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nuckolls.bob(at)aeroelect
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 Posted: Wed Oct 09, 2013 7:04 pm Post subject: B-787 Li-Ion battery story continues |
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I've published a compendium of articles on the B787
battery story at:
http://tinyurl.com/ag2e9xk
but in particular, there's a recent addition that
adds a lot of useful information
http://tinyurl.com/lyc5845
Bob . . .
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jan_de_jong(at)casema.nl
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| Posted: Thu Oct 10, 2013 3:47 am Post subject: B-787 Li-Ion battery story continues |
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I am puzzled by the article of the recent addition, that states that a
li-ion battery is especially prone to destructive thermal runaway when
discharged.
I do not believe this is true, on the contrary.
Jan de Jong
On 10/10/2013 5:03 AM, Robert L. Nuckolls, III wrote:
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nuckolls.bob(at)aeroelect
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| Posted: Thu Oct 10, 2013 5:30 am Post subject: B-787 Li-Ion battery story continues |
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At 06:46 AM 10/10/2013, you wrote:
| Quote: |
I am puzzled by the article of the recent addition, that states that
a li-ion battery is especially prone to destructive thermal runaway
when discharged.
I do not believe this is true, on the contrary.
|
Can you elaborate? I've read from several sources that
the Li-Ion technologies are at greatest risk for unhappy
thermal events when they're discharged and then RECHARGED
without regard to their special needs.
The cell's tendency to dissipate heat internally is highest
when at a low state of charge (a state if higher internal
resistance?) is combined with legacy recharge philosophies
for allowing say a 60A alternator to run essentially full-bore to
bring the battery back up to full charge.
Hence, the "special chargers" that plug into dedicated
connectors on some products for the purpose of achieving
a fully charged battery after deep discharge.
I think this is the condition being described in the
article. It's also a condition that seems to be ignored
the literature by some suppliers of Li-Ion products.
It's a fundamental question to be explored about the
suitability of an Li-Ion product as a drop-in, plug-n-play
replacement for a lead-acid battery.
Boeing seems to have given due diligence to this
phenomenon by stating that a battery allowed to discharge
below some value is considered 'scrap' . . . hence the
multiple replacements of batteries in the field . . .
batteries that were retired much too early. I wonder if
these were 'recycled' in any way . . . perhaps returned
to a battery lab where they were carefully recharged and
perhaps returned to service?
I think I've read elsewhere that some suppliers of
commercial off the shelf Li-Ion batteries suggest that
a battery not be discharged below 30% of full capacity.
If this is good advice, then one would want to (1) either
select new batteries with 30% more headroom for capacity
in the endurance mode and then monitored for load-shedding
at 30% and/or (2) take extra care in recharging the
battery should you take it down too far . . . don't let
your alternator do it.
Our friends at Cessna are still sifting the simple-ideas
that drive this technology. I'll be working in the same
building with these folks which may add to my own
understanding along with some simple-ideas that can be
shared. Got to be careful here. Contractors
and employees alike sign non-disclosure agreements. But
no doubt, the simple ideas that drive the physics of
battery performance are not going to be any kind of
'secret' . . . these are the ingredients that drive
risks and successes in the marketplace and will have
to be well understood by everybody. There is still much to
learn my friends. I'll remain cautious with any advice I
have for dropping this technology into an OBAM aircraft.
Setting airplanes on fire is really bad for business.
Bob . . .
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jan_de_jong(at)casema.nl
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| Posted: Fri Oct 11, 2013 2:00 am Post subject: B-787 Li-Ion battery story continues |
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Hi Bob,
I agree. Over-discharging and then recharging at full speed is a
reported safety issue.
I wondered about the mention of discharge by itself ("starting an APU")
as a safety issue.
Maybe the increased internal resistance (50 to 100% increase at 15% SOC
I saw somewhere) makes it so.
On the other hand, the exothermal reaction starts more slowly and is
less violent in a discharged cell.
Bottom line - I should have kept my peace.
Jan de Jong
On 10/10/2013 3:29 PM, Robert L. Nuckolls, III wrote:
| Quote: |
<nuckolls.bob(at)aeroelectric.com>
At 06:46 AM 10/10/2013, you wrote:
>
> <jan_de_jong(at)casema.nl>
>
> I am puzzled by the article of the recent addition, that states that
> a li-ion battery is especially prone to destructive thermal runaway
> when discharged.
> I do not believe this is true, on the contrary.
Can you elaborate? I've read from several sources that
the Li-Ion technologies are at greatest risk for unhappy
thermal events when they're discharged and then RECHARGED
without regard to their special needs.
The cell's tendency to dissipate heat internally is highest
when at a low state of charge (a state if higher internal
resistance?) is combined with legacy recharge philosophies
for allowing say a 60A alternator to run essentially full-bore to
bring the battery back up to full charge.
Hence, the "special chargers" that plug into dedicated
connectors on some products for the purpose of achieving
a fully charged battery after deep discharge.
I think this is the condition being described in the
article. It's also a condition that seems to be ignored
the literature by some suppliers of Li-Ion products.
It's a fundamental question to be explored about the
suitability of an Li-Ion product as a drop-in, plug-n-play
replacement for a lead-acid battery.
Boeing seems to have given due diligence to this
phenomenon by stating that a battery allowed to discharge
below some value is considered 'scrap' . . . hence the
multiple replacements of batteries in the field . . .
batteries that were retired much too early. I wonder if
these were 'recycled' in any way . . . perhaps returned
to a battery lab where they were carefully recharged and
perhaps returned to service?
I think I've read elsewhere that some suppliers of
commercial off the shelf Li-Ion batteries suggest that
a battery not be discharged below 30% of full capacity.
If this is good advice, then one would want to (1) either
select new batteries with 30% more headroom for capacity
in the endurance mode and then monitored for load-shedding
at 30% and/or (2) take extra care in recharging the
battery should you take it down too far . . . don't let
your alternator do it.
Our friends at Cessna are still sifting the simple-ideas
that drive this technology. I'll be working in the same
building with these folks which may add to my own
understanding along with some simple-ideas that can be
shared. Got to be careful here. Contractors
and employees alike sign non-disclosure agreements. But
no doubt, the simple ideas that drive the physics of
battery performance are not going to be any kind of
'secret' . . . these are the ingredients that drive
risks and successes in the marketplace and will have
to be well understood by everybody. There is still much to
learn my friends. I'll remain cautious with any advice I
have for dropping this technology into an OBAM aircraft.
Setting airplanes on fire is really bad for business.
Bob . . .
|
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james(at)etravel.org
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| Posted: Fri Oct 11, 2013 3:36 am Post subject: B-787 Li-Ion battery story continues |
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Some interesting stuff in there Bob. Two things in particular stood out:
1) Are customers going to have the appetite for the increase in useful load when compared with the risk associated with the new battery technology, when such benign alternatives exist?
2) What is the wisdom of making things so different for ground crew on one Boeing aeroplane? It seems to be tempting fate by making ground operations different. In my line of work the non-functional requirements are often the ones that bite you, and perhaps this is a similar case.
James
On 10 October 2013 04:03, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
I've published a compendium of articles on the B787
battery story at:
http://tinyurl.com/ag2e9xk
but in particular, there's a recent addition that
adds a lot of useful information
http://tinyurl.com/lyc5845
Bob . . .
====================================
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ric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
====================================
MS -
k">http://forums.matronics.com
====================================
e -
-Matt Dralle, List Admin.
t="_blank">http://www.matronics.com/contribution
====================================
[b]
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peter(at)sportingaero.com
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| Posted: Fri Oct 11, 2013 4:40 am Post subject: B-787 Li-Ion battery story continues |
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I think Boeing have got themselves into a difficult place - possibly involving considerable politics.
Its clear the original decision was based on saving weight - I don't know what the value per pound would have been but I project I was involved with not too long ago was up to $10,000 per pound saved and was talking of going to $50K - that's development $$ spent to save one pound. A Li battery was probably very attractive and a low cost weight save. But the technology maturity assessment now seems to be inaccurate.
It has become clear that the actual in service weight saving is negligible with the extra metal work, the maintenance overhead is large, and the reputational impact for all concerned is is difficult to quantify. The big picture view seems to say fit a NiCad for a quiet life, I'm guessing that most airlines would accept a small weight increase (on a 260,000 lb airframe) - is the weight saving equation now around the other way? But what are the internal Boeing political implications of such a change? We'll probably never know ...
Its an interesting saga to watch from the outside and try to guess what is going on!
Peter
On 11/10/2013 12:35, James Kilford wrote:
[quote] Some interesting stuff in there Bob. Two things in particular stood out:
1) Are customers going to have the appetite for the increase in useful load when compared with the risk associated with the new battery technology, when such benign alternatives exist?
2) What is the wisdom of making things so different for ground crew on one Boeing aeroplane? It seems to be tempting fate by making ground operations different. In my line of work the non-functional requirements are often the ones that bite you, and perhaps this is a similar case.
James
On 10 October 2013 04:03, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[b]
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BobsV35B(at)aol.com
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| Posted: Fri Oct 11, 2013 8:50 am Post subject: B-787 Li-Ion battery story continues |
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Along that same venue, is the model T Ford really any better than a good horse? Is that new fangled and short lived electric light any better than those nice whale oil lamps we already have?
Inquiring minds want to know?
Happy Skies,
Old Bob
Do Not Archive
In a message dated 10/11/2013 11:17:36 A.M. Central Daylight Time, peter(at)sportingaero.com writes:
| Quote: | I think Boeing have got themselves into a difficult place - possibly involving considerable politics.
Its clear the original decision was based on saving weight - I don't know what the value per pound would have been but I project I was involved with not too long ago was up to $10,000 per pound saved and was talking of going to $50K - that's development $$ spent to save one pound. A Li battery was probably very attractive and a low cost weight save. But the technology maturity assessment now seems to be inaccurate.
It has become clear that the actual in service weight saving is negligible with the extra metal work, the maintenance overhead is large, and the reputational impact for all concerned is is difficult to quantify. The big picture view seems to say fit a NiCad for a quiet life, I'm guessing that most airlines would accept a small weight increase (on a 260,000 lb airframe) - is the weight saving equation now around the other way? But what are the internal Boeing political implications of such a change? We'll probably never know ...
Its an interesting saga to watch from the outside and try to guess what is going on!
Peter
|
[quote][b]
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edpav8r(at)yahoo.com
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| Posted: Fri Oct 11, 2013 8:58 am Post subject: B-787 Li-Ion battery story continues |
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All true. And GS Yuasa hasn't come out smelling of roses either!
Eric
do not archive
On Oct 11, 2013, at 5:40 AM, Peter Pengilly <peter(at)sportingaero.com (peter(at)sportingaero.com)> wrote:
[quote] I think Boeing have got themselves into a difficult place - possibly involving considerable politics.
Its clear the original decision was based on saving weight - I don't know what the value per pound would have been but I project I was involved with not too long ago was up to $10,000 per pound saved and was talking of going to $50K - that's development $$ spent to save one pound. A Li battery was probably very attractive and a low cost weight save. But the technology maturity assessment now seems to be inaccurate.
It has become clear that the actual in service weight saving is negligible with the extra metal work, the maintenance overhead is large, and the reputational impact for all concerned is is difficult to quantify. The big picture view seems to say fit a NiCad for a quiet life, I'm guessing that most airlines would accept a small weight increase (on a 260,000 lb airframe) - is the weight saving equation now around the other way? But what are the internal Boeing political implications of such a change? We'll probably never know ...
Its an interesting saga to watch from the outside and try to guess what is going on!
Peter
On 11/10/2013 12:35, James Kilford wrote:
| Quote: | Some interesting stuff in there Bob. Two things in particular stood out:
1) Are customers going to have the appetite for the increase in useful load when compared with the risk associated with the new battery technology, when such benign alternatives exist?
2) What is the wisdom of making things so different for ground crew on one Boeing aeroplane? It seems to be tempting fate by making ground operations different. In my line of work the non-functional requirements are often the ones that bite you, and perhaps this is a similar case.
James
On 10 October 2013 04:03, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
|
[b]
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