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787 Batteries and Chargers - Part 1

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787 Batteries and Chargers - Part 1

Old 22nd Jan 2013, 13:39
  #61 (permalink)  
 
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@Chris - agreed, though I'd argue that aviation subjects the batteries to a far wider variety of operating temperatures and humidity levels than domestic use, which probably took a lot of time to engineer around...

@hetfield - Correct, but the 744 and T7 have been in service now for nearly 24 and 18 years respectively. Christ, that makes me feel old...
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Old 22nd Jan 2013, 14:27
  #62 (permalink)  
 
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Doze:

Greater temp range is just an engineering problem, but to have such
failures so early in the life cycle suggests a design issue / inadequate
development and testing. I would be surprised if this comes down
to a "bad batch of batteries".

I think gums said something about li being used in some mil a/c. It's
also used in some Airbus models, fwih. Wonder what their experience is
and if they have had any problems ?.

Regards,

Chris
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Old 22nd Jan 2013, 15:08
  #63 (permalink)  
 
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I just found a very interesting British website with all the information worth knowing about batteries and associated subjects.

It contains over 140 web pages of information and explanations, so just go ahead!

Electropaedia, Energy Sources and Energy Storage, Battery and Energy Encyclopaedia and History of Technology

Last edited by grebllaw123d; 22nd Jan 2013 at 15:10.
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Old 22nd Jan 2013, 15:19
  #64 (permalink)  
 
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The Securaplane fire was a clear warning

@hetfield & @syseng68k re. your posts 54 & 55 this thread:

Electronic tech Leon was fired by Securaplane after he blew the whistle to the FAA that this battery/charger assembly was unsafe for use in an aircraft. A US Department of Labor Administrative Law Judge's report found Leon's firing justified, but the story it tells leaves lots of reason to wonder if this technology was adequately vetted before it flew.

My post #37 earlier in this thread provides a link to the ALJ's report that provides additional detail beyond what was cited from Plane Talking.
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Old 22nd Jan 2013, 15:50
  #65 (permalink)  
 
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Originally Posted by syseng68k View Post
Greater temp range is just an engineering problem, but to have such failures so early in the life cycle suggests a design issue / inadequate development and testing.
Sure. Given prior art when it comes to introducing new technologies to aviation, I suspect it will be some combination of factors, possibly related to environment and power/charging regulation that somehow either slipped through the cracks when the certification specs were drawn up or was hitherto unknown.

I think gums said something about li being used in some mil a/c. It's
also used in some Airbus models, fwih. Wonder what their experience is
and if they have had any problems ?.
Given that even the most modern US military jets were specified and designed upwards of two decades ago, I suspect that the LI batteries were a proposed modification that came later in the development lifecycle. Airbus do use LI batteries on some later models, but as far as I recall to nowhere near the same degree. I'm sure someone will correct me if I'm mistaken.
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Old 22nd Jan 2013, 15:51
  #66 (permalink)  
 
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Salute!

Yeah, syseng, the lithium types are presently being used in military systems. Only problems I have been told about were from folks in the "sand box", and temps there were getting really high, and many units went back to Ni-cads for ground-based systems. I share your opinion that we had a "bad batch", as the failures happened in short order and not spread out over months or years.

As I mentioned on another thread, our original Viper electrical systems were primitive by today's standards. So it turned out that our "last ditch" emergency power system was the most simple - PMG's and some coils, driven by engine bleed air or the hydrazine generator like the ones you see on the space shuttle ( that pffft, pffft, sound you hear after roll out). So uncommanded activation of the bleed air doofer cranked out too many volts because the basic system had not switched over to safe voltage output.

"normally", heh heh, when the system went to back-up it provided AC/DC and hydraulic power. So we had a basic design fault and corrected it after several losses and one fatality.

Secondly, those lithium batteries need high-tech monitoring for the charging system. And if all they are used for is back-up power, then there's no need to charge them all the way to max capacity constantly. Even the Prius does not charge its NiMH batteries to 100%, and they leave about 20% for regenerative charging when braking.

Finally, despite claims about no pure lithium in the batteries, physical and chemical actions could result in catastrophic thermal runaway. So I plan to take my old cell phone ( kids bought me an iPhone for Christmas) and break the sucker with a hammer and throw it in a pail of water. As with other metals of the same class, they react violently with water. Will report back.
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Old 22nd Jan 2013, 16:02
  #67 (permalink)  
 
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syseng68k, I'd stick with the LiON batteries for the short term (excuse that 'short' remark ). If it can be determined that these failures are related to battery age, number of load cycles or some other condition, an accelerated maintenance and replacement program can get the dodgy batteries out of the planes before they become a risk. That would be cheaper than keeping the fleet parked. And Boeing may have to pick up the tab (no cost to operators).

In the long term, a battery/charger/smart load controller may have to be developed and certified. This will be done with far more outside scrutiny by independent experts.
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Old 22nd Jan 2013, 16:08
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Originally Posted by gums View Post
So I plan to take my old cell phone ( kids bought me an iPhone for Christmas) and break the sucker with a hammer and throw it in a pail of water. As with other metals of the same class, they react violently with water. Will report back.
Blimey, gums - not that I'd presume to teach you how to suck eggs, but - if you're really going to try that - then for heavens' sake wear eye protection, heavy-duty gloves and an apron - those things really don't like heavy impact shocks!
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Old 22nd Jan 2013, 17:21
  #69 (permalink)  
 
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Gums:

>> the hydrazine generator

/anorak on

Jeez, such exotic technology in aircraft. I'd love to get my hands on
something like that, though sourcing the hydrazine might attract unwanted
attention here in the uk, even if you could find someone to sell it to you.

The uk Lightning a/c used an IPN (Isopropyl Nitrate), a fairly unstable
monopropellant starter. Apparently, back in the day, the RAF used to keep
the stuff sloshing around in unsealed plastic buckets, ready to fill the
small starter fuel tank. You can still find the starters on the surplus market
and are light enough to lift with one hand. They consist of a small turbine
and reduction gearbox and generate ~100hp short term. It would make an
interesting project to fit one in a car for instant additional acceleration.

As for the mobile, do it. Reminds me of all the kitchen and garden substances
we used to mix together to make "fireworks" when we were at school. You would
get locked up for years now for that sort of thing, such is the security
paranoia, health and safety, control culture, ad nauseum.

/anorak off

I think you misread the line about batteries in that I doubt if the problem
will be as simple as a duff batch. Sticking neck out, from info thus far,
looks like an overall charger / battery system design issue...

Regards,

Chris
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Old 22nd Jan 2013, 17:34
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Originally Posted by syseng68k View Post
Jeez, such exotic technology in aircraft. I'd love to get my hands on something like that, though sourcing the hydrazine might attract unwanted attention here in the uk, even if you could find someone to sell it to you.
The pre-production and first two (non-service) production Concordes had what were known as a MEPU, or Monofuel Emergency Power Unit - powered by hydrazine. Obviously there was no way they could have a substance that unstable on a line aircraft - and that was back in 1976!

Reminds me of all the kitchen and garden substances we used to mix together to make "fireworks" when we were at school. You would get locked up for years now for that sort of thing, such is the security paranoia, health and safety, control culture, ad nauseum.
Don't forget that H&S legislation boomed at the behest of corporate donors in order to minimise their exposure to litigation. Left to their own devices I'm sure the powers that be would have been more than content to simply continue scaring the bejeezus out of us with Public Information Films from an early age!
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Old 22nd Jan 2013, 18:44
  #71 (permalink)  
 
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archae86,

Looking at the Thales/Boeing design and the FAA special considerations, it appears that the approach was to assure cell failure would never occur--as it seems self-evident that no serious measures to avert propagation to adjacent cells were employed, nor were serious measures to contain damage to nearby systems.
I'm not aware of any damage to nearby equipment. I agree with Machaca here that apparently the safety systems (or call it hazard mitigation) did their job.

Also, having designed the venting system apparently so that it can prevent damage to nearbt equipment even in case of a thermal runaway and burn-down of a battery, I don't think the engineers just assumed it would "never happen".

The other issue is, of course, that the battery properties did quite obviously not conform to the special conditions set out by the FAA, in particular I cannot see how any Lithium Cobalt (or even Manganese ...) type battery could fulfil No. 2:
(2) Design of the lithium ion batteries must preclude the occurrence of self- sustaining, uncontrolled increases in temperature or pressure.
It is likely that condition no1 ...
(1) Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition and during any failure of the
charging or battery monitoring system not shown to be extremely remote. The lithium ion battery installation must preclude explosion in the event of those failures.
... was agreed to be fulfilled by the FAA, but is now obiously violated. It is hard to see how the described failures of the charger could be seen to be "extremely remote", taken to mean with a probability of less than once in 10 million operating hours, but more frequent than once per billion op-hours. The qualitative specification of "extremely remote" is "not anticipated during the operational life of a single airplane, but may occur a few times in the lifetime of the entire fleet." (paraphrased from CS.25, similar in FAR Part 25.)


Bernd
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Old 22nd Jan 2013, 20:11
  #72 (permalink)  
 
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EPU stuff

Salute!

No problem with my test, Doze. I'll let all know manana. I may be brave and fearless, but not all that brave!

From the Gums' archives.......

GD thot that the hydrazine EPU was a light, compact source of backup electricity and hydraulics. If we lost our motor, then the sucker had to provide at least one of our hydraulic systems and a very reduced amount of electricity. We paved the way for the space shuttle. That sucker used the same hydrazine doofer that we had, but bigger. If you look at the launches you can tell when the sucker starts to move the flight control surfaces and so forth. On landing, you can hear the thing and see the IR images as it puffs out gases, mostly ammonia. Big deal was our EPU only did that for about 5 minutes unless we had the motor still running and it could run off of bleed air. Shuttle was screwed, as it need the hydrazine power for takeoff and landing.

From my perspective, I see a batch of bad batteries or a design problem with the charging/monitoring system.

I do not advocate the hydrazine EPU that we had or that the shuttle used on a normal mission.

I also think that Ni-MH batteries could satisfy the Boeing requirement and have less problems. Look at Toyota and the Prius versus the Tesla and Volt.

I am glad to discuss the battery problem considering my experience in the first "electric jet". We learned a lot and we passed on our lessons to later and greater planes. There's just something about being "the first", and I was honored to be in the cadre of that neat little jet.
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Old 22nd Jan 2013, 20:15
  #73 (permalink)  
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Dozy, like most things chemical .... it depends.

I've spent a lifetime with Group 1 metals and showing their reaction with water to students.

If gum's pail is big enough and full of tap water at ambient temperature (say 10C and 1 or 2 gallons?) the whole event will be a non event. The Li will just effervesce. Yes I know about H2(g) ignition issues.

I would bet folding money that a pail of water with an iPhone battery would be a big enough thermal sink to keep the thermal runaway of the Li and the resultant kinetics under control.

But do wear full face protection and gloves. Li2O/LiOH in the eye, like that of any alkali, is properly serious

You have to push Li to get it to go "crack". Careful use of English.

If the temperature gets up, the rate of oxide formation on the metal substrate of Li2O (+Li2O2 for the pedants) will form a protective coating that eventually bursts with semi random explosive force/rapid combustion zones. For the record, you get crimson streamers radiating in parabolic curves from the point of release.

CW

Last edited by chris weston; 22nd Jan 2013 at 20:35.
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Old 22nd Jan 2013, 20:34
  #74 (permalink)  
 
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If these are STANDBY BATTERIES (back UP), why are they being charged inflight in the first place? Charging a Battery by definition means the power that the batteries supply can be provided by the charging system alone.

They have to have the juice to start the APU, and then the charging system carries the load. Once the APU starts, the Batteries are done. If the Batteries are charged by the APU, then obviously the APU is powering the system, not the Batteries.

Why even equip the aircraft with a BATTERY CHARGING SYSTEM? If the APU does not start, and the batteries need to power emergency lighting, they will, the APU, having not started, will be unable to charge (power) the system by definition. If the MAIN ship battery powers instruments and cockpit area lighting, same thing, if it needs to be charged, then the charging system (APU) will charge it, if it cannot, the batteries need to have the capacity to satisfy ETOPS, and if they do, they don't need charging....in the first place.

This applies if the BATTERIES are STAND ALONE. If provision for BATT/Charge together is to satisfy the safety reg, then the charger and BATTERIES constitute a dual (interdependent) system.

Last edited by Lyman; 22nd Jan 2013 at 20:42.
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Old 22nd Jan 2013, 22:03
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Lithium test

Salute!

Yeah, I'll be very careful. I still remember my high school teacher dropping a tiny amount of phosphorus or whatever into a jar of water and seeing the reaction. Years later I dropped munitions using the same metal to set off the napalm. No ignitor required, the stuff caused an immediate fire and poof!

I still stick to my story that the charging/monitoring systems need to be examined.

Nothing wrong with the NI-Mh batteries, and they are less susceptible to thermal runaway and such. No need to go back to "car batteries".

As a systems engineer and un-employed fighter pilot, I fully appreciate the advances in many systems. I am not a dinosaur.

The shuttle and Viper hydrazine systems were developed about the same time. Unlike the shuttle, ours had only a few pounds of the nasty stuff. Nevertheless, we had a great emergency system that worked regardless of altitude/air density and speed. Only had about 5 minutes or so to do something, but better than an immediate ejection.
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Old 22nd Jan 2013, 22:21
  #76 (permalink)  
 
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spraying that electrolyte is bad

Originally Posted by bsieker
I'm not aware of any damage to nearby equipment. I agree with Machaca here that apparently the safety systems (or call it hazard mitigation) did their job.
First, I'm honored to have earned a comment from you.

But, second, I think the "no harm done" view voiced by some here is rather too optimistic. The electrolyte in these batteries is itself a hazardous substance. In particular, it is itself flammable (or inflammable in proper English before the insurance companies decided we would not figure out what that meant), corrosive, and conductive. Second, the very high energy production by a cell which reaches thermal runaway practically guarantees that electrolyte will exit at high temperature and high pressure.

While photos of the ANA battery case might suggest that just a little seepage occured at seams, multiple press accounts describe a more energetic event. Recent articles in the Wall Street Journal assert that both incidents included both leaking electrolyte and smoke damage to "nearby portions of the aircraft". An early Seattle Times story described this of the ANA incident:
Hot chemicals sprayed out of the battery on the 787 Dreamliner in this week’s emergency landing in Japan, leaving a gooey dark residue and suggesting a different malfunction than last week’s 787 battery fire in Boston, according to two people with knowledge of the situation.

The residue covered the battery and splattered over nearby instruments inside the forward electronics bay. It left a 12-foot-long dark streak from the battery to an outflow valve through which some of the spray vented overboard during the flight.
I don't think that outer battery case was designed to contain a full thermal runaway event without hazard to surroundings, and I don't think we'd want to see many repetitions to see whether we continue to be lucky with that particular hot fluid spraying about in an electronics bay.

My friend who has blown up a great many lithium ion batteries, in addition to more gentle means of assessing their behavior, does not think a pressure vessel for full containment is practical. His tests are on single cells tiny compared to these, in custom chambers capable past 3000 psi, and he has had chamber failures. Possibly if this is to be designed to fail safely to the degree of all-cell thermal runaway, the outer battery chamber needs to guide the inevitable electrolyte spray to a safe exit channel.
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Old 22nd Jan 2013, 22:48
  #77 (permalink)  
 
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archae86,

thanks for the reply.

I didn't mean to downplay the event(s). This is serious stuff and it is not supposed to happen. And for all we know, there could be worse battery fires.

Just saying that it was an event that was considered during risk analysis, and they seem to have gotten the mitigating measures not totally wrong: chanelling and dumping of hot gases and fumes, instead of trying to contain them.

I don't think that outer battery case was designed to contain a full thermal runaway event without hazard to surroundings, and I don't think we'd want to see many repetitions to see whether we continue to be lucky with that particular hot fluid spraying about in an electronics bay.
I fully agree. I wouldn't want to play my chances on another similar event.

We'll see, but I wouldn't be surprised if Boeing was going back to Ni-Cd, with all the redesign that requires. Airbus may then have to rethink their A350 battery system, as well. I don't see Ni-MH happening here: they cannot deliver discharge currents anywhere near what Li-Ion or Ni-Cd can deliver.


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Old 22nd Jan 2013, 23:21
  #78 (permalink)  
 
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They have to have the juice to start the APU, and then the charging system carries the load. Once the APU starts, the Batteries are done. If the Batteries are charged by the APU, then obviously the APU is powering the system, not the Batteries.
While simple and atractive as a concept I suspect that restricting battery charging to the ground would have ripple effects.

For example what % of the APU battery charge is used by a single start cycle? How long does it take to "top off" after that and how many start attempts must be avaialable in non-nominal flight?

While these factors might have been fairly easily accounted for if "ground charge only" was in play early on, retrofitting it would probably take a signifiicant amount of effort to revisit all the analysis that assumed fully charge batteries, even assuming the basic capacities where adequate.

Of course this also assume that the actual fault involves the charging system rather than an internal battery fault.
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Old 22nd Jan 2013, 23:47
  #79 (permalink)  
 
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MWR,

I agree with all that.

Lyman,

I don't understand your argument, but you might like to see my reply to your post on the "FAA Grounds 787s" thread. Hope it helps, as I'm turning in now.
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Old 23rd Jan 2013, 00:16
  #80 (permalink)  
 
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Hi Chris

Thanks for the reply in the other thread. Some of my comment probably tips a worry that the LITHIUM ION Back up makes a good 'single use' safety system, not ready for prime time....

I think for whatever reason will prevail, current events suggest it is "not suitable for use in aircraft...."

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