's how Boeing views it, and (b) that's how the regulators are likely to view it as well. The critical detail is that Boeing is sure there can be no fire inside the box. I was skeptical of such solid assurance until I listened to what Sinnet was saying. I now understand that when the technical details are evaluated, they're probably right. Certainly, we all hope so.

[Edited 2013-03-21 16:53:17]


Christianity. Islam. Hinduism. Anthropogenic Global Warming. All are matters of faith!
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 87, posted (1 year 9 months 1 week 4 days 12 hours ago) and read 8705 times:

Quoting ContnlEliteCMH (Reply 86):
I was very impressed by this (Mike Sinnett) presentation.



His presentation to the flight crews after the ZA002 incident was just as impressive--excellent, knowledgeable speaker--an engineer first.


User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 88, posted (1 year 9 months 1 week 4 days 6 hours ago) and read 8584 times:

Quoting ContnlEliteCMH (Reply 86):
Quoting twiga (Reply 83): But Sinnett made this big deal about overcharging and 4 levels of protection to stop thermal runaway from happening and in the same sentenece he describes it as an event that has so much heat, energy and flame. According to him the events in Boston and Japan were not thermal runaway events.
Quoting ContnlEliteCMH (Reply 86):
This description of his words does him a disservice. :

I was simply trying to paraphrase what I said in my post #74 and obviously did a bad job. This small quote here puts things out of context without looking at my previous post and article link to what was actually said. There was absolutely no intent to do him a disservice. If it is seen this way I apologize. I watched his presentation in Japan and was extremly impressed. As an engineer he has the ability to communicate complex issues in a clear logical way that the average person can understand. He was also very cool, calm and collect in dealing with the news media. But I must admit I became confused over the definitions of thermal runaway. Hence all the questions about oxidizers etc. I now gather it's basically a non issue.

Quoting ContnlEliteCMH (Reply 86):
Mike's overarching point in all of this was that their design philosophy for safety is to make events improbable and then to imbue sufficient redundancy to the airplane so that a single event cannot prevent continued safe flight and landing.

I agree with Boeing's approach. Hopefully their shotgun approach at the battery issues will nail the root cause or at least mitigate them until they can get a plan B working, and in the meantime their new robust containment vessel will get you down safely regardless of what happens at the battery level. As an engineer you can design for what you know, in this case the containment vessel even if it takes Phd's in thermodynamics, chemistry, aeronautics and others, but you can't design for what you don't know, all the possible battery issues, without knowing the root cause or causes. As I mentioned on another post its probably the most engineered 2 to 3 cubic foot box on the planet.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 89, posted (1 year 9 months 1 week 3 days 23 hours ago) and read 8476 times:

Quoting twiga (Reply 88):
until they can get a plan B working

Hum . . . Plan B may just be the same phylosophy except now make the containment box part of the battery shell itself (sealed battery with stainless or titanium shell) and hook the venting tube directly to the battery   

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinebellancacf From United States of America, joined May 2011, 155 posts, RR: 0
Reply 90, posted (1 year 9 months 1 week 3 days 13 hours ago) and read 8310 times:

Sounds as if that would make replacing the battery a much pricier procedure. Myself, I was wondering if they were going to make the box big enough to handle a Li battery with changed chemistry. I think it may have been Stitch some time back who pointed out that a different Li chemistry would require one additional cell, have the same capabilities, pretty much, and yet would release heat at a far lower rate than the current chemistry -- which sounded like a no-brainer, to me. The thing that I was wondering, though, is whether by trying to cut down the air volume in the box they had deprived themselves of what seems a very sensible change to a far less risky chemistry. Later, though, I think that I read in one of the threads that the currently proposed battery/box combination would have 2 cu ft of air: is this enough wiggle room to permit changing to a larger battery later?

User currently offlinenomadd22 From United States of America, joined Feb 2008, 1903 posts, RR: 0
Reply 91, posted (1 year 9 months 1 week 3 days 11 hours ago) and read 8267 times:

Quoting bellancacf (Reply 90):
I think it may have been Stitch some time back who pointed out that a different Li chemistry would require one additional cell,

I think that was me. Iron phosphate type Lithium batteries are lower voltage and would require 9 cells instead of 8. They have a little less capacity, so each of the nine cells would be about the same weight as each of the eight current cells.



Andy Goetsch
User currently offlinekanban From United States of America, joined Jan 2008, 3875 posts, RR: 27
Reply 92, posted (1 year 9 months 1 week 3 days 11 hours ago) and read 8282 times:
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Quoting bellancacf (Reply 90):
is this enough wiggle room to permit changing to a larger battery later?

There are too many unknowns in this.. yes there is a battery with a different chemistry that would require an extra cell, but if we now have time to test other chemistries, there may be one that doesn't require and extra cell. there may be other considerations that may the 9 cell chemistry insufficient. I believe that there will eventually be a different chemistry used, however it may be awhile before one passes the tests.. and these battery manufacturers are always pushing the envelop with new designs and chemistries.. so they might come up with a more inert battery of 6 cells that meets and exceeds the requirements. My point is it is hard to predict the future.


User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 93, posted (1 year 9 months 1 week 3 days 8 hours ago) and read 8240 times:

Quoting bikerthai (Reply 89):
Hum . . . Plan B may just be the same phylosophy except now make the containment box part of the battery shell itself (sealed battery with stainless or titanium shell) and hook the venting tube directly to the battery

Could be if they are looking at shedding 100 lbs or more, in which case they would likely use titanium to keep the weight down and make it easier to carry and manhandle for installation if its 1/8 inch thick. According to my rough calcs the old blue battery box (aluminum aloy 1/32 inch thick lid and 1/16 inch sides and bottom) only weighed about 5 lbs. They were talking about drilling holes into the bottom to keep moisture out. Don't know how this would work to stop pressurized gas/electrolytes from venting out and then theres the question of introducing external O2. But then again they could have a pressure sealed sump. Many things are possible.

Quoting bellancacf (Reply 90):
Sounds as if that would make replacing the battery a much pricier procedure. Myself, I was wondering if they were going to make the box big enough to handle a Li battery with changed chemistry. I think it may have been Stitch some time back who pointed out that a different Li chemistry would require one additional cell, have the same capabilities, pretty much, and yet would release heat at a far lower rate than the current chemistry -- which sounded like a no-brainer, to me.

See last comment at the bottom.

Quoting bellancacf (Reply 90):
The thing that I was wondering, though, is whether by trying to cut down the air volume in the box they had deprived themselves of what seems a very sensible change to a far less risky chemistry.

Don't quite understand what your question is here.

Quoting bellancacf (Reply 90):
Later, though, I think that I read in one of the threads that the currently proposed battery/box combination would have 2 cu ft of air: is this enough wiggle room to permit changing to a larger battery later?

I'm pretty sure they would be keeping all options open when they sized the stainless steel containment vessel, because who knows it might be mandated as a permanent feature as discussed on another thread. I would think if they went to something like Li Fe P04 as Stitch mentioned they would need one extra cell. Nine's an awkward number for arrangement but say they went to 10 that would add less than 0.2 cu ft so should'nt be a problem. On their existing battery they have lost a little capacity by tightening their charge/ discharge window and may want to keep this option open for new chemistry as well. I think it was me who suggested their was about 2 cu ft of air space between the blue battery box and the containment vessel. That was purely a guess from looking at the photos.


User currently offlinebellancacf From United States of America, joined May 2011, 155 posts, RR: 0
Reply 94, posted (1 year 9 months 1 week 2 days 20 hours ago) and read 8111 times:

Thanks to all for very thoughtful answers. Patient, too! Yes, I hope they have kept all options open. There could be a number of reasons to move to a larger battery in the future, and it would be a shame to have to refit the entire fleet with larger containment boxes. (If you DID have a containment box that was "over-sized" and thus contained "too much" air, couldn't you put in some empty boxes simply for the purpose of displacing air?)

User currently offlineprebennorholm From Denmark, joined Mar 2000, 6545 posts, RR: 54
Reply 95, posted (1 year 9 months 1 week 2 days 10 hours ago) and read 7952 times:

Quoting twiga (Reply 93):
I'm pretty sure they would be keeping all options open when they sized the stainless steel containment vessel, because who knows it might be mandated as a permanent feature as discussed on another thread. I would think if they went to something like Li Fe P04 as Stitch mentioned they would need one extra cell.

To fit in a 28VDC system one more cell will be needed. But that's not the only issue.

Li-Fe has a energy density which is roughly 33% lower than Li-Ion, so a Li-Fe battery with identical capacity would be that much bulkier / heavier.

Charge characteristics are also different, so changes to charging hardware would be needed - like if they changed to any non-Li based chemistry.

Quoting twiga (Reply 93):
Nine's an awkward number for arrangement but say they went to 10 that would add less than 0.2 cu ft so should'nt be a problem.

It's even more complicated than that. All Li-Fe cells, I have heard of, are cylindrical in shape. That means they take up even more space. I will not guarantee that box shaped Li-Fe cells exist, but I doubt it very much.

Li-FePO4 is not a slightly different Li-Ion variant. It's an animal of its own.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlinenomadd22 From United States of America, joined Feb 2008, 1903 posts, RR: 0
Reply 96, posted (1 year 9 months 1 week 2 days 8 hours ago) and read 7936 times:

Quoting prebennorholm (Reply 95):
Li-Fe has a energy density which is roughly 33% lower than Li-Ion, so a Li-Fe battery with identical capacity would be that much bulkier / heavier.

Charge characteristics are also different, so changes to charging hardware would be needed - like if they changed to any non-Li based chemistry.

Quoting twiga (Reply 93):
Nine's an awkward number for arrangement but say they went to 10 that would add less than 0.2 cu ft so should'nt be a problem.

It's even more complicated than that. All Li-Fe cells, I have heard of, are cylindrical in shape. That means they take up even more space. I will not guarantee that box shaped Li-Fe cells exist, but I doubt it very much.

Boeing doesn't just go to Radio Shack and buy cells. They'd be made to spec, in whatever shape they need to be. Cylindrical is just the cheapest way to make them. And nobody is going to care much about half a cubic foot in size and 20 extra pounds at this point.
They're not going to install an entirely new system for a higher voltage battery pack just to avoid "awkwardness" What's awkward about a 3x3 arrangement anyway?



Andy Goetsch
User currently offlineblrsea From India, joined May 2005, 1426 posts, RR: 3
Reply 97, posted (1 year 9 months 1 week 1 day 19 hours ago) and read 7793 times:

How are the batteries cooled in the airtight environment of the sealed box? The batteries will generate some amount of heat naturally as they go through charging cycles. Shouldn't they be cooled?

User currently offlineKaiarahi From Canada, joined Jul 2009, 3072 posts, RR: 37
Reply 98, posted (1 year 9 months 1 week 1 day 17 hours ago) and read 7711 times:

Quoting blrsea (Reply 97):
How are the batteries cooled in the airtight environment of the sealed box? The batteries will generate some amount of heat naturally as they go through charging cycles. Shouldn't they be cooled?

See posts 67-81.



Empty vessels make the most noise.
User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 99, posted (1 year 9 months 1 week 1 day 10 hours ago) and read 7606 times:

Quoting prebennorholm (Reply 95):
Quoting twiga (Reply 93):I'm pretty sure they would be keeping all options open when they sized the stainless steel containment vessel, because who knows it might be mandated as a permanent feature as discussed on another thread. I would think if they went to something like Li Fe P04 as Stitch mentioned they would need one extra cell.
Quoting prebennorholm (Reply 95):
To fit in a 28VDC system one more cell will be needed. But that's not the only issue.

Li-Fe has a energy density which is roughly 33% lower than Li-Ion, so a Li-Fe battery with identical capacity would be that much bulkier / heavier.

Charge characteristics are also different, so changes to charging hardware would be needed - like if they changed to any non-Li based chemistry.

You are responding as if we specifically said they will be going to Li-Fe batteries. I said they would be "keeping all options open" and I also said "if they went to something like Li-Fe." this does'nt mean they are going to Li-Fe batteries. We were simply using Li-Fe as an example to answer the question wheather there was sufficient extra space for changes in future battery chemistry.

Quoting nomadd22 (Reply 96):
They'd be made to spec, in whatever shape they need to be. Cylindrical is just the cheapest way to make them. And nobody is going to care much about half a cubic foot in size

I agree they will be specially designed. A cylindrical shape for a battery does have an advantage in that they can withstand much higher internal pressures due to hoop strength and they are much more likely to hold their shape from thermal effects (from the photos of the existing runnaway cells there was a lot of bulging and wheather this means anything or not I don't know)) - anyway they will use whatever shape suits their design and needs. You maybe right about wheather its 0.2 or 0.5 cu ft extra 'may' not matter, this is as long as the decrease in air volume is relatively small. This would have been taken into account in Boeings calcululations for the design of the containment vessel based on pressures and temperatures from the exothermic reaction from a cell(s) runnaway, because according to Boyle's Law pressure and volume are interrelated, for example if you halve the volume you double the pressure - so at some point the volume does matter. Needless to say it's alot more complicated than this because temperature is also involved in calculating pressures.

Quoting nomadd22 (Reply 96):
What's awkward about a 3x3 arrangement anyway?

I agree awkward maybe the wrong choice of words. Nothing is wrong with a 3x3. I happened to be looking at their containment vessel and it appeared longer than wider. So it seemed logical to go with 2x5 for discussion purposes about extra space not being an issue. A 2x4 + 2x5 didn't make sense hence the word awkward. Anyway we are not trying to thread the needle here we are talking generalities. Kanban had it right in post #92 we just don't know there are too many unknowns.


User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 100, posted (1 year 9 months 1 week 18 hours ago) and read 7436 times:

Here we go, flight plan filed for LOT ZA272.

http://flightaware.com/live/flight/BOE272


User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 101, posted (1 year 9 months 1 week 5 hours ago) and read 7221 times:

Anyone aware of the storage schedule followed on the type.....


Think of the brighter side!
User currently offlinecornutt From United States of America, joined Jan 2013, 338 posts, RR: 1
Reply 102, posted (1 year 9 months 4 days 9 hours ago) and read 6971 times:

Question: Is the ship's battery required for deployment of the RAT? Or is that entirely mechanical?

User currently offlinejoecanuck From Canada, joined Dec 2005, 5478 posts, RR: 31
Reply 103, posted (1 year 9 months 4 days 8 hours ago) and read 6980 times:

Quoting prebennorholm (Reply 95):

I deal with electric bikes and for now, all i use are LiFePo4 batteries and the individual cells are rectangular. There is little preventing having square shapes. Cylinders are used mostly for the ease of manufacture...it's cheap and easy to simply roll the plates into a cylinder.

As for the size, earlier in the thread I laid out a configuration which would satisfy the voltage and capacity requirements and still fit in the current 787 battery box size.

Li ion are trickier to charge and discharge than any other common chemistry and their chargers can often be used to charge other chemistries when the reverse is usually not true


I have no doubts that the systems on the 787 could be adapted to charge just about anything.

That being said, any new battery will have to go through the whole certification process from scratch, and that will take time regardless of the chemistry.

Cessna is using li fe batteries and they have had their own problems with certification, so simply changing chemistries will be no walk in the park.



What the...?
User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 104, posted (1 year 9 months 3 days 23 hours ago) and read 6867 times:

Quoting cornutt (Reply 102):
Is the ship's battery required for deployment of the RAT? Or is that entirely mechanical?

As far as I'm aware and what everyone is telling me, the RAT is gravity deployed when there is a lack of electrical power.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 105, posted (1 year 9 months 3 days 21 hours ago) and read 6848 times:

Quoting bikerthai (Reply 104):
Quoting cornutt (Reply 102):Is the ship's battery required for deployment of the RAT? Or is that entirely mechanical?As far as I'm aware and what everyone is telling me, the RAT is gravity deployed when there is a lack of electrical power.bt

Rat deploys with:

Loss of both engines

Low pressure on all three hydraulic systems

Loss of all power to the Capt's/FO's flight instruments

So what we're generally talking about here is all four engine generators quit at once--the RAT pops out. Assuming you had previously lost the Main battery (which provides momentary power to the pilots instruments in this case) the pilots would lose their instruments for a few seconds as the RAT deploys and comes on line.


User currently offlinetwiga From Canada, joined Mar 2013, 96 posts, RR: 0
Reply 106, posted (1 year 9 months 3 days 18 hours ago) and read 6783 times:

Quoting 7BOEING7 (Reply 105):
So what we're generally talking about here is all four engine generators quit at once--the RAT pops out. Assuming you had previously lost the Main battery (which provides momentary power to the pilots instruments in this case) the pilots would lose their instruments for a few seconds as the RAT deploys and comes on line.

Thanks for your answer. I recall reading back in some threads that their deployment was'nt always that reliable - I was particularly thinking about cold winter, snowy weather, and the possibility of the RATS trap door freezing up and hindering deployment as often happens to my car door in such conditions. Is their activation purely gravity since there are no pneumatics because of lost engines, or is their some reserved compressed air in a tank, or are they mechanically spring loaded. It seems if the trap door was frozen shut it might need more than gravity alone to open. Anyway just wondering.


User currently offlinercair1 From United States of America, joined Oct 2009, 1357 posts, RR: 52
Reply 107, posted (1 year 8 months 2 weeks 6 days 9 hours ago) and read 5623 times:
AIRLINERS.NET CREW
CUSTOMER SERVICE & SUPPORT

This might be of interest to people who have been following the B787 battery issues.

http://www.ntsb.gov/news/events/2013/batteryforum/index.html

Forum - Lithium Ion Batteries in Transportation
On Thursday and Friday, April 11-12, 2013, the National Transportation Safety Board (NTSB) will convene a forum titled, "Lithium Ion Batteries in Transportation." The forum is free and open to the public. No registration is required.

The forum will be held in the NTSB Board Room and Conference Center, located at 429 L'Enfant Plaza E., S.W., Washington, DC. The public can view the forum in person or by live webcast. Webcast archives are generally available by the end of the next day following the forum, and Webcasts are archived for a period of 3 months from after the date of the event.



rcair1
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 108, posted (1 year 8 months 1 week 6 days 20 hours ago) and read 5089 times:

Must not be grounded anymore

Something's happening:

http://flightaware.com/live/flight/BOE380 (GUN LN 34 B-1)

http://flightaware.com/live/flight/BOE512 (ANA LN 83 I'm guessing a C-1 based on the profile)


User currently offlineStitch From United States of America, joined Jul 2005, 31439 posts, RR: 85
Reply 109, posted (1 year 8 months 1 week 6 days 20 hours ago) and read 5099 times:
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Per Matt Cawby, the ANA flight is a functional systems check of the new battery containment system.

That being said, that Boeing is starting "B2" flights to test the new system lends some credence to the rumors that the FAA will lift the grounding as early as tomorrow (19 April 2013).


User currently offlineairtechy From United States of America, joined Dec 2006, 520 posts, RR: 0
Reply 110, posted (1 year 8 months 1 week 2 days 8 hours ago) and read 4623 times:

How do you vent the new battery to the outside via a "hole" without impacting the pressurization of the airplane? Maybe the battery compartment is sealed and will be unpressurized? Battery compartment > pipe > external opening in the fuselage.   

User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 111, posted (1 year 8 months 1 week 1 day 19 hours ago) and read 4464 times:

Quoting airtechy (Reply 110):
How do you vent the new battery to the outside via a "hole" without impacting the pressurization of the airplane? Maybe the battery compartment is sealed and will be unpressurized? Battery compartment > pipe > external opening in the fuselage.

There are already two big holes in the airplane (outflow valves) which modulate throughout the flight to maintain the proper pressurization -- they will just close a little more to make up the difference.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2197 posts, RR: 4
Reply 112, posted (1 year 8 months 1 week 1 day 17 hours ago) and read 4441 times:

Quoting airtechy (Reply 110):
Maybe the battery compartment is sealed and will be unpressurized?

During regular operation, the batter compartment is kept under cabin pressure by a disc which will rupture under a thermal runaway condition.

During and after the venting event, the battery compartment will be at out side air pressure.

Depending on where they locate the disc, the titanium tube (pipe) may or may not be at outside pressure during regular operation.

The batter compartment may or may not be completely sealed with sealant or gasket. Even without sealant or gasket, the amount of leak that is through the fastener interface of the battery compartment cover is expected to be minisculeb6t.

There is a Boeing Video showing a tidbit of the battery cover. There were alot of fasteners . . .

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 113, posted (1 year 8 months 1 week 1 day 16 hours ago) and read 4412 times:

Quoting 7BOEING7 (Reply 111):

There are already two big holes in the airplane (outflow valves) which modulate throughout the flight to maintain the proper pressurization -- they will just close a little more to make up the difference.

Isn't the pressurization system designed with enough margin to keep the cabin pressurized even if a single cabin window blows out?  



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offline7BOEING7 From United States of America, joined Oct 2012, 1772 posts, RR: 16
Reply 114, posted (1 year 8 months 1 week 1 day 15 hours ago) and read 4406 times:

Quoting KELPkid (Reply 113):
Isn't the pressurization system designed with enough margin to keep the cabin pressurized even if a single cabin window blows out?

No, it's good but not that good. Even harder with the 787 larger windows. As opposed to what you see/hear in movies/tv a bullet hole wouldn't be a big issue and could easily be handled.


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