TESLA and new 22700 cylindrical battery coming?

[Hillhater]

Cylindrical cells will contain more volume for a given surface area than any other prismatic shape.
They also are better for manufacturing at high speeds than square, or flat pouch shapes, so there are some definite advantages.
But, all this chat about heat dissipation is to me completely wrong, since heat is wasted energy = inefficient battery chemistry . I would expect the Tesla / Panasonic wiz kids to refine the cell chemistry and performance to make temperature control a feature of "dinosaur " pack design.
Surely they could learn something from those nice A123 , 32150 high output cells ?
As to interchangeability with existing packs,...all they need to do is make the external dimensions and interface connections the same, and they could put any shape cell format inside.
If you have seen the construction of the packs , and attempts to disassemble them,.. You know there won't be much "reuse" of components. Mostly "recycling" and recovering of base materials for reprocessing.

 

[riba2233]

Surely they could learn something from those nice A123 , 32150 high output cells ?

Yes, they could learn how to make pack that is two times heavier and has 3.5x bigger volume.

If they wanted cooler cells, they would have used some of the mighty trio, sony vtc5, lg he2 or samsung 25r, which have smaller capacity than cells that tesla uses, but still 2.4 times more wh per volume unit then a123.

But obviously they had their reasons why they went with lower power cells.

 

[Hillhater]

Oh, sure the energy density was poor, but hell they could pump out the power efficiently with little heat generated.
Considering that the A123 is now ~~10yr old tech, it's only reasonable to think there may have been some progress to either develop that tech for better energy density, or get the LiCo /Imr/NCA tech to generate less heat.
What are all these scientists doing ? Drinking beer and surfing porn sites all day ??
..

 

[riba2233]

I don't know, but they have produced the new generation NMC/NCA which are high power, but also high capacity. (The power trio I've mentioned in my last post.)

I think Tesla uses improved Panasonic ncr18650BE, which is nominally 3200 mAh, and 10A. But I think that they've added battery cooling/heating system because of supercharging, and keeping batteries warm during winter and cool during summer. So those cells are probably good enough for them.
For roadster they used cgr18650cg, which is 2C cell.

It would be cool to see some NMC/NCA cell from a123, but I think that those would be very expensive, and other companies already have huge advantage and much more experience, so I don't know if that's realistic to expect.

 

[dnmun]

scientists do not drink beer and do not spend all day looking at porn. they usually drink wine and porn only takes a minute or two so they have the rest of the day free to figure out why their calculations did not match the experimental results.

i think by now most of us know that the cells need compression and the cans provide compression effectively without having to design large plates to keep the large pouch type cells under adequate compression uniformly across the surface. the way Tesla is cooling these cans may be the simplest solution they have that is already tested and proven and i bet the strength of the cans in the event of damage may be another consideration.

also i think they are planning to be able to keep track of bad cans in the pack at the cell level by using some kind of the thermistor attached to each can so they can monitor each can and keep track of the hot spots and remove that section of the battery, then they can remove the battery, replace the defective can in the parallel array and then reinstall the pack to maintain the warranty provisions. all jmho.

 

[Punx0r]

Some interesting points have been raised in this thread

 

[methods]

They are making like a... 100 billion dollar gamble
Most likely... they made an educated guess (computer model) as to how far they could move away from "known good" and still meet their reliability/risk target for a worst case fail.

Known good being that which we have rock solid data on
Ideal being what people think will work but cant prove
What they came up with being what people *know* will work

Incremental improvement that manages risk well when shooting for the moon.

All this worry about density of round vs square... not even in the decision loop. These guys are swinging for the fence and the ball *is* going over the fans and into the bay. I am out there in the water with an electric kayak (and my mitt) listening to the crowd roar and waiting for my souvenir.

-methods

 

[Hillhater]

I don't know, but they have produced the new generation NMC/NCA which are high power, but also high capacity. (The power trio I've mentioned in my last post.)

It would be cool to see some NMC/NCA cell from a123, but I think that those would be very expensive, and other companies already have huge advantage and much more experience, so I don't know if that's realistic to expect.

Sorry, but we obviously have a different view of what " high power" lithium cells are.
If we simply use "C" ratings for an indicator ...( several other factors could be used)...then the range goes up past 150C.
Even allowing for variations in test procedures, and sales exaggeration , those 10C 18650 cells is not at the "power" end of the scale.
You are simply rating those LG, Sony, Samsung, cells relative to other 18650's which are even lower power capability (2-3C)
The reality is , those cells were developed for portable power tools which have short periods of peak output .
If you look at what happens to those 25R's under load, they heat themselves up to 80+DegC in under 5 mins !....
That is not very efficient or a good sign at relatively low C rates and certainly not anything acceptable in an EV cell.
Even the cheap nasty HK LiPo doesn't do that.

Maybe A123 will surprise us an bounce back into the market with a better cell, but I suspect the research momentum is with other teams currently, but for sure they still have access to some desire able tech.
Even the Chinese suppliers to HK have been able to significantly improve the energy density of LiPo over what was previously thought to be good, getting close to the 200 Whrs/kg of the 18650's.

 

[flathill]

It would be dumb for Tesla to sacrifice range for lower internal impedance (high c rate power cells)

Remember the Tesla Model S can drive for 16 hours at 25mph

Average use does not even average 1C discharge. Even if they did use high power cells that did not need active heating during normal use not in the desert they still would need active heating and cooling for the charging. In that respect the temp control system has no weight penalty and it makes even less sense to use a low energy density high power cell such as the a123

The only reason you need high c cells is for baby packs for people with limited budgets or for drag race or short race apps or maybe low voltage motorcycles or load leveling or .... But not an everyday full size electric car that you want to run much more than just one hour

Also remember the steel can is not providing compression like foam and straps on pouch cells does. The can is solid if it is round. Remember cells shrink also. Overall a cell under compression will experience more growth and shrinkage than a spiral cell in a solid round can (round can also inherently more robust than rectangular can)

 

[Hillhater]

Agreed, I was not suggesting that Tesla should use a high power cell ( just pointing out that there really is no high power 18650, other than the old 30C A 123 M1 )...Tesla , and all EV's , need high energy density cells that don't waste power by heating up when discharged OR charged at high rates.!
I just fell that it should be possible to develop a 10+ Ahr cylindrical cell that does it all !
Theoretically, a 30650 cell could do that using current energy density, so with all the development that has been going on (???), then maybe a 26650 could do it next year ?
..OR maybe that is what the 22700 cell is ??

 

[silviasol]

With all the money they make when will they make their own battery? Every time I think of that car I think of a huge laptop powered car. My god all that money for a car and they just source the most common batteries to make a pack. I would be impressed if I saw one large 3.7v cell 10ah+ completely different then you would see on other cars(or electric devices) and the same or less energy density then 18650. I could only assume it would drop the price drastically not purchasing them from a separate company. Tesla = e-car for noobs, lol.

18650 cells does not equal the future for electric vehicles. Too bad no other company will catch up and be able to create a better electric mainstream car with the price of their stock.

 

[Arlo1]

They are making like a... 100 billion dollar gamble
Most likely... they made an educated guess (computer model) as to how far they could move away from "known good" and still meet their reliability/risk target for a worst case fail.

Known good being that which we have rock solid data on
Ideal being what people think will work but cant prove
What they came up with being what people *know* will work

Incremental improvement that manages risk well when shooting for the moon.

All this worry about density of round vs square... not even in the decision loop. These guys are swinging for the fence and the ball *is* going over the fans and into the bay. I am out there in the water with an electric kayak (and my mitt) listening to the crowd roar and waiting for my souvenir.

-methods

Plain English please

 

[Rexie]

“The 787 batteries have very large cells, the battery cells are very big and they’re quite close together and there’s not enough insulation between the cells..... a battery pack that’s reliable and safe and lasts a long time is to reduce the size of the cells, and have more cells that are smaller and have bigger gaps and better thermal insulation between the cells.” - Elon Musk

Hey Rexie, can you reference that post? Thnks.

Just google a part of the text.
http://tinyurl.com/q5jr22p

 

[Rexie]

Motivations we don't have the insight to see from our limited perspectives would include ability to directly retro-fit into existing battery pack volumes.

Nail on the head. A year from now Tesla will have to upgrade the Roadster batteries for the first customers who opted for a future pack cell replacement. Six years from now the first of the Model S's will undergo the same treatment.

Unless in future they make two different battery systems one for the new cars and another separate battery system for the retrofits they are locked into using battery packs that always will be compatible with their older cars.

http://www.greencarreports.com/news/1093866_tesla-roadster-to-get-replacement-battery-400-mile-range-musk

 

[Rexie]

http://insideevs.com/expert-what-you-know-about-lithium-batteries-is-wrong-can-last-up-to-20-years/

 

[Hillhater]

Motivations we don't have the insight to see from our limited perspectives would include ability to directly retro-fit into existing battery pack volumes.

Nail on the head. A year from now Tesla will have to upgrade the Roadster batteries for the first customers who opted for a future pack cell replacement. Six years from now the first of the Model S's will undergo the same treatment.

Unless in future they make two different battery systems one for the new cars and another separate battery system for the retrofits they are locked into using battery packs that always will be compatible with their older cars.

http://www.greencarreports.com/news/1093866_tesla-roadster-to-get-replacement-battery-400-mile-range-musk

The upgraded Roadster pack will be just the higher capacity 18650 cells that are becoming available.
There is no reason why Tesla should not make two different pack/cells types for different model ranges, since they already have all the tooling and facilities for 18650 cells separate to the new Mega plant which will be configured around the new cell type.
If what we are told about cell supply volumes, and vehicle production forecasts is accurate, then Tesla cannot afford to decommission the 18650 cell pack facilities.
So,.. The new cells do not have to be retrofit able into existing models...but there is no reason why they could not be used that way if sufficient quantities (and costs) are favourable .

 

[BYqSXt8Z]

Cylindrical cells will contain more volume for a given surface area than any other prismatic shape.
They also are better for manufacturing at high speeds than square, or flat pouch shapes, so there are some definite advantages.
But, all this chat about heat dissipation is to me completely wrong, since heat is wasted energy = inefficient battery chemistry . I would expect the Tesla / Panasonic wiz kids to refine the cell chemistry and performance to make temperature control a feature of "dinosaur " pack design.
Surely they could learn something from those nice A123 , 32150 high output cells ?
As to interchangeability with existing packs,...all they need to do is make the external dimensions and interface connections the same, and they could put any shape cell format inside.
If you have seen the construction of the packs , and attempts to disassemble them,.. You know there won't be much "reuse" of components. Mostly "recycling" and recovering of base materials for reprocessing.

But heat dissipation remains important in keeping efficiency high, because after a certain point, heat increases the internal resistance, which increases the heat etc. Does not mean necessarily thermal runaway, but if you stack pouches together so you can compress them (because even good prismatic setups are compressed pouches, because the compression increases the energy density per volume while making the cell more stable), you have no way to have en just air-flow between them.

We aren't talking about very high temperatures either, as little as 60 degrees c (which is hot, but not impossible if you car is sitting in the sun) will start degrading the battery life. easy cooling = good, regardless of how efficient the chemistry is.

As for someone who mentioned the nissan leaf's low use of cooling as proof that you don't need it, the class-action lawsuit brought against them was because their lack of active cooling destroyed 25% of the battery life in the first 12 months. http://www.greenpatentblog.com/2012/10/10/class-action-charges-nissan-with-leaf-greenwash/

 

[Hillhater]

Oh I agree thermal management has been a critical advantage of Tesla's design, but as with their apparent intention to change the cell format, I whorls assume they would also have progressed cell chemistry and construction to improve electro/chemical efficiency to reduce heat generation at source, and thus reduce the level of waste heat that has to be dealt with. After all , heat is just wasted battery power !.
In short, I am expecting Tesla/Panasonic to have progressed cell Developemnt such that they can scale up the cell physically whilst improving performance and efficiency at the same time.

 

[BYqSXt8Z]

In short, I am expecting Tesla/Panasonic to have progressed cell Developemnt such that they can scale up the cell physically whilst improving performance and efficiency at the same time.

But at the end of the day, do you think effort (and research $) would be better spent trying to recoup those lost % of capacity that are currently being converted to heat, or increasing the energy density of the pack and / or charging speed? (obviously they all impact each other, eg. better thermal efficiency means easier faster charging; but for the sake of the discussion, let us assume they are separate).

I am curious how much energy is transformed to heat. I will get the calculations started, if someone can help with the specific heat, we can finish this.

-Considering that 1Wh equals roughly 0.3 BTU or roughly 310 joules
-18650 cell = 16.54 cubic cm
-1 cubic cm = 1 g or ml of water
-1 joule = +0.24K per g of water
-so for each 0.24 degree increase of 1 degree C (kelvin for what we care here just has a different scale, but same interval, so it translates) we need 16.54 joules, which means that 1wh can heat up the volume of water that an 18650 would occupy by 4.5 degrees C.

Now what we need... what would be the approximate specific heat of an 18650 cell (anode, cathode, electrolyte, casing)? Anyone have enough experience to be able to ballpark that one? It is way out of my abilities.

-Specific heat of cell / 4.18j/g (water's specific heat) x 4.5 = temp change in cell per Wh of wasted energy (tccpWh).

Assuming a 10 wh cell (nothing great, but not shabby either for an 18560...), how much does a cell heat just from running at a normal C (say 1 C if you are pushing it, given how huge those packs are)?

 

[parabellum]

Maybe they just made calculation on current spacing in existing 18650 package and came up with possibility of 4mm D and 5mm L increase without changing cell count and pack size, with minor changes to packaging and heat managment. They increase capacity, decrease discharge rate (and loses/heating hopefully decreasing IR).
Finally, there was some talking about Gen 3 and 1000km range somewhere.

 

[Hillhater]

Very interesting (informed ?) comment on the Tesla forum regarding the Model S pack design with the new cells .
Suggests a totally different method of construction and cell connection (pressure contacts) and cooling via the cell base ?

......Rob Ferber. He built the 18650 pack for the T-Zero at AC propulsion and then went on to found Tesla. Now he builds 18650 packs with no welds (flex pcb with foam cusion also like Neal Saiki). You will note Tesla is trying to patent flex PCB bus bars but with cooling on the neg terminal. Both the positive and negative connections will be made on the postive side of the cell on the next pack so the other side can be baseplate cooled. Much simpler than the current system with curvy aluminum pipes wrapped in Kapton. Also the current bond wire technique is senstive to vibration induced cracking of the bond wire. This means the pack is very heavy with all the cells glued in place. The Model 3 pack will be much more elegant and lighter than this over engineered tank pack.....

 

[Punx0r]

It would be very interesting if an OEM like Tesla went with a pressure-contact system rather than spot-welding, as the main advantage with the former is expediency for the home-constructor, and a spot-welded joint seeming inherently better.

Also interesting that they are continuing to file patents following Musk's diatribe against the system some time ago.

 

[kfong]

One thing I haven't heard, you don't need to sell just to the auto market. This format lends itself to the bigger consumer market, guarantees a demand base. Volume is where things become affordable.

 

[spinningmagnets]

Also interesting that they are continuing to file patents following Musk's diatribe against the system some time ago

There is a strategy I have seen in the past where someone who has a deep-seated hate for patents...has actually patented something, and then made the device/idea open-license. Some people believe this would prevent a competitor from patenting the device/idea and then "locking it up" to prevent its use by the general industry.

 

[johnrobholmes]

They already opened up their patent on the charging system, so there is merit to the method of patenting. Although I would think a flex PCB patent would be a great manufacturing advantage to them that would not be opened to all. Just think how easy pack rebuilds would become. Bad cell string? Open it up, plop in new cells, close it back. No welds or solders to undo, and removed cells that are still viable could be reclaimed for other uses like grid storage.