Our club is kicking around the idea of buying a Pipistrel Electro 2.5 to supplement our current training ships (L23, K21 and Grob Twin), one of which would probably be sold. Preliminary impressions are pretty favorable. I'm looking for any first-hand experience anyone may have with this particular glider. Thanks in advance.

Mike

On Thursday, November 3, 2022 at 10:02:53 AM UTC-5, mdfa...@gmail.com wrote:
> Our club is kicking around the idea of buying a Pipistrel Electro 2.5 to supplement our current training ships (L23, K21 and Grob Twin), one of which would probably be sold. Preliminary impressions are pretty favorable. I'm looking for any first-hand experience anyone may have with this particular glider. Thanks in advance.
>
> Mike
A recent discovery I found is that it can actually be trailered in a Cobra trailer and assembled without much trouble. Big plus I think.

Curt Lewis
CFIG/ASEL
Genesis 2 (95)
SGS 1-26B (216)

On 11/3/2022 8:02 AM, Michael Fadden wrote:
> Our club is kicking around the idea of buying a Pipistrel Electro 2.5 to supplement our current training ships (L23, K21 and Grob Twin), one of which would probably be sold. Preliminary impressions are pretty favorable. I'm looking for any first-hand experience anyone may have with this particular glider. Thanks in advance.
>
> Mike
Contact the dealer for names of customers that have used it for training or in a club. Or
just start calling Taurus owners in the FAA register - not that many to go through.

On Thursday, November 3, 2022 at 10:36:23 AM UTC-7, 6A wrote:
> On 11/3/2022 8:02 AM, Michael Fadden wrote:
> > Our club is kicking around the idea of buying a Pipistrel Electro 2.5 to supplement our current training ships (L23, K21 and Grob Twin), one of which would probably be sold. Preliminary impressions are pretty favorable. I'm looking for any first-hand experience anyone may have with this particular glider. Thanks in advance.
> >
> > Mike
> Contact the dealer for names of customers that have used it for training or in a club. Or
> just start calling Taurus owners in the FAA register - not that many to go through.

Review ALL of the NZ accident reports regarding this glider before pulling the trigger:
https://groups.google.com/g/rec.aviation.soaring/c/hBC6dag98qo/m/JZzil_psBwAJ

Tom

Thanks, Curt. I don't how much consideration has been given to trailer options but that's good to know. While its not listed as definite cause of the fire/crash, its clear the owner of the NZ Taurus didn't maintain the battery in accordance with the manufacturer's instructions. The whole battery safety issue is part of the discussion we are having. I was hoping that some owners (worldwide, not just U.S.) of the Electro 2.5 were users of this group and might relay their real world experiences. Pipistrel has been very responsive to our inquiries.

Mike

"A recent discovery I found is that it can actually be trailered in a Cobra trailer and assembled without much trouble. Big plus I think."

You need to know that the Cobra trailer designed for the Taurus is substantially larger than the normal models designed for single seat or tandem seat gliders. The Taurus' side-by-side cockpit means the fuselage is almost twice the width of a conventional glider, and the trailer has to be specially built for it. The wing is also substantially larger. I have built a couple of specialized WingRiggers for the Taurus, and they too have to be specialized, as the wing has a very wide chord and is set low to the ground. The wings are pretty light, so rigging is not particularly difficult with two people and no rigging aid. Using a WingRigger can make it a single person effort, but it will take some practice.

Another concern about using a Taurus for instruction is whether it is registered as "Experimental." There is a debate going on about using Experimental aircraft for training, primarily in the cases where the instruction is for compensation or not. You should check with the FSDO to find out whether a "Letter Of Deviation Authority" (LODA) is required for instructing in an Experimental aircraft, and whether it is legal to charge for it.

On 11/3/2022 8:02 AM, Michael Fadden wrote:
> Our club is kicking around the idea of buying a Pipistrel Electro 2.5 to supplement our current training ships (L23, K21 and Grob Twin), one of which would probably be sold. Preliminary impressions are pretty favorable. I'm looking for any first-hand experience anyone may have with this particular glider. Thanks in advance.
>
> Mike

Operating a MG is substantially different from a towed glider, and the PIC needs to know
these differences, and use the MG often enough to remain competent. For your training
purposes, I think this is practical if the pilots (PIC) are limited to instructors who
really learn how to operate the Taurus, and do so routinely. It's not just flying the
launch, but the basic operations of "fueling", preflight, and emergencies.

An electric powered glider is going to have features new to most instructors, even if they
are also airplane or towpilots. A primary difference is the batteries, which must be
handled carefully when out of the glider, and when they are charged and stored. Their
operation in flight also differs considerably from fuel management in combustion engine
powered aircraft.

If the club can maintain competent instructors, I think this would a good addition to the
club fleet, in part because it would prepare pilots the electric gliders they'd likely be
flying in the future.

Thanks, this is all good information. The plan is to have only instructors be the PIC, at least initially, and use it both in MG mode and aero-towed like a non-MG. We have excellent instructors with experience in all kinds of aircraft. There is no charge for instruction but checking with the FSDO (probably) wouldn't hurt. I'm not on the committee but those who are don't frequent RAS, as far as I know. Personally, I zero power time but would like the challenge of becoming competent in motorglider.

Mike

On Friday, November 4, 2022 at 6:41:16 AM UTC-7, mdfa...@gmail.com wrote:
> Thanks, Curt. I don't how much consideration has been given to trailer options but that's good to know. While its not listed as definite cause of the fire/crash, its clear the owner of the NZ Taurus didn't maintain the battery in accordance with the manufacturer's instructions. The whole battery safety issue is part of the discussion we are having. I was hoping that some owners (worldwide, not just U.S.) of the Electro 2.5 were users of this group and might relay their real world experiences. Pipistrel has been very responsive to our inquiries.
>
> Mike

Mike, that is simply not true. The final report on the accident (https://www.aviation.govt.nz/assets/publications/fatal-accident-reports/ZK-GEL-Final-Report-7-December-2020.pdf) stated:

"At some time between 1415 and 1730 hours, the glider, while soaring, experienced an inflight battery thermal event."

A "thermal event" is also called a fire, which is exactly what it was called later:

"1.14 Fire
1.14.1 During the wreckage examination, evidence of an in-flight fire was identified. The
fire appeared to have originated from, and was isolated to, the battery pack located
behind the pilot’s seat (see Figure 3)."

The fire intruded into the cockpit:

"1.14.3 The pilot’s seat and rudder control cables showed evidence of in-flight heat damage
and sooting. These components were separated from the heat source during the
impact sequence."

and

"1.15.1 Evidence of significant smoke within the cockpit prior to the glider impacting the
ground was identified."

Finally, the analysis concludes that there WAS a fire:

"2. Analysis
2.1 While airborne on a local flight the pilot was faced with a difficult in-flight
emergency, in the form of a battery thermal event.
2.2 The thermal event originated in the lithium polymer battery pack located behind
the pilot’s seat, resulting in fumes and smoke filling the cockpit. This would have
likely had the effect of degrading the pilot’s performance and ability to control the
glider while dealing with the in-flight emergency."

Manufacturing defects were found in another electric glider:

"1.16.1 Following an in-flight battery fire incident involving an HPH Glasflugel 304 eS type
glider in West Sussex, England, the Air Accidents Investigation Branch (AAIB)
conducted an investigation. Their subsequent report could not identify the cause of
the battery fire. They conducted independent testing, however, which revealed the
presence of metallic debris in 7 of the 11 lithium polymer cells sampled.
Furthermore, vibration testing identified that metallic debris could cause fretting on
the cell pouch. The metallic fretting was not significant enough during testing to
penetrate the cell pouch which would cause arcing. However, during other testing
where penetration was achieved ‘the electrical arcing was immediately followed by
rapid inflation of the pouch, followed by light grey smoke, followed by flames.’ For
further information refer to AAIB Bulletin: 9/2018 G-GSGS EW/C2017/08/01."

The owner did not follow the recommended charging of the batteries:

"1.16.4 During significant absences from New Zealand, the pilot would fully charge the
glider batteries and leave them charged while the glider was stored in its trailer. The
pilot was also known to leave the batteries charging for substantial periods of time
between flights. This is contrary to the manufacturer’s Flight manual and
Maintenance manual."

and the report concluded this:

"1.16.5 Research shows that, if the manufacturer’s instructions for charging are not
followed, lithium polymer batteries are prone to hydrogen and dendrite build-up,
that may lead to a battery short circuit, failure, smoking and/or fire"

This, to me, renders this technology unsuitable for aircraft. You will want to fully charge the battery prior to flight, which contributes to hydrogen and dendrite build-up and, ultimately, battery failure. It is just a question of time. I can fill up the fuel tank of my ASH 31 Mi, on the other hand, and leave it that way for months without risk of fire.

Tom

>> ... the electrical arcing was immediately followed by rapid inflation of the pouch, followed by light grey smoke, followed by flames. <<

If you want to see the above in action, watch a few episodes of 'Battle Bots', where the contestants build robots with the expressed purpose of beating the crap out of their opponents. These robots are all powered by LiPo-type batteries. Some of them sustain incredible blows, which compromises their batteries. The 'light grey smoke' is heavier than air and creeps out of the stricken bot along the floor, which then - much to the delight of the spectators - is typically followed by fire. The clean-up crew only enters the venue with full-face respirators.
Battery technology will advance and improve with the advent of EVs, so I will wait a little more before placing my order for an electric motor glider.

Uli
'AS'

On 11/5/2022 12:35 PM, AS wrote:
> Battery technology will advance and improve with the advent of EVs, so I will wait a little more before placing my order for an electric motor glider.

How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
years due to order backlogs. But, if you are waiting for batteries that can survive
sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
you'll have to wait much longer.

Eric

On Saturday, November 5, 2022 at 1:44:49 PM UTC-7, Eric Greenwell wrote:
> On 11/5/2022 12:35 PM, AS wrote:
> > Battery technology will advance and improve with the advent of EVs, so I will wait a little more before placing my order for an electric motor glider.
> How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
> years due to order backlogs. But, if you are waiting for batteries that can survive
> sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
> you'll have to wait much longer.
>
> Eric

These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.

The gray or white smoke is the electrolyte on fire. This produces toxic smoke, so using full respirators is not just a good idea, but is mandatory. The cargo ship fire, Felicity Ace, with all of the EVs on board put out a tremendous amount of white smoke.

We will be getting a lot more answers to these battery issues with all of the EVs that are now out on the road. One issue, dendrite growth, occurs over a period of time regardless of whether the battery is or is not being used. This phenomenon is not understood, which is very troubling when your life depends upon it (https://www.nature.com/articles/s41524-022-00788-6):

"Some such issues are uncontrolled dendrite formation, large volume changes, and irreversible electrolyte degradation reactions inherent in lithium-metal-based batteries, resulting in severe safety concerns and low Coulombic efficiency."

"However, only a few studies have focused on the aggressive formation or growth of dendrites in organic electrolytes. Even these few previously reported approaches have failed to successfully reproduce and access the experimentally observed lithium electrodeposition behavior during the cyclic charging/discharging process. This is because existing modeling studies involve simplifying assumptions that cannot capture some atomic-scale details."

Dendrites, if you haven't followed the previous discussions, cause internal shorts in lithium batteries which lead to thermal runaway and fires. I would be a lot more comfortable driving an EV than flying an electric glider. If the EV catches fire you can pull over to the side of the road and get out - this is much more problematic if you are airborne.

Tom

On 11/5/2022 9:19 PM, 2G wrote:
>> How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
>> years due to order backlogs. But, if you are waiting for batteries that can survive
>> sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
>> you'll have to wait much longer.
>>
>> Eric
> These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.

Is there more evidence for these concerns than this Taurus, particularly for the later
generation batteries from FES?

Of course, Uli can choose to wait for an electric glider using cylindrical lithium
batteries, which are inherently more rugged than the pouch style.

On Sunday, 6 November 2022 at 13:53:01 UTC+1, Eric Greenwell wrote:
> On 11/5/2022 9:19 PM, 2G wrote:
> > These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.
> Is there more evidence for these concerns than this Taurus, particularly for the later
> generation batteries from FES?

The Taurus Electro is not a FES system. In fact it's one of the first electrical gliders (after Antares), and predates the first FES equipped glider by a couple of years. And being built to ultra light rules, it both predates and is not required to follow the certification requirements as current sailplane certified batteries do. That said, I don't know the exact battery type it does use.

On 11/6/2022 5:29 AM, Arne Martin Güettler wrote:
> On Sunday, 6 November 2022 at 13:53:01 UTC+1, Eric Greenwell wrote:
>> On 11/5/2022 9:19 PM, 2G wrote:
>>> These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.
>> Is there more evidence for these concerns than this Taurus, particularly for the later
>> generation batteries from FES?
>
> The Taurus Electro is not a FES system. In fact it's one of the first electrical gliders (after Antares), and predates the first FES equipped glider by a couple of years. And being built to ultra light rules, it both predates and is not required to follow the certification requirements as current sailplane certified batteries do. That said, I don't know the exact battery type it does use.

I agree, and did not mean to imply it was an FES system; however, it did have batteries of
similar design, and the design was revised after the accident, as were important details
in the Taurus airframe. The FES system also has had important revisions in the design and
manufacture of it's batteries, and EASA regulations are more comprehensive now.

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

On Sunday, November 6, 2022 at 4:53:01 AM UTC-8, Eric Greenwell wrote:
> On 11/5/2022 9:19 PM, 2G wrote:
> >> How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
> >> years due to order backlogs. But, if you are waiting for batteries that can survive
> >> sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
> >> you'll have to wait much longer.
> >>
> >> Eric
> > These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.
> Is there more evidence for these concerns than this Taurus, particularly for the later
> generation batteries from FES?
>
> Of course, Uli can choose to wait for an electric glider using cylindrical lithium
> batteries, which are inherently more rugged than the pouch style.

Yes, this is an of intense interest. Here is one surprising scientific review that surveyed all studies in this area (https://journals.sagepub.com/doi/full/10.1177/14613484211008112):

"The authors concluded that the pouch cells showed no degradation or failure in any of the tests; however, the cylindrical cells shaken in the y-direction experienced mandrel loosening during the shock and long-term vibration tests. In addition, it was found that the cylindrical cells stressed in the z-direction also experienced degradation and failures."

and

"The reliability analysis and optimization of internal and external complex structures are urgently needed in the development of battery pack to eliminate all kinds of potential safety hazards in the design stage especially under the shock and vibration environment."

These results are in direct contradiction to your claim that pouch cells are more dangerous than cylindrical cells. The construction of cylindrical cells involves the rolling of four layers simultaneously; apparently this rolling action introduces stresses into the material, especially the separation layers.

Tom

On 11/6/2022 11:54 AM, 2G wrote:
> On Sunday, November 6, 2022 at 4:53:01 AM UTC-8, Eric Greenwell wrote:
>> On 11/5/2022 9:19 PM, 2G wrote:
>>>> How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
>>>> years due to order backlogs. But, if you are waiting for batteries that can survive
>>>> sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
>>>> you'll have to wait much longer.
>>>>
>>>> Eric
>>> These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.
>> Is there more evidence for these concerns than this Taurus, particularly for the later
>> generation batteries from FES?
>>
>> Of course, Uli can choose to wait for an electric glider using cylindrical lithium
>> batteries, which are inherently more rugged than the pouch style.
>
> Yes, this is an of intense interest. Here is one surprising scientific review that surveyed all studies in this area (https://journals.sagepub.com/doi/full/10.1177/14613484211008112):
>
> "The authors concluded that the pouch cells showed no degradation or failure in any of the tests; however, the cylindrical cells shaken in the y-direction experienced mandrel loosening during the shock and long-term vibration tests. In addition, it was found that the cylindrical cells stressed in the z-direction also experienced degradation and failures."
>
> and
>
> "The reliability analysis and optimization of internal and external complex structures are urgently needed in the development of battery pack to eliminate all kinds of potential safety hazards in the design stage especially under the shock and vibration environment."
>
> These results are in direct contradiction to your claim that pouch cells are more dangerous than cylindrical cells. The construction of cylindrical cells involves the rolling of four layers simultaneously; apparently this rolling action introduces stresses into the material, especially the separation layers.
>
> Tom

"More rugged" was too vague a claim, I think; regardless, the study only used automotive
vibration patterns to test the cells for the equivalent of 100,000 miles, and did not
consider things like damage propagation from a failed cell to adjacent cells, tolerance of
debris while constructing the battery pack, etc. I do think both types of cells can be
used for battery packs suitable for electric glider use.

The study's vibration pattern may not a good representation of glider vibration, and the
tests lasted for the equivalent of 100,000 road miles. That's about 2000 hours of
vibration. Glider vibrations with the intensity of ground vehicles might occur during the
takeoff and landing roll, and perhaps also under power (unlikely, given the smooth
operation of electric motors). My ASH26E, with 4300 flight hours, has only 215 engine
hours, so I don't think flight related vibration is going to be a problem for electric
gliders.

There is also vibration during trailering, but I don't know how that compares to the
vibration they used in the study. Frame mounted batteries in car may be subjected to far
more vibration than a glider carried in a trailer.

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

On Sunday, November 6, 2022 at 2:54:07 PM UTC-5, 2G wrote:
> On Sunday, November 6, 2022 at 4:53:01 AM UTC-8, Eric Greenwell wrote:
> > On 11/5/2022 9:19 PM, 2G wrote:
> > >> How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
> > >> years due to order backlogs. But, if you are waiting for batteries that can survive
> > >> sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
> > >> you'll have to wait much longer.
> > >>
> > >> Eric
> > > These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.
> > Is there more evidence for these concerns than this Taurus, particularly for the later
> > generation batteries from FES?
> >
> > Of course, Uli can choose to wait for an electric glider using cylindrical lithium
> > batteries, which are inherently more rugged than the pouch style.
> Yes, this is an of intense interest. Here is one surprising scientific review that surveyed all studies in this area (https://journals.sagepub.com/doi/full/10.1177/14613484211008112):
>
> "The authors concluded that the pouch cells showed no degradation or failure in any of the tests; however, the cylindrical cells shaken in the y-direction experienced mandrel loosening during the shock and long-term vibration tests. In addition, it was found that the cylindrical cells stressed in the z-direction also experienced degradation and failures."
>
> and
>
> "The reliability analysis and optimization of internal and external complex structures are urgently needed in the development of battery pack to eliminate all kinds of potential safety hazards in the design stage especially under the shock and vibration environment."
>
> These results are in direct contradiction to your claim that pouch cells are more dangerous than cylindrical cells. The construction of cylindrical cells involves the rolling of four layers simultaneously; apparently this rolling action introduces stresses into the material, especially the separation layers.
>
> Tom
Pouch cells are much more prone to damage that could lead to a fire as has happened a few times with FES ships and the referenced Taurus.
Lion cylinder type cells may fail from vibration but the just die due to open circuits.
That said my battery comes out of the glider for trailering.
UH

On 11/6/22 4:22 PM, Hank Nixon wrote:
> On Sunday, November 6, 2022 at 2:54:07 PM UTC-5, 2G wrote:
>> On Sunday, November 6, 2022 at 4:53:01 AM UTC-8, Eric Greenwell wrote:
>>> On 11/5/2022 9:19 PM, 2G wrote:
>>>>> How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
>>>>> years due to order backlogs. But, if you are waiting for batteries that can survive
>>>>> sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
>>>>> you'll have to wait much longer.
>>>>>
>>>>> Eric
>>>> These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.
>>> Is there more evidence for these concerns than this Taurus, particularly for the later
>>> generation batteries from FES?
>>>
>>> Of course, Uli can choose to wait for an electric glider using cylindrical lithium
>>> batteries, which are inherently more rugged than the pouch style.
>> Yes, this is an of intense interest. Here is one surprising scientific review that surveyed all studies in this area (https://journals.sagepub.com/doi/full/10.1177/14613484211008112):
>>
>> "The authors concluded that the pouch cells showed no degradation or failure in any of the tests; however, the cylindrical cells shaken in the y-direction experienced mandrel loosening during the shock and long-term vibration tests. In addition, it was found that the cylindrical cells stressed in the z-direction also experienced degradation and failures."
>>
>> and
>>
>> "The reliability analysis and optimization of internal and external complex structures are urgently needed in the development of battery pack to eliminate all kinds of potential safety hazards in the design stage especially under the shock and vibration environment."
>>
>> These results are in direct contradiction to your claim that pouch cells are more dangerous than cylindrical cells. The construction of cylindrical cells involves the rolling of four layers simultaneously; apparently this rolling action introduces stresses into the material, especially the separation layers.
>>
>> Tom
> Pouch cells are much more prone to damage that could lead to a fire as has happened a few times with FES ships and the referenced Taurus.
> Lion cylinder type cells may fail from vibration but the just die due to open circuits.
> That said my battery comes out of the glider for trailering.
> UH

Perhaps in your experience they only fail with open circuits, but there
have been quite a few cases where cylindrical cells have combusted.

Sure glad these things are getting so much safer:

https://gothamist.com/news/e-bike-fire-injures-38-in-midtown-east-apartment-building

On Sunday, November 6, 2022 at 7:01:04 PM UTC-8, kinsell wrote:
> On 11/6/22 4:22 PM, Hank Nixon wrote:
> > On Sunday, November 6, 2022 at 2:54:07 PM UTC-5, 2G wrote:
> >> On Sunday, November 6, 2022 at 4:53:01 AM UTC-8, Eric Greenwell wrote:
> >>> On 11/5/2022 9:19 PM, 2G wrote:
> >>>>> How long did you want to wait? Place an order now, and you'll likely wait 2, 3, or more
> >>>>> years due to order backlogs. But, if you are waiting for batteries that can survive
> >>>>> sledgehammer attacks and multiple 10 foot drops onto a steel floor (as Battlebots endure),
> >>>>> you'll have to wait much longer.
> >>>>>
> >>>>> Eric
> >>>> These batteries can't even survive the bouncing and jarring that typical trailering causes. The Taurus Electro had a gear-up landing that may have contributed, and probably did, to its battery failure. Gear-up landings are not the same as a 10-foot drop.
> >>> Is there more evidence for these concerns than this Taurus, particularly for the later
> >>> generation batteries from FES?
> >>>
> >>> Of course, Uli can choose to wait for an electric glider using cylindrical lithium
> >>> batteries, which are inherently more rugged than the pouch style.
> >> Yes, this is an of intense interest. Here is one surprising scientific review that surveyed all studies in this area (https://journals.sagepub.com/doi/full/10.1177/14613484211008112):
> >>
> >> "The authors concluded that the pouch cells showed no degradation or failure in any of the tests; however, the cylindrical cells shaken in the y-direction experienced mandrel loosening during the shock and long-term vibration tests. In addition, it was found that the cylindrical cells stressed in the z-direction also experienced degradation and failures."
> >>
> >> and
> >>
> >> "The reliability analysis and optimization of internal and external complex structures are urgently needed in the development of battery pack to eliminate all kinds of potential safety hazards in the design stage especially under the shock and vibration environment."
> >>
> >> These results are in direct contradiction to your claim that pouch cells are more dangerous than cylindrical cells. The construction of cylindrical cells involves the rolling of four layers simultaneously; apparently this rolling action introduces stresses into the material, especially the separation layers.
> >>
> >> Tom
> > Pouch cells are much more prone to damage that could lead to a fire as has happened a few times with FES ships and the referenced Taurus.
> > Lion cylinder type cells may fail from vibration but the just die due to open circuits.
> > That said my battery comes out of the glider for trailering.
> > UH
> Perhaps in your experience they only fail with open circuits, but there
> have been quite a few cases where cylindrical cells have combusted.
>
> Sure glad these things are getting so much safer:
>
> https://gothamist.com/news/e-bike-fire-injures-38-in-midtown-east-apartment-building

The clear attitude of eglider enthusiasts here is that we skeptics must prove that lithium batteries are unsafe (which I think I have done, BTW). My attitude is that the proponents, especially the manufacturers, MUST prove that they are safe. This HAS NOT happened to date. Conclusion: fly at your OWN RISK!

Tom

On 11/6/2022 7:01 PM, kinsell wrote:
> On 11/6/22 4:22 PM, Hank Nixon wrote:
....
>>>
>>> Tom
>> Pouch cells are much more prone to damage that could lead to a fire as has happened a
>> few times with FES ships and the referenced Taurus.
>> Lion cylinder type cells may fail from vibration but the just die due to open circuits.
>> That said my battery comes out of the glider for trailering.
>> UH
>
> Perhaps in your experience they only fail with open circuits, but there have been quite a
> few cases where cylindrical cells have combusted.
>
> Sure glad these things are getting so much safer:
>
> https://gothamist.com/news/e-bike-fire-injures-38-in-midtown-east-apartment-building

The article says the fire started in an apartment where a guy was repairing e-bikes, with
over 5 found in his room. Seems likely it was case of improper repair and storage in an
unsuitable location, rather than batteries failing from normal use.

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

On 11/6/2022 8:40 PM, 2G wrote:
> Conclusion: fly at your OWN RISK!

It's always been that way, Tom, even before the Wright brothers. Corollary: since it's OUR
risk, we don't have to prove anything to you.

You are welcome to offer opinions, but understand you do so at your own risk. Corollary:
If you don't want people to question your claims, don't offer them.

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

On Sunday, November 6, 2022 at 8:59:48 PM UTC-8, Eric Greenwell wrote:
> On 11/6/2022 8:40 PM, 2G wrote:
> > Conclusion: fly at your OWN RISK!
> It's always been that way, Tom, even before the Wright brothers. Corollary: since it's OUR
> risk, we don't have to prove anything to you.
>
> You are welcome to offer opinions, but understand you do so at your own risk. Corollary:
> If you don't want people to question your claims, don't offer them.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications

Well, that is refreshing - you don't claim that egliders are risk free. I am only trying to offer OBJECTIVE scientific data (not opinion as you say) on the risks of lithium batteries. In my judgment the technology is not ready for CRITICAL life-dependent applications. Remember, it was YOU that asked for this information!

Tom

On 11/6/2022 9:24 PM, 2G wrote:
> On Sunday, November 6, 2022 at 8:59:48 PM UTC-8, Eric Greenwell wrote:
>> On 11/6/2022 8:40 PM, 2G wrote:
>>> Conclusion: fly at your OWN RISK!
>> It's always been that way, Tom, even before the Wright brothers. Corollary: since it's OUR
>> risk, we don't have to prove anything to you.
>>
>> You are welcome to offer opinions, but understand you do so at your own risk. Corollary:
>> If you don't want people to question your claims, don't offer them.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications
>
> Well, that is refreshing - you don't claim that egliders are risk free. I am only trying to offer OBJECTIVE scientific data (not opinion as you say) on the risks of lithium batteries. In my judgment the technology is not ready for CRITICAL life-dependent applications. Remember, it was YOU that asked for this information!
>
> Tom

I don't think anyone here has claimed egliders are risk free, or that any motor/engine
installation is risk free, but many of us believe the risk can be managed to an acceptable
level. We've learned to manage the risks of unconnected controls, of leaving spoilers
unlocked, of kiting during tow, and all the other risks involved in flying gliders, and we
can learn to manage our propulsion systems, too.

Note that it's an inclusive "we": pilots, soaring organizations, manufacturers, and
regulators.

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

On 11/6/2022 11:40 PM, 2G wrote:
> The clear attitude of eglider enthusiasts here is that
> we skeptics must prove that lithium batteries are unsafe
> (which I think I have done, BTW).
> My attitude is that the proponents, especially the manufacturers,
> MUST prove that they are safe.
> This HAS NOT happened to date. Conclusion: fly at your OWN RISK!

I recently returned from the OSTIV SDP and WEP meetings in Stuttgart.
The WEP (working group on electric propulsion) spent most of the day
discussing certification requirements and means of compliance for
battery safety (manufacturers and certification authorities attended).
This is not being taken lightly!
However:
- Light gliders aren't certified and those manufacturers may or
may not actually do the hard testing. VERY hard testing.
- older gliders and battery packs had 'less rigorous' testing
- cell availability is driving pack redesign with associated
retest and re-certify efforts.

The packs are better but still not all glider-pilot proof.
We also discussed means of tracking abuse and the pack
disabling itself (drop it on the pavement and it shuts off
permanently). Not currently in certification requirements!

Some of us enthusiasts are also healthy skeptics and engineers
and live in the real world. And try to improve it.