On Saturday, August 14, 2021 at 7:59:37 AM UTC-7, Eric Greenwell wrote:
> On 8/13/2021 10:13 AM, 2G wrote:
> > On Thursday, August 12, 2021 at 11:31:37 PM UTC-7, Christoph Barniske wrote:
> >> 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.
> >
> > 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.
> >
> 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.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

The NZ Taurus Electro exploded in mid-air.

Tom

On 8/13/21 7:41 PM, 2G wrote:
> On Friday, August 13, 2021 at 1:24:55 PM UTC-7, Eric Greenwell wrote:
>> On 8/13/2021 12:15 PM, kinsell wrote:
>>> On 8/13/21 11:21 AM, Eric Greenwell wrote:
>>
>>>>
>>>> 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.
>>>>
>>>
>>> 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.
>> 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 - 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
>

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.

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.

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.

On Sunday, August 15, 2021 at 6:42:39 PM UTC-7, jfitch wrote:
> 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.

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

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

Bogs

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

On 8/15/2021 8:38 PM, 2G wrote:
> On Sunday, August 15, 2021 at 6:42:39 PM UTC-7, jfitch wrote:
>> 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.
>
> 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

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

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

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

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'

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.

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

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."

On Monday, August 16, 2021 at 7:34:44 AM UTC-7, Eric Greenwell wrote:
> On 8/15/2021 8:38 PM, 2G wrote:
> > On Sunday, August 15, 2021 at 6:42:39 PM UTC-7, jfitch wrote:
> >> 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.
> >
> > 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
> You called it "Taurus Electro exploded in mid-air".
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

And it did.

Tom

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

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.

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).

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

On Monday, August 16, 2021 at 5:00:03 PM UTC-7, 2G wrote:
> On Monday, August 16, 2021 at 7:34:44 AM UTC-7, Eric Greenwell wrote:
> > On 8/15/2021 8:38 PM, 2G wrote:
> > > On Sunday, August 15, 2021 at 6:42:39 PM UTC-7, jfitch wrote:
> > >> 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.
> > >
> > > 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
> > You called it "Taurus Electro exploded in mid-air".
> > --
> > Eric Greenwell - USA
> > - "A Guide to Self-launching Sailplane Operation"
> > https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> And it did.
>
> Tom

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

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

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).

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

On Tuesday, August 17, 2021 at 7:27:10 AM UTC-7, 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?
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

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

On 8/18/2021 9:47 PM, 2G wrote:
> On Tuesday, August 17, 2021 at 7:27:10 AM UTC-7, 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?
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>
> 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
>
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.

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

On Thursday, August 19, 2021 at 6:49:25 AM UTC-7, Eric Greenwell wrote:
> On 8/18/2021 9:47 PM, 2G wrote:
> > On Tuesday, August 17, 2021 at 7:27:10 AM UTC-7, 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?
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> >
> > 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
> >
> 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.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

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

On 8/19/2021 2:32 PM, 2G wrote:
> On Thursday, August 19, 2021 at 6:49:25 AM UTC-7, Eric Greenwell wrote:
>> On 8/18/2021 9:47 PM, 2G wrote:
>>> On Tuesday, August 17, 2021 at 7:27:10 AM UTC-7, 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?
>>>> --
>>>> Eric Greenwell - USA
>>>> - "A Guide to Self-launching Sailplane Operation"
>>>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>>>
>>> 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
>>>
>> 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.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>
> 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
> 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.

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

On Thursday, August 19, 2021 at 4:58:44 PM UTC-7, Eric Greenwell wrote:
> On 8/19/2021 2:32 PM, 2G wrote:
> > On Thursday, August 19, 2021 at 6:49:25 AM UTC-7, Eric Greenwell wrote:
> >> On 8/18/2021 9:47 PM, 2G wrote:
> >>> On Tuesday, August 17, 2021 at 7:27:10 AM UTC-7, 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?
> >>>> --
> >>>> Eric Greenwell - USA
> >>>> - "A Guide to Self-launching Sailplane Operation"
> >>>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> >>>
> >>> 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
> >>>
> >> 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.
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> >
> > 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
> > 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.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
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.

I think it's time the Tom & Eric "Wander in the Weeds" tour ended, as neither Tom nor I
seem to be learning anything new, we don't have much general knowledge in the glider
battery area, and most important: we don't know the details of the process AS, JS, and
their partners went through to arrive their respective solutions, nor do we know the
details of the solutions.

I hope there will be some speakers at the 2022 SSA Convention that discuss electric
gliders and their systems in detail. Finding those speakers (or at least encouraging those
in charge to do so) might be the best way to pursue the discussion. There is a lot to talk
about:
- battery systems: design, inflight use, charging, storage, and safety
- motors and the controllers
- operational differences from gasoline gliders
- how they might change soaring for individuals and clubs
- electric launch with airplanes and winches

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