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Lithium batteries for OBAM aircraft

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dlj04(at)josephson.com
Guest

Posted: Sun May 12, 2013 5:53 pm Post subject: Lithium batteries for OBAM aircraft

I attended the Electric Aircraft Symposium put on by CAFE a few weeks 

ago. One of the speakers was Dr Eric Darcy of the NASA Johnson 

Spaceflight Center in Houston, on "Mitigating Catastrophic Failures with 

Li-ion Batteries." He has the task of figuring out how to change out the 

batteries in the International Space Station, and for now they are 

planning to use the same GS-Yuasa LVP lithium cobalt cells that are in 

the Boeing 787. As you might imagine, he's not quite ready to give the 

green light for using them in the Space Station.



We learned a lot about keeping lithium batteries from doing bad things, 

and about some things that amateurs can do to test cells for likely 

problems.  All variants (LiPo, LiFe, Li-poly etc.) have the same thermal 

runaway problem that seems to have been the failure mechanism in the 

incidents to date, some just take more abuse to start it. Besides that, 

the lithium cobalt chemistry (used in the 787, Tesla cars, laptops and 

many other applications) uses a flammable electrolyte that isn't used in 

the lithium/manganese or lithium/iron used in some others. He thought 

they were all just as dangerous, though, and were subject to all of the 

same problems.



Once the cell develops a short, all of its energy gets released as heat, 

potentially causing the neighboring cells to do the same. Of course the 

known limits for charge voltage and discharge current must be followed. 

You also need to avoid mechanical damage that could cause a short 

between the plates of the cell (drive a nail through and they will 

explode.) But the famous failures so far have probably not been due to 

any of those things. Dr. Darcy was clear to point out that he didn't 

know what happened with the 787 batteries but discussed failures that he 

had seen in many other cell types, both prismatic and "jelly roll." Two 

main events can happen: a small inclusion like a tiny snip of metal or 

dirt can be trapped in the separator between the battery plates that 

ultimately starts forming a current path between them, or the edges of 

the plates which are supposed to be overlapped by insulating material 

can come close to touching if they are misaligned, causing the same sort 

of contact.



Many of these cell failures can be caught long before the cell melts 

down, because each of these almost-short-circuits usually causes some 

discharge before the full battery current can flow. Darcy suggested two 

tests that anyone could do. One is when receiving a lot of cells, that 

have been partially charged and then shipped a long distance, measure 

the open circuit voltage of each one. They should all be very close to 

each other, like within 1%. The other test is to charge each cell to 

full capacity and then discharge to 10%, say 3.25 volts. Disconnect the 

charger and measure the open circuit voltage a few times a day for two 

weeks. Good cells will climb at a uniform rate back to their original 

voltage, suspect cells will have a very different curve, either much 

slower or much faster (typically followed by a droop). At the end of two 

weeks, trust the cells that are all clustered with the same open circuit 

voltage.



I would imagine that the folks packaging cells into aircraft batteries 

do some of this testing, but it's good to know that some simple methods 

can be used to check cells beforehand.



--

David Josephson

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henador_titzoff(at)yahoo.
Guest

Posted: Sun May 12, 2013 6:43 pm Post subject: Lithium batteries for OBAM aircraft

David,

Thanks for giving us insight on what Dr. Darcy said at the JSC on mitigating catastrophic failures with lithium batteries. I have the opinion that lithium batteries are not ready for prime time in aircraft, but I can always be talked out of it if someone has done sufficient analysis and testing to prove me wrong.  I see that Dr. Darcy isn't ready to install lithium cobalt batteries in the ISS.  I wonder if he would install them in his OBAM aircraft and  fly his family around?  I suspect not.

 I have a problem with his advice about how to detect cell failures.  We typically do not have access to cells, because they are packaged in series to build up the voltage to 12V+. I certainly wouldn't drill into the packaging material to measure individual cells. Therefore, we only have access to two points: GND and POS.  Without destroying the battery's usefulness, we can't perform the cell tests he mentioned.



Does anyone see it differently?

 

Henador Titzoff

        From: David Josephson <dlj04(at)josephson.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Sunday, May 12, 2013 9:51 PM

 Subject: Lithium batteries for OBAM aircraft

  

 

--> AeroElectric-List message posted by: David Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)>



I attended the Electric Aircraft Symposium put on by CAFE a few weeks 

ago. One of the speakers was Dr Eric Darcy of the NASA Johnson 

Spaceflight Center in Houston, on "Mitigating Catastrophic Failures with 

Li-ion Batteries." He has the task of figuring out how to change out the 

batteries in the  International Space Station, and for now they are 

planning to use the same GS-Yuasa LVP lithium cobalt cells that are in 

the Boeing 787. As you might imagine, he's not quite ready to give the 

green light for using them in the Space Station.



We learned a lot about keeping lithium batteries from doing bad things, 

and about some things that amateurs can do to test cells for likely 

problems.  All variants (LiPo, LiFe, Li-poly etc.) have the same thermal 

runaway problem that seems to have been the failure mechanism in the 

incidents to date, some just take more abuse to start it. Besides that, 

the lithium cobalt chemistry (used in the 787, Tesla cars, laptops and 

many other applications) uses a flammable electrolyte that isn't used in 

the lithium/manganese or lithium/iron used in some others. He thought 

they were all just as dangerous, though, and were subject to all of the 

same problems.



Once  the cell develops a short, all of its energy gets released as heat, 

potentially causing the neighboring cells to do the same. Of course the 

known limits for charge voltage and discharge current must be followed. 

You also need to avoid mechanical damage that could cause a short 

between the plates of the cell (drive a nail through and they will 

explode.) But the famous failures so far have probably not been due to 

any of those things. Dr. Darcy was clear to point out that he didn't 

know what happened with the 787 batteries but discussed failures that he 

had seen in many other cell types, both prismatic and "jelly roll." Two 

main events can happen: a small inclusion like a tiny snip of metal or 

dirt can be trapped in the separator between the battery plates that 

ultimately starts forming a current path between them, or the edges of 

the plates which are supposed to be overlapped by insulating material 

can  come close to touching if they are misaligned, causing the same sort 

of contact.



Many of these cell failures can be caught long before the cell melts 

down, because each of these almost-short-circuits usually causes some 

discharge before the full battery current can flow. Darcy suggested two 

tests that anyone could do. One is when receiving a lot of cells, that 

have been partially charged and then shipped a long distance, measure 

the open circuit voltage of each one. They should all be very close to 

each other, like within 1%. The other test is to charge each cell to 

full capacity and then discharge to 10%, say 3.25 volts. Disconnect the 

charger and measure the open circuit voltage a few times a day for two 

weeks. Good cells will climb at a uniform rate back to their original 

voltage, suspect cells will have a very different curve, either much 

slower or much faster (typically followed by a droop). At  the end of two 

weeks, trust the cells that are all clustered with the same open circuit 

voltage.



I would imagine that the folks packaging cells into aircraft batteries 

do some of this testing, but it's good to know that some simple methods 

can be used to check cells beforehan========================http://www.matronics.com/Nhttp://forums.ma                     &nbs//www.matronics.com/contribution" target="_blank">http://www.matronics.co==================

 

 

  

 [quote][b]

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rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Mon May 13, 2013 8:58 am Post subject: Lithium batteries for OBAM aircraft

David, " Disconnect the charger and measure the open circuit voltage a few times a day for two weeks." This would suggest to me that this technology, at least in airplanes, is completely immature. I don't know about you, but when I buy an SLA battery I ask the sales person if it's charged. If the answer is affirmative it goes in the airplane and VROOM! Just sayin'. 



Rick Girard

do not archive

 

On Sun, May 12, 2013 at 8:51 PM, David Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: David Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)>

  

 I attended the Electric Aircraft Symposium put on by CAFE a few weeks ago. One of the speakers was Dr Eric Darcy of the NASA Johnson Spaceflight Center in Houston, on "Mitigating Catastrophic Failures with Li-ion Batteries." He has the task of figuring out how to change out the batteries in the International Space Station, and for now they are planning to use the same GS-Yuasa LVP lithium cobalt cells that are in the Boeing 787. As you might imagine, he's not quite ready to give the green light for using them in the Space Station.

  

 We learned a lot about keeping lithium batteries from doing bad things, and about some things that amateurs can do to test cells for likely problems.  All variants (LiPo, LiFe, Li-poly etc.) have the same thermal runaway problem that seems to have been the failure mechanism in the incidents to date, some just take more abuse to start it. Besides that, the lithium cobalt chemistry (used in the 787, Tesla cars, laptops and many other applications) uses a flammable electrolyte that isn't used in the lithium/manganese or lithium/iron used in some others. He thought they were all just as dangerous, though, and were subject to all of the same problems.

  

 Once the cell develops a short, all of its energy gets released as heat, potentially causing the neighboring cells to do the same. Of course the known limits for charge voltage and discharge current must be followed. You also need to avoid mechanical damage that could cause a short between the plates of the cell (drive a nail through and they will explode.) But the famous failures so far have probably not been due to any of those things. Dr. Darcy was clear to point out that he didn't know what happened with the 787 batteries but discussed failures that he had seen in many other cell types, both prismatic and "jelly roll." Two main events can happen: a small inclusion like a tiny snip of metal or dirt can be trapped in the separator between the battery plates that ultimately starts forming a current path between them, or the edges of the plates which are supposed to be overlapped by insulating material can come close to touching if they are misaligned, causing the same sort of contact.

  

 Many of these cell failures can be caught long before the cell melts down, because each of these almost-short-circuits usually causes some discharge before the full battery current can flow. Darcy suggested two tests that anyone could do. One is when receiving a lot of cells, that have been partially charged and then shipped a long distance, measure the open circuit voltage of each one. They should all be very close to each other, like within 1%. The other test is to charge each cell to full capacity and then discharge to 10%, say 3.25 volts. Disconnect the charger and measure the open circuit voltage a few times a day for two weeks. Good cells will climb at a uniform rate back to their original voltage, suspect cells will have a very different curve, either much slower or much faster (typically followed by a droop). At the end of two weeks, trust the cells that are all clustered with the same open circuit voltage.

  

 I would imagine that the folks packaging cells into aircraft batteries do some of this testing, but it's good to know that some simple methods can be used to check cells beforehand.

 

 --

 David Josephson

 

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