TESLA and new 22700 cylindrical battery coming?

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TESLA and new 22700 cylindrical battery coming?

Post by Doctorbass » Aug 28 2014 10:21pm

I am very curious about this new battery format that i have read that Tesla want to use for reducing price of their battery.

The 22700 format would replace the popular 18650 format.

The 22700 would be 22mm diameter and 70.0mm long witch mean that these new cells would be larger ddiameter but similar lenght.

We know that the smaller teh cylindrical cell are the more you can stack in the same volume.. so increasing their diameter appear to me to be a strange desicion... I need more details about that...
Now, Musk says he will cut costs further by building a “gigafactory,” a gigantic plant that will at once double the global production of lithium-ion batteries. That scale, he reckons, will shave another 30% off the cost per kWh. He also plans to add one-third more energy volume per battery by using larger cylindricals, known as 22700s, according to Navigant. Thus, Musk expects his battery costs to drop to $175 per kWh by 2017, making that same 60 kWh battery $10,500. But that cuts just $4,500 off the cost of the Model S; he needs another $30,000 or so.
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Re: TESLA and new 22700 cylindrical battery coming?

Post by Hillhater » Aug 28 2014 10:40pm

I suspect it's just a non tech journo ,misinterpreting the information.
That simple increase in cell dia to 22mm would add ~50% more volume to each cell! which means more Whrs per cell.
(Possibly a 5-6 Ahr cell ?)
I always suspected Musk would be looking for a bigger cell for the EV packs.
I am just surprised it is not going to be a even bigger cell..!
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Re: TESLA and new 22700 cylindrical battery coming?

Post by Ohbse » Aug 28 2014 10:47pm

Volumetric efficiency is only one piece of the puzzle. By increasing capacity per cell you can drastically reduce the number of interconnections, reduce monitoring complexity, move the split of the BOM towards a higher percentage of 'active' ingredients, decrease time required to assemble packs and probably 2,000 other good reasons I can't think of immediately. Makes sense to me..

Also considering the cooling requirements in the Tesla application the slight decrease in volumetric efficiency might not matter very much at all either.

18650's are far from an optimal package for EV's - they just happen to already exist in large quantities. If you're building a clean sheet factory why would you use the same tooling?

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Re: TESLA and new 22700 cylindrical battery coming?

Post by Punx0r » Aug 29 2014 11:36am

Ohbse wrote: 18650's are far from an optimal package for EV's - they just happen to already exist in large quantities. If you're building a clean sheet factory why would you use the same tooling?
Exactly. The question for me is: Why take a baby step to 22700? Maybe it's a practical consideration based on reusing 18650 technology/tooling. I would have thought they'd move to much larger cells, possibly pouches, possibly a 1P pack.

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Re: TESLA and new 22700 cylindrical battery coming?

Post by TheBeastie » Aug 29 2014 12:43pm

Punx0r wrote:
Ohbse wrote: 18650's are far from an optimal package for EV's - they just happen to already exist in large quantities. If you're building a clean sheet factory why would you use the same tooling?
Exactly. The question for me is: Why take a baby step to 22700? Maybe it's a practical consideration based on reusing 18650 technology/tooling. I would have thought they'd move to much larger cells, possibly pouches, possibly a 1P pack.
I think the reason why they wont use pouches are a no-brainer because it lacks general safety, when a Tesla crashed a few months ago the media reported fireworks like sparks at the crash site, this is due to the steal canisters of 18650s holding their ground.
I am just wondering why they didn't just go with the 26650 standard if they wanted a bigger cell the standard, there is plenty of hard yards already done behind it.
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Re: TESLA and new 22700 cylindrical battery coming?

Post by r3volved » Aug 29 2014 12:53pm

maybe they'll be hexagonal cylindrical for max volume :D
...is that even possible? I'm just shooting from the hip

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Re: TESLA and new 22700 cylindrical battery coming?

Post by teslanv » Aug 29 2014 2:21pm

I don't think there would be any loss of volumetric efficiency by changing the diameter of the cells. The ratio of empty space to Cell space would not change with cell diameter size. (I verified that with AutoCAD)
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Re: TESLA and new 22700 cylindrical battery coming?

Post by arkmundi » Aug 29 2014 5:45pm

Thus, Musk expects his battery costs to drop to $175 per kWh by 2017
That would be great! Someone needs to start tapping Musk for the cells now, to source them for the rest of us poor folk who can't afford a Tesla, even the half-price economy version.

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Re: TESLA and new 22700 cylindrical battery coming?

Post by Arlo1 » Aug 29 2014 8:29pm

You guys are all forgetting or maybe you don't know but tesla spaces all cells out as well so when they calculate their spacing it maybe different.

Round cells don't work for tight spaces but tesla found a way to make very good use of them. IN a Motorcycle its different because you have less room to work with so pouch cells seem to be more common place.
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Re: TESLA and new 22700 cylindrical battery coming?

Post by jonescg » Aug 30 2014 8:01am

Yeah, I'd say reducing the number of interconnects would be a main reason for upping the volume/capacity. But it is interesting that the 26650 format wasn't chosen.

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Re: TESLA and new 22700 cylindrical battery coming?

Post by gogo » Aug 30 2014 8:04am

jonescg wrote:Yeah, I'd say reducing the number of interconnects would be a main reason for upping the volume/capacity. But it is interesting that the 26650 format wasn't chosen.
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Re: TESLA and new 22700 cylindrical battery coming?

Post by Punx0r » Aug 30 2014 11:12am

Tesla wouldn't be worried about accidentally buying counterfeit cells and an odd cell format wouldn't stop aftermarket companies offering (potentially dodgy) replacement modules using different cell formats.
TheBeastie wrote:I think the reason why they wont use pouches are a no-brainer because it lacks general safety, when a Tesla crashed a few months ago the media reported fireworks like sparks at the crash site, this is due to the steal canisters of 18650s holding their ground.
I am just wondering why they didn't just go with the 26650 standard if they wanted a bigger cell the standard, there is plenty of hard yards already done behind it.
Tesla use properly engineered modules so each cell having its own sturdy container isn't much of an advantage IMO. You're just driving down the energy density of your pack by including lots of unnecessary steel. I don't see why pouch cells in a properly engineered module would be any risk at all.

The 18650 format is mature and impressively reliable. That Tesla can make a reliable pack with thousands of components is impressive. A typical path to reliability is to reduce the number of parts in a system.

Good point on the 26650.

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Re: TESLA and new 22700 cylindrical battery coming?

Post by Hillhater » Aug 30 2014 7:27pm

I assume Elon and his boys have done some thinking about this ?
There are many established formats.... 32620, 32900 321570 (A123 ), etc, all of which have proven manufacturing equipment and processes in operation. They could easily have a 10-15Ahr can type cell if they had wanted to.
So why Tesla settled for a simple 4mm increase in dia is puzzelling
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Re: TESLA and new 22700 cylindrical battery coming?

Post by spinningmagnets » Aug 30 2014 7:45pm

When you're small, it makes a LOT of sense to use established formats as much as possible. I think this new format is simply the engineering team decided that since they plan to make billions of cells, they will not need to use an existing format. Perhaps all of the manufacturing machines will be all-new (but similar to existing)?

I seem to recall that Tesla was getting very cozy with Mercedes and BMW. Perhaps computer modeling of various packaging formats picked this size and shape? making a new cylinder size might at first seem to prevent the new cells from becoming an alternative for established E-cars/hybrids, but...I think it is the other way around.

If Tesla, Mercedes, and BMW go in a certain direction and it turns out to be a big success, perhaps the industry...will follow them?

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Re: TESLA and new 22700 cylindrical battery coming?

Post by macribs » Aug 30 2014 9:54pm

I agree spinningmagnets. Musk have done amazing things in his past. From paypal to Tesla.
Already he is cozy with Mercedes and he gets various bits and bobs from Mercedes for the model S. Like turnsignal handles, headlights knob and air matic suspension is also from Mercedes. And him building a new plan from scratch I am sure he has planned well ahead and made room for production capacity so large that Tesla/Panasonic can easily sell to other brands as well. After all, he already made loads of Tesla's patents open source. So he seems believable when he claims spreading the technology and make EV mainstream is his number one goal.

So if Musk is heading in a new direction regarding battery diameter I am sure he has already planned well ahead and probably already lined up a few heavy hitters as customers. As more and more established car manufacturers are exploring EV's they will need a tried and tested partner to avoid huge R & D costs. And what better partner to team up with then the man and his company that was able to make EV "mainstream". In Norway model S is "as common as a VW" these days, and AFAIK we are the biggest importers of Tesla's today. Cos due to freiendly EV taxation - zero taxas and zero VAT. For now at least. :)

And hat off to Musk for implementing vast amount of robots and streamline production so they can keep assembly in the US. It is nice to see companies think alternative ways then outsourcing it all to China like we've seen the past 10 years or so.

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Re: TESLA and new 22700 cylindrical battery coming?

Post by Hillhater » Aug 31 2014 3:44am

macribs wrote: So if Musk is heading in a new direction regarding battery diameter ?...."
There is nothing "new direction". about a 22mm cell diameter.
That size has been in production for over 40 years in various lengths ( remember "C" , and "Sub C" cells ?)
Much as I admire Musk, I think this is a lost opportunity .
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Re: TESLA and new 22700 cylindrical battery coming?

Post by Rexie » Aug 31 2014 11:10am

Punx0r wrote:
Ohbse wrote: 18650's are far from an optimal package for EV's - they just happen to already exist in large quantities. If you're building a clean sheet factory why would you use the same tooling?
Exactly. The question for me is: Why take a baby step to 22700? Maybe it's a practical consideration based on reusing 18650 technology/tooling. I would have thought they'd move to much larger cells, possibly pouches, possibly a 1P pack.
Musk offered his help with the batteries of the Boeing DreamLiner, (of course they refused) and later said that it was more troublesome to manage the heat of bigger batteries all packed in a tight space.
Maybe he found the sweet spot...

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Re: TESLA and new 22700 cylindrical battery coming?

Post by Hillhater » Aug 31 2014 6:24pm

Rexie wrote: Musk offered his help with the batteries of the Boeing DreamLiner, (of course they refused) and later said that it was more troublesome to manage the heat of bigger batteries all packed in a tight space.
Maybe he found the sweet spot...
Doubtful, ...when you compare the complexity of the cooling systems required in the "3C" Tesla packs,....compared to the relative simplicity of the higher "C" potential Leaf pouch packs, and the much simpler cooling system of the Volt pack.
The fundamental fault of the Dreamliner pack was the failure of the BMS systems to do their job.
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Re: TESLA and new 22700 cylindrical battery coming?

Post by Rexie » Aug 31 2014 8:16pm

Hillhater wrote:
Rexie wrote: Musk offered his help with the batteries of the Boeing DreamLiner, (of course they refused) and later said that it was more troublesome to manage the heat of bigger batteries all packed in a tight space.
Maybe he found the sweet spot...
Doubtful, ...when you compare the complexity of the cooling systems required in the "3C" Tesla packs,....compared to the relative simplicity of the higher "C" potential Leaf pouch packs, and the much simpler cooling system of the Volt pack.
The fundamental fault of the Dreamliner pack was the failure of the BMS systems to do their job.
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The approach we take at Tesla and SpaceX is we have smaller battery cells with gaps between them, and we make sure that if there’s a thermal runaway event which creates quite a bit of fire and smoke that it directs that fire away from other cells, so you don’t have this domino effect….

The long term solution for having 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.”
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Re: TESLA and new 22700 cylindrical battery coming?

Post by arkmundi » Aug 31 2014 8:35pm

Rexie wrote:“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.

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Re: TESLA and new 22700 cylindrical battery coming?

Post by liveforphysics » Aug 31 2014 9:21pm

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.

If you are using round cells, it doesn't matter if you make them tiny diameter or large diameter, the percentage of unused space is equal.

It does enable better temperature control if you don't have as much distance from the center of the cell to the sides/edges you can cool.

That said, I personally think using little thousands of tiny round cans is silly, yet Tesla did solve how to do it with excellent results, so more power to them.
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Re: TESLA and new 22700 cylindrical battery coming?

Post by Joseph C. » Aug 31 2014 10:27pm

liveforphysics wrote: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.
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Re: TESLA and new 22700 cylindrical battery coming?

Post by flathill » Aug 31 2014 11:07pm

Prismatics are built like puff pastries. Ignoring the steel case a sprial cell is naturally a better form (for long life)

They could make bigger cylindrical spiral cells that would only be true if they could go longer

They cant go wider for heat transfer

They cant go longer/taller for the skateboard chassis packing with the cells stacked like they are now

"Identical electrodes wound in both a cylindrical and a prismatic configuration provided different capacity fade rates. At the completion of 300 cycles with a C/2 charge and 1C discharge, the prismatic cells faded 24% and the cylindrical cells faded 16%. In the cylindrical-type cell, the fade was primarily caused by a reduction in the capacity of the cathode. The higher fade rate in the prismatic cell was attributed to lower cell stack pressure which resulted in more anode swelling during cycling."
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Re: TESLA and new 22700 cylindrical battery coming?

Post by Doctorbass » Sep 01 2014 12:04am

That is becoming an interesting debate guys :D

BEst cell shape and size !.. That will remain a long debate i believe!

About the question of diameter of the cells that wold impact the energy density I remember i have read in some document of Battery University or Sandia Lab that more small cylindrical cells allow more energy density than less larger cell but i dont remember wahat was the reason..

I agree that the math show that it's the same volume fill but there was otehr interesting reasons that i can't remember :lol: :roll:

anyway...


Luke I agree with you: it does enable better temperature control if you don't have as much distance from the center of the cell to the sides/edges you can cool.

I remember i saw many thermal imaging of cylindrical cells that was showing that..

What i have found interesting is that the thermal dissipation of the cells is also taking account of the heat sinked thru the tabs and connections.

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Re: TESLA and new 22700 cylindrical battery coming?

Post by flathill » Sep 01 2014 12:20am

Tesla can predict it all using Comsol and Abaqus

http://imechanica.org/files/Yeow_AVL_final_2202012.pdf

Tesla still stuck with cylindrical it seems

I think the reason is the puff pastry factor. You can make both prismatic and cyclindrical perform well thermally but by the time you squeeze prismatics together and use silicone foam in between them the costs add up and even then you have not full solved the puff pastry factor inherent in the stacking design. As energy density goes up the need for cell spacing to prevent fire become more critical. Prismatic cells with spacing and you end up with a can and now you are back at square one but still dont have the spiral inherently more resistant to expansion contraction. Now mix in liquid cooling to the mix and you sway even more to the spiral design. For all out performance prismatic will always win though. For long life spiral cells will always have a slight edge

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