787 Batteries and Chargers - Part 1
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Originally Posted by cockney steve
Each of the 24 sub-cells should be heat and electrically insulated in a ceramic enclosure and connect to the cell's internal busbar/strap via a fusible link...thus any failed cell will automatically drop out and allow the whole battery to stay on-line at correct voltage (though capacity reduced by 1/3 due to the weakest link in the series-arrangement.
How would you propose to detect that a portion of the battery's capacity has taken a vacation? Are you sure that the weaker cell will not just deliver more current per plate as it tries to keep up with the applied load and then completely destroy itself?
Maybe it would be better to discharge a defective cell under controlled conditions and then crowbar across it with a contactor. You would have full rated amperage at ~4 volts less potential. Would the loads still run satisfactorily under those conditions? Probably, although the engineers might have to tweak the load characteristics a bit.
Last edited by RetiredF4; 15th Mar 2013 at 10:36.
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The last link is broken, try:
Boeing Provides Details on 787 Battery Improvements - Mar 14, 2013
It would appear to be a bit more than a fudge.
Boeing Provides Details on 787 Battery Improvements - Mar 14, 2013
It would appear to be a bit more than a fudge.
The improvements include enhanced production and operating processes, improved battery design features and a new battery enclosure.
"As soon as our testing is complete and we obtain regulatory approvals, we will be positioned to help our customers implement these changes and begin the process of getting their 787s back in the air," said Boeing Commercial Airplanes President and CEO Ray Conner. "Passengers can be assured that we have completed a thorough review of the battery system and made numerous improvements that we believe will make it a safer, more reliable battery system." Battery system changes include changes to the battery itself, the battery charging unit and the battery installation.
Earlier this week the FAA approved Boeing's certification plan, which lays out the discrete testing to be done to demonstrate that the battery improvements address the conditions laid out in the Airworthiness Directive that has suspended 787 commercial operations.
"As soon as our testing is complete and we obtain regulatory approvals, we will be positioned to help our customers implement these changes and begin the process of getting their 787s back in the air," said Boeing Commercial Airplanes President and CEO Ray Conner. "Passengers can be assured that we have completed a thorough review of the battery system and made numerous improvements that we believe will make it a safer, more reliable battery system." Battery system changes include changes to the battery itself, the battery charging unit and the battery installation.
Earlier this week the FAA approved Boeing's certification plan, which lays out the discrete testing to be done to demonstrate that the battery improvements address the conditions laid out in the Airworthiness Directive that has suspended 787 commercial operations.
Last edited by green granite; 15th Mar 2013 at 10:30.
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@ Machinbird...
yes, but we're not talking huge earthenware jugs here,- lightweight modern ceramics can do the job and minimise the possibility of a short-circuit to the firebox as well as containing the heat.
We're talking a posh kludge here. Given that Boeing refuse to admit they rushed ahead with a novel emergency-supply system and no backup plan,that they refuse to abandon the current Lithium Ion technology, we have to think how this may be made safe and reliable-enough that you or I would venture forth across a wide pond in the aircraft.
Every cell insulated/isolated....thermal runaway is minimised
every cell monitored.....we've already discussed this....electronic components are cheap as chips, there are plenty of multipole Mil-spec plugs of the type currently used, which would accomodate the extra harness needed to monitor and balance every sub-cell (24 per battery in current design)
fusible connections would not be significantly bulkier than the present arrangements. "crowbaring" would add 8 contactors under your proposal and it would also reduce both the voltage and capacity of the battery.....assuming only ONE cell popped and self-isolated, you'd still have full voltage AND 66% capacity available from that cell better than being 12.5% down on both capacity and volts when in dire need!....remember, these batteries are "supposed" to be a last-resort backup...(they're not!)
the APU battery is routinely used for nav-lights at pushback, as well as APU start when main engines aren't turning.
the essential instrument and braking battery is routinely used to power a refuelling valve /flap!
Latest news seems to confirm what I said very early on.... these batteries CAN be used for high-rate applications , but both charge and discharge must be monitored and controlled rigorously.
In a situation where these batteries are used in anger, I'd think the destruction and fire risk would be pretty low on the list of worries
yes, but we're not talking huge earthenware jugs here,- lightweight modern ceramics can do the job and minimise the possibility of a short-circuit to the firebox as well as containing the heat.
We're talking a posh kludge here. Given that Boeing refuse to admit they rushed ahead with a novel emergency-supply system and no backup plan,that they refuse to abandon the current Lithium Ion technology, we have to think how this may be made safe and reliable-enough that you or I would venture forth across a wide pond in the aircraft.
Every cell insulated/isolated....thermal runaway is minimised
every cell monitored.....we've already discussed this....electronic components are cheap as chips, there are plenty of multipole Mil-spec plugs of the type currently used, which would accomodate the extra harness needed to monitor and balance every sub-cell (24 per battery in current design)
fusible connections would not be significantly bulkier than the present arrangements. "crowbaring" would add 8 contactors under your proposal and it would also reduce both the voltage and capacity of the battery.....assuming only ONE cell popped and self-isolated, you'd still have full voltage AND 66% capacity available from that cell better than being 12.5% down on both capacity and volts when in dire need!....remember, these batteries are "supposed" to be a last-resort backup...(they're not!)
the APU battery is routinely used for nav-lights at pushback, as well as APU start when main engines aren't turning.
the essential instrument and braking battery is routinely used to power a refuelling valve /flap!
Latest news seems to confirm what I said very early on.... these batteries CAN be used for high-rate applications , but both charge and discharge must be monitored and controlled rigorously.
In a situation where these batteries are used in anger, I'd think the destruction and fire risk would be pretty low on the list of worries
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From Boeing...
Told ya' it was just a question of scale (quantity), not type (quality)....
The problem is one of 'perception', and Boeing takes a more forgiving position; as the chief regulator, Boeing has that 'option'.
Nothing visible in the new program hasn't been broached on PPRuNe, at length, with numbers, by professionals.
So here is a prime example of Political process leaking into the industrial. When caught out, "damage control", deny, and divert attention. Bamboozle the majority, and wait things out...
Two new braided and robust ground straps, better QC in Japan, tweaks to BMU and BCU, a nifty box and tube, BYU......
(bob's yer uncle). The waiting game....
In Boeing's view, neither incident met the company's internal definition for the condition called "thermal runaway". That is a situation in which there "is so much energy, so much heat and so much flame that it would put the airplane at risk", Sinnett says. "We know very clearly this was not the case in the Logan event and the Takamatsu event."
The problem is one of 'perception', and Boeing takes a more forgiving position; as the chief regulator, Boeing has that 'option'.
Nothing visible in the new program hasn't been broached on PPRuNe, at length, with numbers, by professionals.
So here is a prime example of Political process leaking into the industrial. When caught out, "damage control", deny, and divert attention. Bamboozle the majority, and wait things out...
Two new braided and robust ground straps, better QC in Japan, tweaks to BMU and BCU, a nifty box and tube, BYU......
(bob's yer uncle). The waiting game....
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Lyman,
Wasnt this approach the same used by Clinton with Monica Lewinsky affair?
The battery system did not meet the 'technical' definition of a fire?!?!?!
What about the other issues with arcing panels, burnt relay, miswired systems???
Wasnt this approach the same used by Clinton with Monica Lewinsky affair?
The battery system did not meet the 'technical' definition of a fire?!?!?!
What about the other issues with arcing panels, burnt relay, miswired systems???
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FP
I was thinking more along the lines of Nixon. Because Clinton's ploy worked, but Nixon had to resign.
Sinnett (Boeing):
Confucius (Free lancer):
"A half truth is a Whole Lie..."
Lyman (Nobody):
Sinnett chose his prose carefully, for what he means is there will be no "Aircraft FIRE", not "No Battery FIRE...."
That makes his comment sleazy, sly, and at least to me, dishonest....
I was thinking more along the lines of Nixon. Because Clinton's ploy worked, but Nixon had to resign.
Sinnett (Boeing):
“This enclosure keeps us from ever having a fire to begin with,” Sinnett told the Tokyo briefing.
"A half truth is a Whole Lie..."
Lyman (Nobody):
Sinnett chose his prose carefully, for what he means is there will be no "Aircraft FIRE", not "No Battery FIRE...."
That makes his comment sleazy, sly, and at least to me, dishonest....
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Lyman
I think you may be getting a little overexcited for the Tech Log thread and even for the R&N thread.
From the briefing:
What is it about demonstrating that fire cannot occur inside the new enclosure that you fail to grasp?
These guys who are internal and external experts on these batteries seem to have accepted that they don't know what caused the problems but have grouped potential causes for problems into categories then ensured that those causes do not cause the battery problems and -even it they did- any battery issue would be safely contained without fire.
The FAA is not going to be caught out again 'not testing enough' and nor is EASA so you can be assured that this is not a 'political' fix.
Would you prefer Boeing just left all the 787s on the ground until they can be rebuilt with canvas covered wood stringers and radial engines with propellers? Or would the danger of a gasoline fire in a wooden aircraft make you stick to ground travel?
Sinnett chose his prose carefully, for what he means is there will be no "Aircraft FIRE", not "No Battery FIRE...."
That makes his comment sleazy, sly, and at least to me, dishonest....
That makes his comment sleazy, sly, and at least to me, dishonest....
From the briefing:
During engineering testing, which occurs prior to certification testing, the team demonstrated that the new housing could safely contain a battery failure that included the failure of all eight cells within the battery. The "ultimate" load is the equivalent of 1.5 times the maximum force ever expected to be encountered during a battery failure. The housing easily withstood this pressure and did not fail until the pressure was more than three times the ultimate load.
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. The design also vents all vapors by venting directly outside of the airplane rather than into the equipment bay.
"We put this new design through a rigorous set of tests. We tried to find a way to introduce a fire in the containment but it just wouldn't happen. Even when we introduced a flammable gas in the presence of an ignition source, the absence of oxygen meant there was no fire.
"We drew from the new industry standard, DO311, established by RTCA, to establish our testing plan," said Sinnett. "These standards weren't available when we set the testing plan for the baseline battery and they helped us ensure the new design is robust and safe. We intend to show, during certification, that the 787 battery meets all objectives of DO-311 and only deviates from specific requirements where the 787-unique items are not covered by the standards." RTCA is a not-for-profit organization that serves as a federal advisory committee in establishing guidelines for the aviation industry.
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. The design also vents all vapors by venting directly outside of the airplane rather than into the equipment bay.
"We put this new design through a rigorous set of tests. We tried to find a way to introduce a fire in the containment but it just wouldn't happen. Even when we introduced a flammable gas in the presence of an ignition source, the absence of oxygen meant there was no fire.
"We drew from the new industry standard, DO311, established by RTCA, to establish our testing plan," said Sinnett. "These standards weren't available when we set the testing plan for the baseline battery and they helped us ensure the new design is robust and safe. We intend to show, during certification, that the 787 battery meets all objectives of DO-311 and only deviates from specific requirements where the 787-unique items are not covered by the standards." RTCA is a not-for-profit organization that serves as a federal advisory committee in establishing guidelines for the aviation industry.
These guys who are internal and external experts on these batteries seem to have accepted that they don't know what caused the problems but have grouped potential causes for problems into categories then ensured that those causes do not cause the battery problems and -even it they did- any battery issue would be safely contained without fire.
The FAA is not going to be caught out again 'not testing enough' and nor is EASA so you can be assured that this is not a 'political' fix.
Would you prefer Boeing just left all the 787s on the ground until they can be rebuilt with canvas covered wood stringers and radial engines with propellers? Or would the danger of a gasoline fire in a wooden aircraft make you stick to ground travel?
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I think you have not understood the nature of the chemistry involved.
"Inerting" the enclosure, by eliminating Oxygen, accomplishes nothing. This battery will spontaneously ignite without the presence of Oxygen. The electrolyte is an organic, and burns fine without ambient O2. At one time it was believed that because some Oxygen is produced in the burning of the electroyte, and the LithiumCobaltOxide, that it is somehow self sustaining, and that is why it resists extinguishment. That is a myth.
If you would like a reference I would be happy to supply one, but instead, you may want to read the paper that was the standard in 2011.
I have linked it here before.
"Burning" is not the problem, anyway. Temperatures in a runon cell push 3000 degrees, far hotter than any Fire".
The problem remains, IGNITION. NOT Oxygenation....Boeing still have a humongous obstacle ahead, to prove that retention of a volatile Battery system is worth allowing something that has never before been allowed, Fuel, and Ignition, present on an aircraft. If some wag wants to bring up Engines, have on. Kerosene does not spontaneously ignite.
It's an interesting discussion, but the basic problem, still, is reliability, and the regulations that do not allow fire.
The specific regulations won't allow even the production of excess pressure and temperature. Boeing needs to get around that, isolation in a box does not satisfy that rule. Not yet, anyway.
I think a fair question is what happens to the ejecta from the box? The composition and construction of the vent tube must sustain temperatures approaching 3000 degrees intermixed with carbon, ash, molten aluminum, and dense toxic smoke. All this is to be dumped along the belly of a plastic aircraft possibly hours from any place to land? Into an OXYGEN rich environment for, how long? twenty minutes? Can you think of a better way to ignite CFRP? Super heated oxygen starved solvents, metals, and vapors, blown into a 400 knot jet of Oxygen? Has anyone thought that through?
Convince me. The benefit of the doubt has passed away, and was given a burial in January.
For one second, Ian, do you think this scheme would have passed original certification?
"Inerting" the enclosure, by eliminating Oxygen, accomplishes nothing. This battery will spontaneously ignite without the presence of Oxygen. The electrolyte is an organic, and burns fine without ambient O2. At one time it was believed that because some Oxygen is produced in the burning of the electroyte, and the LithiumCobaltOxide, that it is somehow self sustaining, and that is why it resists extinguishment. That is a myth.
If you would like a reference I would be happy to supply one, but instead, you may want to read the paper that was the standard in 2011.
I have linked it here before.
"Burning" is not the problem, anyway. Temperatures in a runon cell push 3000 degrees, far hotter than any Fire".
The problem remains, IGNITION. NOT Oxygenation....Boeing still have a humongous obstacle ahead, to prove that retention of a volatile Battery system is worth allowing something that has never before been allowed, Fuel, and Ignition, present on an aircraft. If some wag wants to bring up Engines, have on. Kerosene does not spontaneously ignite.
It's an interesting discussion, but the basic problem, still, is reliability, and the regulations that do not allow fire.
The specific regulations won't allow even the production of excess pressure and temperature. Boeing needs to get around that, isolation in a box does not satisfy that rule. Not yet, anyway.
I think a fair question is what happens to the ejecta from the box? The composition and construction of the vent tube must sustain temperatures approaching 3000 degrees intermixed with carbon, ash, molten aluminum, and dense toxic smoke. All this is to be dumped along the belly of a plastic aircraft possibly hours from any place to land? Into an OXYGEN rich environment for, how long? twenty minutes? Can you think of a better way to ignite CFRP? Super heated oxygen starved solvents, metals, and vapors, blown into a 400 knot jet of Oxygen? Has anyone thought that through?
Convince me. The benefit of the doubt has passed away, and was given a burial in January.
For one second, Ian, do you think this scheme would have passed original certification?
Last edited by Lyman; 15th Mar 2013 at 19:40. Reason: add detail
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.
The cathode material of their batteries is lithium cobalt oxide, which gives off oxygen when decomposed by heat which then merrily reacts (burns) with the organic solvents, carbon, etc. which the rest of the battery is made from.
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I believe that the non-technical person would have a hard time accepting the argument that even though temperatures inside the battery could still reach over 2000F, since there is no open flame there is by definition no fire.
The uncontrolled release of the chemical energy stored in the active materials of the battery is technically not fire, but it is capable of doing all of the damaging things that fire can do.
BTW, charcoal does not burn by that same narrow definition, since there is no open flame once it is started. But it sure does oxidize well and gives off a lot of heat.
The uncontrolled release of the chemical energy stored in the active materials of the battery is technically not fire, but it is capable of doing all of the damaging things that fire can do.
BTW, charcoal does not burn by that same narrow definition, since there is no open flame once it is started. But it sure does oxidize well and gives off a lot of heat.
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interesting factoid...
yesterday the fire sprinkler system went off in the entire engineering building, (where the fix is being designed/tested) causing about $3 million in damage...
yesterday the fire sprinkler system went off in the entire engineering building, (where the fix is being designed/tested) causing about $3 million in damage...
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Fullwings, the J-2 engines used on the second and third stages burned LH2 and LOx. The first stage F-1 engines burned kerosene and LOx. The NERVA engine, never operational, used only liquid hydrogen for fuel, but it was a nuclear reactor. The Apollo 13 accident was caused by an explosion in a LOx tank in the service module.
A very explicit graph of the battery designs
battery design before mod
battery design after mod
not much changed? Mainly "improved for electrical isolation".
But no wonder, design change due to safety aspects seems to be of no concern
The Boing design change process
battery design before mod
battery design after mod
not much changed? Mainly "improved for electrical isolation".
But no wonder, design change due to safety aspects seems to be of no concern
The Boing design change process
Last edited by RetiredF4; 16th Mar 2013 at 00:03.
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Inerting is a step above fire detection and extinguishing as it prevents a fire from ever occurring.
Assuming that Boeing is able to sell the concept of a fire proof/heat proof containment and overboard discharge of effluents for the Lixx batteries, I wonder how long the airlines will be able to stand what was already an apparently abnormally high battery replacement rate prior to the fire/overheats. These batteries cannot be cheap and moving them to outstations may be a problem. Are you going to be able to carry a COMAT shipment of a Lixx battery on a passenger airplane?
From the maintenance aspect, changing a NiCad battery on a turnaround was only a grunt job, opening a sealed battery container and possibly finding the contents fried will probably cause some delay.
The maintenance shop where they maintain the Lixx batteries will certainly be a more interesting place too. Maintaining NiCads is a pretty demanding chore what with the necessity for depleting them completely and then charging and making sure the cells are balanced. Having cells that may erupt should keep the techies on their toes.
I also wonder if all the weight involved in the containment and venting systems plus the extra monitoring systems, etc, hasn't wiped out the theoretical weight saving of going to this new technology?
From the maintenance aspect, changing a NiCad battery on a turnaround was only a grunt job, opening a sealed battery container and possibly finding the contents fried will probably cause some delay.
The maintenance shop where they maintain the Lixx batteries will certainly be a more interesting place too. Maintaining NiCads is a pretty demanding chore what with the necessity for depleting them completely and then charging and making sure the cells are balanced. Having cells that may erupt should keep the techies on their toes.
I also wonder if all the weight involved in the containment and venting systems plus the extra monitoring systems, etc, hasn't wiped out the theoretical weight saving of going to this new technology?
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Lyman writes:
I think you have not understood the nature of the chemistry involved.
I think you have not understood the nature of the chemistry involved.
I'm calling you on pure hubris - you think you know more than ANYONE involved in the process of designing and building these batteries and the system they are a part of.
What are your qualifications? If you don't mind, and it's not too much trouble for you, could you please drop a few airframe names or electrical systems you've had a key position in designing?
Or at least a few key projects you've worked on?
Or a few accident investigations you've assisted with?
Or...
Hell, it's not worth it.
From the very bottom of every Pprune page:
"As these are anonymous forums the origins of the contributions may be opposite to what may be apparent. In fact the press may use it, or the unscrupulous, or sciolists*, to elicit certain reactions."
Glove fit.
Lyman, you're an old man who has taken up internet forum trolling as a hobby, and I personally wish you'd find a different site to troll.
Aside from your comments I generally enjoy Pprune.
Best of luck.
RR