cornutt
Posts: 333
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 5:51 pm

Quoting keegd76 (Reply 239):
Do Yuasa also supply the charging system for the battery?

No, that's Securaplane, with some involvement from Thales although I'm not sure what their role is.
 
RottenRay
Posts: 220
Joined: Thu Jun 24, 2010 1:43 am

RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:02 pm

Quoting spacecadet (Reply 247):
Well, it may be what the design is supposed to do. It doesn't seem to be what it actually does. The battery in the ANA incident reportedly dropped to near zero voltage before it went belly up. "Unexpected drops" in voltage seems to be one of the big problems here.


Great post, Space, except for this last paragraph.

The ANA battery wasn't in use when this voltage glitch appeared, and therefore, wasn't connected to the load - you can't say that the load controller failed, as it wasn't in use.

The glitch to almost zero is probably related to the internal failure of that battery rather than being over discharged.
 
AeroWesty
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:13 pm

Quoting RottenRay (Reply 251):
The ANA battery wasn't in use when this voltage glitch appeared, and therefore, wasn't connected to the load - you can't say that the load controller failed, as it wasn't in use.

A question I asked early on, but never got answered, was how long it takes from a 'battery event' which would cause a thermal runaway, and the actual runaway taking place. The ANA plane wasn't in the air all that long before the pilots realized something was amiss, and they needed to make an emergency landing.

Could it be that whatever the battery was used for on the ground triggered a chain of events that simply took some time to show up as a threat to the flight?
International Homo of Mystery
 
PlanesNTrains
Posts: 9526
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:18 pm

Quoting RottenRay (Reply 215):
Merely repeating a convenient but incorrect number makes one sound hysterical and misinformed.

Sadly, he's neither. There is a more nefarious reason that may be present. But that's not for me to decide.

Quoting flood (Reply 216):
Looks like Boeing is going full steam ahead

"It said it plans to manufacture between 635 and 645 Dreamliners by year-end"

"Overall, Boeing says it plans to produce almost 61,000 airplans in 2013."

LOL


A couple of important comments:

Quoting rheinwaldner (Reply 219):
I have no idea.

and

Quoting ncfc99 (Reply 221):
As far as I know, we don't know the different failure mode quantities

Which I think apply to the vast majority of the dialogue here. Essentially, "we don't know". That's why the aircraft are grounded. That some people seem to want to see it one way or another is really irrelevant as in the end, "we don't know".

Quoting tdscanuck (Reply 226):
As far as damaged reputation, it's far too late for that.

Isn't that the truth! I must say, though, that I'm pretty much at peace with the whole 787 debacle finally. It's been one issue after another but I think I'm finally just going to accept whatever comes without really getting worked up over it. What's the point?

Quoting tdscanuck (Reply 226):
They are investigated and there isn't a common cause. Running a battery down until it shuts off is not the same as it catching fire when it's not over-discharged.

Seems simple.

-Dave
-Dave


MAX’d out on MAX threads. If you are starting a thread, and it’s about the MAX - stop. There’s already a thread that covers it.
 
tdscanuck
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:19 pm

Quoting BoeingVista (Reply 236):
This isn't what the article says, it say that "Most of the batteries were returned because they had run down so far that a low-voltage cutout was activated." it does not directly state why they ran down, so the question of why the batteries ran down is open.

I said they discharged in service...I have no idea how that conflicts with what you're saying or what the articles are saying. If you run the battery down (regardless of how or why), the low-voltage cutout activates to protect the battery. You have to swap it out with a good battery on the airplane...the low-voltage battery isn't damaged (that's why the cutout is there in the first place), you just can't recharge in on the aircraft. You need to recharge it on a bench somewhere.

Quoting BoeingVista (Reply 236):
Also a "sensible' design would maybe stop the drain before the batteries became unusable?

It does. When you replace a battery due to low-voltage cutout, you run through the CMM procedures *off the airplane* to release the interlock, test, and recharge the battery. Then you put it back in service. It's the "off the airplane" part that, by design, forces you to replace the battery in the aircraft.

Quoting BoeingVista (Reply 236):
Plus you say I assign all of the battery changes to failure, you seem to assign all the changes to inadverant discharge, what about the others or are you maintaining that there were no unexpected failures?

No, I'm not assigning all the failures to inadvertent discharge. Some were honest to god failure (unknown cause or symptom), two caught fires (widely reported), and a bunch were discharged and shut down as designed. The accusation that you've repeatedly made is that there were 100+ replacements and that this should have informed the safety decisions around the 2 fires...that only makes sense if you're attaching those replacements to the same underlying cause as the fires.

Quoting BoeingVista (Reply 236):
Semantics but I'll give you that bricked may not be "damaged" as in dangerous though as the batteries are rendered unusable through some sort of cut out I don't think that "damaged" as in beyond repair is an unreasonable description.

It's not symantics...the batteries aren't damaged beyond repair. They're not even damaged. They're just unsuitable for use prior to a bench check and recharge because they've been discharged to their lower limit on the airplane.

Quoting markalot (Reply 238):
So there is protection placed on these batteries for certain conditions, and many of the batteries bricked because those conditions were met. What about batteries that came close but did not exceed those conditions? What about batteries that came really really close?

What about them? If you hit the limit, the battery protects itself. If you don't, it doesn't, it charges back up, and you go about your day. If there is some evidence somewhere that discharge to the lower limit actually causes cell damage that might later result in a thermal runaway that would certainly be very relevant (and means the lower limit is probably in the wrong place) but, so far, I haven't seen *any* evidence anywhere that that's what's going on.

Quoting keegd76 (Reply 239):
Do Yuasa also supply the charging system for the battery?

No, Securaplane.

Quoting keegd76 (Reply 239):
Having said that, what would happen if you tried to charge a 'bricked' battery? I'd imagine the design would prevent that but again I don't know.

On the airplane, you can't. Off the airplane, you have to follow the CMM.

Quoting ncfc99 (Reply 240):
From what I can gather from your posts, I have assumed the batteries would have more capacity than they do before they would 'brick' themselves to eliminate the chore of replacement. Sorry if I'm making you go in circles.

The question becomes, how much capacity do you want? The batteries have a finite capacity, which can run the airplane for a finite time, and all the maintenance people are told how long that is. If you accidentally run over that time, or you leave a load on the battery and forget, it's going to run down until it shuts itself off. You could double the size of the battery but that doesn't fix the underlying cause...you can't run a battery longer that it's designed to be run. No airplanes are designed to run on battery on the ground for long...modern widebodies (not just the 787) do not do well on ground battery power. The battery is just there to get you powered up long enough to take care of quick maintenance tasks like towing, or to get the ground power/APU connected. These aren't laptops, they're not designed to be on battery power for any significant length of time.

Quoting cornutt (Reply 242):
If I understood what I read up-thread, a battery that bricks itself can be restored to service by the manufacturer. So it's still useable; it just needs service. Kind of like an engine that has reached its TBO time.

Exactly. Closer to an engine that's had a prop strike...it's probably not damaged, but you're not going to fly with it until you make sure.

Quoting Shenzhen (Reply 243):
Quoting tdscanuck (Reply 237):
..if you want to do anything, even something as simple as refuel, you need to power up at least one of the common computing resource (CCR) cabinets, since they host the fuel indicating system and fuel valve control. That means you power up the whole computer, it's associated cooling fans, the indicating system probes, and the power distribution units that power the probes and valves.

You sure about this? All the control / indication is on the re-fuel panel. I could see the fuel quantity system, and a few valves and lights.

Yes, I'm sure about this. Although the control/indication is on the refuel panel, the fuel quantity indicating and control functions are hosted on the CCR. Without the CCR powering up, you got nothing.

Quoting Shenzhen (Reply 243):
They also stated that there were no delays or cancellations, therefore the issues must have been discovered well before any scheduled departure (like when they tried to power the airplane).

You'll know...if the battery is dead, you can't power the airplane up. Large highly integrated airliners don't like to go from cold/dark to flight-ready very quickly (if nothing goes goofy you're still talking 15-20 minutes). As a result, maintenance usually powers them up and gets them set to go well ahead of any scheduled flight. If the battery is dead, you know then, you put in a new charged one, and you go about your day.

Quoting Stitch (Reply 244):
As to why this must be done off the airplane, I expect it's a safety measure. It has been noted that once a Li-Ion battery has been deeply discharged, it is more susceptible to thermal runway when re-charged. A shop offers a more isolated environment should the battery enter thermal runaway and catch fire and you can more easily apply extinguishing agents to said fire in a lab than in the EE bays

Exactly. The battery shut itself down to protect itself. Until you get it on a bench, you don't know why. Discharge to the cutoff is one reason, but there are others (for example, the battery could have faulted and the BMS properly shut it down, as the FAA special conditions require). You don't want to power it back up on the airplane until you know why it shut down.

Quoting Stitch (Reply 244):
I expect Boeing has published time limits for powering various functions off the battery based on the draw of those functions.

They have.

Quoting Stitch (Reply 244):
As such, it sounds like that in at least some cases, the aircraft support crew are not properly "minding the clock" and are exceeding these limits, with the result that the battery hits the threshold and the protection circuitry kicks in.

Exactly. That's what the articles are saying. There's certainly an argument about the alignment between battery capacity and real-world operating procedures but that's purely economic, not reliability or safety.

Quoting PITingres (Reply 245):
What you keep insisting, without any proof or reasonable basis as far as I can tell, is that these drained, shut-off batteries are permanently damaged. I don't think that is the case, from what Tom is saying

That's what Tom's saying.

Quoting PITingres (Reply 245):
By the way, if you're saying that the battery should shut down the aircraft while there's still enough charge left to boot the system for ground power recharge

The risk there is that, if you give the battery the ability to shut down the aircraft, you have the huge problem of how to demonstrate that that function will *never* activate in flight, as well as introducing a new potential failure point into the last line of defense for the electrical system.

Quoting PITingres (Reply 245):
Now, if the design is such that the handler has no indication of battery level except for the airplane going dead, that's a different issue.

There's a battery status indicator on the P5 panel in the flight deck.

Quoting Shenzhen (Reply 248):
I don't really believe that re-fueling or towing is the main cause for battery replacements. I can't think of too many occasions when an airplane would be re-fueled without the airplane being powered

You physically can't refuel a 787 without power...there's nothing to open the refuel valves.

Quoting Shenzhen (Reply 248):
Towing, the brakes should really only be used once it is over, to set the parking break.

You need power to release the brakes. Many SOP's also require that a towed airplane have position lights on, enough main deck lighting for the maintenance crew to see what they're doing (safety in an evacuation), and a VHF to communicate with the ramp.

Tom.
 
trex8
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:31 pm

Quoting tdscanuck (Reply 237):
Quoting trex8 (Reply 232):
And if they are running down "inadvertently" from things like fueling up causing drain charge as gauges light up, as cited in the article and then locking out, the electrical system should be designed to cut off the power before the battery drops that low

The electrical system *is* designed to cut off the power before the battery drops that low. That's why they have to replace the battery if they run it down .I feel like this is going in circles...people demand that the system cut off the battery to prevent over-discharge, then complain when the over-discharge protection does its job and results in the battery being replaced.

Perhaps the issue is that the charging system on the two planes which had an incident were malfunctioning and the batteries were left in a dangerously under charged state where problems then arose. Also maybe they need to change the parameters as to what level it can be discharged to.
 
FlyingAY
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:38 pm

Quoting tdscanuck (Reply 226):
You're running the causation chain backwards...the battery has finite capacity. If you run it down far enough that it's *going* to be rendered potentially unsafe by continued discharge, you stop discharging it. This was an explicit requirement of the FAA special condition for the battery in the first place.

Thank you for taking the time to answer me. So what you are saying, this is not true what Seattle Times writes:

"At that stage, the batteries, which cost about $16,000 each, are essentially dead and cannot be recharged."
 
cornutt
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:47 pm

Quoting trex8 (Reply 255):
Perhaps the issue is that the charging system on the two planes which had an incident were malfunctioning and the batteries were left in a dangerously under charged state where problems then arose. Also maybe they need to change the parameters as to what level it can be discharged to.

That would be the built-in battery management rather than the charging system, if I understand the design, but your point holds. It's possible that these two batteries were batteries that should have bricked themselves but didn't.

Also, since I'm here: I wonder if UAL has seen the same battery replacement rates as ANA and JAL. If not, one might wonder about differences in operational procedures.
 
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Stitch
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:50 pm

Quoting FlyingAY (Reply 256):
So what you are saying, this is not true what Seattle Times writes:

"At that stage, the batteries, which cost about $16,000 each, are essentially dead and cannot be recharged."

As The Seattle Times statement appears written as it was a blanket statement, then yes, it is incorrect.

If they had specifically noted that the batteries could not be recharged on the 787, they would have been correct.
 
Shenzhen
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 6:58 pm

Quoting tdscanuck (Reply 254):
You need power to release the brakes. Many SOP's also require that a towed airplane have position lights on, enough main deck lighting for the maintenance crew to see what they're doing (safety in an evacuation), and a VHF to communicate with the ramp.

Really nothing more then any other airplane except releasing the brake (if set) and applying the brake after the tow. I wounder if it is a standard operating procedure at some airlines to run the APU (if available) during a tow. I would think it would be safer to have electrical or hydraulic power available (other then a battery or accumulator).

I may be wrong, but I think position lights are powered from the 115 volt bus, not the 28 VDC (don't have a clue for the 787). I think main deck lighting isn't on the 28 VDC buss either (most airplanes).

Thanks

[Edited 2013-01-30 11:12:20]
 
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7BOEING7
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:05 pm

Quoting Shenzhen (Reply 259):
I would think it would be safer to have electrical or hydraulic power available (other then a battery or accumulator).

The brakes are electric not hydraulic.
 
Shenzhen
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:10 pm

Quoting 7BOEING7 (Reply 260):
Quoting Shenzhen (Reply 259):
I would think it would be safer to have electrical or hydraulic power available (other then a battery or accumulator).

The brakes are electric not hydraulic.

Sorry, was talking airplanes in general (battery for 787 and accumulator for airplanes with hyd brakes).

Cheers
 
rheinwaldner
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:18 pm

Quoting RottenRay (Reply 222):
Quoting rheinwaldner (Reply 219):
So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.

I missed where there were 100 destroyed batteries, only that those which had been discharged past a certain level had to be returned as their safety interlock had made them inoperable.

These batteries are essentially dead. It is written in the article with those words.

Quoting AeroWesty (Reply 223):
Quoting rheinwaldner (Reply 219):
So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.

You have to go back and read the Seattle Times article. It wasn't 100 destroyed batteries because of over-discharging. Many, many were disabled simply due to mechanics disconnecting the batteries improperly.

So the article basically confirms that the battery lacks capacity for the given demand. Demand should include easily possible cases of handling errors.
And the second thing comfirmed by the article, is that the charging system is not up to the job if it lets run the battery into locked mode jusgt because a fuel gauge stays lit. The BMS must remove the load from the battery before that happens.

Flightglobal did publish this image:


When I see the wiring and the connectors between the cells on the left picture I really wonder, whether there a) is a balancer functionality and b) if yes, whether these thin stripes would be able to apply enough balancing current. As I have said earlier a) would be a crime and b) still looks very unsophisticated. I also have to say, that I still think the thin wires are there to apply the balancing currents. Because only a fraction of the main-current is needed to keep the cells in balance.

But looking at that picture I also fully agree with the folks from Tesla and SpaceX. Boeing's Sinnet said: "I design a cell to not fail and then assume it will and the ask the next 'what-if' questions. And then I design the batteries that if there is a failure of one cell it won't propagate to another. And then I assume that I am wrong and that it will propagate to antoher and then I design the enclosure and the redundancy of the equipment to assume that all the cells are involved and the airplane needs to be able to play through that."

What he claims, is that three safety-nets have been designed into that battery. So reality has proven two of them to not work good enough. This is not acceptable.

And even worse:
I would say, calling the propagation to the other cells an "assumption" is simply dishonest, because that would be a given with that battery. And claiming, that this design is made to prevent cells from propagating failures is almost a joke.

No, wonder Boeing seems to be more sorry about the impact to their bottomline, than about what they have delivered in the first place. They somehow still don't see, how this story could turn out.

I bet that saying up to very recent times, that they "believe" in the sound design of the aircraft will be very embarrasing once the root cause and the resolution will be clear. Not anticipating that root cause will not appear to come across as very competent I fear.

Quoting AeroWesty (Reply 252):
Could it be that whatever the battery was used for on the ground triggered a chain of events that simply took some time to show up as a threat to the flight?

Yes it can.

Quoting PlanesNTrains (Reply 253):
Essentially, "we don't know".

This is not correct. There are a lot of things that we know and I bet that the root cause, that will turn out, has been correctly predicted countless times in these threads.

I also have to say, that you misquoted me in a very selective way.
Many things are difficult, all things are possible!
 
Shenzhen
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:22 pm

Boeing CEO......

Responding to questions from analysts and reporters, McNerney said people and resources are not being diverted from other areas to solving the 787 problems. Asked about reports that Boeing has replaced dozens of batteries on the 787, he said, "Batteries are replaced on our airplanes every day" and that safety concerns have not played a role. However, the replacement cycle is "slightly higher than predicted," he said.
 
Shenzhen
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:29 pm

Quoting rheinwaldner (Reply 262):
These batteries are essentially dead. It is written in the article with those words.

If the battery no longer provides any power to the airplane because it turned itself off doesn't mean it is dead at the component level, but certainly when looking at the overall airplane system, as it no longer provides power to the airplane.

example.... was late today because my battery died. Oh, how did you get here? I charged it.

Quoting rheinwaldner (Reply 262):
So the article basically confirms that the battery lacks capacity for the given demand. Demand should include easily possible cases of handling errors.
And the second thing comfirmed by the article, is that the charging system is not up to the job if it lets run the battery into locked mode jusgt because a fuel gauge stays lit. The BMS must remove the load from the battery before that happens.

The battery is only used when there is no other source of power. If you had power to charge the battery, the battery wouldn't discharge, as there would be no need for it to power anything.

If the BMS cuts off power from the battery at some point before it locks itself out, you are basically reducing the amount of power that is available in case of emergency. I think most airlines would rather replace a few batteries then not have the power when really needed.

Cheers

[Edited 2013-01-30 11:41:56]
 
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scbriml
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:31 pm

Quoting tdscanuck (Reply 237):
"Bricked" is probably not the right term

I think we need to use something like "disabled by design", maybe?

It is clear that batteries in this state are unusable, but not damaged. They can easily be returned to service, but have to be removed from the plane to do so.
Time flies like an arrow. Fruit flies like a banana!
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RottenRay
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:32 pm

Quoting rheinwaldner (Reply 262):
Quoting RottenRay (Reply 222):
Quoting rheinwaldner (Reply 219):
So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.

I missed where there were 100 destroyed batteries, only that those which had been discharged past a certain level had to be returned as their safety interlock had made them inoperable.

These batteries are essentially dead. It is written in the article with those words.


I guess you'll have to choose who you trust with regards to technical info regarding the 787:

A reporter with limited knowledge, or Tom, who lives and breathes Boeing.



Quoting tdscanuck (Reply 254):
Quoting BoeingVista (Reply 236):
This isn't what the article says, it say that "Most of the batteries were returned because they had run down so far that a low-voltage cutout was activated." it does not directly state why they ran down, so the question of why the batteries ran down is open.

I said they discharged in service...I have no idea how that conflicts with what you're saying or what the articles are saying. If you run the battery down (regardless of how or why), the low-voltage cutout activates to protect the battery. You have to swap it out with a good battery on the airplane...the low-voltage battery isn't damaged (that's why the cutout is there in the first place), you just can't recharge in on the aircraft. You need to recharge it on a bench somewhere.

Quoting BoeingVista (Reply 236):
Also a "sensible' design would maybe stop the drain before the batteries became unusable?

It does. When you replace a battery due to low-voltage cutout, you run through the CMM procedures *off the airplane* to release the interlock, test, and recharge the battery. Then you put it back in service. It's the "off the airplane" part that, by design, forces you to replace the battery in the aircraft.

Quoting BoeingVista (Reply 236):
Plus you say I assign all of the battery changes to failure, you seem to assign all the changes to inadverant discharge, what about the others or are you maintaining that there were no unexpected failures?

No, I'm not assigning all the failures to inadvertent discharge. Some were honest to god failure (unknown cause or symptom), two caught fires (widely reported), and a bunch were discharged and shut down as designed. The accusation that you've repeatedly made is that there were 100+ replacements and that this should have informed the safety decisions around the 2 fires...that only makes sense if you're attaching those replacements to the same underlying cause as the fires.


The TL;DR version - DON'T ASSUME THEY'RE DEAD, they might just be in a locked-out self-protection mode until a bench test can be performed prior to recharging.
 
AeroWesty
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:35 pm

Okay, this sure made me blink. In the LA Times article regarding Boeing's fourth-quarter earnings call with analysts:

"Boeing expects earnings this year to be $5 to $5.20 per share, with revenue of $82 billion to $85 billion. The company expects “no significant financial impact” from the 787 ongoing grounding."

Source: Boeing says it will find cause of 787 problems, defends batteries
International Homo of Mystery
 
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PITingres
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:43 pm

Quoting rheinwaldner (Reply 262):
So the article basically confirms that the battery lacks capacity for the given demand. Demand should include easily possible cases of handling errors.
And the second thing comfirmed by the article, is that the charging system is not up to the job if it lets run the battery into locked mode jusgt because a fuel gauge stays lit. The BMS must remove the load from the battery before that happens.

This has all been gone over, above. Do you really think that ground handling time on battery alone wasn't part of the agreed-on spec accepted by a sufficient preponderance of buyers? If I agree (contractually!) that say 45 minutes on battery is enough, and if my operations then exceeds that time, that's my problem, not the airplane's and not the battery's.

As for your "second thing", a) if the battery is the sole power source, the charging system has nothing to do with it, so your statement is off base, b) as was explained above it's not just one light bulb that has to be powered up, it's quite a bit more load, c) the BMS is doing *exactly* what you state -- removing the load from the battery. The only difference is that you are apparently asking the battery to retain enough charge to re-power the electrical system to take an external charge, and a) why would that be more important than powering the original load as long as possible (especially since by accepting the specs you agreed to not exceed the load available time!), and b) how would you know that you've retained enough charge to power up long enough to recharge (because if you don't it was a wasted effort).

I have no real comment on the rest of your post other than to say that you're apparently assuming that the square building-blocks are full of cell without much or any insulation, and that your language is (IMHO) inappropriately emphatic to the point of being inflammatory. I'm no battery engineer and I won't pretend to interpret the photos.
Fly, you fools! Fly!
 
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Stitch
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:49 pm

Quoting rheinwaldner (Reply 262):
These batteries are essentially dead. It is written in the article with those words.


And that is incorrect as a blanket statement.

The batteries cannot be recharged on the plane.

The batteries can be recharged outside the plane.

And not being able to recharge the batteries on the plane when they have been deeply discharged is a safety feature to take into account how deeply discharged Li-Ion batteries can at times respond to being charged.

One would think that Boeing implementing this on the grounds of safety instead of choosing expedience would be something people would be in favor of, not something to be castigated...  

[Edited 2013-01-30 11:51:39]
 
tdscanuck
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:50 pm

Quoting trex8 (Reply 255):
Perhaps the issue is that the charging system on the two planes which had an incident were malfunctioning and the batteries were left in a dangerously under charged state where problems then arose. Also maybe they need to change the parameters as to what level it can be discharged to.

That's certainly a possibility, although I think the FAA/NTSB said they found no fault with the charger, didn't they? Although, even if the charger/BMS fails to cut the battery off, it should still throw a "MAIN BATTERY LOW" or equivalent message to the flight crew so I'm not sure how you'd takeoff in that situation.

Quoting FlyingAY (Reply 256):
Thank you for taking the time to answer me. So what you are saying, this is not true what Seattle Times writes:

"At that stage, the batteries, which cost about $16,000 each, are essentially dead and cannot be recharged."

It's correct *on the airplane*. I went and read the battery CMM (it's actually fascinatingly detailed)...the return-to-service procedure is very thorough (as you'd expect) but if the battery shut down because the battery monitoring unit (BMU) opened the contactor to protect the battery, you replace the BMU, run the battery through it's full test gauntlet including recharge, then put it back in service. If the battery failed because an individual cell failed, that will show up during the check and the mechanic replaces the dead cell.

It's important to note that all this requires test equipment that isn't present on the airplane and requires you to open the battery case, which you don't do on the airplane. You cannot do any of this without replacing the battery (or grounding the airplane while you do the check). This is totally normal for LRU's...when they have a hard fault, you replace the LRU to get the airplane back in service and then do the CMM checks in the back shop to return the LRU to service. This is almost a service that the vendors will do (for a fee), so many smaller airline shops may choose to send it back to the supplier rather than do it themselves.

Quoting Shenzhen (Reply 259):
I may be wrong, but I think position lights are powered from the 115 volt bus, not the 28 VDC (don't have a clue for the 787). I think main deck lighting isn't on the 28 VDC buss either (most airplanes)

You definitely get lights on battery power. The main deck lighting is 115VAC. Position lights are 28VDC. There may be an inverter in the system to provide 115VAC from 28VDC or they may have a subset of 28VDC lighting, I'm not sure which.

Tom.
 
trex8
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 7:57 pm

Quoting AeroWesty (Reply 267):
Okay, this sure made me blink. In the LA Times article regarding Boeing's fourth-quarter earnings call with analysts:

"Boeing expects earnings this year to be $5 to $5.20 per share, with revenue of $82 billion to $85 billion. The company expects “no significant financial impact” from the 787 ongoing grounding."

Source: Boeing says it will find cause of 787 problems, defends batteries

What did you expect them to say??

They said similar with the 737NG production issues 15 yrs ago. Gee, I think I'm still writing off some of my capital loss carryover from that!
 
SonomaFlyer
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 8:03 pm

Thanks for the info Tom.

It looks like there is a disconnect in the reporting which isn't a huge surprise given the technical nature of the issues and the fact this 787 story is sexy to report on at the moment.

So this leads us back to the fact it appears to be an issue as to the batteries on the JAL and NH aircraft.
*The charging system did what it's supposed to regarding over/under charging
*There likely will be issues addressed on containment and possibly spacing of the individual cells plus possibly some additional margins built into the software to protect the batteries further.
*Airlines will need to have spare batteries at their various stations in case replacement is warranted. That should be easy at hubs (such as LAX or IAH for UA) but not at outlying stations such as LOS when UA begins service on the 787.

Given how much this a/c relies on electric power for so much of its operation, tremendous demands are put on the batteries from time to time. You'd think all of this was part of the design of the battery itself and perhaps its robust enough but additional work is likely needed to provide some further safeguards against thermal run away and beefing up containment.
 
max550
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 8:04 pm

Quoting spacecadet (Reply 247):
My guess as a project manager - because that's the only way I know to approach this - is that in the absence of a "smoking gun", you're going to see strengthened containment, additional software and/or hardware safeguards in the charging system, and a redesigned lithium ion battery. It's not going to be one thing; it's going to be all of them. Boeing is probably in fact working on this right now, because there's no point waiting. No system is perfect even if it is working as intended; this is a chance for Boeing to further improve the entire battery and charging system. If the investigation drags on, Boeing can go to the FAA and say "look, we've redesigned all this stuff, we can demonstrate its safety" and maybe that will be enough to get the grounding lifted.

That sounds very likely, it just seems to me that the battery design is an especially weak point. In my very limited experience with hybrid and electric cars I've never seen a lithium ion battery like this with such large cells packed so closely together. Even when you consider that the car batteries are much larger than the 787 batteries they still use far more cells per kWh. For example, the Fisker Karma uses ~32 cells for each 2kWh (approx capacity of the 787 battery), the Chevy Volt uses ~57 cells per 2kWh, Nissan Leaf ~16 cells, and the Tesla Model S ~160 cells. All but the Leaf have active liquid cooling systems while the Leaf uses air (and has had its own problems with batteries degrading from heat build-up).

It could be that technology has advanced so much since the 787 battery was certified that many of these technologies simply didn't exist when they designed the battery.

Whatever the problem, let's hope Boeing gets it fixed soon.
 
AeroWesty
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 8:16 pm

Quoting trex8 (Reply 271):
What did you expect them to say??

They said similar with the 737NG production issues 15 yrs ago.

That was prior to Sarbanes-Oxley, which came into effect in 2002. Even though I'm on the record that I expect most of the costs of the grounding for the airlines would be covered by insurance, and not become Boeing's responsibility, I was expecting that there'd be some thought given to an allowance for the obvious engineering costs to isolate the battery problem and its correction in both delivered and undelivered airframes. Knowing how expensive warranty refits can be, I was expecting Boeing would take some hit for the costs involved, and begin to estimate those costs now.
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XT6Wagon
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 8:29 pm

Quoting AeroWesty (Reply 274):
Knowing how expensive warranty refits can be, I was expecting Boeing would take some hit for the costs involved, and begin to estimate those costs now.

Its possible that Boeing (or its suppliers) was already working on upgrading the batteries to the latest chemistry, and other advances. If so, it likely will save costs as the FAA will have massive incentive to cut the red tape wherever possible right now. So far more time doing tests, far less time wating on paper to get pushed whenever someone gets around to it.
 
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AirlineCritic
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 8:53 pm

Quoting PlanesNTrains (Reply 253):
Which I think apply to the vast majority of the dialogue here. Essentially, "we don't know". That's why the aircraft are grounded. That some people seem to want to see it one way or another is really irrelevant as in the end, "we don't know".

  

Folks, you are relying on news articles that might be incorrect, or at least not tell the whole story.

Some batteries got changed, in addition to the two ones that burned. The reasons could be safeguard shutdown, running to the end of the designated lifetime, operator error, or unknown failure. It is very likely that most are benign reasons, perhaps even all. But this should be investigated. At the very least, to understand the failure of the burned batteries, you'd like to know whether the battery came from the manufacturer as new, was reset in maintenance due to an earlier shutdown, or went through some not-so-standard operating practices at the airport. Because only then you know what the history of the device was. A mistake anywhere in this chain could have caused the trouble. NOT only manufacturing problems.

Here's one theory. Batteries get bricked by the boatloads in the field, Boeing applies a software change to the shutdown safety limit to reduce the bricking, no one realizes that under some special conditions that new limit is actually not conservative enough, ANA and JAL happen to hit those special conditions and their batteries burn.

Plausible? Perhaps? Likely? Maybe not. But I'd investigate this angle, too, if I were Boeing. Again we are only guessing here because we do not know the battery histories, we do not know if there was a software change and what it changed, we know none of the details.

I'm hoping this gets solved soon. But there is an issue somewhere. Lets not rule out all the possibilities just yet.
 
starrion
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 8:55 pm

Quoting AeroWesty (Reply 274):
Quoting trex8 (Reply 271):What did you expect them to say??

They said similar with the 737NG production issues 15 yrs ago.
That was prior to Sarbanes-Oxley, which came into effect in 2002. Even though I'm on the record that I expect most of the costs of the grounding for the airlines would be covered by insurance, and not become Boeing's responsibility, I was expecting that there'd be some thought given to an allowance for the obvious engineering costs to isolate the battery problem and its correction in both delivered and undelivered airframes. Knowing how expensive warranty refits can be, I was expecting Boeing would take some hit for the costs involved, and begin to estimate those costs now.

I thought SOX would require Boeing not to make obviously false statements to the press also, but if you consider that Boeing was blithely saying that ZA001 was going to fly three months after the 7/8/7 rollout, and missed that mark by...
checking...
checking...
checking...
More that two years... then it would appear that SOX is mostly toothless.
Knowledge Replaces Fear
 
tdscanuck
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 8:56 pm

Quoting rheinwaldner (Reply 262):
So the article basically confirms that the battery lacks capacity for the given demand. Demand should include easily possible cases of handling errors.

I'm not sure how you relate a handling error to running the battery down. The battery has a finite capacity (measured in time, for maintenance purposes). If you run it beyond it's required time, it runs down. This is always true, regardless of what the design time is.

Quoting rheinwaldner (Reply 262):
And the second thing comfirmed by the article, is that the charging system is not up to the job if it lets run the battery into locked mode jusgt because a fuel gauge stays lit. The BMS must remove the load from the battery before that happens.

The BMS must, by regulation, remove the load from the battery before the battery reaches a dangerous discharge state. The FAA special conditions *require* that the battery be electrically disconnected before that occurs. Once that happens, you can't recharge the battery on aircraft because it's been electrically disconnected. There is no way to get current back in.

If you're running on battery power, there is nothing the charger can do. It's not a perpetual motion machine, there's no other energy source to charge the battery with. If you're running on battery power alone you've got to get another source of power for the airplane or shut down before the battery runs out of juice. You may want to argue that the current amount of time the battery can run the airplane is too short for ground operations but, as I said before, that's just an economic argument. There will *always* be some time period beyond which you can't run on battery power alone and you will *always* want to disconnect the battery before it discharges too far.

Quoting rheinwaldner (Reply 262):
No, wonder Boeing seems to be more sorry about the impact to their bottomline, than about what they have delivered in the first place.

I'd love to see any evidence that they're more sorry about the bottom line than their customers. I've seen a lot of evidence that suggests the complete reverse.

Quoting rheinwaldner (Reply 262):
I bet that saying up to very recent times, that they "believe" in the sound design of the aircraft will be very embarrasing once the root cause and the resolution will be clear. Not anticipating that root cause will not appear to come across as very competent I fear.

Sinnett flat out said they designed for a battery fire...how can you say that they didn't anticipate the root cause?

Quoting RottenRay (Reply 266):
A reporter with limited knowledge, or Tom, who lives and breathes Boeing.

I've said this a few times on and off over the years but it bears repeating...NEVER trust me just because of who you think I work for or what I do for a living. Trust me, if you choose to, because I try to use rational discussion, facts, and data. I've been wrong before, I certainly will be again, and I suspect (given the thread length) that I've already been wrong more than once over this topic and just haven't realized it yet.

Quoting RottenRay (Reply 266):
The TL;DR version - DON'T ASSUME THEY'RE DEAD, they might just be in a locked-out self-protection mode until a bench test can be performed prior to recharging.

Correct. One of the first checks to return a failed battery to service is to check the voltage at the connector...if it's low, then check what the voltage is inside the battery. If that's low too, some interior component has failed. If the voltage inside the battery is fine, then the BMS opened the contactor (as it should have) to protect the battery. Replace the BMS, run the battery through the remaining tests to make sure there is no other fault, recharge it, return it to the shelf.

Quoting Stitch (Reply 269):
The batteries cannot be recharged on the plane.

The batteries can be recharged outside the plane.

From a strictly physical standpoint, it's possible to recharge on the aircraft if you drag the right equipment out there and are willing to open the battery case on the aircraft. But that's nobody's standard procedure and would be a terrible waste of aircraft time. Better to replace it with a known good battery, then check out the failed one offline to find out what happened to it.

Quoting SonomaFlyer (Reply 272):
So this leads us back to the fact it appears to be an issue as to the batteries on the JAL and NH aircraft.
*The charging system did what it's supposed to regarding over/under charging

We believe...I think the NTSB statement was actually that they'd found no problem with the charger. This doesn't rule out some kind of transient defect that's no longer showing up but it makes it a lot less likely.

Quoting SonomaFlyer (Reply 272):
*Airlines will need to have spare batteries at their various stations in case replacement is warranted. That should be easy at hubs (such as LAX or IAH for UA) but not at outlying stations such as LOS when UA begins service on the 787.

This is part of the reason that the APU and main battery are the same part number. At an outstation, you can swap the batteries using normal mechanics' tools, MEL the APU, and get the airplane on its way to somewhere that has a replacement battery. Effectively, the airplane carries it's own spare main battery.

Quoting SonomaFlyer (Reply 272):
Given how much this a/c relies on electric power for so much of its operation, tremendous demands are put on the batteries from time to time.

That's not really related to the more-electric architecture of the 787. Normal aircraft can't run their pneumatic system on the battery either. The main and APU batteries on a 787 power the same basic bits they do on the 777. The 787 has more integrated avionics so I suspect the basic load is higher but none of the major electrical changes on the 787 drive up the battery draw. Some, like having an all electric APU and LED lighting, actually reduce the battery loads.

Quoting SonomaFlyer (Reply 272):
You'd think all of this was part of the design of the battery itself and perhaps its robust enough but additional work is likely needed to provide some further safeguards against thermal run away and beefing up containment.

I don't think anyone's going to argue that.

Quoting max550 (Reply 273):
In my very limited experience with hybrid and electric cars I've never seen a lithium ion battery like this with such large cells packed so closely together.

Car's don't have anything like the power density requirements of airplanes. There are quite a few components in airplanes that would be considered absurdly dense by automotive standards. That's not to say that this battery is right or wrong, I'm not a battery designer, but it's normal that aircraft bits look quite a bit different than their terrestrial analogs.

Tom.
 
abba
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:08 pm

Quoting rheinwaldner (Reply 219):
So as a summary: 100 destroyed batteries because of over-discharging indicate a poor charger design and a wrongly dimensioned battery.
Quoting tdscanuck (Reply 237):
Replaced != destroyed. According to the articles, most were pulled for expiration (not destroyed) or the low-voltage interlock cutting in to *prevent* them being over-discharged and destroyed (also not destroyed).


No matter what (we do not need to spilt hair here) - is this indicative of a deeper design flaw? The designers not knowing precisely how much power the systems will need to draw from the batteries in normal operation?
 
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scbriml
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:13 pm

Quoting AeroWesty (Reply 267):
"Boeing expects earnings this year to be $5 to $5.20 per share, with revenue of $82 billion to $85 billion. The company expects “no significant financial impact” from the 787 ongoing grounding."

At this point in time, they can't really say anything else. Until the root cause of the 787 issue has been identified, nobody knows how much it will cost to fix. However, the longer this goes on, the more it will cost even if the fix is relatively simple.
Time flies like an arrow. Fruit flies like a banana!
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AeroWesty
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:16 pm

Quoting starrion (Reply 277):
More that two years... then it would appear that SOX is mostly toothless.

Not necessarily. Knowing that you will have costs vs. not knowing you'd have an unexpected delay are two different things. When Boeing announced 787 production delays, they also discussed the affect it would have on earnings via the normal channels.

Boeing coming right out and stating today that it expects no significant financial impact due to the 787 grounding, leaves a lot of room for speculation one way or the other. As long as the statement is believed to be true when made, there's no SOX violation.
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Kaiarahi
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:21 pm

Quoting tdscanuck (Reply 270):
Quoting trex8 (Reply 255):
Perhaps the issue is that the charging system on the two planes which had an incident were malfunctioning and the batteries were left in a dangerously under charged state where problems then arose. Also maybe they need to change the parameters as to what level it can be discharged to.

That's certainly a possibility, although I think the FAA/NTSB said they found no fault with the charger

Yes, they announced last week that they found no anomalies with the BCU (Securaplane). At the same time, they also said the BMS (Kanto) circuit board was too damaged to provide useful information. However, the JTSB and NTSB have been at Kanto now for 5+ days with no (public) news.
Empty vessels make the most noise.
 
nomadd22
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:23 pm

http://www.flightglobal.com/news/art...ttery-fundamentally-unsafe-381627/

Gotta say I've come to agree with Elon's philosophy over the years.

"Both Boeing and Tesla use batteries fueled by lithium cobalt oxide, which is among the most energy-dense and flammable chemistries of lithium-ion batteries on the market. While Boeing elected to use a battery with a grouping of eight large cells, Tesla's batteries contain thousands of smaller cells that are independently separated to prevent fire in a single cell from harming the surrounding ones.
"Moreover, when thermal runaway occurs with a big cell, a proportionately larger amount of energy is released and it is very difficult to prevent that energy from then heating up the neighboring cells and causing a domino effect that results in the entire pack catching fire," says Musk."

The Tesla pack puts out around 100kw even though they use tiny cells and it fits in a car, so it can't be that big. I use to think using thousands of small cells was inefficient, but there's obviously a good case for it.
Anon
 
tdscanuck
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:27 pm

Quoting abba (Reply 279):
No matter what (we do not need to spilt hair here) - is this indicative of a deeper design flaw? The designers not knowing precisely how much power the systems will need to draw from the batteries in normal operation?

The designers know exactly how much power the systems need to draw in normal operation and how much time the battery can sustain that load. Then they tell the people operating the aircraft how long that is (it's almost certain that the time window was a design requirement and that drove the battery capacity). It's possible that the field procedures take more time than expected, so they're not getting the airplane onto other power sources, in which case it's a design flaw but not one that could have been known in advance...this issue (you have a finite battery power window until you have to shut down or get onto other power) is common to all airliners, there's nothing unique about the 787 with respect to that design requirement.

I think people may be under the mistaken impression that the battery is providing power during normal operations...it's not. The main battery is just there to power the airplane up so you can tow it, get it on APU power, or get it on ground power. The APU battery is just there to start the APU if you're not on ground power. The normal state of the airplane is ground power > APU power > engine power and back down. The battery has vastly more capacity than needed to do a normal startup onto ground power or APU. The design driver is, almost certainly, the backup power requirement for when all other power sources quit in flight, in which case you need enough battery power to get you to the ground.

Tom.
 
abba
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:34 pm

Quoting tdscanuck (Reply 284):
It's possible that the field procedures take more time than expected, so they're not getting the airplane onto other power sources, in which case it's a design flaw but not one that could have been known in advance...


Are you sure that there would be no way you could have known about that in advance? To me it seems as if someone hasn't done his/her homework properly. I can think of a few ways that this could have been predicted.... However, whether this is just a source for irritation or a real problem is another matter.
 
rcair1
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 9:54 pm

Quoting JerseyFlyer (Reply 196):
Intuitively this makes sense. An explanation from Boeing for their choice of eight large cells when presumably they discounted options comprising larger numbers of smaller cells would be of interest.

Intuition is not always right. Perfect example - "intuitively" a quad should be more reliable than a twin. But - what we see populating the skys is a bunch of large twins. What you have is 2 big engines instead of 4 smaller ones. Reliability is one of the factors driving that. That may or may not translate to LiIon cells perfectly, but it is not intuitive.

Quoting AeroWesty (Reply 199):
When you say "over discharge", is your meaning discharging too quickly or discharging below a certain value, or both?

To deep, not to quickly.

Quoting max550 (Reply 218):
think he might be on to something. With about 2,400 Tesla Roadsters on the road I can't find a single report of a fire involving their li-ion battery.

But some have bricked. The new ones don't brick because they stop allowing power to be pulled sooner.

Quoting PlanesNTrains (Reply 253):
That some people seem to want to see it one way or another is really irrelevant as in the end, "we don't know".

Thank you.

Quoting abba (Reply 279):
No matter what (we do not need to spilt hair here) - is this indicative of a deeper design flaw? The designers not knowing precisely how much power the systems will need to draw from the batteries in normal operation?

More likely - indicative of an underestimate of how far ground ops will push their luck in running on batts.
rcair1
 
cornutt
Posts: 333
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 10:02 pm

Quoting AirlineCritic (Reply 276):
Here's one theory. Batteries get bricked by the boatloads in the field, Boeing applies a software change to the shutdown safety limit to reduce the bricking, no one realizes that under some special conditions that new limit is actually not conservative enough, ANA and JAL happen to hit those special conditions and their batteries burn.

I've been wondering about that ever since the rumor about the software update started circulating. Thinking about it in the context of what you said, updating limits would be the sort of thing that could probably be changed with a parameter load, which is a lot less work than making changes to actual code. That kind of clicks.
 
Kaiarahi
Posts: 1807
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 10:06 pm

Quoting AirlineCritic (Reply 276):
Boeing applies a software change to the shutdown safety limit to reduce the bricking,

That would be Yuasa + Kanto + Securaplane.
Empty vessels make the most noise.
 
Shenzhen
Posts: 1666
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 10:08 pm

Quoting rcair1 (Reply 286):
Intuition is not always right. Perfect example - "intuitively" a quad should be more reliable than a twin. But - what we see populating the skys is a bunch of large twins. What you have is 2 big engines instead of 4 smaller ones. Reliability is one of the factors driving that. That may or may not translate to LiIon cells perfectly, but it is not intuitive.

A quad has twice as many engines when compared to a twin, therefore the reliability has to be lower (everything else being equal) at the airplane level.  
 
RickNRoll
Posts: 1857
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RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 10:25 pm

Quoting tdscanuck (Reply 237):
The electrical system *is* designed to cut off the power before the battery drops that low. That's why they have to replace the battery if they run it down .I feel like this is going in circles...people demand that the system cut off the battery to prevent over-discharge, then complain when the over-discharge protection does its job and results in the battery being replaced.

Wouldn't it be better to shut it off before it gets to the point where it locks itself? Would save everyone a lot of time and trouble.
 
ComeAndGo
Posts: 815
Joined: Thu Mar 31, 2005 5:58 pm

RE: FAA Grounds 787 Part 6

Wed Jan 30, 2013 11:15 pm

Quoting Shenzhen (Reply 264):
If the battery no longer provides any power to the airplane because it turned itself off doesn't mean it is dead at the component level, but certainly when looking at the overall airplane system, as it no longer provides power to the airplane.

example.... was late today because my battery died. Oh, how did you get here? I charged it.

except that the charging has to be done at the OEM in Japan. So in other words the battery is useless.

Quoting scbriml (Reply 265):
It is clear that batteries in this state are unusable, but not damaged. They can easily be returned to service, but have to be removed from the plane to do so.

no, they have to be sent to the OEM in Japan to be recharged.

Quoting RottenRay (Reply 266):
The TL;DR version - DON'T ASSUME THEY'RE DEAD, they might just be in a locked-out self-protection mode until a bench test can be performed prior to recharging.
Quote:
Boeing officials said the need to replace the batteries also suggested that safeguards were activated to prevent overheating and keep the drained batteries from being recharged. Company officials said the batteries can drain too deeply if left on without being connected to power sources. Trying to recharge such batteries could generate excessive heat, so safety mechanisms lock out any attempts to do that.

I read "overheating" and "safety mechanisms"

also:

Quote:
Kelly Nantel, a spokeswoman for the National Transportation Safety Board, said investigators had only recently heard that there had been “numerous issues with the use of these batteries” on 787s. She said the board had asked Boeing, All Nippon and other airlines for information about the problems.

“That will absolutely be part of the investigation,” she said.
http://www.nytimes.com/2013/01/30/bu...-the-fires.html?smid=tw-share&_r=0

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