Dreamliner Grounded.
Batteries
Hi,
All three battery types discussed here have their pros and cons. Lead
acid are probably the most robust and some versions use gell instead
of liquid electrolyte, which makes them even safer in terms of electrolyte
spills. Major disadvantage for a/c use is the poor energy density to weight
ratio. Aircraft style nicads are also quite robust, have long life and are
lighter than lead acid for equivalent capacity. Both the above will withstand
moderate rates of overcharge with no damage at all, other than electrolyte
loss. Lithium Iron are well proven, have been in use for years and are quite
safe, despite the occasional scare story re portable computers. However,
they have far more critical requirements in terms of charge / discharge
currents, voltages and temperatures. Energy density / weight ratio is very
high for these batteries.
I don't know what the dc rail is in the a/c, but if at 270v or so, as
someone else mentioned, it becomes very difficult to ensure that individual
cells within the pack match in terms of charge / discharge characteristics.
If there is mismatch, either in capacity or self discharge, some cells
discharge faster and will take differing times to recharge. Over time,
some cells become overcharged, while others never reach full capacity. This
is exacerbated by high charge current and discharge loads, in relation to
battery capacity.
The best way to solve this is to have separate monitor and charge circuits
for each individual cell, but his becomes expensive for large groups of cells.
Users like telcos do monitor in this way to maximise battery life, but
typically in groups of 3 or 6 cells. On a 28v system, there are typically 14
cells in series, whereas a 270v system needs 135. This just makes the problem
of mismatch monitoring more difficult, especially for Lithium Iron.
Yuasa are a world class manufacturer and my guess is that there is a problem
with the charging / monitoring electronics, or cooling. That or the batteries
are being driven too close to their design limit to save weight...
All three battery types discussed here have their pros and cons. Lead
acid are probably the most robust and some versions use gell instead
of liquid electrolyte, which makes them even safer in terms of electrolyte
spills. Major disadvantage for a/c use is the poor energy density to weight
ratio. Aircraft style nicads are also quite robust, have long life and are
lighter than lead acid for equivalent capacity. Both the above will withstand
moderate rates of overcharge with no damage at all, other than electrolyte
loss. Lithium Iron are well proven, have been in use for years and are quite
safe, despite the occasional scare story re portable computers. However,
they have far more critical requirements in terms of charge / discharge
currents, voltages and temperatures. Energy density / weight ratio is very
high for these batteries.
I don't know what the dc rail is in the a/c, but if at 270v or so, as
someone else mentioned, it becomes very difficult to ensure that individual
cells within the pack match in terms of charge / discharge characteristics.
If there is mismatch, either in capacity or self discharge, some cells
discharge faster and will take differing times to recharge. Over time,
some cells become overcharged, while others never reach full capacity. This
is exacerbated by high charge current and discharge loads, in relation to
battery capacity.
The best way to solve this is to have separate monitor and charge circuits
for each individual cell, but his becomes expensive for large groups of cells.
Users like telcos do monitor in this way to maximise battery life, but
typically in groups of 3 or 6 cells. On a 28v system, there are typically 14
cells in series, whereas a 270v system needs 135. This just makes the problem
of mismatch monitoring more difficult, especially for Lithium Iron.
Yuasa are a world class manufacturer and my guess is that there is a problem
with the charging / monitoring electronics, or cooling. That or the batteries
are being driven too close to their design limit to save weight...
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I had a lead acid battery do the equivalent of a thermal runaway in a helicopter. After emergency landing the air base's firemen emptyed a 6' high CO2 extinguisher on the battery, and an hour later it was still boiling. Lots of thermal mass!
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syseng68k
Thanks for a splendid overwiew. In an absence of reliable data, it is most welcome. My guess is that there will be no "gotchas" here, the silence from the principals is more indicative of embarrassment than the desire to protect new "magic".....
Spec. Operations. Maintenance. Safety.
At a guess, this new airplane was the victim of unwarranted excitement followed by intense worry, and an inability to accept some limitations in an ego driven project. Leading to secrecy, then desperation..
What a surprise.
It is a BATTERY. With a useful life, a performance profile that demands monitoring, and a payoff that demands attention, and 'useful insecurity' on the part of the operator/builder.
Insufficient capacity, (spec), overconfidence (ops), and fear (the tail wags the dog). No one, NO ONE, expects perfection. In a wild flurry to avoid the perception of imperfection, the project is put on the chopping block.
Nevermind, when all else fails (it might) there is the RAT.
Thanks for a splendid overwiew. In an absence of reliable data, it is most welcome. My guess is that there will be no "gotchas" here, the silence from the principals is more indicative of embarrassment than the desire to protect new "magic".....
Spec. Operations. Maintenance. Safety.
At a guess, this new airplane was the victim of unwarranted excitement followed by intense worry, and an inability to accept some limitations in an ego driven project. Leading to secrecy, then desperation..
What a surprise.
It is a BATTERY. With a useful life, a performance profile that demands monitoring, and a payoff that demands attention, and 'useful insecurity' on the part of the operator/builder.
Insufficient capacity, (spec), overconfidence (ops), and fear (the tail wags the dog). No one, NO ONE, expects perfection. In a wild flurry to avoid the perception of imperfection, the project is put on the chopping block.
Nevermind, when all else fails (it might) there is the RAT.
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Have LION batteries been used on any military a/c?
Or is the 787 the 1st application in any a/c?
Or is the 787 the 1st application in any a/c?
From that, I would suggest that this is either a manufacturing fault in the batteries or a problem with the circuitry/management of the battery.
I very much look forward to finding out what the probelm is, as I think most of us do!
The B-2 uses them.
have to check, but F-22 and F-35 may also use them.
The Nickel metal hydride batteries are used in the Toyota Prius after an attempt with the Li-ion doofers. Those nickel ones don't have the energy per weight/volume, but are less susceptible to burning up when over-charged. Less charging system protections and such requirements, so easier to engineer and employ.
Secondly, although the Li-ion ones dont have pure lithium ( highly reactive to water), they can still react to water once going into the thermal runaway stage. Damned hard to put the fire out.
We don't need to go back to lead-acid or even NI-Cad, but the new Li-ion doofers seem a little too risky for the applications in aircraft.
have to check, but F-22 and F-35 may also use them.
The Nickel metal hydride batteries are used in the Toyota Prius after an attempt with the Li-ion doofers. Those nickel ones don't have the energy per weight/volume, but are less susceptible to burning up when over-charged. Less charging system protections and such requirements, so easier to engineer and employ.
Secondly, although the Li-ion ones dont have pure lithium ( highly reactive to water), they can still react to water once going into the thermal runaway stage. Damned hard to put the fire out.
We don't need to go back to lead-acid or even NI-Cad, but the new Li-ion doofers seem a little too risky for the applications in aircraft.
Hard to fix with so many involved
Afaik, the overall power system in the 787 is a UTX responsibility, with Thales managing the auxiliary power aspects. Thales in turn ordered the batteries from Yuasa, but deleguated the battery management to Meggits Arizona based Securaplane subsidiary, which built the chargers. Some reports are circulating that a defective batch of PC boards made in Mexico made their way into the charge controllers.
How Boeing or the FAA for that matter are ever going to get to the bottom of this daisy chain of buck passing and determine both a probable cause as well as a confidence restoring fix remains TBD.
My guess is a switch to NiMH batteries, to distance the plane from any taint of 'lithium batteries on board'.
That might mean a grounding stretching well into spring, while the new approach is certified.
Does anyone from the regulatory side have any insights to offer?
How Boeing or the FAA for that matter are ever going to get to the bottom of this daisy chain of buck passing and determine both a probable cause as well as a confidence restoring fix remains TBD.
My guess is a switch to NiMH batteries, to distance the plane from any taint of 'lithium batteries on board'.
That might mean a grounding stretching well into spring, while the new approach is certified.
Does anyone from the regulatory side have any insights to offer?
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I have always been a fan of Boeing, but I think they screwed the pooch on the 787. In an effort to reduce costs and put the screws to their own labor unions, they lost complete control of their supply chain. They outsourced not only production, but development of many components. Some of the subcontractors can handle it, some could not.
I think they will solve this battery problem fairly quickly, but I also believe it is just the tip of the iceberg.
I hope I am wrong about this last part, but I don't think so. The 787 has many features never tried before on a commercial aircraft. Maybe the B2 or F22 have some of the same stuff, but those aircraft were low production run, VERY low flight time airframes. They will never be put through the same number of cycles that 787s will in 2-3 years, let alone 20-40 years that the 787's will be in service.
I think they will solve this battery problem fairly quickly, but I also believe it is just the tip of the iceberg.
I hope I am wrong about this last part, but I don't think so. The 787 has many features never tried before on a commercial aircraft. Maybe the B2 or F22 have some of the same stuff, but those aircraft were low production run, VERY low flight time airframes. They will never be put through the same number of cycles that 787s will in 2-3 years, let alone 20-40 years that the 787's will be in service.
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Batteries
syseng68k:
The focus of the issue!
Indeed requiring a quite "complex" management. (algorithms)
and why not to separate better each cell from adjacent? The weight could be similar and the volume would compensate for the better safety under higher temp cell operation, an usual condition.
8 cells of 3,7 V ea.
The focus of the issue!
...difficult to ensure that individual cells within the pack match in terms of charge / discharge characteristics. If there is mismatch, either in capacity or self discharge, some cells discharge faster and will take differing times to recharge. Over time, some cells become overcharged, while others never reach full capacity. This is exacerbated by high charge current and discharge loads, in relation to battery capacity.
The best way to solve this is to have separate monitor and charge circuits for each individual cell, but his becomes expensive for large groups of cells. Users like telcos do monitor in this way to maximise battery life, but typically in groups of 3 or 6 cells.
and why not to separate better each cell from adjacent? The weight could be similar and the volume would compensate for the better safety under higher temp cell operation, an usual condition.
On a 28v system, there are typically 14 cells in series,...
Yuasa are a world class manufacturer and my guess is that there is a problem with the charging / monitoring electronics, or cooling. That or the batteries are being driven too close to their design limit to save weight...
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Some of the subcontractors can handle it, some could not.
USMCProbe
Outsourcing demands very wise managers, i agree with your concern.
Outsourcing demands very wise managers, i agree with your concern.
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Li Ion batteries requires better "management"
Hi, gums
I would complement:
She are wonderful but critical and requires competent management.
The model in my mind is: The problem is not with the battery.
I would complement:
She are wonderful but critical and requires competent management.
The model in my mind is: The problem is not with the battery.
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She may present terrible surprises to us
Bear Lyman,
Unfortunately when the wonderful and critical battery fail she does an scandal: Heat (intense), smoke, hot and evil fluids and ultimately FIRE.
This is a very special kind of failure behavior.
Unfortunately when the wonderful and critical battery fail she does an scandal: Heat (intense), smoke, hot and evil fluids and ultimately FIRE.
This is a very special kind of failure behavior.
The problem is that with any project of such complexity and wide range
of technologies, there's no alternative but to outsource a lot of systems
and parts. Systems get more complex and need specialist manufacturers to
build them. Engines, avionics and more have been sourced this way for decades.
Duff batch of charger control boards may be true, but where was the inspection
procedure for incoming goods ?. Why didn't the BITE / system diagnostics pick
up the fault once the kit was installed ?. How much testing had been done under
worst case conditions over long periods ? and, why wasn't the battery electrically
isolated once the temperature or charge characteristics exceeded limits ?. Duff
batch of boards from *Mexico* ?. That's ok then, problem solved, or a smoke
screen ?.
Sad day for Boeing though. As slf, always thought of their kit as first class
and teething troubles like this probably won't change that view. The 380 intro
wasn't exactly trouble free either, just for the balance :-)...
of technologies, there's no alternative but to outsource a lot of systems
and parts. Systems get more complex and need specialist manufacturers to
build them. Engines, avionics and more have been sourced this way for decades.
Duff batch of charger control boards may be true, but where was the inspection
procedure for incoming goods ?. Why didn't the BITE / system diagnostics pick
up the fault once the kit was installed ?. How much testing had been done under
worst case conditions over long periods ? and, why wasn't the battery electrically
isolated once the temperature or charge characteristics exceeded limits ?. Duff
batch of boards from *Mexico* ?. That's ok then, problem solved, or a smoke
screen ?.
Sad day for Boeing though. As slf, always thought of their kit as first class
and teething troubles like this probably won't change that view. The 380 intro
wasn't exactly trouble free either, just for the balance :-)...
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You talk a lot of sense syseng68k and make it easy for a low tech chap like myself to understand. Thank you for that.
I read in the paper that the 787 has four times the battery power of a 777, if that is correct why would that be?
I read in the paper that the 787 has four times the battery power of a 777, if that is correct why would that be?
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787 innovations
ian16th:
Boeing introduced Li Ion as the main battery (single) and for APU start for the first time to an airliner.
The toll for that is being paid. IMO not because a problem in the selected batteries. Because the more complex management she requires. I hope (and somewhat believe) a tweak in the management System will solve the problem.
But there are other possible and probable causes like defective parts or even algorithms.
Boeing introduced Li Ion as the main battery (single) and for APU start for the first time to an airliner.
The toll for that is being paid. IMO not because a problem in the selected batteries. Because the more complex management she requires. I hope (and somewhat believe) a tweak in the management System will solve the problem.
But there are other possible and probable causes like defective parts or even algorithms.
TNKs, RR et al.
We went thru this 40 years ago with the power supply system for the Viper.
The whiz kids working the flight control computers were given carte blanche. So the basic run-of the-mill folks that did the power supplies provided the specified volts and amps. They also had a simple emergency DC power system using PMG's and run off bleed air from the engine versus the hydrazine-powered "real" emergency system.
Unfortunately, the computer folks used voltage regulators that did not tolerate over-voltage, and would shut down when volts got above "x". So when an uncommanded EPU came on line, the PMG generator exceeded the critical voltage and POOF! No more flight controls. Not good.
We fixed the problem and also had newer solid-state voltage regulators that could handle 90 volts versus 37 volts +/-.
With known problems of the Li-ion batteries going out of control due to over-charging and such, my personal engineering decision would be to use the nickel-metal ones and have slightly less amp-hours, a little more weight, but be safe.
We went thru this 40 years ago with the power supply system for the Viper.
The whiz kids working the flight control computers were given carte blanche. So the basic run-of the-mill folks that did the power supplies provided the specified volts and amps. They also had a simple emergency DC power system using PMG's and run off bleed air from the engine versus the hydrazine-powered "real" emergency system.
Unfortunately, the computer folks used voltage regulators that did not tolerate over-voltage, and would shut down when volts got above "x". So when an uncommanded EPU came on line, the PMG generator exceeded the critical voltage and POOF! No more flight controls. Not good.
We fixed the problem and also had newer solid-state voltage regulators that could handle 90 volts versus 37 volts +/-.
With known problems of the Li-ion batteries going out of control due to over-charging and such, my personal engineering decision would be to use the nickel-metal ones and have slightly less amp-hours, a little more weight, but be safe.
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Options to kill the problem
gums:
The engineering task force certainly will provide options to the high rocks of the involved players: Yuasa, Thales and Boeing. From an strategical POV the issue deserve a strong and clear response. The change of the battery type has this "feature".
But there are chances the problem is simpler. I personnaly would bet in how the wonderful and critical batteries are being "managed". The engineers will have this info if not yet and in a scenario of this type the not trivial retrofit could be not necessary.
Another alternative (not immediate to introduce) would be have two options of batteries and associated devices. This would not be "free". There are reasons they specified the Li Ion as main and APU batteries.
I question why they not used two as main. With different "regimes" could be nice. In R&D we brainstorm continuously.
I can imagine how the problem was handled by the people involved.
Regards,
PS
My son (copilot during the RTW flight) made his first solo by December 16.
The engineering task force certainly will provide options to the high rocks of the involved players: Yuasa, Thales and Boeing. From an strategical POV the issue deserve a strong and clear response. The change of the battery type has this "feature".
But there are chances the problem is simpler. I personnaly would bet in how the wonderful and critical batteries are being "managed". The engineers will have this info if not yet and in a scenario of this type the not trivial retrofit could be not necessary.
Another alternative (not immediate to introduce) would be have two options of batteries and associated devices. This would not be "free". There are reasons they specified the Li Ion as main and APU batteries.
I question why they not used two as main. With different "regimes" could be nice. In R&D we brainstorm continuously.
We went thru this 40 years ago with the power supply system for the Viper.
Regards,
PS
My son (copilot during the RTW flight) made his first solo by December 16.
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With known problems of the Li-ion batteries going out of control due to over-charging and such, my personal engineering decision would be to use the nickel-metal ones and have slightly less amp-hours, a little more weight, but be safe.
yeah, Feline, I am not a dinosaur and flew the latest and greatest fom 1971 until they made me quit.
I also had an engineering degree and fully understood all the workings of the aircraft systems, and the software. So I'll go with the best we have, but only after we fully undrstand the risks versus the perceived gain in performance or weight reduction or......
Not much different in form factor or weight. Just look at the Prius. Ten pounds on that sucker is a lot of weight fraction compared to 100 pounds on a 787. Hell, just one obese SLF would wipe out the weight savings, ya think?
I like the latest and greatest ( not to be just "cool"), but we have to make engineering decisions and production decisions. Safety is paramount, as they say.
787 is an engineering marvel from aero to mechanical to..... In the long run it's the stuff that you take for granted that bites you. And we learned that back in 1981 with the Viper power supply and computer power supply.
I also had an engineering degree and fully understood all the workings of the aircraft systems, and the software. So I'll go with the best we have, but only after we fully undrstand the risks versus the perceived gain in performance or weight reduction or......
but how much bigger would a nickel-metal battery be? Would they have the space? Looks pretty size limited from the pics I have seen
I like the latest and greatest ( not to be just "cool"), but we have to make engineering decisions and production decisions. Safety is paramount, as they say.
787 is an engineering marvel from aero to mechanical to..... In the long run it's the stuff that you take for granted that bites you. And we learned that back in 1981 with the Viper power supply and computer power supply.