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787 and Li-ion

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George Marsh
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PostPosted: Sun Jan 20, 2013 9:03 am    Post subject: 787 and Li-ion Reply to specific post Reply with quote

Seems like the 787 fires may be linked to the Li-ion batteries being overcharged. Or is the Li-ion battery have an issue with thermal run away?

When it's cold, my charger won't charge Li-ion batteries. It has to be very cold at 35000 feet.

I have 2 Li-ion batteries that are 4 years old. They hold their charge and take a full charge. However, they can't hold a candle to the batteries found in a Toyota prius, Ni-MH.

The price of Ni-MH batteries is close to the price of Ni-cd, but last for years. My 5 year old Ni-MH batteries are as good as the day I bought them.

Do you think Boeing will use Ni-MH?

George
 
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MarkB_MI
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PostPosted: Sun Jan 20, 2013 9:35 am    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

George, the batteries in question are within the pressurized fuselage, so ambient temperature is not an issue. And should the aircraft lose pressure, the passengers and crew are at much greater risk of dying than those batteries.

The choice of battery type is an engineering decision based on a number of factors, primarily cost and weight. Of course, mass reduction is an overriding concern in aircraft design, second only to safety. Lithium ion offers the highest energy density of the commercially available battery technologies, so it's hardly surprising that Boeing went with li-ion. My guess it was a global decision: "every battery in the aircraft must be li-ion". I don't think the batteries in question are that large, so they could have gone with a different technology for those particular batteries with a small weight penalty.

I doubt Boeing will switch to a different technology. More likely they will go with a modified battery or charging system. Switching technologies would require modifications to the charging system, so there's little to be saved in terms of cost by switching to NiMH.

With regards to your Prius, a hybrid like the Prius doesn't need a huge amount of storage capacity. Ni-MH makes a lot of sense, since it offers very good energy density, is reasonably cheap and reliable. On the other hand, a plug-in EV or hybrid like the Volt needs a lot of storage capacity. That's why the Volt uses li-ion batteries.
 
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Ken Macfarlane
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PostPosted: Sun Jan 20, 2013 9:47 am    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

I've got 20 year old Nicads that still sort of work but my 10 year old NIMH's are all garbage. They just don't seem to have a good lifespan.

I moved all my tools to lithium ion, they have been great. The cold weather isn't the best for them but warm them up even a bit and they are fine.
 
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guido
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PostPosted: Sun Jan 20, 2013 10:20 am    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

Hello George Marsh,

I Have NiCad's, they work for me!
I get extra packs whenever someone gets tired of them. I recycle and make one out of two or three.
Original packs are as old as your Li-ion, and still going strong! With 4 packs I think I can drill all day,

Guido.

 
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scotc
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PostPosted: Sun Jan 20, 2013 11:38 am    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

Somehow I doubt that the entire fuselage is heated, even though it is all pressurized.
 
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BigMarv1085
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PostPosted: Sun Jan 20, 2013 11:45 am    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

it doesn't take a whole lot of smoke to make a whole cabin seem as if its on fire. Most likely its getting over charged some how. The MD 88 still have a problem with the generator control units going bad. Use to have to do a test on one every time it landed. It will be figured out shortly.
 
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GarryinNC
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PostPosted: Sun Jan 20, 2013 12:24 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

All of the volume contained between the forward and aft pressure bulkheads is heated/cooled. Air is bled off the compressor sections on the engines and run through an air cycle machine if it needs to be cooled. That is true on transport category jets since the 707 days, but I think I did read that the 787 is somewhat different. It may use an electrically driven compressor to accomplish AirCon/Pressurization.

The FAA has certified 2 engine jets for over water operation since the advent of the Boeing 757/767 under a program called ETOPS, for extended range operations. Under a 180 minute ETOPS rule you can lose an engine and be allowed to fly for 180 minutes at single engine cruise to get to the nearest land.

Seems like the biggest worry with this 787 battery problem would be to have a battery fire or thermal runaway over the ocean and still have to fly 3 hours or so to land. UPS lost an airplane in Dubai when some computer batteries they were carrying as cargo shorted or ran away and started a fire. The pilots overflew a suitable airport while trying to get back to their departure airport. They were overcome by the smoke/fumes which was believed to be so thick they could not see, even with O2 masks and smoke goggles.
 


Last edited by GarryinNC on Sun Jan 20, 2013 5:08 pm; edited 2 times in total
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MarkB_MI
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PostPosted: Sun Jan 20, 2013 1:11 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

Did you ever have your luggage frozen solid when you arrived? The entire pressure vessel uses the same conditioned air, including the baggage compartment. If it didn't, Fido and Fluffy would arrive as freeze-dried pets.
 
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buickanddeere
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PostPosted: Sun Jan 20, 2013 2:58 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

No air bleed on the 787 . It's all electric driven everything with
1.45MW capacity.
 
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buickanddeere
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PostPosted: Sun Jan 20, 2013 3:02 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

Depends on the plane. Not every cargo hold is pressurized and/or heated on every aircraft.
 
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buickanddeere
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PostPosted: Sun Jan 20, 2013 3:09 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

Just simple matter of too many watts of power pushed into the battery and could not dissipate the heat.
System voltage has to be dropped to limit charging current and heating.
There should have been rtd's or thermal couples throughout the battery pack to monitor voltage.
Given the price of fuel over the lifetime of the airframe. Manufactures go to extreme lengths such as the lithium batteries and carbon fibre composite structure.
The more complicated you make anything, the more it will come back to bite you in the behind.
 
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GarryinNC
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PostPosted: Sun Jan 20, 2013 3:24 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

What passenger carrying, pressurized, jet transport aircraft does not have the cargo areas pressurized/heated?
 
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big fred
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PostPosted: Sun Jan 20, 2013 3:50 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

One that's parked overnight in Greenland.
 
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GarryinNC
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PostPosted: Sun Jan 20, 2013 5:13 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

big fred wrote:
(quoted from post at 19:50:44 01/20/13) One that's parked overnight in Greenland.


I guess that would apply to everywhere, not just Greenland. I stand corrected.
 
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steve706
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PostPosted: Sun Jan 20, 2013 5:53 pm    Post subject: Re: 787 and Li-ion Reply to specific post Reply with quote

Out of interest buickanddeere, are you an AME?
 
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