EEVblog #1340 - New Tesla 4680 Battery Cell EXPLAINED

[tszaboo]

But this, I couldn't predict. It's funny how trivial idea this is, yet it never crossed my mind!

https://en.wikipedia.org/wiki/Egg_of_Columbus

Well, no. Anyone who worked in engineering knows, that ideas are somewhat worthless.
You are an engineer, working at a big company, your job is to do the welding of the battery tabs. Let's say you have an idea, same idea what Tesla is doing right now. You work with the welding of the cells days and night, your thoughts are around the subject, you are bound to have ideas, you are an engineer. Your idea is good, it should improve the battery. You turn to your boss with it. He is the leader of the welding group, he's been welding tabs for 30 years. He seen welding tabs in the olden days. Lets say he even passes this idea to his boss, he is not going to be as enthusiastic about it, as you. You are supposed to fill out Form 342 for an  ECR, but you are supposed to attach budget estimation, ROI calculation, impact assessment, approval from someone you never met.
You have no idea how to fill this out, it could take months to research even how much impact this would have. And you are actually only good at tab welding calculation, the tab bending is an entirely different department, with Chris. Nobody likes Chris, you would need to work with him. But you also have your regular tasks to carry out, and nobody approved the research project, to fill out the stupid form, so an MBA trained idiot can bin the project. So you go home miserable, because you know it is not worth fighting over, and putting your job on the line. The company doesnt even give bonuses for ideas, and Molly is expecting the second child.
15 years later you become a manager, who doesnt care anymore. You are not even good at management, but you accept the position, because it pays more. A year later, some youngster comes to you with his new idea...

[Fungus]

But this, I couldn't predict. It's funny how trivial idea this is, yet it never crossed my mind!

https://en.wikipedia.org/wiki/Egg_of_Columbus

Well, no. Anyone who worked in engineering knows, that ideas are somewhat worthless.
You are an engineer, working at a big company, your job is to do the welding of the battery tabs. Let's say you have an idea, same idea what Tesla is doing right now. You work with the welding of the cells days and night, your thoughts are around the subject, you are bound to have ideas, you are an engineer. Your idea is good, it should improve the battery. You turn to your boss with it. He is the leader of the welding group, he's been welding tabs for 30 years. He seen welding tabs in the olden days. Lets say he even passes this idea to his boss, he is not going to be as enthusiastic about it, as you. You are supposed to fill out Form 342 for an  ECR, but you are supposed to attach budget estimation, ROI calculation, impact assessment, approval from someone you never met.
You have no idea how to fill this out, it could take months to research even how much impact this would have. And you are actually only good at tab welding calculation, the tab bending is an entirely different department, with Chris. Nobody likes Chris, you would need to work with him. But you also have your regular tasks to carry out, and nobody approved the research project, to fill out the stupid form, so an MBA trained idiot can bin the project. So you go home miserable, because you know it is not worth fighting over, and putting your job on the line. The company doesnt even give bonuses for ideas, and Molly is expecting the second child.
15 years later you become a manager, who doesnt care anymore. You are not even good at management, but you accept the position, because it pays more. A year later, some youngster comes to you with his new idea...

It's almost as if you didn't read the wikipedia page before replying.

[fsr]

According to this site, the price of puch cells was getting closer to that of the cylindric cells back in 2013, so what's the advantage of the cylindric cells nowadays for this kind of use?: https://batteryuniversity.com/learn/article/types_of_battery_cells

No doubt that those metal cylinders are going to weight a great deal, so why not getting rid of all that, by using flat cell construction?

Couldn't the pouch cells just have a big tab as long as the cell itself? Positive at one side of the pack, and negative at the other? That would bring the same advantages of improved thermal dissipation and current capability to that kind of cells.

[wraper]

According to this site, the price of puch cells was getting closer to that of the cylindric cells back in 2013, so what's the advantage of the cylindric cells nowadays for this kind of use?: https://batteryuniversity.com/learn/article/types_of_battery_cells

Batteryuniversity is trash I would not blindly trust. Pouch cells are harder to produce than cylindrical cells.

No doubt that those metal cylinders are going to weight a great deal, so why not getting rid of all that, by using flat cell construction?

It's not like pouch cells exist in vacuum. Shell of tesla 2170 batteries is 0.15mm thick IIRC.

That would bring the same advantages of improved thermal dissipation and current capability to that kind of cells.

Pouch cells have the same cooling issues like regular cylindrical cells.

[Siwastaja]

Batteryuniversity is totally meaningless as a source for cell prices. (For that matter, it's a meaningless source for almost anything else as well, Spreading Confusion since 2003.)

The only way you can know about the cell prices is going to the source; getting quotes from the manufacturers or distributors. Anything else is speculation. Tesla has claimed cylindrical cells were economically more viable in large scale, and I trust them; I did the same evaluation in small scale (thousands of cells) and got the same result.

The metal case of a cylindrical cell is very thin, not a significant portion of the total weight. A pouch cell uses aluminium-plastic laminate which is of course saves a small amount of weight (maybe 1%-ish?), but OTOH, then it needs more external protection, whereas the metal cylinder has a great ratio between weight and mechanical strength.

Don't know about the situation now, but 18650 cells leaded in energy density (actual, not theoretical) still a decade ago. For some reason I don't fully understand, pouch cells have shown slightly inferior energy density despite small weight savings due to not having the metal case. This may have nothing to do with the form factor or chemistry itself; it could have been due to corporate policies putting the cutting edge recipes into 18650 form factors (laptops being the driving force for 18650 energy cells).

One clear positive factor in cylindrical form is that there is no issue with having to do sharp bends with the foils. It's an uniform roll, very easy to wind with a machine, then insert into the can. Not having to weld the tabs will make it even easier. Of course, there is some wasted space in the middle of the roll (exactly due to avoiding tight bending radius, which pouch cells need to deal with).

[tszaboo]

18650 made sense, and it was economical, because there were multiple suppliers for it. If you didn't like the pricing of the 18650 of supplier A, you could turn to supplier B and ask them a quote. You could pressure them to give you better pricing by pitting them against each other. Pouch cells are custom size. If you ask B to make you pouch cell in X size, they are going to tell you that you need to send them millions first, to set up or adopt the production line for you. And maybe you need to commit buying millions of cells as well.

This was the situation five years ago, integrating the battery into the car was time consuming and expensive. But this is not the case anymore. The MEB platform from VW takes 8-12 battery packs. They showed the pack compatible with 3 different cell configuration already, 2 pouch cell, and a prismatic cell, different manufacturers. It is just a standard square box, so you only need to integrate the battery into the box, which then can go into dozens of different cars. For a range of cars, starting from a hatchback, ending with an SUV. If someone leapfrogs the others in battery technology, integrate into the box, done. Probably you can fit a Tesla cell into the box, if they decide to sell the battery.
And that's just VW, Kia has their EV platform ready, and Nissan and Toyota is working on it. By not betting on a single technology, you have the possibility to adopt your car faster.

[timmytool]

This was the situation five years ago, integrating the battery into the car was time consuming and expensive. But this is not the case anymore. The MEB platform from VW takes 8-12 battery packs. They showed the pack compatible with 3 different cell configuration already, 2 pouch cell, and a prismatic cell, different manufacturers. It is just a standard square box, so you only need to integrate the battery into the box, which then can go into dozens of different cars. For a range of cars, starting from a hatchback, ending with an SUV. If someone leapfrogs the others in battery technology, integrate into the box, done. Probably you can fit a Tesla cell into the box, if they decide to sell the battery.
And that's just VW, Kia has their EV platform ready, and Nissan and Toyota is working on it. By not betting on a single technology, you have the possibility to adopt your car faster.

By making the batteries bigger it makes it harder to optimise for every car. MEB would be great for low scale jobs but at scale you cant do things like Tesla's doing, like a highly dense structural pack.

With Tesla's system they can go 2 ways:
Optimise the cell content to the best technology then each car has its optimal structural cell layout. If voltage changes adjust electronics or the cell interconnects to a different series/parallel, ± cells if the math does not add up as its trivial at 1000 cell packs.
-or-
The new tech is so fundamentally different they need to redesign the whole structure to get optimal performance anyway.

The MEB platform on the other hand is going to be so inflexible on the box size and voltage, it will require custom cell sizes to optimise different voltage cells or accept pack density losses to avoid extensive retooling. To top that off they are going to be non-structual or be engineered to fit a standard stress model that is far from optimised for any one car, raising costs and weight.

The metal case of a cylindrical cell is very thin, not a significant portion of the total weight. A pouch cell uses aluminium-plastic laminate which is of course saves a small amount of weight (maybe 1%-ish?), but OTOH, then it needs more external protection, whereas the metal cylinder has a great ratio between weight and mechanical strength.

Don't know about the situation now, but 18650 cells leaded in energy density (actual, not theoretical) still a decade ago. For some reason I don't fully understand, pouch cells have shown slightly inferior energy density despite small weight savings due to not having the metal case. This may have nothing to do with the form factor or chemistry itself; it could have been due to corporate policies putting the cutting edge recipes into 18650 form factors (laptops being the driving force for 18650 energy cells).

From my understanding of the situation, cell layer pressures can be maintained in a cylindrical cell stopping layer delaminations and requiring less electrolyte. Cylindrical cells also use the best properties of the can for mechanical strength while lowering weight and mechanical/electrochemical distress on the cell. Pouch cells often have a higher C rating necessitating thicker current collectors, allowing a smaller pack to service the same load for a smaller time.

This is why many Tesla swapped cars use pouch cells like LG chem's to get a physically smaller with cost and energy reduced packs that has the capacity to power the motor.

[micheljull]

I agree with Schwump, the volumetric efficiency of packing cylinders is always 90.69%, regardless of dimensions. So not sure what's being referring to by "improved volumetric efficiency"??

True. Dave may have missed this 90.69% packing density regardless of diameter thing, however that’s for closely packed cylinders. This will be the case for the 4680 cells  (attached screenshot) but not for present 2170s where room is wasted by the cooling snake and by module walls. So the energy density per unit pack area should definitely increase wrt present packs.

[micheljull]

But this, I couldn't predict. It's funny how trivial idea this is, yet it never crossed my mind!

https://en.wikipedia.org/wiki/Egg_of_Columbus

Well, no. Anyone who worked in engineering knows, that ideas are somewhat worthless
...and Molly is expecting the second child.
15 years later you become a manager, who doesnt care anymore. You are not even good at management, but you accept the position, because it pays more. A year later, some youngster comes to you with his new idea...

👍 Excellent

[micheljull]

Congrats Dave, this is by far the best video on the subject, so I joined the forum!

[micheljull]

Has anyone noticed that the 16% increase in range —by form factor alone— was almost entirely due to the increase in height/length ? 4680 is 14% taller than 2170, thanks to module removal.

[Neilm]

The other issue with pouch cells is that they expand and contract during the charging cycle. This means they are a bit harder to mount as this movement has to be accounted for. With the metal wall the 18650s et al don't have that issue

[wraper]

Has anyone noticed that the 16% increase in range —by form factor alone— was almost entirely due to the increase in height/length ? 4680 is 14% taller than 2170, thanks to module removal.

There are lower losses in the battery as well.

[Dr Bob]

While it's been rumored that GM has sold their Bolt at a loss, doing so may earn them Carbon Credits that allow them to sell more very high margin SUVs and Trucks so the bottom line for the company is positive even if it's red for the Bolt. That might also be why they keep production limited. Tesla, on the other hand, has only shown a profit through the sale of credits. They may have a positive "gross margin" on the cars but the cost of operating the business burns right through that percentage. Tesla also does their accounting differently than the rest of the automotive world so it's exceptionally hard to compare them to anybody else.

Other makers may be making a profit on their EVs. It's not often clear in published financials. I expect that we are only now starting to see more and more EV models announced and released as it's getting to be possible to sell them at a price with enough buyers. A couple of decades ago there was a decent size DIY trend in converting small pickup trucks into electric but it was expensive and if you wanted Li chemistry batteries, it was stupid expensive. The GM EV1 was monstrously expensive and had a cubic km of R&D in it which is why they only leased them. The EV1 was strictly a compliance car when California had passed a law that would have required automakers to sell/lease a certain number of ZEVs in the state to be able to sell any ICE cars. The was overturned (bribes paid, politicians bought, I'm sure).

There is an old saying that "you can't railroad until it's time to railroad". The tech for EVs is hear and now it's a matter of getting the costs down so enough people can purchase them to make them financially viable to manufacture. Big car companies can't efficiently run production lines at less than full speed. A factory that isn't open all hours is losing money given what they cost to build and equip. It's getting even more complex with all of the robotics and other automation. The interest on the loans for the bots goes on 24/7 whether cars are being built or not.

[Dr Bob]

I was very surprised when Panasonic announced further investment at their facility in the Gigafactory and now Tesla is saying they are going to start producing they own cells in house. I'd love to be a fly on the wall of the Panasonic board room. A downside to bringing cell production in house is that Tesla has to make a significant capital investment in machinery. Added to that, since the cell is a custom size unique to them, if anything goes wrong, they are dead in the water.

A pouch cell seems to be easier to make. There is no processing of the outer shell and equipment can be easily designed to rapidly change the pouch sizes. I was just helping a friend look at food packaging machinery for a new product line and we were looking at pouch type packaging. To change sizes and even aspect ratios is not hard to do with off-the-shelf equipment. I'm not so sure that if you have machinery that makes 18650 cells that it would be possible to convert to 46800 and back again. Up until now, nobody has had that requirement. That means that if Tesla's battery plant suffers some sort of catastrophe, they can't just buy cells on the open market or contract with another firm until they are back up and running.

[Dr Bob]

(I believe their current cars have to wait around and cool off a bit if you do too many launches)

Likely, but that's not a common problem for the average driver.

[Dr Bob]

Sandy Munro has done a couple of videos recently and he's a huge Tesla convert. While there does seem to be some good improvements to the new size, Sandy was guessing Tesla would epoxy the cells into the pack for added rigidity. The old pack was loaded with some sort of potting compound. Both approaches make the battery packs extremely hard to recycle, break down to reuse good cells or repair. This is a huge penalty clause in my book. As engineers, it's our responsibility to be thinking about End-of-Life and repairability issues. Recycling batteries is going to be monumentally important going forward. Making large packs so individual cells can be recovered is also a big deal. The idea is that car batteries will continue living on in stationary applications. If duff cells can be removed and used cells from another retired pack swapped in, the maximum usage of the raw materials can be obtained.

I love the YouTube channels of people that take vintage high quality tools and restore them to better than new condition so they live another century or more. It's worth it when the tool was very well made to start with. A cheap tool repaired isn't likely to repay the time put into the repair since something else will break in short order.

[wraper]

Sandy was guessing Tesla would epoxy the cells into the pack for added rigidity. The old pack was loaded with some sort of potting compound. Both approaches make the battery packs extremely hard to recycle, break down to reuse good cells or repair.

Elon himself told that battery will be a structural part of the car thus reducing overall weight. And he also said there will be hard compound instead of soft compound in model 3/Y batteries. Reusing old cells is not really a good/safe way of recycling. Also even as of now reusing cells from model 3/Y batteries is a big PITA.

[Fungus]

That means that if Tesla's battery plant suffers some sort of catastrophe, they can't just buy cells on the open market or contract with another firm until they are back up and running.

I doubt they'll able to buy 18650s in the quantities they need, either.

Plus: They'll have more than one factory. It would take more than one asteroid strike to kill them off.

[peepsalot]

@ 21:00 You compare the power loss at the same amp rating, but for larger cells, they will presumably be providing more current per cell.  Say 5-6x the current per cell, depending on if you keep energy or power of the overall pack the same. 

So a better comparison would be 2W loss @ 10A for 2170, vs 5W @ 50A, or 7.2W @ 60A for 4680 (per cell)

Then to make it "comparing apples to apples" again, we can divide that loss by 5 or 6 and get 1-1.2W loss per 10A current for an equivalent pack.  Its still theoretically a nice improvement, but about half rather than an order of magnitude less.

[wraper]

According to Elon, German built model Y will have these batteries and all other fancy stuff. A completely different car internally. And I guess we Europeans will be beta testers of sort.
https://twitter.com/elonmusk/status/1313854912212750346?ref_src=twsrc%5Etfw

Berlin will use 4680 cell with structural battery pack & front & rear single piece castings. Also, a new paint system.

Lot of new technology will happen in Berlin, which means significant production risk. Fremont & Shanghai will transition in ~2 years when new tech is proven.

[sandalcandal]

Dave spotted @16:58

Also a long winded discussion of the 4680 tabless cell. I didn't find anything particularly new or interesting though but a decent overview looking at the battery day claims.

[mnementh]

Mhmmmm... this is hardly a revolutionary design idea, as has been stated in here already. I believe I've seen exactly this design used in alkaline disposable cells decades ago. Part of the reason tabbed design remains in the world of rechargeable battery tech is the inherent resistance of the welded-tab design to increased resistance over time vs a compression-only means of making contact with the plates. These engineers understand that their product is not disposable; that it needs to actually work for a considerable length of time as it is by its nature a long-term rechargeable technology.

While these cells may be the schizz when new, I have misgivings aboot how their low iR will persist over 10 years... or even as little as 2 to 5 years, while the vehicles are supposedly still under warranty. Given the horrible reputation Tesla has earned with regard to post-consumer product support (even reneging wholesale on their "Certified Pre-owned" marketing promises as has been suggested in certain videos), I'm not exactly convinced that any of it is any more than a kick-the-can-down-the-road ploy to aggregate liquid funds today while claiming to eliminate their "dependence" on existing cell manufacturers.

mnem
 

[wraper]

I believe I've seen exactly this design used in alkaline disposable cells decades ago.

100% nonsense which is as far from the truth as it could possibly be. Alkaline cells are nothing like that. They don't even have layers to begin with.

[wizard69]

people are also assuming that the partnership is completely dissolved.    Panasonic could setup their own compatible battery factory.    It would be good for the industry, Tesla and the alternative users.   Just consider how popular 18650's have become in the last few years, they are in power tools, cars, phone chargers, radios and a bunch of other stuff.   

In fact I could see Tesla driving the tech out of their factories to make sure there is a strong supply of the form factor.    If battery production is as big of an issue as many have implied then having multiple sources for the same basic battery would be Tesla's goal.   In fact I can already see power tool manufactures getting onboard the minute these batteries where available outside of Tesla's volume.

That means that if Tesla's battery plant suffers some sort of catastrophe, they can't just buy cells on the open market or contract with another firm until they are back up and running.

I doubt they'll able to buy 18650s in the quantities they need, either.

Plus: They'll have more than one factory. It would take more than one asteroid strike to kill them off.