How to fight a lithium battery fire

[2G]

So you own an electric glider with a sizeable lithium-based battery, how do you fight a battery fire? Experience with fighting electric car fires is not encouraging because you can't cut off the supply of oxygen to the fire like you can with a carbon fuel such as gasoline - the chemistry of the battery supplies its own oxygen.

There was a very large (mega) battery fire in OZ that took three days to extinguish. The fire really wasn't extinguished, just all of the lithium was consumed. Firefighters were given advice on how to fight the fire by Tesla, the batterie's designer, and UGL, the installer (https://www.theguardian.com/australia-news/2021/aug/02/tesla-big-battery-fire-in-victoria-burns-into-day-three):

“They are difficult to fight because you can’t put water on the mega packs … all that does is extend the length of time that the fire burns for.”

Firefighters have taken advice from experts including Tesla, the battery’s creators, and UGL, who are installing the battery packs.

“The recommended process is you cool everything around it so the fire can’t spread and you let it burn out,” Beswicke said.

It is somewhat like fighting large forest fires: you wait for Nature to put it out naturally with rain and/or snow, except worse. A fire in aircraft lithium battery pack will likely result in the complete destruction of the plane, even if it is on the ground when the fire started. If the fire starts while airborne your only option is to bail out (if you are not incapacitated by smoke first like the Taurus Electro fatal accident in NZ). The original GP-15 design did not provide for this option, but it is now included as an option. Obviously, the GP-15 designers had not thought thru the consequences of a battery fire.

Tom

[Eric Greenwell]

On 8/8/2021 4:00 PM, 2G wrote:
>
> It is somewhat like fighting large forest fires: you wait for Nature to put it out naturally with rain and/or snow, except worse. A fire in aircraft lithium battery pack will likely result in the complete destruction of the plane, even if it is on the ground when the fire started. If the fire starts while airborne your only option is to bail out (if you are not incapacitated by smoke first like the Taurus Electro fatal accident in NZ). The original GP-15 design did not provide for this option, but it is now included as an option. Obviously, the GP-15 designers had not thought thru the consequences of a battery fire.
>
> Tom

Please note that the cells, the battery packs, and their placement in the Taurus are
significantly different than in the GP15.

Anyone interested in the GP 15 should not rely on 2G's remarks, as he does not have any
particular knowledge of what the designers have thought about; instead, contact the dealer
for information, or the factory.

--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[2G]

Yeah, I probably don't know what the GP-15 battery pack design is because GP is redesigning the WHOLE GLIDER. So, neither does Eric. And if you go to GP's website you will learn nothing about it except that the batteries are lithium ion (ALL lithium batteries are "lithium ion"). Nonetheless, all lithium batteries share the common characteristic that they have oxygen atoms as an integral part of their chemistry, which makes fighting lithium battery fires so difficult (actually impossible).

One interesting thing on GP's website is:

GP 15 E/SE JETA
is the most sophisticated, multitask 15 m, electric self-launching GP GLIDER to date, designed and developed fully in-house.

This is precisely contrary to Schleicher's approach which, as Eric pointed out, uses experts in different disciplines from universities and industry. Let's face it: GP Glider's expert is ONE GUY! I honestly don't see how GP can do this "fully in-house."

Tom

[kinsell]

On 8/8/21 11:48 PM, 2G wrote:
> I honestly don't see how GP can do this "fully in-house."

Well they can't, that was just Marketing puffery.

They actually have MGM-Compro doing the electrical system, a company
with considerable experience in the area.

[krasw]

On Monday, 9 August 2021 at 02:00:46 UTC+3, 2G wrote:
> So you own an electric glider with a sizeable lithium-based battery, how do you fight a battery fire?
>

> A fire in aircraft lithium battery pack will likely result in the complete destruction of the plane, even if it is on the ground when the fire started. If the fire starts while airborne your only option is to bail out (if you are not incapacitated by smoke first like the Taurus Electro fatal accident in NZ).

> Tom

Wait didn't you just answer your question? Yes it burns like hell, and no you can't extinguish it before the fire burns trough the structure. Two solutions: 1) insure it and hope for the best, 2) don't buy it and fly pure gliders.

[wtwisn...@gmail.com]

Fire has never mixed well with airframes and probably never will. The goal is necessarily isolating the fire and its gas products. I don't see any solution other than holding the battery in an appropriate flameproof container that vents outside the glider. Perhaps a double walled box with insulation in between. A new glider design may make it possible to also eject the battery in flight or on the ground. There must be provision for an emergency landing and protecting most of the glider for future use would be nice. Bailing out is not an option in many circumstances. What are the solutions that allow certification of VTOL air taxis?

[Mark Mocho]

The FAA released a pretty good report in March 2017 entitled "Fire Hazard Analysis for Various Lithium Batteries." https://www.fire.tc.faa.gov/pdf/TC-16-17.pdf

It is fairly technical, but the conclusions are easily understood. I don't have a dog in this fight, as I probably won't ever be able to afford a motorglider, electric or not. I am basically happy to just rent an airplane for a six or seven minute tow and then fly around for five hours or so on the energy in the atmosphere. I get to look down on all the wind farms and solar arrays springing up in New Mexico. All of which pop up from magic beans and happy thoughts, with absolutely NO environmental impact at all. (Yes, that was sarcasm.)

[kinsell]

On 8/9/21 7:32 AM, Mark Mocho wrote:
> The FAA released a pretty good report in March 2017 entitled "Fire Hazard Analysis for Various Lithium Batteries." https://www.fire.tc.faa.gov/pdf/TC-16-17.pdf
>
> It is fairly technical, but the conclusions are easily understood. I don't have a dog in this fight, as I probably won't ever be able to afford a motorglider, electric or not. I am basically happy to just rent an airplane for a six or seven minute tow and then fly around for five hours or so on the energy in the atmosphere. I get to look down on all the wind farms and solar arrays springing up in New Mexico. All of which pop up from magic beans and happy thoughts, with absolutely NO environmental impact at all. (Yes, that was sarcasm.)
>

The article that Tom cited had a quote from the incident commander,
saying that the Australia fire was the first at an energy storage
facility like that.

Actually, there was one in Arizona, with cells made from our friends at
LG Chem, which are implicated in the GM and Hyundai car fires:

https://www.greentechmedia.com/articles/read/lg-chem-battery-cell-mcmicken-arizona-fire

They've also had five 'thermal events' in home storage systems.

A link in that article points out S. Korea has had 23 fires in energy
storage facilities, leading to a shutdown in 522 of the country's 1490
energy storage projects!

https://www.spglobal.com/marketintelligence/en/news-insights/trending/bVy2KGU3Opsle5Vv8QG0-Q2

Apparently this is what happens when governments start throwing around
big bucks to promote virtue signalling, instead of common sense and good
engineering practices.

-Dave

[Mike the Strike]

Many decades ago, I worked at a research lab where colleagues were developing a sodium/sulfur battery (molten sodium and molten sulfur separated by a porous ceramic membrane). It was abandoned after many years of development. I witnessed some of the fires, if you could call them that! (The firefighting technique was to run away as fast and as far as possible!)

I note that lithium is the metal next to sodium on the periodic table, but inside a battery is probably orders of magnitudes safer than molten sodium! However, as a seasoned Luddite, all my glider batteries are still lead acid.

Mike

[Kenn Sebesta]

On Monday, August 9, 2021 at 7:26:49 AM UTC-4, wtwisn...@gmail.com wrote:
> Fire has never mixed well with airframes and probably never will. The goal is necessarily isolating the fire and its gas products.

I think this is about the best comment here. I am unaware of any plan to extinguish fuel tank fires in aircraft, and the tragic tale of TWA 800 shows the consequences. We have learned through many years to manage the risk of gasoline and other flammables.

The energy required for self-launching a 500kg plane is on the order of 200mL of gasoline so it's easy to think this is a much more manageable problem than it seems at first glance.

(If three days for a massive battery farm sounds like a long time, consider that it took *two years* to extinguish a tire fire in California: https://www.sfgate.com/bayarea/article/After-2-Years-Smoking-Tires-Close-to-3236405.php. And we're still dealing with the fire consequences of Chernobyl and Fukushima. In general, anytime you concentrate energy, the fires last for a long time.)

When it comes to managing lithium fires, it must be understood that the lithium fire is not the problem but the problem's source. Think of it like a fire starter cube you'd throw under the charcoal to get the charcoal fire going. You can't really extinguish the firestarter (battery) once it's going, but if you can keep it from igniting the charcoal (airframe), then once it source burns itself out you've dodged a bullet. And it will burn itself out somewhat quickly, as the amount of oxygen generated inside the decomposing battery is not that much.

If the battery is fuselage-mounted[*], there are two possible routes which come to mind for doing this. One is to eject the battery, and the other is place it in an airtight and fireproof box with a vent to the outside. Ejecting the battery can be dicey because of its impact on the CG, but venting the battery to the outside sounds plausible.

The design we're considering is a large metal tube with a pressure release valve. If a battery starts outgassing, then the pressure rises and the valve pops, allowing the hot gasses to escape to the underside of the aircraft. A variety of strategies for fireproofing the box are things such as intumescent paint or simply wrapping it in ceramic insulation.

[*] If the battery is wing-mounted you have as many options as the towplane with its 50gal of gasoline does: none.

[2G]

These incidents should be sobering for anyone considering an electric MG. These battery farms are controlled environment installations not subjected to the shock, vibration and altitude of aircraft use. And even given the onsite monitoring inherent to these facilities, they can't definitively identify the root cause of the fire.

Also troubling is the lithium dendritic growth failure mechanism, which creates an internal short in the cell, which leads to thermal runaway. Well, there's good news! The root cause of dendritic growth has been found by my former employer, the Pacific Northwest National Laboratory. But, wait, there is also bad news: the culprit is ethylene carbonate, an indispensable solvent added to the electrolyte to achieve the necessary energy densities (https://www.sciencedaily.com/releases/2019/10/191014111723.htm). PNNL is working on alternatives to ethylene carbonate with promising alternatives, but current generation batteries still use it and probably will for some time.

Tom

[kinsell]

Interestingly, the same folks involved in the 2019 Arizona fire had a
pilot project go up in flames in 2012. Apparently there were more
lessons to be learned. Maybe third time's a charm?

https://www.spglobal.com/marketintelligence/en/news-insights/latest-news-headlines/burning-concern-energy-storage-industry-battles-battery-fires-51900636

But there's hope on the way, IEEE says the dreaded sodium isn't so
dangerous after all, it offers promise for large scale storage projects
even cheaper and safer than lithium.

https://spectrum.ieee.org/sodium-ion-battery

Probably about two years away.

-Dave

[Herbert Kilian]

Tom, this may have been the by far largest Lithium battery fire in history, it just happened at the end of June in Morris IL, about 10 miles from the Chicago Glider Club. Start at the bottom, notice that the fire was never extinguished but burned out, all 184,000 lbs of batteries. It took about 4 days, a retardant called Purple K was used by the fire department but without visible success. The warehouse this happened at was an illegal storage and Internet sales operation and had all sizes of batteries in it.
https://response.epa.gov/site/site_profile.aspx?site_id=15259
Herb

[Eric Greenwell]

On 8/9/2021 3:17 PM, 2G wrote:
> On Monday, August 9, 2021 at 7:06:38 AM UTC-7, kinsell wrote:

...

>> The article that Tom cited had a quote from the incident commander,
>> saying that the Australia fire was the first at an energy storage
>> facility like that.
>>
>> Actually, there was one in Arizona, with cells made from our friends at
>> LG Chem, which are implicated in the GM and Hyundai car fires:
>>
>> https://www.greentechmedia.com/articles/read/lg-chem-battery-cell-mcmicken-arizona-fire
>>
>> They've also had five 'thermal events' in home storage systems.
>>
>> A link in that article points out S. Korea has had 23 fires in energy
>> storage facilities, leading to a shutdown in 522 of the country's 1490
>> energy storage projects!
>>
>> https://www.spglobal.com/marketintelligence/en/news-insights/trending/bVy2KGU3Opsle5Vv8QG0-Q2
>>
>> Apparently this is what happens when governments start throwing around
>> big bucks to promote virtue signalling, instead of common sense and good
>> engineering practices.
>>
>> -Dave
>
> These incidents should be sobering for anyone considering an electric MG. These battery farms are controlled environment installations not subjected to the shock, vibration and altitude of aircraft use. And even given the onsite monitoring inherent to these facilities, they can't definitively identify the root cause of the fire.
>
> Also troubling is the lithium dendritic growth failure mechanism, which creates an internal short in the cell, which leads to thermal runaway. Well, there's good news! The root cause of dendritic growth has been found by my former employer, the Pacific Northwest National Laboratory. But, wait, there is also bad news: the culprit is ethylene carbonate, an indispensable solvent added to the electrolyte to achieve the necessary energy densities (https://www.sciencedaily.com/releases/2019/10/191014111723.htm). PNNL is working on alternatives to ethylene carbonate with promising alternatives, but current generation batteries still use it and probably will for some time.
>
> Tom

At the end of March, Schleicher had over 60 orders for the AS33 and AS34; JS also has
"many" orders for their JS3 with electric self-launch. This indicates a very strong
interest in electric propulsion. Are these pilots fools to take what Tom thinks are huge
risks? Or are they correct to believe that AS and JS are demonstrably competent sailplane
designers and manufacturers that have a good safety record, and would not put their
customers at undue risk? That they have carefully evaluated the technology and implemented
it with their resources, and those of multiple experienced individuals and companies?
That's an easy question for me: go with AS or JS.

And for anyone that feels fires in huge power stations is relevant to glider design, I
suggest you stay away from gasoline engine self-launchers, because huge refineries making
gasoline have exploded and burned with incredibly intense heat all around the world.

[Eric Greenwell]

How about a 6 foot long metal tube/tray (doesn't have to be round) that slides into the D
tube in the wing? Having the tube in the wing, with external venting, would keep battery
gases out of the cockpit.

There is plenty volume in that area, and it could hold 200+ 18650 cells easily, over 2.2
kWh. Or use a high temperature composite if the tray needs to be a complex shape. The
interior of the D tube (or the exterior of the tray) could be painted with intumescent
paint to protect the wing. A fire suppression system that released gas into the tray
during a cell fire might keep the composite tube from burning until the cell's energy was
exhausted.

[Christoph Barniske]

I'm one of these fools who ordered an electric self-launcher :-). I am also a bit sceptic about electric cars being the solution to all future mobility problems. But in case of self-launching gliders, I am convinced that electric propulsion is a significant improvement of current technology available in gliding, both in terms of reliability and operational safety. I did not place the order for environmental reasons.

Our Ventus2cM has a fire warning light in its panel, for a reason. A lot of fire potential is stored behind my back (or in troublesome plastic bags inside of the wings) and there were quite a few instances where the combustion process took place outside of the engine of self-launching motorgliders. But what worries me more is the operational and technical complexity of the engine system itself. We do the annualy checks quite thoroughly and there is always something to be adjusted, replaced or repaired. Sure, Li-Ion batteries will have to be treated with care. But the same goes for the fuel system in any other motorglider.

The glider manufacturers have different safety concepts about storing the batteries on board. To me, storing the batteries in the wings with wider separation between the cells seemed the best mitigation towards the risk of a battery fire.

[2G]

Obviously I haven't called anyone a "fool" as Eric suggests. This subject is very complex, even for a degreed electronic engineer, such as myself, because it is multidisciplinary. Indeed, I am in the learning mode on this subject, and the more I learn the more concerned I get. The Pipistrel Taurus Electro fatal accident was a real eye-opener for me, both in how a hard landing can trigger a battery failure and an on-board fire that incapacitates the pilot in seconds.

The difference between batteries and fuel is that fuel does not spontaneous combust in the fuel tank. If you have a fire you can shut off the fuel valve which cuts off the fuel supply to the fire. And gasoline fires can be fought with standard fire extinguishers, while lithium battery fires cannot (which was the original subject of this thread).

I have no knowledge as to what battery chemistry either Schleicher or Jonkers is using, but it is very likely that it includes the problematic ethylene carbonate. German interest in electric motorgliders is being driven, in part, by their airport noise abatement regulations. Perhaps a German MG owner can expound more on this.

Finally, as I have said before, we are all adults here (mostly) and must make our own decisions about equipment and safety. I am merely presenting the scientific and accident evidence on the subject - whether you even read it, let alone follow it, is entirely up to you.

Tom

[kinsell]

Not sure what gas you would propose to suppress a fire, but it wouldn't
be effective. In the warehouse fire Herb noted, they tried dumping 28
tons of dry concrete powder on the batteries, they kept right on burning.

Interesting video from Germany, with typical Teutonic efficiency, they
rollout the big RedBox to deal with a car fire. They must have done this
before.

https://www.youtube.com/watch?v=2W4NzUQffcE

[Martin Gregorie]

Looks like a BMW i3, so an 18-38 kWh battery and 80 - 150 mile range
without the range extender which was, originally a 650cc petrol generator
pack and, later models, just a bigger battery extending the range to 200
miles. In case you're wondering, my neighbour has one of the older ones
with the 650cc range extender generator pack.



--
--
Martin | martin at
Gregorie | gregorie dot org

[Eric Greenwell]

On 8/10/2021 2:34 PM, kinsell wrote:
>> There is plenty volume in that area, and it could hold 200+ 18650 cells easily, over 2.2
>> kWh. Or use a high temperature composite if the tray needs to be a complex shape. The
>> interior of the D tube (or the exterior of the tray) could be painted with intumescent
>> paint to protect the wing. A fire suppression system that released gas into the tray
>> during a cell fire might keep the composite tube from burning until the cell's energy
>> was exhausted.
>
>
> Not sure what gas you would propose to suppress a fire, but it wouldn't be effective.  In
> the warehouse fire Herb noted, they tried dumping 28 tons of dry concrete powder on the
> batteries, they kept right on burning.

CO2 maybe, just something to keep the composite tube from burning, to help move the hot
gases to the external vent, and is compatible with cell gases, It's not something intended
to extinguish the cell fire, but to mitigate the effects of the fire. The situation I
described was one cell, not 100 TONS of batteries!

I wonder what that mountain of batteries cost, and owner of the batteries (and the
building) said he didn't have insurance.

[Tony]

Eric - the D-tube area is primary structure...if you can only paint it white I think you can forget about using it for heat containment. Just bail out!

[Martin Gregorie]

On Tue, 10 Aug 2021 15:39:24 -0700, Eric Greenwell wrote:

> On 8/10/2021 2:34 PM, kinsell wrote:
>> Not sure what gas you would propose to suppress a fire, but it wouldn't
>> be effective.  In the warehouse fire Herb noted, they tried dumping 28
>> tons of dry concrete powder on the batteries, they kept right on
>> burning.
>
> CO2 maybe, just something to keep the composite tube from burning, to
> help move the hot gases to the external vent, and is compatible with
> cell gases, It's not something intended to extinguish the cell fire, but
> to mitigate the effects of the fire. The situation I described was one
> cell, not 100 TONS of batteries!
>

I don't think what gas you use matters much provided it doesn't contain
oxygen and isn't flammable: nitrogen is probably as good as any and
cheaper than a lot of other possibilities. Colder would be better too.

[2G]

Any fire in that tube is going to generate very high temperatures very quickly that will heat up the rest of the cells in the tube. Obviously, adjacent cells will get the brunt of the heat, but the only way to vent the gases is out the ends of the tube structure. A necessary test during development is setting one cell on fire and measuring the temperatures of the other cells in the tube. The tube would have to be metal because of the temperatures. These battery fires go very quickly as the video shows, so an emergency landing is likely not possible unless you are on short final - bailing out is a better option if you are high enough. A BRS would only make things worse.

To repeat myself, lithium battery fires CANNOT be "put out," only slowed down until all of the fuel is consumed, because they inherently provide their own oxygen. Pouring A LOT of water on a battery fire MAY keep adjacent cells below the critical combustion temperature while the burning cells complete their combustion. This seems unlikely if they are sealed up in a tube inside a wing.

Tom

[AS]

>
> Interesting video from Germany, with typical Teutonic efficiency, they
> rollout the big RedBox to deal with a car fire. They must have done this
> before.
>
> https://www.youtube.com/watch?v=2W4NzUQffcE

No, they haven't! As the gentleman from 'OelWehr', who spoke last explained, this was the first 'hot' application of this Red Box. They had practiced with another car before, which was not on fire but this was the first real one for them. He mentioned that the container was specifically built for this application and that is has been tested to make sure it is leak-proof, since the e-vehicle will remain flooded for 24 hours. The company is also equipped to dispose of the water after the cool-down period in an environmentally safe and approved way.

Uli
'AS'

[AS]

> > https://www.youtube.com/watch?v=2W4NzUQffcE
> Looks like a BMW i3, so an 18-38 kWh battery and 80 - 150 mile range
> without the range extender which was, originally a 650cc petrol generator
> pack and, later models, just a bigger battery extending the range to 200
> miles. In case you're wondering, my neighbour has one of the older ones
> with the 650cc range extender generator pack.
>
>
>
> --
> --
> Martin | martin at
> Gregorie | gregorie dot org

No, Martin - it is an Opel (GM) model, not a BMW. ;-)
Take a look at the video at time stamp 12:50.

Uli
'AS'

[Eric Greenwell]

The battery tube could be insulated in a number of ways, and perhaps provided with a
sufficient flow of CO2 or similar through the interior to carry heat away. The D tube in
the battery area could be made of high temperature carbon composite (eg, prepreg that
cures at 150C/300F) so it would retain it's strength longer, and made stronger to allow
for high temperatures. The interior of the D tube could be painted with intumescent paint
to provide additional insulation at the hot spot.

All those features can buy time. With a 1500 fpm descent rate (full spoilers), you'd need
7 minutes to descend 10,000'. Is seven minutes enough? Calculations and testing would be
needed to know.

[Eric Greenwell]

Did you read the OSTIV presentation that Dave Nadler referenced? It indicated keeping the
adjacent cells from thermal runaway was not difficult for 18650 cells with adequate
spacing, given the relatively small energy in each cell. It did not even propose a metal case.

[2G]

Yes, I read it, and no, you HAVE to test it - opinions are best left to the opinion page of the newspaper. Nothing but metal will melt and catch fire itself, and, then, the wrong kind of metal will melt - perhaps you should look at pictures of the aftermath of electric car fires.

Tom

[2G]

Does this answer your question?
"Fire ignition establishes that the cathode of the battery can catch fire. The burning lithium creates a metal fire existing at temperatures of 2,000 degrees Celsius/3632 degrees Fahrenheit. Attempting to douse the fire with water is inadvisable since this could lead to a hydrogen gas explosion!"

https://www.envistaforensics.com/blog/electrical-fires-what-you-need-to-know-about-lithium-ion-batteries/#:~:text=Fire%20ignition%20establishes%20that%20the,degrees%20Celsius%2F3632%20degrees%20Fahrenheit.

[Martin Gregorie]

On Tue, 10 Aug 2021 16:34:45 -0700, AS wrote:

> No, Martin - it is an Opel (GM) model, not a BMW. ;-)
> Take a look at the video at time stamp 12:50.
>

Happy to take your word for that. What battery capacity does that model
have?

[AS]

Hi Martin - I had to look up the model myself - GM doesn't sell this vehicle over here in the US. The German Opel site shows this as a 'Mokka' and it has a 50kWh battery.
https://www.opel.de/fahrzeuge/mokka-modelle/mokka-e/uebersicht.html
One paragraph talks about '216 high density cells with the most advanced thermal management system for maximum range and longevity'.
Well - I guess that didn't work out well for at least that one car .... ;-)

Uli
'AS'

[Kenn Sebesta]

You make a good point, I will back off my assertion that there are no effective fire mitigation strategies for a wing-mounted battery. What I should say is that any successful strategy for the wing will be the fruit of a lot of R&D. This likely has to be paid for by a grant because there's nothing patentable about testing to destruction in order to figure out the right blend of spacing, isolation, insulation, and fire resistant material.

We could easily imagine compartmentalizing the batteries into many fireproof bays, each with individual venting. Maybe even blow-off caps which fully open the bay preventing preventing gasses from spreading laterally. But this kind of product testing won't be done by individuals upgrading their existing gliders nor by manufacturers already struggling to stay in business.

In the meanwhile, awaiting the grant to do the fundamental research, I think we can work with mitigation of wing-mounted battery fires. If you have a fire at >1000', bail out. If it's at fewer than 1000', the airframe only needs to survive 60 seconds. (I have the same strategy in my gasoline self-launcher, which places a hot engine next to a 2gal gas tank.)

It goes without saying that a plane with stored energy is more flammable than one without. Getting a plane up in the air takes releasing that stored energy at some point in the pipeline, and I like to think we're not so egocentric as to assume that it's okay for the tow-pilot to take this fire risk, but not we.

[kinsell]

Described as an Opal Ampera-E at this website (European version of the
Chevy Bolt)

https://electrek.co/2021/07/28/everything-we-know-about-the-chevy-bolt-ev-fires/

[AS]

Interesting! Thanks for the correction.

Uli
'AS'

[Dan Marotta]

Was the point of that video to show how difficult (impossible) it was to
douse the fire?  Because the crash didn't start the fire nor did kicking
the battery.  In fact, they had to shove a tray of burning gasoline
under the car for a while to get the fire to start.

Dan
5J

On 8/11/21 7:26 AM, AS wrote:

[Eric Greenwell]

On 8/10/2021 9:59 PM, 2G wrote:

>>> Did you read the OSTIV presentation that Dave Nadler referenced? It indicated keeping the
>>> adjacent cells from thermal runaway was not difficult for 18650 cells with adequate
>>> spacing, given the relatively small energy in each cell. It did not even propose a metal case.
>>> --
>>> Eric Greenwell - USA
>>> - "A Guide to Self-launching Sailplane Operation"
>>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>> Yes, I read it, and no, you HAVE to test it - opinions are best left to the opinion page of the newspaper. Nothing but metal will melt and catch fire itself, and, then, the wrong kind of metal will melt - perhaps you should look at pictures of the aftermath of electric car fires.
>>
>> Tom
>
> Does this answer your question?
> "Fire ignition establishes that the cathode of the battery can catch fire. The burning lithium creates a metal fire existing at temperatures of 2,000 degrees Celsius/3632 degrees Fahrenheit. Attempting to douse the fire with water is inadvisable since this could lead to a hydrogen gas explosion!"
>
> https://www.envistaforensics.com/blog/electrical-fires-what-you-need-to-know-about-lithium-ion-batteries/#:~:text=Fire%20ignition%20establishes%20that%20the,degrees%20Celsius%2F3632%20degrees%20Fahrenheit.
>

No, it doesn't, because I haven't even mentioned water. But you have answered my question
about reading the OSTIV article. Their opinion was based on tests they ran, and their
opinion is shared by others: 18650 cells in battery packs can be spaced so that a runaway
cell does not cause runaway in the cells adjacent to it. It is much easier to protect a
pack from one burning cell than several cells, and that's one reason car batteries are not
good comparison to glider use: the cells in car batteries are packed much more densely
than they are in glider packs. More pertinent to gliders is the Antares, which uses
cylindrical cells: 17 years since the first delivery, and no battery fires.

[AS]

On Wednesday, August 11, 2021 at 10:15:04 AM UTC-4, Dan Marotta wrote:
> Was the point of that video to show how difficult (impossible) it was to
> douse the fire? Because the crash didn't start the fire nor did kicking
> the battery. In fact, they had to shove a tray of burning gasoline
> under the car for a while to get the fire to start.
>
> Dan
> 5J

Hi Dan - we must be talking about two different videos here. The vehicle in the 'Red Box' video was parked at a charging station. They showed the signage pointing out that this is a spot reserved for e-vehicles during charging. In the link kinsell provided, you can find the narrative by the owner of the 'Langenfeld Fire'. He confirmed that the vehicle was on charge and that it sent him two text messages when the fire started and during the fire fighting activities, informing him of theft and break-in.
There was no crash or tray of gasoline involved here.

Uli
'AS'

[Martin Gregorie]

So, BTW, were the Lithium battery packs that, a few years ago, were self-
combusting in Boeing 787s. Has anybody seen what Boeing's end solution
was?

IIRC their initial change was to fireproof the area containing the
battery pack and add a conduit that would vent the smoke etc overboard
while the battery burnt itself out. Their original battery was densely
packaged in a steel casing, i.e. a very similar arrangement to the self-
launching glider battery packs that caught fire, but I haven't heard
whether they redesigned it later.

[Eric Greenwell]

On 8/11/2021 6:51 AM, Kenn Sebesta wrote:
> On Tuesday, August 10, 2021 at 4:16:26 PM UTC-4, Eric Greenwell wrote:

...

> You make a good point, I will back off my assertion that there are no effective fire mitigation strategies for a wing-mounted battery. What I should say is that any successful strategy for the wing will be the fruit of a lot of R&D. This likely has to be paid for by a grant because there's nothing patentable about testing to destruction in order to figure out the right blend of spacing, isolation, insulation, and fire resistant material.
>
> We could easily imagine compartmentalizing the batteries into many fireproof bays, each with individual venting. Maybe even blow-off caps which fully open the bay preventing preventing gasses from spreading laterally. But this kind of product testing won't be done by individuals upgrading their existing gliders nor by manufacturers already struggling to stay in business.
>
> In the meanwhile, awaiting the grant to do the fundamental research, I think we can work with mitigation of wing-mounted battery fires. If you have a fire at >1000', bail out. If it's at fewer than 1000', the airframe only needs to survive 60 seconds. (I have the same strategy in my gasoline self-launcher, which places a hot engine next to a 2gal gas tank.)
>
> It goes without saying that a plane with stored energy is more flammable than one without. Getting a plane up in the air takes releasing that stored energy at some point in the pipeline, and I like to think we're not so egocentric as to assume that it's okay for the tow-pilot to take this fire risk, but not we.
>

I don't think it'd be that hard at all: my casual search came across several studies and
articles on just this problem (The OSTIV reference is one of them, Feb 2018 Soaring
article on AS efforts is another), so some those may be enough to get a jump start on the
tray design. Even better, find out what AS is doing for their wing mounted batteries in
the AS33/34. AS or one of owners could send pictures of the battery packs and copies of
useful pages from the manuals. That might be all you need to know.

If you want to invent it all, then ...
- sketch the basic tray you'd use, build a one foot section of it, populate with cells,
trigger thermal runaway in the cell in the most critical location. After a few tests, you
will likely know what the tray materials need to be, if insulation is needed, and if you
have the inter-cell spacing right.
- trigger cells a few times in a volume about the same as the tray to get the pressures
and gas volumes a runaway cell produces. Now you can do the basic design for venting the
tray externally. I'm guessing a 4" x 6" g flap on the bottom of the wing, normally held
closed by a weak spring, would be sufficient.

[Martin Gregorie]

I checked what Wikipedia had to say about Opel cars:
https://en.wikipedia.org/wiki/Opel#Current_model_range

That says that the Mokka is an petrol or diesel SUV, sold in the US as
the Buick Encore.

However, there is an externally similar car, the Opel Ampera/
Ampera-e, which is a rebadged Chevrolet Bolt. The latter is known to be
inflammable: two recalls so far, the second for catching fire while being
charged. - saw that in Ars Technica, 7/23/2021

At one point in the video it looks as though there's a charger on the
sidewalk near the front of the burning Opel, so is it possible it was on
charge when it caught fire? The Bolt's charging socket is just behind the
top of the front left wheel arch.

[kinsell]

On 8/11/21 10:54 AM, Martin Gregorie wrote:

> So, BTW, were the Lithium battery packs that, a few years ago, were self-
> combusting in Boeing 787s. Has anybody seen what Boeing's end solution
> was?
>
> IIRC their initial change was to fireproof the area containing the
> battery pack and add a conduit that would vent the smoke etc overboard
> while the battery burnt itself out. Their original battery was densely
> packaged in a steel casing, i.e. a very similar arrangement to the self-
> launching glider battery packs that caught fire, but I haven't heard
> whether they redesigned it later.
>
>

They separated the cells a bit, and used a stainless steel containment
box vented to the outside with blowout plugs. That was their final
'solution'.

AFAIK, the FES folks have always used a carbon fiber box for their
batteries. They do recommend stainless steel boxes for transporting the
batteries in cars.

[Dan Marotta]

Thanks Uli.  I guess I clicked on the wrong link.

Dan
5J

[Kenn Sebesta]

> I don't think it'd be that hard at all: my casual search came across several studies and
> articles on just this problem (The OSTIV reference is one of them, Feb 2018 Soaring
> article on AS efforts is another), so some those may be enough to get a jump start on the
> tray design. Even better, find out what AS is doing for their wing mounted batteries in
> the AS33/34. AS or one of owners could send pictures of the battery packs and copies of
> useful pages from the manuals. That might be all you need to know.
>
> If you want to invent it all, then ...
> - sketch the basic tray you'd use, build a one foot section of it, populate with cells,
> trigger thermal runaway in the cell in the most critical location. After a few tests, you
> will likely know what the tray materials need to be, if insulation is needed, and if you
> have the inter-cell spacing right.
> - trigger cells a few times in a volume about the same as the tray to get the pressures
> and gas volumes a runaway cell produces. Now you can do the basic design for venting the
> tray externally. I'm guessing a 4" x 6" g flap on the bottom of the wing, normally held
> closed by a weak spring, would be sufficient.

I don't disagree with the approach, but proving it out at a variety of cell configurations, altitudes, and environmental conditions inevitably takes a lot of money and time. There's just a lot of question marks and we need a large body of evidence before we can be sure we've fully understood the problem.

Much of it might come from modeling, but at a certain point we've got to intentionally sabotage the batteries in flight and then test the wings to destruction to ensure the models are correct. I don't know how many airframes I would want to see go through this process, but I suspect at least 5 before we can truly be sure we've found the edge cases. That gets pricey.

I'm not saying it won't work if you don't do the testing and just rely on the literature, but there will inevitably be lessons to be learned about our specific use case, and I don't think we want to trust our safety to an untested concept when we can simply bail out.

The reason why venting is straightforward in a fuselage is because we can vent everything through just one tube and we don't (necessarily) need to keep the fire from spreading between cells because we can do a much better job of insulating the batteries. So every test can be a worst-case test and in the event of a fire it's much easier, relative to a wing skin and spar, to inspect and repair the fuselage before reuse.

[Hank Nixon]

It would not seem to be a good idea to use a conductive box to contain pouch type cells that could be prone to abrasion and shorting.
I suspect that the new boxes in the FES gliders are glass. The box in my electric ASW-24E is glass. I'm using 18650 cells.
"Nail tests" have been done on grouped 18650 cells that did not exhibit runaway when a cell was shorted. Soaring magazine had a photo of
such a test.
FWIW
UH

[Eric Greenwell]

That's the Feb 2018 issue. From the article "Electric Propulsion in Gliders Is More Than
an Alternative to Traditional Combustion Engines"

"The temperature near the nailed cell was measured with a thermocouple, and indicated >
500C. These tests have been made several times. At no time was there a chain reaction
leading to thermal runaway or short-circuit of surrounding cells. The voltage level of the
cell package after the test was nearly the same as before. Figure 15 shows different cell
packages after a nail-test."

[2G]

Here is the report on the Arizona ESS fire:
https://www.aps.com/-/media/APS/APSCOM-PDFs/About/Our-Company/Newsroom/McMickenFinalTechnicalReport.ashx?la=en&hash=50335FB5098D9858BFD276C40FA54FCE

I draw your attention to section 3.2 How thermal runaway is different from a fire. The point out that a chemical reaction takes place that requires no O2 whatsoever. They continue on and make this point:

"In fact, the potential of a non-flame thermal runaway event creates a scenario where high heat and combustible gases can coexist without igniting."

This happened at the McMicken facility, which ultimately resulted in an explosion that blew the doors off the compartment (fig. 5). The entire event was triggered by the failure of a single cell in one rack. And they had a fire suppression system - that was triggered - which had no effect on the fire whatsoever.

The batteries in the NZ Taurus Electro were in a metal container which was blown open, catapulting the cells in all directions. This points to an explosive event.

This report was referenced in the McMicken report, detailing the generation of toxic gases in a lithium thermal runaway (I am going to stop using the word "fire" to describe this event because it is inaccurate and misleading):
https://www.nature.com/articles/s41598-017-09784-z.pdf
One, or more, of these gases is likely what incapacitated the pilot of the Taurus. I am not sure that wing mounted batteries would be that much better because there are openings between the wing root and the fuselage for control linkages and water ballast controls.

I checked the Schleicher website to see what type of battery chemistry is used in the AS 34 Me, but they only mention battery capacity (probably don't want to divulge design secrets). I sent an email to GP Gliders to see what battery chemistry and cell manufacturer they are using and got no reply. This secretiveness will make it more difficult to independently assess battery safety. They will probably have to be more forthcoming to EASA, however.

Tom

[Kenn Sebesta]

That points toward a LiFePo4 cell. Those are notoriously stable, to the point that causing a physical breach hardly affects their internal voltage.

LiFePo4 are popular in busses and other EVs which require frequent power surges. The takeoff and initial climbout of a glider are a natural fit for them, although their power density is 20-40% lower than other lithium batteries so they have their limitations.

I applaud your careful reading and study of the science and experience, as they show the daily truth for the billions of lithium batteries out there. I encourage you to join myself and others in not engaging with those who wear their confirmation bias too proudly. They shout out there was an explosion in NZ, despite the accident report to the contrary: https://www.aviation.govt.nz/assets/publications/fatal-accident-reports/ZK-GEL-Final-Report-7-December-2020.pdf. They would have us believe that every cell is an inevitable catastrophe, despite that in the APS Arizona thermal runaway event four of the five primary contributing factors were insufficient design and insufficient response.

Those who have expressed clearly they have no interest in being part of the future have little role to play in a conversation about how we're going to get there.

[Eric Greenwell]

On 8/11/2021 5:42 PM, 2G wrote:
> On Wednesday, August 11, 2021 at 3:23:38 PM UTC-7, Eric Greenwell wrote:

...

The Jeta uses VTC6 cells (18650 cells), formerly made by Sony, now made by Murata. It's
not a secret, GP are just poor communicators. I contacted JS about their cells, and didn't
get an answer, but I don't think their chemistry is secret, either. The Taurus had lithium
polymer cells, either pouches or prismatic - very different from the cylindrical 18650
cells Li-ion cells I've been talking about. Same for the BESS - it used pouch cells.

Wing mounted batteries are in the D tube ahead of the spar; the control linkages are
behind the spar. The D tube can be sealed off from the fuselage, and vented out of the wing.

Here's a quote from the McMicken BESS report:

"Another method for mitigating cascading thermal runaway in battery design is to use
smaller cells and compartmentalization of batteries. Put simply, limited mass means
limited fuel, and limited fuel means less energy released over time, which in turn
decreases the overall power of the event."

That's what I'm talking about: 18650 cells have low mass (45g) and can be easily spaced to
prevent a runaway cell from triggering runaway in adjacent cells. There are plenty of
articles on avoiding cascading runaway with 18650 cells that are spread out, as they are
in a battery pack in the wing.

[Arne Martin Güettler]

On Thursday, 12 August 2021 at 06:37:47 UTC+2, Eric Greenwell wrote:
> The Jeta uses VTC6 cells (18650 cells), formerly made by Sony, now made by Murata. It's
> not a secret, GP are just poor communicators. I contacted JS about their cells, and didn't
> get an answer, but I don't think their chemistry is secret, either.

JS lists in their FAQ what batteries they use for their RES system (https://jonkersailplanes.co.za/faq-3/):
Cell Type/Brand is Sony/Murata US18650VTC6

Also from their design, they have a vent from the batteries to the outside in case of a thermal runaway.

[Eric Greenwell]

On 8/11/2021 7:50 PM, Kenn Sebesta wrote:
> On Wednesday, August 11, 2021 at 6:23:38 PM UTC-4, Eric Greenwell wrote:
>> On 8/11/2021 2:22 PM, Hank Nixon wrote:

>...

>>> It would not seem to be a good idea to use a conductive box to contain pouch type cells that could be prone to abrasion and shorting.
>>> I suspect that the new boxes in the FES gliders are glass. The box in my electric ASW-24E is glass. I'm using 18650 cells.
>>> "Nail tests" have been done on grouped 18650 cells that did not exhibit runaway when a cell was shorted. Soaring magazine had a photo of
>>> such a test.
>>> FWIW
>>> UH
>> That's the Feb 2018 issue. From the article "Electric Propulsion in Gliders Is More Than
>> an Alternative to Traditional Combustion Engines"
>>
>> "The temperature near the nailed cell was measured with a thermocouple, and indicated >
>> 500C. These tests have been made several times. At no time was there a chain reaction
>> leading to thermal runaway or short-circuit of surrounding cells. The voltage level of the
>> cell package after the test was nearly the same as before. Figure 15 shows different cell
>> packages after a nail-test."
>
> That points toward a LiFePo4 cell. Those are notoriously stable, to the point that causing a physical breach hardly affects their internal voltage.
>
> LiFePo4 are popular in busses and other EVs which require frequent power surges. The takeoff and initial climbout of a glider are a natural fit for them, although their power density is 20-40% lower than other lithium batteries so they have their limitations.
>
> I applaud your careful reading and study of the science and experience, as they show the daily truth for the billions of lithium batteries out there. I encourage you to join myself and others in not engaging with those who wear their confirmation bias too proudly. They shout out there was an explosion in NZ, despite the accident report to the contrary: https://www.aviation.govt.nz/assets/publications/fatal-accident-reports/ZK-GEL-Final-Report-7-December-2020.pdf. They would have us believe that every cell is an inevitable catastrophe, despite that in the APS Arizona thermal runaway event four of the five primary contributing factors were insufficient design and insufficient response.
>
> Those who have expressed clearly they have no interest in being part of the future have little role to play in a conversation about how we're going to get there.
>

I engage with the doubters because their pessimism and bias may dissuade other pilots from
considering electric gliders, and because once in a while, I learn something useful from
them ("even a blind squirrel sometimes finds a nut"). I do wish they would focus on glider
applications instead of utility-scale power banks with their huge energies, and also
ignore cars, which have 10 times the cell quantities in dense, water cooled assemblies.

The cell used in the Soaring article's "nail test" was a Panasonic 18650PD, which is NMC
chemistry like the Murata VTC6.

[Ramy]

Eric, thanks for engaging. As someone on the fence in regards to electric, I find this thread and similar very valuable. In fact I thank the doubters as well, as without them we wouldn’t have these discussions.

Ramy

[son_of_flubber]

On Monday, August 9, 2021 at 7:26:49 AM UTC-4, wtwisn...@gmail.com wrote:

>...A new glider design may make it possible to also eject the battery in flight or on the ground. ...

This could start a wildfire, but I guess that is preferable to the glider crashing and starting a wildfire. The battery could melt a hole and drop it. Glider could fly clear. Forest fire would destroy the traceable evidence, so no bad PR for the sport, and no liability for the pilot.

Seriously though. We've already seen that improvements in design and manufacturing can greatly reduce the possibility of a battery fire. The goal should be Zero battery fires.

[Ramy]

Hmm, I guess if the battery melts a hole, drops and starts a fire it will be less of a liability/conscious issue than the pilot ejecting the battery and starting a fire…

Ramy

[Eric Greenwell]

It's nice to know there are some "lurkers" and its not just Tom, Dave, me, and sometimes
Kenn wandering around in the weeds :^)

On 8/12/2021 1:11 PM, Ramy wrote:
> Eric, thanks for engaging. As someone on the fence in regards to electric, I find this thread and similar very valuable. In fact I thank the doubters as well, as without them we wouldn’t have these discussions.
>
> Ramy
>
> On Thursday, August 12, 2021 at 6:38:45 AM UTC-7, Eric Greenwell wrote:

...

[2G]

As before, I look at the evidence: scientific and accident reports. The only "doubters" here are those that dismiss this evidence. Ignoring accidents in cars and large battery banks means ignoring the bulk of the data available because this represents the vast majority of lithium battery uses. Are you promoters going to ignore the findings of PNNL on dendritic growth? Do you really think that gliders are somehow exempt from this phenomena? The single fatal accident of the Taurus Electro puts gliders at the VERY TOP of the fatal accident rate for battery powered vehicles by orders of magnitude - check it out. I have seen exactly ZERO rebuttals citing scientific evidence to the contrary (it is mostly a testimony of faith that the glider manufacturers will produce a "safe" product - save your breath, it is not convincing).

Tom

[Christoph Barniske]

In an article on Nordicgliding, Uli Kremer from Schleicher stated that they are using LG cells for AS34/AS33Me. These are different cells from AS32El with a slighly higher capacity (see https://nordicgliding-com.translate.goog/uli-kremer-100-km-er-minimum/?_x_tr_sl=da&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=ajax,elem). These are not of the LiFePO4-type.

In my view, the significant interest in electric motorgliding here in Germany is driven by a few factors:
1) Antares and FES systems have proven that such systems are significantly easier to operate and require less maintenance compared with current 2-stroke/Wankel designs
2) The limited battery capacity is not considered a major limitation.
3) Electric propulsion is seen as the engine technology of the future and the new models are following that trend. Many European countries have announced to stop new models of gas/diesel driven cars from entering their market around 2030. There are also several other projects with electric propulsion in aviation.
4) While there are safety concers with regards to Li-Ion cells (in particular with FES), there is trust in manufacturers to have overcome these.

The first AS34 are expected to be shipped late 2021 once type certificate has been granted by EASA. Current regulations prevent new glider models from being shipped with a temporary Permit to Fly, which was common practice until about 2018.

[Tango Eight]

On Friday, August 13, 2021 at 2:31:37 AM UTC-4, Christoph Barniske wrote:
> there is trust in manufacturers to have overcome these.

Is a certain German manufacturer still delivering aircraft with wiring all one color? I'm simply curious.

T8

[Eric Greenwell]

Battery fires are not the only dangers we face when flying motorized gliders. Gasoline
gliders have had fires, even models like the one you fly. They can come from exhaust
leaks, bearing failures, even the starter battery! The complexity of the gasoline glider
engine management has contributed to crashes that could be avoided with simpler systems.
Engines have failed during the launch, leading to accidents. Our goal should be the
reducing the overall danger, and not just the danger from one specific item in the power
system.

[kinsell]

Certainly a lot of hope and trust displayed in your posting. We can
hope and trust LG cells won't be a problem in gliders as they have been
in other applications.

You would think that electric motorgliders would be highly reliable but
the reality is that they've demonstrated their own set of problems.
Antares was not a low-maintenance aircraft, at least according to the
former U.S. dealer, who dealt with a number of problems in his own ship.
FES gliders got off to a terrible start with the fires, but even
beyond that they have overheat issues, prop strikes, and other things.

Maybe someday they'll mature into the fantastic products that some
people think they already are. For now, they're just another option
with their own set of limitations and problems.

-Dave

[2G]

That article only lists who the battery manufacturer is, not which battery or chemistry they are using (this is critical).

I was particularly interested in German aircraft noise regulations are their impact on ICE motorgliders. I have been told (by a German) that each motorglider in Germany has to be tested for noise levels before getting an airworthiness certificate.

The bottom line is that the fatality rate with electric gliders is very high on a per-hour operation basis. I know of no gas motorgliders that have exploded in mid-air or on the ground. The science behind these battery fire events is undeniable by an unbiased person. Trust is not a logically based decision - it is an emotional one.

Tom

[Eric Greenwell]

To see all the nitty-gritty problems the FES owners are facing, I suggest you visit the
FES owners groups. I was able to find two: one for the miniLak (link on the US dealer's
site), and one to which Matthew Scutter directed me (I've lost the link). Both were quite
boring, with *very* few posts, none particularly interesting. I asked Matthew about why
there was so little activity on them, and he replied (summarizing): You charge it, you fly
it; you charge it, you fly it; there's not much to talk about.

I've also monitored the Schleicher and DG self-launch groups, and as you know, there is
almost continuous discussion of various issues. I should not have been surprised at the
FES groups lack of discussion, as the FES is much simpler mechanically than the "gas
engine on a stick" systems used by DG and Schleicher. I'm not suggesting they are
trouble-free, but I am saying they seem to trouble their owners a lot less than the
fossil-fueled variety.

[Ramy]

If anyone has the link to the FES group please share.

Ramy

[kinsell]

I agree that's not too much you can work on with FES. If you overheat
your batteries, or your inverter, or your motor, you reduce power or
shut it off. Nothing you can really fix. If your batteries catch fire,
you call the fire department, ditto if you crash through a rooftop.
Second call is to the insurance company.

If these FES ships are so great, I am curious why a substantial portion
of the U.S. Silent 2 fleet seems stuck on W&W. Three there currently,
there have been a couple others taken off without being sold. Super low
time, like new condition, you'd think they'd sell like hotcakes.

[Eric Greenwell]

I don't know why they aren't selling well, but if I was really interested, I'd call the
people offering them for sale and ask them. An obvious possible reason is it's the
particular model of glider that people don't like, even if it has an FES. I'd prefer a
miniLak, for example, though I was impressed with how well Jeff Banks did with his at
Nephi and Richfield last year. But it's not just the Silents that can sit on W&W for a
long time. Last year, there were 3 or 4 ASH26Es on W&W for months and months, including
Tom's for over a year.

[Eric Greenwell]

On 8/13/2021 1:24 PM, Eric Greenwell wrote:

> I'd prefer a
> miniLak, for example, though I was impressed with how well Jeff Banks did with his at
> Nephi and Richfield last year. But it's not just the Silents that can sit on W&W for a
> long time. Last year, there were 3 or 4 ASH26Es on W&W for months and months, including
> Tom's for over a year.

That should be "... though I was impressed with how well Jeff Banks did with his SILENT at

Nephi and Richfield last year."

[andy l]

The conjunction in that sentence is though, not and.

I thought it was clear enough in its full context, before you reduced the quote.

[kinsell]

You're talking about Jeff Banks, who bought an ASH-31Mi this year??

https://www.onlinecontest.org/olc-3.0/gliding/flightbook.html?sp=2021&st=olcp&rt=olc&pi=10497


Calling owners is one possibility, but hate to since I don't have a real
interest in buying. Plus, somebody trying to sell something generally
is not very candid on what its limitations are.

[2G]

I can tell you why my ASH26e didn't sell for over 2 years: an Eastern European company offered a brand-new electric motorglider with comparable performance at a lower price. Only catch? They never delivered the goods, but are excellent at producing excuses.

Tom

[Eric Greenwell]

On 8/13/2021 5:53 PM, kinsell wrote:
> On 8/13/21 2:24 PM, Eric Greenwell wrote:

...

>> I don't know why they aren't selling well, but if I was really interested, I'd call the
>> people offering them for sale and ask them. An obvious possible reason is it's the
>> particular model of glider that people don't like, even if it has an FES. I'd prefer a
>> miniLak, for example, though I was impressed with how well Jeff Banks did with his at
>> Nephi and Richfield last year. But it's not just the Silents that can sit on W&W for a
>> long time. Last year, there were 3 or 4 ASH26Es on W&W for months and months, including
>> Tom's for over a year.
>>
>>
>
> You're talking about Jeff Banks, who bought an ASH-31Mi this year??
>
> https://www.onlinecontest.org/olc-3.0/gliding/flightbook.html?sp=2021&st=olcp&rt=olc&pi=10497
>
>
> Calling owners is one possibility, but hate to since I don't have a real interest in
> buying.  Plus, somebody trying to sell something generally is not very candid on what its
> limitations are.

I sort of remember he'd had a JS3 RES on order for while, bought the Silent to bridge the
gap till he got it, discovered an ASH31Mi he could get immediately instead of waiting a
long time for the JS3, so he bought it. I think it's the one from Brazil.

[kinsell]

On 8/14/21 7:09 AM, Eric Greenwell wrote:
> On 8/13/2021 5:53 PM, kinsell wrote:
>> On 8/13/21 2:24 PM, Eric Greenwell wrote:
> ...
>>> I don't know why they aren't selling well, but if I was really
>>> interested, I'd call the people offering them for sale and ask them.
>>> An obvious possible reason is it's the particular model of glider
>>> that people don't like, even if it has an FES. I'd prefer a miniLak,
>>> for example, though I was impressed with how well Jeff Banks did with
>>> his at Nephi and Richfield last year. But it's not just the Silents
>>> that can sit on W&W for a long time. Last year, there were 3 or 4
>>> ASH26Es on W&W for months and months, including Tom's for over a year.
>>>
>>>
>>
>> You're talking about Jeff Banks, who bought an ASH-31Mi this year??
>>
>> https://www.onlinecontest.org/olc-3.0/gliding/flightbook.html?sp=2021&st=olcp&rt=olc&pi=10497
>>
>>
>>
>> Calling owners is one possibility, but hate to since I don't have a
>> real interest in buying.  Plus, somebody trying to sell something
>> generally is not very candid on what its limitations are.
>
> I sort of remember he'd had a JS3 RES on order for while, bought the
> Silent to bridge the gap till he got it, discovered an ASH31Mi he could
> get immediately instead of waiting a long time for the JS3, so he bought
> it. I think it's the one from Brazil.
>

Yep, bought the one from Brazil. He landed his Electro out when flying
from Heber City, didn't have the juice to make it back. Maybe that
factored in his decision to go ICE?

FAA registry shows he still owns the Electro, make him an offer and you
too can be flying electric.

Dave

[Eric Greenwell]

On 8/13/2021 6:41 PM, 2G wrote:
> On Friday, August 13, 2021 at 1:24:55 PM UTC-7, Eric Greenwell wrote:

...

> But it's not just the Silents that can sit on W&W for a
>> long time. Last year, there were 3 or 4 ASH26Es on W&W for months and months, including
>> Tom's for over a year.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>
> I can tell you why my ASH26e didn't sell for over 2 years: an Eastern European company offered a brand-new electric motorglider with comparable performance at a lower price. Only catch? They never delivered the goods, but are excellent at producing excuses.
>
> Tom
>

Ah, so that's why GP Gliders and their Jetta are on your hit list ;^)

You started with a price on the high side, so it was unlikely to sell quickly; Covid came
along before you had a chance to adjust it and BOOM! even glider pilots were thinking
spending a big pile of money was not a good plan. Bad luck - not something you could have
anticipated.

[Eric Greenwell]

The only LG 18650 cell that fits the description is the LG18650HG2 (NMC chemistry),
essentially the same as the Sony/Murata VTC6.

The German noise regulations have impacted glider design for at least 30 years, and are
the main reason gliders have "buried" engines instead of the previous "engine on a stick"
configuration. My ASH26E POH list the noise emissions standards used for certification,
and the noise level measurement of 60.7 dB(A).

Which motorglider exploded in the air? I think I'd remember that, but I don't.

[Christoph Barniske]

Motorgliders in German register require a noise certificate ("Lärmschutzzeugnis") from the federal aviation authority LBA. This certificate contains a noise rating. Some airfields have operational restrictions for aircraft with a higher noise rating. However, there are usually no restrictions for self launching gliders with their engine mounted within the fuselage.

I witnessed a launch of the AS34 prototype last Friday. It is indeed relatively quite compared to the noise level of usual self launchers. The AS34 and the Silent 2 are difficult to compare in many aspects. The Silent 2 is certified in the Ultralight category, the AS34 will be a CS-22 certified glider.

[2G]

GP Gliders is on my "hit list" because they are frauds. Yes, they have defrauded me as well as you!

Tom

[2G]

No, I didn't start on the "high side" - I started on the fair side. In fact a 26e in worse condition than mine sold for more during this ordeal (I have names and numbers to back this up). The Wuhan virus certainly didn't help as people became more defensive, but that was well after the GP-15 fiasco, so it just extended the pain. But it did get me looking into what was going on at GP Gliders. At least I sold my 26e - you are left holding a bag of promises.

Tom

[2G]

The NZ Taurus Electro exploded in mid-air.

Tom

[kinsell]

Yes, they certainly are creative at making excuses. One particularly
innovative excuse was that the batteries didn't fit in the wings.

They're also great at making glitzy videos for social media, and for
getting people to pay upfront based on unsubstantiated promises. Bernie
Madoff could have taken lessons from these guys.

[jfitch]

On Sunday, August 15, 2021 at 5:52:38 PM UTC-7, 2G wrote:
> The NZ Taurus Electro exploded in mid-air.
>
> Tom

You seem to be reading a lot of things into the NZ accident report that aren't there. It did not explode in mid-air. There is speculation in the report that fumes may have contributed but no forensic evidence and that is not in the conclusions in the report. It is known that the owner did not follow the safety cautions on maintaining the battery.

One question I am left with after reading the report: would that aircraft have an ejectable canopy? Maybe not because of the ballistic parachute? It seems like a temporary solution to fumes in the canopy would be to get rid of it. Speeding back to the airport at over redline did not work.

[kinsell]

On 8/15/21 2:57 PM, Christoph Barniske wrote:
> Motorgliders in German register require a noise certificate ("Lärmschutzzeugnis") from the federal aviation authority LBA. This certificate contains a noise rating. Some airfields have operational restrictions for aircraft with a higher noise rating. However, there are usually no restrictions for self launching gliders with their engine mounted within the fuselage.
>
> I witnessed a launch of the AS34 prototype last Friday. It is indeed relatively quite compared to the noise level of usual self launchers. The AS34 and the Silent 2 are difficult to compare in many aspects. The Silent 2 is certified in the Ultralight category, the AS34 will be a CS-22 certified glider.
>

The article you provided earlier said they added rubber bushings to the
motor and drivetrain to improve pilot comfort. I fly with a rotary, and
it doesn't have objectionable vibration, unlike the two-cycle engines.

[2G]

You can call it a fire or you can call it an explosion - whatever it was it was very violent. The photo of the battery box showed delamination. The heat damage included the seat pan and rudder control cables. The pilot lost complete of the glider less than one mile from the airfield - why? He could have made an emergency landing in only one minute, or he could have used the ballistic chute, which he did not. The only explanation that makes sense is that he was incapacitated by fumes from the fire.

They call them battery fires, but what happens after an internal short is the pressure inside the cell builds rapidly until the cell ruptures violently. I call that an explosion.

Tom

[jfitch]

Not going to argue with you, I'd just encourage anyone interested to read the report, the link is referenced above, it is in plain English and very clear. The conclusions you are drawing are highly speculative, the report is not and does not draw those conclusions.

[Waveguru]

Here is a video of a scooter with small batteries catching on fire: https://www.youtube.com/watch?v=8HZ7qh_t46w

Bogs

[Eric Greenwell]

On 8/15/2021 8:38 PM, 2G wrote:
> Taurus Electro exploded in mid-air

You called it "Taurus Electro exploded in mid-air".

[Eric Greenwell]

You called it "Taurus Electro exploded in mid-air".

[kinsell]

On 8/16/21 7:38 AM, Waveguru wrote:
> Here is a video of a scooter with small batteries catching on fire: https://www.youtube.com/watch?v=8HZ7qh_t46w
>
> Bogs
>

It's a pity Elon Musk doesn't read R.A.S. He could learn from all the
experts out here that some heat-resistant paint and a CO2 cartridge is
all it takes to handle a lithium battery fire.

https://www.theverge.com/2021/7/2/22560662/tesla-model-s-plaid-fire-driver-battery-pennsylvania

[AS]

On Monday, August 16, 2021 at 9:38:20 AM UTC-4, Waveguru wrote:
> Here is a video of a scooter with small batteries catching on fire: https://www.youtube.com/watch?v=8HZ7qh_t46w
>
> Bogs

Would have been interesting to see the front side of the white car parked a few feet away from the scooter to see if or how much damage from the heat it sustained. The flames looked pretty intense.

Uli
'AS'

[Eric Greenwell]

On 8/16/2021 7:56 AM, kinsell wrote:

> It's a pity Elon Musk doesn't read R.A.S.  He could learn from all the experts out here
> that some heat-resistant paint and a CO2 cartridge is all it takes to handle a lithium
> battery fire.
>
> https://www.theverge.com/2021/7/2/22560662/tesla-model-s-plaid-fire-driver-battery-pennsylvania
>

You missed the biggest points: 18650 NMC cells, a few mm of spacing between them, low
density packs, and external venting. If more is needed, intumescent paint (not just heat
resistant) like your glider uses in the engine bay, and high volume air (or low volume
CO2/similar) are secondary measures if more mitigation after a cell overheat is desired.

[Mark Mocho]

I am reminded of the famous line from Butch Cassidy and the Sundance Kid:

"You just keep thinking, Butch. That's what you're good at."

[2G]

And it did.

Tom

[kinsell]

On 8/16/21 2:19 PM, Eric Greenwell wrote:
> On 8/16/2021 7:56 AM, kinsell wrote:
>
>> It's a pity Elon Musk doesn't read R.A.S.  He could learn from all the
>> experts out here that some heat-resistant paint and a CO2 cartridge is
>> all it takes to handle a lithium battery fire.
>>
>> https://www.theverge.com/2021/7/2/22560662/tesla-model-s-plaid-fire-driver-battery-pennsylvania
>>
> You missed the biggest points: 18650 NMC cells, a few mm of spacing
> between them, low density packs, and external venting. If more is
> needed, intumescent paint (not just heat resistant) like your glider
> uses in the engine bay, and high volume air (or low volume CO2/similar)
> are secondary measures if more mitigation after a cell overheat is desired.
>

Hate to say this, but you're a little naive about the effects of thermal
runaway in those lithium cells.

Here's an easy link to that Soaring article on the ASG32EL glider.
Notice the nice picture of 18650 cells all welded together in a tight
little matrix. Hard to call that low density.

http://ourdigitalmags.com/publication/?m=32960&i=472908&p=29&pp=1&ver=html5

Note that the Tesla Plaid has 18650 cells also, but each one is in
contact with a manifold for pumped liquid cooling. You obviously can't
have a tight matrix of cells if each one is water cooled.

So the question is, is it better to have tightly packed cells with air
cooling, or much lower density packing with forced liquid cooling?

The ASG32EL was designed as a university project, I.E. one step above a
science fair project. When things go bad, where will all the people be
who worked on this? Yes the cells are in the fuselage instead of the
wing, but there's not much you can do to mitigate a thermal runaway
event in the wing.

Interestingly, initial reports said that Plaid was one out of the first
250 delivered. But Musk said there were only 25 ready for delivery.
One out of 25, in the first month of operation, aren't good odds.

Reminds me of that scene from Dirty Harry:

https://www.youtube.com/watch?v=I530sPVQSc8

[George Haeh]

Hmmmm. No sense letting all that thermal energy go to waste. Maybe the turbine engineers could direct the hot gases to the rear through a turbine. How about a twin spool setup for thrust efficiency. Might need a compressed gas cylinder to start. Likely best not to use the O2 cylinder.

House the battery in a burner can from an old jet.

[Eric Greenwell]

On 8/16/2021 7:09 PM, kinsell wrote:
> On 8/16/21 2:19 PM, Eric Greenwell wrote:
>> On 8/16/2021 7:56 AM, kinsell wrote:
>>
>>> It's a pity Elon Musk doesn't read R.A.S.  He could learn from all the experts out here
>>> that some heat-resistant paint and a CO2 cartridge is all it takes to handle a lithium
>>> battery fire.
>>>
>>> https://www.theverge.com/2021/7/2/22560662/tesla-model-s-plaid-fire-driver-battery-pennsylvania
>>>
>> You missed the biggest points: 18650 NMC cells, a few mm of spacing between them, low
>> density packs, and external venting. If more is needed, intumescent paint (not just heat
>> resistant) like your glider uses in the engine bay, and high volume air (or low volume
>> CO2/similar) are secondary measures if more mitigation after a cell overheat is desired.
>>
>
> Hate to say this, but you're a little naive about the effects of thermal runaway in those
> lithium cells.
>
> Here's an easy link to that Soaring article on the ASG32EL glider. Notice the nice picture
> of 18650 cells all welded together in a tight little matrix.  Hard to call that low density.
>
> http://ourdigitalmags.com/publication/?m=32960&i=472908&p=29&pp=1&ver=html5
>
> Note that the Tesla Plaid has 18650 cells also, but each one is in contact with a manifold
> for pumped liquid cooling.  You obviously can't have a tight matrix of cells if each one
> is water cooled.
>
> So the question is, is it better to have tightly packed cells with air cooling, or much
> lower density packing with forced liquid cooling?

So, even with zero spacing, the cell with thermal runway did not trigger thermal runaway
in the other cells. The Soaring article is not the only one with this result. Isn't that
what is desired - no cascading effect? Doesn't that at least suggest a 1 or 2 mm (or more)
space would make it even less likely for a failing cell to trigger the others?

I did misuse the term "density". What I meant was "compact": the glider wing batteries are
in a long string, the car batteries are clustered closer to each other.

The JS3 uses boxes in the fuselage, so the pack is "compact". The cells are spaced a few
mm apart. This page has pictures of the box and the cell spacing:

https://nordicgliding.com/solo-flugmotoren-satsar-paa-el/

Scroll down about to the 2nd picture (boxes) and pictures 7 & 8 (cell placement).

[2G]

Also, the HPH Glasflugel 304 eS "fire" had a battery explosion on landing that blew the battery access cover off (https://assets.publishing.service.gov.uk/media/5f5a3f27e90e07208106a72c/HPH_Glasflugel_304_eS_G-GSGS_09-18.pdf):

"The G-GSGS battery fire started in the forward FES battery due to an electrical arcing
event that occurred at the top of cells 5 and 6, as evidenced by melted copper and
aluminium cell electrodes. The available evidence suggests that the electrical arcing
began when the glider touched down during a normal landing. The temperature reached
in the electrical arcing event exceeded 1,085°C and probably exceeded 1,400°C, based
on the results of AAIB tests. The release of pressurised combustible gas from the forward
battery caused over-pressurisation of the glider’s battery compartment, leading to the
detachment of the battery compartment cover. Once the battery’s gel electrolyte had
ignited, the fire continued to burn and consumed all of the electrolyte and also ignited
the glider’s composite structure, until the fire was extinguished by the application of
AFFF foam retardant."

Over-pressurization is also known as an explosion. Examination of the Kokam cells found metal particles in 7 of 11 tested cells (3 of them had multiple particles), an abysmal quality control record.

Tom

[Eric Greenwell]

On 8/16/2021 7:09 PM, kinsell wrote:

> The ASG32EL was designed as a university project, I.E. one step above a science fair
> project.  When things go bad, where will all the people be who worked on this?  Yes the
> cells are in the fuselage instead of the wing, but there's not much you can do to mitigate
> a thermal runaway event in the wing.

"Science Fair project" brings to mind a few dozen high school students with poster board
reports on tables in the gym. Do you really think Schleicher would base the safety of
their customers and future on something that trivial? The truth is much more than that:
The University of Kassel is a large (25,000 students) institution with research in
multiple scientific and engineering fields. The consortium included the University
Baden-Württemberg at Mosbach (34,000 students) and companies with expertise in battery
technology.

And yes, you can mitigate a thermal runaway event. The article in soaring magazine you
referenced showed how a failing cell does not trigger thermal runaway in the other cells.
Again: do you really think Schleicher would risk their customers and the reputation of
their company on a system that depends on every cell being perfect, and where a failing
cell would bring disaster?

[Eric Greenwell]

On 8/17/2021 7:27 AM, Eric Greenwell wrote:
> On 8/16/2021 7:09 PM, kinsell wrote:
>> The ASG32EL was designed as a university project, I.E. one step above a science fair
>> project.  When things go bad, where will all the people be who worked on this?  Yes the
>> cells are in the fuselage instead of the wing, but there's not much you can do to
>> mitigate a thermal runaway event in the wing.
>
> "Science Fair project" brings to mind a few dozen high school students with poster board
> reports on tables in the gym. Do you really think Schleicher would base the safety of
> their customers and future on something that trivial? The truth is much more than that:
> The University of Kassel is a large (25,000 students) institution with research in
> multiple scientific and engineering fields. The consortium included the University
> Baden-Württemberg at Mosbach (34,000 students) and companies with expertise in battery
> technology.
>
> And yes, you can mitigate a thermal runaway event. The article in soaring magazine you
> referenced showed how a failing cell does not trigger thermal runaway in the other cells.
> Again: do you really think Schleicher would risk their customers and the reputation of
> their company on a system that depends on every cell being perfect, and where a failing
> cell would bring disaster?
>

I forgot to mention "The propeller and control unit were also developed with expert
specialty firms" (AS website - ASG 32 EL page).

[2G]

The article in Soaring DOES NOT show "a failing cell does not trigger thermal runaway in the other cells" - it shows that they could not REPLICATE the event. Obviously, thermal runaway CAN occur because it HAS occurred in multiple electric glider events already mentioned here as well as in cars. You must be completely blind to the evidence.

Tom

[Eric Greenwell]

The article in Soaring tested 18650 cells, as used in Schleicher and JS electric
self-launchers. There have been no thermal runaway events in 18650 cells used in gliders,
and my remarks for this entire thread have applied to 18650 cells, as I have stated
repeatedly. I am not a fan of pouch cells, which have caused problems in gliders, and do
not know much about them.

[2G]

Of course there have been no thermal runaway of 18650 cells in gliders because there ARE NO gliders currently flying with 18650 cells. Here are 18650 cells in thermal runaway:
https://www.youtube.com/watch?v=24fYrV2vCPk
This event took only 2.5s:
https://www.youtube.com/watch?v=yhwPf7DTZ9o
and this describes the experiment:
https://onlinelibrary.wiley.com/doi/full/10.1002/advs.201700369
Important to realize that 18650 is just a case size - it says nothing about the chemistry or the construction of the cell, so deeming 18650 cells as universally safe is complete folly. The ESS fires all used cylindrical cells. The PNNL study on dendritical formation pertained to the chemistry, not the packaging. There is FAR MORE that we don't know than we do know about lithium battery safety.

Tom

[Eric Greenwell]

> 18650 cells have been used in the ASG32EL for 5 years, so there is some commercial glider experience with them. The cells used are NMC chemistry, same as the JS3 will use.

The first video uses LiCoO2 cells, which are a poor choice for gliders. NMC is the usual
choice, because it is much less likely to propagate thermal runway to a neighbor cell, as
illustrated in tests by NASA and others.

The second video shows tests of individual cell, not in a typical pack. The goal was to
get a better understanding of the failure mechanisms by purposely placing a heat triggered
short circuiting device in the cell. It was not a using quantities of specific commercial
cells, repeatedly tested, that could guide selection by an engineer designing a battery pack.

For whatever it's worth, four of the NMC cells vented but otherwise contained the thermal
runway in the cell, the fifth one tested burst. The other chemistries did not fare as
well. No one has suggested 18650 NMC type cells will not suffer runaway or remain intact.

And again I ask: do you really think AS and JS would risk their customers' lives and their
companies reputation without thoroughly considering all the facts about these batteries?
AS, JS, and their partners have far more experience and knowledge in this area than either
of us, so I don't think we can assess the risks nearly as well as they can.

[jfitch]

The xray study was interesting, what I learned from it is that it would be inadvisable to purchase your glider with the optional nichrome wire wrap heating each cell with 33 watts, as it may cause thermal runaway.