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787 Batteries and Chargers - Part 1

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787 Batteries and Chargers - Part 1

Old 21st Jan 2013, 17:30
  #41 (permalink)  
 
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In- service samples?

If I were running the forensic program, I'd be asking some of the airlines to provide samples of their batteries with varying service histories (together with the charger's history records) for some lab testing. Surely the cost of 100 new batteries (whoever picks up the tab) has got to be a drop in the bucket compared to the cost of aircraft down time being incurred.

Anyone know (or can say) if the regulatory agencies have requested battery samples to be sent to their labs?
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Old 21st Jan 2013, 18:06
  #42 (permalink)  
 
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EEngr,

Don't you think that flight recorder readouts of the battery system performance from a number, or from all, of the grounded 787s would do the job?

Easy and not very expensive.
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Old 21st Jan 2013, 19:22
  #43 (permalink)  
 
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Don't you think that flight recorder readouts of the battery system performance from a number, or from all, of the grounded 787s would do the job?
Not if there is some deficiency in the parameters read or the battery model inherent in the system. The goal is to compare what the charger/controller/FDR sees to the actual internal state of the batteries.
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Old 21st Jan 2013, 19:44
  #44 (permalink)  
 
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Perhaps grebllaw123d is one of the many who believe that whatever you read out from a computer is 1000% accurate to unlimited significant figures. No need to get your hands dirty (yecch!) with the actual physics and you can always wear a suit and look corporate.
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Old 21st Jan 2013, 21:01
  #45 (permalink)  
 
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Adding to the above.....

Go look up the "off the grid" folks' charging systems. Many turn off the charging and look at the batteries. Maybe apply a small discharge mechanism, even as simple as a resistor.

As I posted on another thread, sometimes it's the simple things versus the high-tech, latest and greatest stuff that gives you problems. Like the charging system.

The Li-ion batteries are great for power density, size and such. But ya gotta be careful when using them without good monitoring systems for charge and such.

One biggie is the failure mechanism of the Li-ion batteries when they decide to go "thermal". They are not like the older batteries, including the nickel-metalic ones that are not that old. No need to go back to Ni-cad or lead-acid car batteries. The item of concern is what the Li-ion batteries do when they go into thermal runaway.

The FAA rules on shipping large amounts of the Li-ion batteries seem to take into account the catastrophic effects of a problem with those suckers. And do I need to remind all of the infamous Value Jet crash due to the emergency oxygen bottles starting to burn? Still cry about that one.
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Old 21st Jan 2013, 22:04
  #46 (permalink)  
 
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Gums,

Pulling sources together, summary, to be confirmed of course:

1) The cells look much like the rectangular cells found in the traditional
nicad aircraft batteries, as does the overall enclosure.

2) It doesn't look like there is temp monitoring for each cell. I would
think that this less than optimal, as the cells have little thermal
mass and would heat up very quickly. This may not be detected in time
with a single / global enclosure sensor.

3) It does look like there is individual voltage monitoring for each cell.

4) It doesn't look like there is a separate charge circuit for each cell,
perhaps not ideal for such a sensitive application.

5) Very high charging currents are being used, together with a patented
charge algorithm based around a model of the actual cell. Not
clear if this takes account of cell aging over time, which could
invalidate the model. Also, cell production spreads and how the set of
8 is matched / selected / toleranced. If all cells are charged in series,
at high current, matching is not a trivial issue.

That's about it at the mo, but perhaps you can add more...
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Old 21st Jan 2013, 22:15
  #47 (permalink)  
 
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RR_NDB:

Google US patent 5780994. On google patents, among others...
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Old 21st Jan 2013, 22:57
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As with any design and the components and the manufacturing and finally the actual implementaion/fielding, things show up that nobody had considred.

Apparent;y, the Boeing warning system alerted the crew (Nippon emergency landing) that the battery was getting hot.

I have no problem with the Li-ion batteries. OTOH, I also believe that using them in an airliner should have really good charging systems and monitoring systems.

The only problems I have are related to the effects of the thermal runaway characteristics. Saw a BMW or similar catch fire one night after a fuel leak caused the driver to pull over and then grab a fire extinguisher. I couldn't do much and neither could he ( no cell phones back n late 70's). Next thing you know is the transmission casing start to burn - aluminum/magnesium alloy. Fire department showed up, but once that metal started to burn all was lost.

So my feeling is Boeing will add some fire protection capability and also look long and hard on the battery charging/monitoring circuits.
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Old 21st Jan 2013, 23:10
  #49 (permalink)  
 
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gums

value jet had oxygen generators in cargo section, not bottles.

on a DC9 the oxgyen bottles are actually at the 4 o'clock position to the copilot...one for crew one for pax with valves in reach on top of bottles.

AS to the 787...someone will work out the problem...it is interesting to me that both offending batteries are/were in japanese operated airplanes. perhaps mx issues? we shall see...

of course the japanese planes were in the first batch and there might be nothing to really understand except that the batteries might have to be changed every six months as part of the solution.
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Old 21st Jan 2013, 23:17
  #50 (permalink)  
 
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Originally Posted by sevenstrokeroll View Post
value jet had oxygen generators in cargo section, not bottles.
And a tyre in the same cargo hold - not good.

...it is interesting to me that both offending batteries are/were in japanese operated airplanes. perhaps mx issues? we shall see...
I can't think of an issue with Japanese MX in recent times. As you say, far more likely to be simply that ANA was the launch customer and they've had more airframes for longer than anyone else.

Last edited by DozyWannabe; 21st Jan 2013 at 23:18.
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Old 22nd Jan 2013, 01:43
  #51 (permalink)  
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The worse-case scenario -- an in-flight battery meltdown -- did occur on the ANA aircraft and the safety systems all performed as designed to allow a safe landing and pax to deplane.



The containment is designed to sustain the duration of a battery burn down. It did prevent damage to the surrounding equipment, nothing else caught fire, the smoke was evacuated via the venturi port, and the hull wasn't breached.
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Old 22nd Jan 2013, 01:45
  #52 (permalink)  
 
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Sevenstrokeroll,
The JAL airplane is line #84 and delivered in December. The ANA airplane is about a year older.
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Old 22nd Jan 2013, 02:11
  #53 (permalink)  
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The battery in the ANA aircraft was replaced in October, so there is a greater chance of having cells from the same production batch in both.
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Old 22nd Jan 2013, 11:29
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Boeing Warned Of Battery Safety In 2006



Aviation reporter and blogger Ben Sandilands writes in Plane Talking that while employed at Securaplane, which brought together mission critical battery assemblies for the 787, Leon wrote a report on the battery technology planned for the 787 saying it was a flight of safety risk and that substitute battery technology should be used. A month later, Securaplane's main buildings were burned to the ground when a battery test went wrong. Leon was injured in the blaze. Securaplane reportedly tried to force Leon out of the company when he refused to ship what he considered an unsafe battery assembly to Boeing for use in the 787. That assembly later malfunctioned when installed in a prototype airframe.
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Old 22nd Jan 2013, 12:24
  #55 (permalink)  
 
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hetfield

That's pretty serious stuff if true and there was a similar report in
this week's Sunday Times business section.

So what are the options ?.

Revert to nicad batteries, which would add weight (100lbs ?), need
different charge electronics, may not meet the rapid charge requirements
(why did they need this anyway ?) and may have to be recertified.

Stick with the current li batteries, but rework the battery assembly and
charger design to be a bit more proactive in terms of temperature sensing,
recovery and shutdown.

Both option involve a lot of work and it doesn't look like a 5 minute
fix...

Regards,

Chris
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Old 22nd Jan 2013, 12:25
  #56 (permalink)  
 
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Affiliation

Maybe Boeing should have purchased Securaplane at that point, just as it later "bought Vought".....

There was an industry wide evolution in manufacturing to offshore, or at least "SUB contract" the actual work, and retain "Project Management". Capital investment was deferred, then eliminated, and the cream of the project, "management" stayed in house.

So how much is "Control" worth? Fracturing any part of the construction of an airliner and scattering it to remote and iconoclastic regions is a problem.

There is nothing more important in a complicated, technologically complex project than "integration".

Starting a project by eliminating success friendly paradigm (integration) at the outset is problematic.....

Is Thales a "BUY".....?

syseng68k..... Another option? Lithium technology remains certified until it is decertified. It is merely grounded (sic).

Why does it have to be "on-line" in flight? Does it? It is down the chain of redundancy merely by virtue of the 787's electrical architecture, having plugged the bleeds, and added a genset to each engine.

The argument then becomes (if I am airframer), why must the 787 be super redundant in the first place? two extra generators, and the RAT, how much is the Battery requirement just "overkill"?


Last edited by Lyman; 22nd Jan 2013 at 12:33.
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Old 22nd Jan 2013, 12:39
  #57 (permalink)  
 
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@syseng68k


If I were Mr. Boeing I would revert to NiCd.

Why?

- proved for decades
- simple chargers (one current for all cells)
- bad publicity for LiIon


Nobody would understand if, for whatever reason, another LiIon incident happens after these two....

BTW, NiCd batteries and their reliable proved chargers may be cheaper, but I'm not sure.


But I'm sure, I have overseen/not considered some facts...., therefore I'm not Bill Boeing
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Old 22nd Jan 2013, 13:12
  #58 (permalink)  
 
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NiCds have been supplanted by NiMH for some time now, as Cadmium is very difficult and expensive to dispose of.
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Old 22nd Jan 2013, 13:20
  #59 (permalink)  
 
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@Dozy

You are right, nevertheless 747-400 an T7 have Ni-Cd.
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Old 22nd Jan 2013, 13:28
  #60 (permalink)  
 
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Gums:

If you have a load of vendors, it's the gaps in the specs shared between
them that cause the problems. In one company I worked for many years ago,
the alternatives and feasability studies and initial specs to the client
always specified what was *not* going to be done, as well as what was. It
was quite good at catching stuff the client hadn't considered. Even then,
there's stuff round the edges and misalignment in understanding of the
specs that either no one thought of, or never considered relevant. The more
complex the project, the worse it gets.

I would stick with the li batteries. Why ?, because it's a proven and
reliable technology that's been around for years, despite the occasional
duff batch of laptop batteries, which is really just noise in the terms
of the numbers shipped. In some ways, the consumer electronics use is a
much greater engineering achievement, in that they are built down to a
price, shipped in millions, take hundreds os charge / discharge cycles
and cause very few problems. Aviation, on the other hand, throws
thousands, perhaps millions of $ at the problem and still can't get it
right. Amazing really...

Regards,

Chris
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