EEVblog #1340 - New Tesla 4680 Battery Cell EXPLAINED - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: October 02, 2020, 11:58:33 am
content: Dave explains why Tesla have switched from a 2170 cell to a bigger 4680 cell announced at Battery Day. What is the new tabless technology and what are the thermal cell and battery pack implications?Discussion on Lithium Ion battery cell construction, chemistry, manufacture, thermal design, internal resistance, heat sinking, and how cylindrical cells compare to large pouch cell construction.Tesla Patent:https://patents.google.com/patent/US20200144676A1/en?oq=20200144676

author: Schwuuuuup
author_rank: Newbie
timestamp: October 02, 2020, 02:11:32 pm
content: Maybe I'm overseeing a very simple thing, but stacking smaller cylinders or stacking bigger ones of same length, should result in the same density... or the at least in the same ratio of battery vs. void in between: Big cylinders -> big voids, but just a few, small cylinders -> small voids, but many of them.I guess that one benefit of the bigger batteries is that the inner core can be the same small size. There must be a limit how small you can make the innermost layer. So making a bigger roll, means you get pure additional usable volume.On the other hand.. using big cylinders with therefore bigger voids, you could fill this voids with smaller cylinders, thus archiving a better battery to void ratio ... but I don't think that this is practical.

author: Bud
author_rank: Super Contributor
timestamp: October 02, 2020, 02:27:59 pm
content: @3:18"Longer and thicker is better...Obviously!"

author: rs20
author_rank: Super Contributor
timestamp: October 02, 2020, 03:10:18 pm
content: 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"??

author: bristpi176
author_rank: Contributor
timestamp: October 02, 2020, 03:37:53 pm
content: I just did some 8th grade science on the subject of packing density with a compass and paper. If the new cells are packed squarely an 18650 or maybe even a 2170 will fit in the space in between. I know nothing about connecting them together with the larger cell and assume the two sizes would have to be separate circuits, but your ultimate density would be greater than any single size cell.

author: wraper
author_rank: Unknown
timestamp: October 02, 2020, 03:48:53 pm
content: The reason Tesla uses cylindrical cells is because they are easier and cheaper to mass produce. Companies using prismatic or pouch cells usually make no profit or even sell their cars at loss. While tesla makes about 25% gross profit margin. By increasing battery size they can make them faster and cheaper. Old technology did not allow to increase battery size due to inability to transfer the heat away.As already mentioned in other eevblog thread and youtube comments there are many other improvements besides the form factor.https://www.eevblog.com/forum/renewable-energy/why-tesla-cars-are-the-best-evs-and-tesla-is-the-best-car-company/msg3246970/#msg3246970

author: wraper
author_rank: Unknown
timestamp: October 02, 2020, 03:55:32 pm
content: Quote from: bristpi176 on October 02, 2020, 03:37:53 pmThey don't pack squarely. And using different cells is a big no from manufacturing standpoint.

author: tszaboo
author_rank: Super Contributor
timestamp: October 02, 2020, 05:32:15 pm
content: The wall thickness is about 0.15mm. On the top of the cell,there is about 3-4mm lost for PTC, tab connection, vent holes, insulator, cathode cover. The internal 1-1.5mm is lost, because you cannot roll it up. Back of the napkin calculations:A=9*9*65*3.14 #volumeB=2*9*9*3.14*0.15+9*9*3.14*4 # lost on top and bottomC=65*3.14*18*0.15 # lost on sidesD = 1.5*1.5*65 # lost in the middleE=(A-B-C-D)/A # total efficiencyE = 89%The 18650 cell has about 89% of the volume left for the guts.The same would be 93% for the, if the top part would stay the same. I expect, it isnt. I really think Tesla might have done away with the PTC. That would place us at 98% of the cell volume. That is still only like 10% improvement. The rest could come from the smaller ESR losses, or they use thinner material.Here is a link for a 73430 battery, so everyone can chill out, and see how much improvement was made:https://nl.aliexpress.com/i/32919620579.htmlThe investment/GWH reduction graph doesnt really make sense. Somehow the cathode material made the factory cheaper?They showed the inside of the factory for some 10s clip, that was indeed impressive. It is around 1:27:00 in their video. I've designed machines like this. We had individual machines, that are hundreds of KGs, but you could walk in between them, tough they were automated. I dont want to go into details, probably I would break my NDA. They made some multi stock monstrosity.But then solid state lithium comes along, integrates the anode and cathode into one sheet, makes ie 48V packs with only two terminals, and makes everything else obsolete.

author: bristpi176
author_rank: Contributor
timestamp: October 02, 2020, 06:10:34 pm
content: My thought was that if your goal is storage density and the space between cells could be better used with a smaller cell than a staggered configuration, given the life span and cost of these, would the added complexity of manufacturing be worth it? It's not like it can't be done.

author: wraper
author_rank: Unknown
timestamp: October 02, 2020, 06:25:54 pm
content: Quote from: NANDBlog on October 02, 2020, 05:32:15 pmThe question is can you affordably mass produce it and if technology is anywhere near to be ready for mass production to begin with.

author: pickle9000
author_rank: Super Contributor
timestamp: October 02, 2020, 07:33:35 pm
content: Don't forget about Tesla integrating the battery holder into the frame to lower the overall weight of the vehicle. Marketing may imply things like power density but the overall design of the vehicle counts, cooling included.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 02, 2020, 08:06:32 pm
content: You forgot to count squares.Assume 45mm height for the guts, that's 800/45 = 17.78 squares.So the resistance goes from 17.8 squares in series to the same number parallel, which is a factor of 316, which is much more then "an order of magnitude".I'd also find it quite sad if something like this is patent-able. Capacitors have been made this way for some 30+ years.But these days you can get a patent for any fart in a plastic bag, and if you need to fight or defend it, then the lawyers stand in line waiting for you to fill their wallets.Fair? No. Profitable? Yes, Yes, Yes...I do wonder if any use can be made by making the cells pressure resistant, which is much easier with the round cells then with the flat packs.Since the can is only open on one side maybe something can be done with venting in a safe direction, or when a faulty cell blows, it ejects itself from the battery pack.On the other hand. Li-Ion chemistry seems to be pretty well under control, and most cells that die are due to gross abuse, such as the deliberate overcharge video's on youtube.

author: wraper
author_rank: Unknown
timestamp: October 02, 2020, 08:25:54 pm
content: Quote from: Doctorandus_P on October 02, 2020, 08:06:32 pmThey were not. It's a completely different process. There is no laser cutting or folding while producing capacitors.

author: Poe
author_rank: Frequent Contributor
timestamp: October 02, 2020, 08:47:43 pm
content: Can't believe Telsa's marketing is so effective that people are talking about such marginal process improvements.

author: wraper
author_rank: Unknown
timestamp: October 02, 2020, 09:05:38 pm
content: Quote from: Poe on October 02, 2020, 08:47:43 pmIt's not a marginal improvement. It's being able to produce battery with 5x higher capacity and better thermals. There were no larger cylindrical cells because it wasn't possible to cool them. Not to say way reduced machinery and improved manufacturing speed.

author: sibeen
author_rank: Frequent Contributor
timestamp: October 03, 2020, 02:34:03 am
content: Is the tabless design actually used for low ESR electrolytic capacitors?

author: wraper
author_rank: Unknown
timestamp: October 03, 2020, 04:44:20 am
content: Quote from: sibeen on October 03, 2020, 02:34:03 amNo, they still have usual tabs.

author: Fungus
author_rank: Super Contributor
timestamp: October 03, 2020, 06:39:36 am
content: Quote from: bristpi176 on October 02, 2020, 06:10:34 pmThat's only if you pack them in a square grid. In reality you'd pack them in a hex grid.I'd have thought the biggest advantage of this "tabless" design would be better thermals for rapid charging and discharging.(I believe their current cars have to wait around and cool off a bit if you do too many launches)

author: sandalcandal
author_rank: Unknown
timestamp: October 03, 2020, 06:55:45 am
content: People seem to be confused with the meaning of the improvements and their implications. I agree with everything wraper has said.Cylinderical cells far outperform prismatic cells with the only slight disadvantage of increased costs in pack integration due to the larger number required to make up an equivalent capacity; power density as well as weight and volumetric energy efficiency has always been better using cylindrical cells because the jelly roll internal structure is most efficient in a hard cylindrical casing. Cylindrical cells have previously not been able to maintain the performance required for high power applications with larger sizes due to thermal and ESR limitations. The tab less design implemented by Tesla solves these size limiting problems elegantly and practically. The tab less design should also see general improvement in battery life and max charge/discharge speed due to: the lowered ESR, improved thermal homogeneity and improved current density homogeneity.The implications of a larger cylindrical cell (ignoring the tabless implementation) are improved manufacturing efficiency and improved energy density + specific energy. Manufacturing efficiency is improved due to the lower number of cells which must be managed and integrated for the battery pack manufacturing process. Slight improvements in energy density and specific energy are due to the fact internal void (at the centre of the jelly roll) and casing thickness remains roughly equivalent with increased size/diameter thus the ratio of active jelly roll material vs inactive void + casing material is improved. Again, neither of these benefits can be realised by simply increasing the size of a conventional cylindrical cell due to typical trade off size increases bring with ESR and thermal limitations worsening with increased size. For the previous conventional cell construction, the optimal trade off for size vs thermal + ESR limitations was the 2170 in most high power applications but it appears the optimal point for Tesla's application is now a 4680 size using tabless construction.What the larger form factor + tabless design DOES NOT MEAN is improvements in packing efficiency of the cylinders themselves, as others have pointed out this is a geometric constant for any single cylinder size. Some people speculate smaller cells could be packed in interstitial spaces between larger cells but this is not going to happen because A. Tesla shows their planned battery pack construction using only a single cell size and B its a bad idea. Mixing cell sizes hugely complicates the manufacturing process due to the need to now manage another entire line feeding and integrating the second cell size. Safety and performance is also compromised by the second cell which will either need some heavy design and control to match performance characteristics of ESR and thermal of the larger cells or otherwise cause internal mismatching issues. Perhaps in the far future where competition is strong and the absolute limits of all other improvement avenues have been exhausted will multi cell-size packs be a sensible idea for the challenges it introduces.I've honestly wondered why no one else has done tabless/continuous tab cells before Tesla's announcement myself. I have heard hearsay that other people have also been working on continous tab designs before Tesla. My guess is that the impetus has not been present or sufficient to surplant the conventional design but here Tesla and Elon Musk is again pushing things towards their fundamental first principal limits.

author: Per Hansson
author_rank: Unknown
timestamp: October 03, 2020, 07:45:14 am
content: Quote from: wraper on October 03, 2020, 04:44:20 amAlso remember that radial caps used on all modern PCB's have the tabs on the same side of the capacitor.You would need an axial capacitor to be able to make it tabless, but it sure is an interesting thought why they have not been made?I don't see any reason we could not just take the same calculations and end up with a capacitor with an order of magnitude lower ESR!

author: sandalcandal
author_rank: Unknown
timestamp: October 03, 2020, 08:32:45 am
content: Quote from: Per Hansson on October 03, 2020, 07:45:14 amI believe in the case of most (older) electrolytic capacitors, the ESR is limited by charge carrier mobility in the electrolyte used to convey the electric field into intimate contact with the electrodes. Some newer solid/polymer caps seem to be pushing past this limit towards the ESR of MLCC and foil caps which do use full endcap type connection so I wonder what these advanced electrolytic capacitors use?Edit: Aside, while I was reviewing my knowledge of electrolytic caps I came across thishttps://en.wikipedia.org/wiki/Electrolytic_capacitor#Water_based_electrolytesQuote from: WikipediaApparently capacitor plague was due to a bad stolen recipe? That was interesting and new to me.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 03, 2020, 10:11:30 am
content: Note that classically cylindrical cells dissipate heat through the cylinder walls, not the ends, because there are voids at both ends. 18650 cools very well because it's only 18mm in diameter; heat flow needs to travel only a few mm on average; surface-to-volume ratio is good; hence this was the choice for Tesla. 25650 was available, but the cooling was inadequate. Tesla's first micro-optimization was to find the sweet spot where the cooling is still good enough, but casing and assembly costs are reduced, and that was just at 21mm diameter, between standard 18650 and 25650 size. All this makes sense and, as an anecdote, I actually happened to predict their exact 21700 cell size before they published it.But this, I couldn't predict. It's funny how trivial idea this is, yet it never crossed my mind!The new idea is to change the primary cooling path from the cylinder walls, to the endcaps, by removing the void and replacing it with solid connection to the electrodes. This is actually quite a big fundamental change. As a result, the diameter can be arbitrary; increasing the dincreasesthe cooling area at the endcaps. I suppose, this means a big design change in their liquid cooling system, as well.Much of the Teslas original choice to go for cylindrical cells was their off-the-shelf availability, superior cost ($/kWh) and superior energy density (Wh/kg) back when they were designing the Roadster. They had 200Wh/kg cells available from the big manufacturers like Panasonic while the other EV pioneers were struggling with in-house custom-specified pouch or prismatic cells, using new weird chemistries, somewhere around 90 - 150 Wh/kg depending on case. Tesla's initial success is because of all the development seen in laptops at the time; they used predominantly 18650 cells. BTW, this market situation was still similar while designing Model S.The history shows their choice of cylindrical cell was clearly a correct one, and it seems that even when the market situation has changed so that the original main driving force, using a superior COTS product, has become completely irrelevant as they can design anything they want now, they are still not going to abandon it; clearly cylindrical cells work well.And, finally,Quote from: Poe on October 02, 2020, 08:47:43 pmClaimed 15% energy density gain is far from marginal. It's one level up from micro-optimization; and even micro-optimization makes sense at such scales. And they didn't even talk about the actual numbers in process cost savings.The optimizations need to be done everywhere. As a result ofdozensof different small improvements, li-ion cells are approaching 300Wh/kg as we speak, being some 100Wh/kg originally when introduced in late 90's. There is no single big breakthrough in the history.PTCs were mentioned earlier, note that since Model S, Tesla has custom-ordered their Panasonic cellswithoutthe PTC, replacing it with their fusible link wires instead. This is likely a significant cost saving, and also improves performance.

author: Fungus
author_rank: Super Contributor
timestamp: October 03, 2020, 10:49:12 am
content: Quote from: Siwastaja on October 03, 2020, 10:11:30 amhttps://en.wikipedia.org/wiki/Egg_of_Columbus

author: Fungus
author_rank: Super Contributor
timestamp: October 03, 2020, 11:05:39 am
content: Quote from: Poe on October 02, 2020, 08:47:43 pmI bet one of these can be manufactured for approx the same cost as a standard 18650 but Tesla will need to manufacture 5x less of them per car. That's not trivial.I also assume that this construction could have a massive impact on charge times. If a supercharger can charge your car 6x faster than before then it's ahugewin for Tesla. If their power-grid batteries need an order of magnitude less cells and electronics to control them then it could have an enormous impact, too.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 03, 2020, 11:58:19 am
content: Obviously it's not going to be a 6x improvement in power density. This is marketing; maybe it is 6x improvement in power per cell, but since only one fifth of the cells are used, the actual improvement in total power is 6/5x. Which still is a remarkable optimization.But charge current especially isn't limited by the metal resistance, it's limited by the anode lithium intercalation reaction rate (that's why charge and discharge rates are asymmetric; anode can't accept lithium ions as easily as cathode can).Dave's video is a very good explanation about how the resistance of the metal sheet goes down by an order of magnitude, but the total cell ESR isn't dominated by the metal resistance; it's the ion transfer itself. Dave completely ignores this biggest part of the ESR, as does Tesla in their presentation. This is OK, they are deliberately talking about one aspect in separation from the complete picture. But be careful this isn't about the cell current capability or cell resistance, only about the metal sheet capability.Thermally, it's really a Big Deal. ESR wise, it's a good small optimization among others but not the game changer. Capacity wise, it may be actually hurting their energy density; they have more copper and aluminium adding weight. At their 2C charge and ~3C peak discharge rates though, reducing losses in the bonding may pay pack for the "lost" energy density. This would be different if these were non-performance cars with just huge range and slow charging. OTOH, their design of laser-cutting or stamping the sheets allows precise optimization; they can calculate the optimum amount of metal to be cut out. The photo shown shows quite a lot of copper, with just small cutouts that allow folding. I'm sure they will fine-tune the amount of removed metal to maximize the product-level energy density where the efficiency is also a factor.Say, a typical energy 18650 cell has DC ESR of approx. 50mOhms at room temperature. My guesstimate is that maybe 5-10mOhms comes from the PTC (which Tesla got rid of for good reasons IMHO) and some 5-10mohms from the metal, but rest is chemistry. The fact that increasing temperaturesignificantlyreduces the DC ESR, even halving it down to some 25mOhms, proves this; the resistance contributed by the PTC and the metal isincreasedslighly, so the chemistry-related ESR must go down even more.

author: tszaboo
author_rank: Super Contributor
timestamp: October 03, 2020, 02:57:30 pm
content: Quote from: Fungus on October 03, 2020, 10:49:12 amWell, 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...

author: Fungus
author_rank: Super Contributor
timestamp: October 03, 2020, 05:39:00 pm
content: Quote from: NANDBlog on October 03, 2020, 02:57:30 pmIt's almost as if you didn't read the wikipedia page before replying.

author: fsr
author_rank: Regular Contributor
timestamp: October 03, 2020, 07:58:13 pm
content: 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_cellsNo 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.

author: wraper
author_rank: Unknown
timestamp: October 03, 2020, 08:42:26 pm
content: Quote from: fsr on October 03, 2020, 07:58:13 pmBatteryuniversity is trash I would not blindly trust. Pouch cells are harder to produce than cylindrical cells.QuoteIt's not like pouch cells exist in vacuum. Shell of tesla 2170 batteries is 0.15mm thick IIRC.QuotePouch cells have the same cooling issues like regular cylindrical cells.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 04, 2020, 10:19:27 am
content: 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).

author: tszaboo
author_rank: Super Contributor
timestamp: October 05, 2020, 08:55:15 am
content: 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.

author: timmytool
author_rank: Newbie
timestamp: October 05, 2020, 02:25:51 pm
content: Quote from: NANDBlog on October 05, 2020, 08:55:15 amBy 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.Quote from: Siwastaja on October 04, 2020, 10:19:27 amFrom 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.

author: micheljull
author_rank: Newbie
timestamp: October 05, 2020, 04:31:10 pm
content: Quote from: rs20 on October 02, 2020, 03:10:18 pmTrue. 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.

author: micheljull
author_rank: Newbie
timestamp: October 05, 2020, 04:40:47 pm
content: Quote from: NANDBlog on October 03, 2020, 02:57:30 pm👍 Excellent

author: micheljull
author_rank: Newbie
timestamp: October 05, 2020, 04:43:30 pm
content: Congrats Dave, this is by far the best video on the subject, so I joined the forum!

author: micheljull
author_rank: Newbie
timestamp: October 05, 2020, 06:16:09 pm
content: 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.

author: Neilm
author_rank: Super Contributor
timestamp: October 05, 2020, 06:18:23 pm
content: 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

author: wraper
author_rank: Unknown
timestamp: October 05, 2020, 06:47:22 pm
content: Quote from: micheljull on October 05, 2020, 06:16:09 pmThere are lower losses in the battery as well.

author: Dr Bob
author_rank: Contributor
timestamp: October 07, 2020, 03:14:25 am
content: 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.

author: Dr Bob
author_rank: Contributor
timestamp: October 07, 2020, 03:25:40 am
content: 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.

author: Dr Bob
author_rank: Contributor
timestamp: October 07, 2020, 03:28:49 am
content: Quote from: Fungus on October 03, 2020, 06:39:36 am

author: Dr Bob
author_rank: Contributor
timestamp: October 07, 2020, 03:39:48 am
content: 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.

author: wraper
author_rank: Unknown
timestamp: October 07, 2020, 04:07:16 am
content: Quote from: Dr Bob on October 07, 2020, 03:39:48 amElon 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.

author: Fungus
author_rank: Super Contributor
timestamp: October 07, 2020, 06:09:25 am
content: Quote from: Dr Bob on October 07, 2020, 03:25:40 amI 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.

author: peepsalot
author_rank: Newbie
timestamp: October 09, 2020, 02:44:58 am
content: @ 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)Thento 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.

author: wraper
author_rank: Unknown
timestamp: October 09, 2020, 03:28:00 am
content: 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%5EtfwQuote

author: sandalcandal
author_rank: Unknown
timestamp: October 28, 2020, 07:43:04 pm
content: Dave spotted @16:58Also 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.

author: mnementh
author_rank: Super Contributor
timestamp: November 21, 2020, 06:48:00 pm
content: 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

author: wraper
author_rank: Unknown
timestamp: November 21, 2020, 07:35:57 pm
content: Quote from: mnementh on November 21, 2020, 06:48:00 pm100% 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.

author: wizard69
author_rank: Super Contributor
timestamp: November 25, 2020, 01:13:11 pm
content: 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.Quote from: Fungus on October 07, 2020, 06:09:25 am

author: wraper
author_rank: Unknown
timestamp: November 25, 2020, 02:38:27 pm
content: Quote from: wizard69 on November 25, 2020, 01:13:11 pmTesla never said they will ditch their battery suppliers. They explicitly said they will not be able to produce all of the batteries they need, since they will need astonishing amounts of them.