FAA Grounds 787s
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The problem as I see it is that Boeing designed the Backup Battery systems to take on other tasks. That means it will be connected in the distributed system and any problem becomes a systems problem, a 'systemic' problem.
Talk of "isolation" should have stopped with the "Backup Function". If the breakers that remove the Backup system from the distributed system are within the Batteries' enclosure, how is that a dependable "open"?
The switching is remote from the Batteries' case, right?
SoS... There is your "Fusible Link", eh? That is battery #6 @ #5? Let's hope that was not the source of the Captain's "Zero Voltage"....Hopefully the breaker tripped prior?
Talk of "isolation" should have stopped with the "Backup Function". If the breakers that remove the Backup system from the distributed system are within the Batteries' enclosure, how is that a dependable "open"?
The switching is remote from the Batteries' case, right?
SoS... There is your "Fusible Link", eh? That is battery #6 @ #5? Let's hope that was not the source of the Captain's "Zero Voltage"....Hopefully the breaker tripped prior?
Last edited by Lyman; 15th Feb 2013 at 12:48.
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Inter cell connection was lost
Zero voltage (very probably) happened when cell # 3 lost it´s plus terminal due intense heat generated in internal Ohmic losses after a severe short circuit to ground.
There are evidences for this "model". This, likely will be publicized by JTSB.
In earlier posts i commented thoroughly on that.
There are evidences for this "model". This, likely will be publicized by JTSB.
In earlier posts i commented thoroughly on that.
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Airbus dumping Lithium batteries on A350
http://www.nytimes.com/aponline/2013...ries.html?_r=0
It is, of course, the right course of action. I wonder if Boeing have even started the drawings for going back to previous battery technology.
http://www.nytimes.com/aponline/2013...ries.html?_r=0
It is, of course, the right course of action. I wonder if Boeing have even started the drawings for going back to previous battery technology.
Last edited by Jetdriver; 15th Feb 2013 at 16:37.
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Subcells? Really?
Lyman (and others ...),
Again, please.
Where does this information come from? All I see in the labs are completely unfolded, long, continuous strips. One strip, i. e. one cell, per cell.
The cells are folded. There are no subcells. Neither is it necessary to achieve higher currents. The only relevant parameters are electrode chemistry and effective surface.
Also, it does not matter whether there is a short circuit in one larger cell, or in one of three parallel "subcells".
Each Battery system is a group of eight separate batteries. Each battery has three cells.
Where does this information come from? All I see in the labs are completely unfolded, long, continuous strips. One strip, i. e. one cell, per cell.
The cells are folded. There are no subcells. Neither is it necessary to achieve higher currents. The only relevant parameters are electrode chemistry and effective surface.
Also, it does not matter whether there is a short circuit in one larger cell, or in one of three parallel "subcells".
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RR
God help us all...
I am saying it was severed by a metallic Lithium flare in the battery beneath.
If the system had not shut down (electrically, continuity interrupt), Thales has some "splainin" to do....
Bernd
NO. Not in my understanding. In each battery are three separate electrodes, cells, consisting of a continuous "stack" ten meters long, folded. The length of all three is 30 meters, nominally...
Stand to be corrected....
Zero voltage (very probably) happened when cell # 3 lost it´s plus terminal due intense heat generated in internal Ohmic losses after a severe short circuit to ground.
I am saying it was severed by a metallic Lithium flare in the battery beneath.
If the system had not shut down (electrically, continuity interrupt), Thales has some "splainin" to do....
Bernd
The cells are folded. There are no subcells. Neither is it necessary to achieve higher currents. The only relevant parameters are electrode chemistry and effective surface.
Stand to be corrected....
Last edited by Lyman; 15th Feb 2013 at 14:00.
C/mon guys, haven't we been through all this stuff about cells ad nauseum already ?.
Boeing should stick with lithium imho. Just bring in some decent systems engineering
bods to fix the problem and lock away the beancounters for a few months
. Just
because airbus have run scared for political / business reasons doesn't mean the
original ideas were invalid. It's a proven technology and just needs to be properly
engineered.
It will probably take months to fix this, but that's the price you pay when you hand
off responsibity to many vendors, with inadequate engineering oversight and thus
lose track of the big picture...
Boeing should stick with lithium imho. Just bring in some decent systems engineering
bods to fix the problem and lock away the beancounters for a few months
. Justbecause airbus have run scared for political / business reasons doesn't mean the
original ideas were invalid. It's a proven technology and just needs to be properly
engineered.
It will probably take months to fix this, but that's the price you pay when you hand
off responsibity to many vendors, with inadequate engineering oversight and thus
lose track of the big picture...
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syseng68k
Given there may have been misunderstanding right along, apparently not?
C/mon guys, haven't we been through all this stuff about cells ad nauseum already ?.
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Great opportunity for a "Political" move
Just bring in some decent systems engineering bods to fix the problem and lock away the beancounters for a few months . Just because airbus have run scared for political / business reasons doesn't mean the original ideas were invalid.
It's a proven technology and just needs to be properly engineered.
I am saying it was severed by a metallic Lithium flare in the battery beneath.
Did you see the ground wire destroyed? Did you understand the equivalent circuit i posted showing a HIGH current path capable to fuse the (ground) wire? Fire crews had to fight against fire in TAK taxiway? (in BOS they had)
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Hi RR NDB
To make your conclusion requires the circuit breaker to have failed. That is unlikely.
To make your conclusion requires the geometry of the deficit to resemble other melted events, which it does not.
The geometry resembles, clearly, the action of a gas Jet, not a fusing failure.
Look again at the deficit on the top of the Battery. It too is shaped in a triangular, wedge form, suggesting an explosive escape of typical gas flares from this type of battery.
If the Thales designed system worked (I think it did), there would have been no battery voltage available to separate the connecting bar.
This damage is from Thermal runaway; the entire design is structured to avoid the type of event you describe.
I also believe the quantity of heat necessary to so seriously corrupt that connector is not available via Battery voltage alone.
Occam is our friend?
To make your conclusion requires the circuit breaker to have failed. That is unlikely.
To make your conclusion requires the geometry of the deficit to resemble other melted events, which it does not.
The geometry resembles, clearly, the action of a gas Jet, not a fusing failure.
Look again at the deficit on the top of the Battery. It too is shaped in a triangular, wedge form, suggesting an explosive escape of typical gas flares from this type of battery.
If the Thales designed system worked (I think it did), there would have been no battery voltage available to separate the connecting bar.
This damage is from Thermal runaway; the entire design is structured to avoid the type of event you describe.
I also believe the quantity of heat necessary to so seriously corrupt that connector is not available via Battery voltage alone.
Occam is our friend?
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Porous silicon particle anode 'triples capacity' of lithium-ion battery.
Read more: Porous silicon particle anode 'triples capacity' of lithium-ion battery | News | The Engineer technology
Read more: Porous silicon particle anode 'triples capacity' of lithium-ion battery | News | The Engineer technology
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“Airbus considers this to be the most appropriate way forward in the interest of program execution and reliability,” said Marcella Muratore, an Airbus spokeswoman.
Last edited by Mark in CA; 16th Feb 2013 at 06:04.
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"I thought some 595+ orders sort of negates that statement?"
595 historical orders, you could start a new thread on the impact this will have on Boeing's sales, suffice to say that Airbus (shrewdly) taking the initiative on reverting to NiCd puts Boeing between a rock and hard place.
To be fair, if Airbus hadn't had the A380 delivery issues and then the AF447, the A350 might be in a similar situation. However, Airbus have scored with this one albeit an own goal by Boeing.
595 historical orders, you could start a new thread on the impact this will have on Boeing's sales, suffice to say that Airbus (shrewdly) taking the initiative on reverting to NiCd puts Boeing between a rock and hard place.
To be fair, if Airbus hadn't had the A380 delivery issues and then the AF447, the A350 might be in a similar situation. However, Airbus have scored with this one albeit an own goal by Boeing.
Do a Hover - it avoids G
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There must be a not-insignificant public relations aspect to this decision
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Since this thread has gotten to be much about battery technology I feel free to ask "why NiCd (as mentioned upthread re A350 etc) and not NiMH?"
Wikipedia says in part "A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell.
The typical specific energy for ... larger NiMH cells is about 75 W·h/kg (270 kJ/kg). This is significantly better than the typical 40–60 W·h/kg for NiCd, and similar to the 100-160 W·h/kg for lithium-ion batteries. NiMH has a volumetric energy density of about 300 W·h/L (1080 MJ/m³), significantly better than NiCd at 50–150 W·h/L, and about the same as lithium-ion at 250-360 W·h/L.
Useful discharge capacity is a decreasing function of the discharge rate, but up to a rate of around 1×C (full discharge in one hour), it does not differ significantly from the nominal capacity.
The significant disadvantage of NiMH batteries is the high rate of self-discharge; NiMH batteries lose up to 20% of their charge on the first day and up to 4% per day of storage after that. In 2005, a low self-discharge (LSD) variant was developed. LSD NiMH batteries significantly lower self-discharge, but at the cost of lowering capacity by about 20%."
Wikipedia says in part "A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell.
The typical specific energy for ... larger NiMH cells is about 75 W·h/kg (270 kJ/kg). This is significantly better than the typical 40–60 W·h/kg for NiCd, and similar to the 100-160 W·h/kg for lithium-ion batteries. NiMH has a volumetric energy density of about 300 W·h/L (1080 MJ/m³), significantly better than NiCd at 50–150 W·h/L, and about the same as lithium-ion at 250-360 W·h/L.
Useful discharge capacity is a decreasing function of the discharge rate, but up to a rate of around 1×C (full discharge in one hour), it does not differ significantly from the nominal capacity.
The significant disadvantage of NiMH batteries is the high rate of self-discharge; NiMH batteries lose up to 20% of their charge on the first day and up to 4% per day of storage after that. In 2005, a low self-discharge (LSD) variant was developed. LSD NiMH batteries significantly lower self-discharge, but at the cost of lowering capacity by about 20%."
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poorjohn,
The following extract from www.mpoweruk.com may provide more insight into the shortcomings of NiMH cells.
The following extract from www.mpoweruk.com may provide more insight into the shortcomings of NiMH cells.
- High self discharge rate.
- Can be stored indefinitely either fully charged or fully discharged, but
- Suffers from memory effect though not as pronounced as with NiCad batteries
- Battery deteriorates during long time storage. This problem can be solved by charging and discharging the battery several times before reuse. This reconditioning also serves to overcome the problems of the "memory" effect.
- High rate discharge not as good as NiCads
- Less tolerant of overcharging than NiCads
- As with NiCads the cells must incorporate safety vents to protect the cell in case of gas generation.
- The coulombic efficiency of nickel metal hydride batteries could be up to 85% but is typically only around 65% and diminishes the faster the charge although this is projected to improve.
- While the battery may have a high capacity it is not necessarily all available since it may only deliver full power down to 50% DOD depending on the application.
- Cell voltage is only 1.2 Volts which means that many cells are required to make up high voltage batteries. The competing Lithium cells typically have 3 times the cell voltage (3.2 Volts to 3.7 Volts) and a much higher energy density.
- Lower capacity and cell voltage than alkaline primary cells.
- Limited supplies of rare earth element Lanthanum. Mostly in China.
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mm43: I appreciate the additional input but only a couple of the points as noted below might argue for NiCd vs NiMH for aircraft use, so I still wonder what really drives the designers in that direction.
"High self-discharge" of little concern in machines that fly much of every day. Plenty of ways to manage exceptions.
"memory effect...not as much as NiCads" is a plus, when comparing to NiCads
the bean-counters hope that ops avoids "long-time-storage" of their fleet
"high discharge" performance would need to be evaluated. Maybe that's a problem.
"less tolerant of overcharge" should be managed by design
"safety vents...as with NiCads" is a null argument in this comparison
"coulombic efficiency" - NiCad is better?
"capacity ... not necessarily all available" - NiCad is better?
"Cell voltage is only 1.2 Volts" sounds exactly like NiCad
"[worse] than alkaline primary cells" makes no sense in the comparison
"Lanthanum [is scarce]" doesn't seem to be an issue for the millions [?] of NiMH cells sold in the consumer market. (I understand that rare earths are in fact present in the U.S. but cheap Chinese supply made mining uneconomical a few years ago.)
"High self-discharge" of little concern in machines that fly much of every day. Plenty of ways to manage exceptions.
"memory effect...not as much as NiCads" is a plus, when comparing to NiCads
the bean-counters hope that ops avoids "long-time-storage" of their fleet
"high discharge" performance would need to be evaluated. Maybe that's a problem.
"less tolerant of overcharge" should be managed by design
"safety vents...as with NiCads" is a null argument in this comparison
"coulombic efficiency" - NiCad is better?
"capacity ... not necessarily all available" - NiCad is better?
"Cell voltage is only 1.2 Volts" sounds exactly like NiCad
"[worse] than alkaline primary cells" makes no sense in the comparison
"Lanthanum [is scarce]" doesn't seem to be an issue for the millions [?] of NiMH cells sold in the consumer market. (I understand that rare earths are in fact present in the U.S. but cheap Chinese supply made mining uneconomical a few years ago.)
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seems the eneloop over come a few of the issues of traditional nimh.
really good write up of the tech details, be sure to read the updates from sanyo.
http://www.stefanv.com/electronics/sanyo_eneloop.html
really good write up of the tech details, be sure to read the updates from sanyo.
http://www.stefanv.com/electronics/sanyo_eneloop.html
"High self-discharge" of little concern in machines that fly much of every day. Plenty of ways to manage exceptions.
"memory effect...not as much as NiCads" is a plus, when comparing to NiCads
the bean-counters hope that ops avoids "long-time-storage" of their fleet
"high discharge" performance would need to be evaluated. Maybe that's a problem.
"less tolerant of overcharge" should be managed by design
"safety vents...as with NiCads" is a null argument in this comparison
"coulombic efficiency" - NiCad is better?
"capacity ... not necessarily all available" - NiCad is better?
"Cell voltage is only 1.2 Volts" sounds exactly like NiCad
"[worse] than alkaline primary cells" makes no sense in the comparison
"Lanthanum [is scarce]" doesn't seem to be an issue for the millions [?] of NiMH cells sold in the consumer market. (I understand that rare earths are in fact present in the U.S. but cheap Chinese supply made mining uneconomical a few years ago.)
"memory effect...not as much as NiCads" is a plus, when comparing to NiCads
the bean-counters hope that ops avoids "long-time-storage" of their fleet
"high discharge" performance would need to be evaluated. Maybe that's a problem.
"less tolerant of overcharge" should be managed by design
"safety vents...as with NiCads" is a null argument in this comparison
"coulombic efficiency" - NiCad is better?
"capacity ... not necessarily all available" - NiCad is better?
"Cell voltage is only 1.2 Volts" sounds exactly like NiCad
"[worse] than alkaline primary cells" makes no sense in the comparison
"Lanthanum [is scarce]" doesn't seem to be an issue for the millions [?] of NiMH cells sold in the consumer market. (I understand that rare earths are in fact present in the U.S. but cheap Chinese supply made mining uneconomical a few years ago.)
Surely the 787 engineers and their bosses in Chicago realize that all eight Special Conditions for the use of Lithium Ion batteries (posted at #111) are US Federal Law. It is not a legal option to just contain any battery fire, Boeing must also prove:
(1) Safe cell temperatures and pressures must be maintained during any foreseeable …. condition ….
(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure.
Nor would containment alone be publicly acceptable. Boeing had best follow Airbus and revert to NiCads.
FWIW my views with historic context are published at: Dreamliner's assault and battery on Boeing's name
(1) Safe cell temperatures and pressures must be maintained during any foreseeable …. condition ….
(2) Design of the lithium ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure.
Nor would containment alone be publicly acceptable. Boeing had best follow Airbus and revert to NiCads.
FWIW my views with historic context are published at: Dreamliner's assault and battery on Boeing's name
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Is it possible that loads of humid sweaty passengers are the reason the batteries are having troubles?
The Plane Talking blog often comes at things from a different angle not really technical but this had me wondering if there isn't some left field reason for this all happening once the 787s are in service.
Dreamliner woes: Are sweaty passengers to blame? | Plane Talking
The Plane Talking blog often comes at things from a different angle not really technical but this had me wondering if there isn't some left field reason for this all happening once the 787s are in service.
Dreamliner woes: Are sweaty passengers to blame? | Plane Talking