• Dec 15th 2010 at 7:57PM
  • 29
Toyota RAV4 EV – Click above for high-res image gallery

Toyota, Daimler and BMW have all turned to the laptop battery cell technology utilized by Tesla in the Roadster to power at least one of their electric car models. For Toyota, the laptop-style cells will find a home in the automaker's limited test fleet of battery-powered RAV4s. Daimler has chosen to power its Smart ForTwo Electric Drive and Mercedes-Benz A-Class E-Cell with the small, cylinder-shaped cells while BMW outfitted its Mini E prototype with the Tesla Roadster-like power supply. Judging by these inclusions, it could be argued that the small-format cell pack is the way to go with electric vehicles.

But wait. BMW's upcoming Megacity and ActiveE electrics will forego the laptop-style cells in favor of large-format ones provided by SB LiMotive. Additionally, Toyota has not committed to a single battery type for its mass-produced electric vehicles and will try out large-format units on the upcoming plug-in Prius and iQ-based battery electric and even Daimler has enlisted the help of Evonik to develop large format cells for use in the company's future EVs.

Choosing between laptop cells and the larger format, car-only batteries, according to Automotive News (sub. req.), is a decision that's based on cost and availability. Large format lithium-ion batteries cost around $700-$800 per kilowatt hour to manufacture. Whereas mass-produced packs that utilize laptop-type cells could set automakers back as little as $200 per kWh and are an off-the-shelf item that allows companies to build EVs while adhering to a strict time schedule. What all of the small-format programs listed above had in common is that they were quick-out-of-the-gate programs that OEMs used as promotional and test programs and, since they needed something fast, they were able to make use of Tesla's available and tested technology. Other automakers, like Nissan, Chevrolet and Mitsubishi, have chosen to only use large-format cells for their mass-market plug-in vehicles. There's no obvious right answer today about which size format is right for every EV and, with automakers flip-flopping between battery types, could we see another Beta-versus-VHS-style battle in the near future? If it results in better EVs, maybe that'd be a good thing.



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Live photos copyright ©2010 Sebastian Blanco / AOL


[Source: Automotive News – sub. req.]


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    • 1 Second Ago
  • 29 Comments
      • 4 Years Ago
      Large format cells are by far the way to go. Less connections = Less failure points. It simplifies the BMS and is cheaper to build than a complex array of small cells. Everything is cheaper and easier to assemble, plus they can deliver enough current for most applications and charge back fast.
        • 4 Years Ago
        While I agree less connections = less failure points, one has to consider that many parallel strings allow for any single, series circuit to fail and all other series circuits continue to work at operating voltage w/ little issue with the increased current draw from losing a string. I believe Tesla's configuration uses something like 22 parallel strings. Depending on 1 or even 2 strings of 99 cells is asking for potential trouble in the event of a single cell failure.
        • 4 Years Ago
        Well unfortunately it won't simplify BMS since you can't monitor individual cells in a parallel string.

        You just have a huge failure point there, which is actually already a problem in laptops. Many laptops use parallel strings, and if one cell goes bad in that string, you get that classic problem where you have a 100% charge.. then it suddenly drops down to 25% since one cell has lost most of it's capacity and your voltage drops fairly rapidly when that one cell has reached the end of it's charge.

        The idea here is to eliminate parallel strings altogether and use high quality, appropriately sized cells. This is common with lithium polymer batteries. It can be done with other chemistries as well.

        Oh and the cell configuration ( tons of small ones or 1 big one ) doesn't necessarily affect the discharge/charge amp rating at all. That is an effect of the cell chemistry and design itself. For example, low end lifepo4 will do 1c.. low end lipo will do 15c..

        As far as being easier to assemble, hell yeah. That's the main reason why we should be using appropriately sized cells.
        • 4 Years Ago
        Well, the battery management isn't much different, as it only controls each voltage level in the series wiring, not individual cells. But on other aspects you're right.

        Tesla is currently using small format cells in spite of those disadvantages because the price is lower and energy density higher than other large format cells. Eventually, that will change, the price of large format batteries will drop and the energy density improves, and when that happens Tesla Motors will happily switch.
      • 4 Years Ago
      It's car design so nice and there are some different looks ..
      http://twitter.com/#!/Sulliviajenssy
      • 4 Years Ago
      In an interview sometime back with ex-Tesla engr - says the basic reason why consumer cells are better is that the innovations come first to them. So you pay more in BMS (and some space) but gain in others innovation & cost cutting.
      • 4 Years Ago
      Well, from the earlier article today, it seems to me it maybe the combination of the nano wires in the cells that could make the difference. No expert on this , but with these nano wire "ropes" made from the individual wires joined together, the size of the cell would be less consequential. Small and large cells would benefit in reliability and life, then they just need to fill their correct role (car vs. Phones, laptops). My concern is the production of these nano wires that reform properly after charging. Anyone know how hard it will be to produce these on a large scale?
      • 4 Years Ago
      Competition for the consumer electronic market ensures that small cell laptop batteries are already cutting edge for price/size/performance. Keeping $ for kwh and kwh/kg down when you have a low production volume is very appealing.

      On the other hand having all those thousands of small batteries (any one of them potentially a dud because of bad chemistry or a faulty connection) with inherent dead space around them (cylinders packed in a box) makes them unattractive from a production perspective.

      Furthermore the power demands of the laptop are not necessarily those of a car. Yes both laptops and cars will have to be able to deep cycle, but you also want to be able to run a large number of amps through when accelerating.

      Someone starting with a tabula rasa and with anticipated production volume, will get the exact chemistry they want in the format that they want for the same price per Kg of the laptop cells. Less connections, easier balancing, easier construction, easier battery conditioning will improve reliability and performance and reduce construction costs.

      I suspect that laptop cells in anything other than a remote control car will be viewed as quaint and "hobbyist" very soon.
        • 4 Years Ago
        While you are indeed correct that consumer electronics are designed to be disposable (change the battery on an iPhone?) that is partly the design of the device and not the battery.

        All batteries prefer room temperature operation, slow 'trickle' charging, and most new cells benefit from shallow discharge cycles.

        Give them to a consumer who leaves the phone in the car, desires quick charging, and charges when it is dead and you see the result.

        Conversely put them in a situation where there is careful battery management (eg Prius for NiCad, Leaf, Hyndai, GM, Tesla for Lithium chemistries although you can argue about air versus fluid temperature regulation) then they may do quite a bit better. Certainly for the older designs there is no cry that the Prius battery needs replacement even after a long time. GM has done battery testing so it has some idea of what an 8 year warranty means to them, same with Nissan.
        • 4 Years Ago
        Remote controlled cars don't even use laptop cells anymore, they've moved on to prismatic lithium polymer that is lighter, dumps out amps like a waterfall, and runs at higher voltages.

        This 'tons of tiny cells' setup is already losing it's appeal in the RC/eBike/motorcycle/etc markets. They will lose their hobbyist appeal in a year or two.

        Nobody wants to solder / tab weld hundreds or thousands of cells together when you can buy appropriately sized cells that use less space and are lighter.

        I suspect this whole idea of using laptop cells will be passe in less than 5 years. It is already passe right now in my opinion. Made since in 2006, doesn't make sense in 2011.
        • 4 Years Ago
        Consumer electronic batteries are only designed to last a few years. Many people replace their cell phones and laptops after only a few years because the batteries no longer hold a charge. The longevity of many consumer electronic batteries would be unacceptable in a car. (As someone said, Tesla's battery warranty is relatively short.)
        • 4 Years Ago
        PS
        On a strict volume basis the cylindrical cell will take up pi r(2) x length while a rectangular cell will take up 4 r(2) x length

        This is 27% improved power density of the rectangular pack over a cylindrical pack (ignoring the savings in space for conductors)
      • 4 Years Ago
      For the cells, go big or go home!

      Small format cells may be cheaper but they take up more space. They also require a lot of soldering. Also, if one cell dies, good luck finding it as they are all wired up in parallel groups.

      Which battery pack would you rather diagnose/fix down the line? one with 100-200 cells, or one with 30,000+ cells?
        • 4 Years Ago
        The Tesla battery pack is designed to bypass single individual bad cells. No need to do anything with them. Just keep going with the individual bad cells being ignored.

        And there are only 6,831 cells, not 30,000. There would be little point in having a 30,000 cell small format commodity 18650 batteries. Using the 2.2ah batteries in the current pack, that would be approx. a 250 kWh battery pack. Using 4.0ah 18650's that Panasonic is slated for production in 2012, that is about a 450 kWh pack. 450 kWh would propel a roadster over 2,000 miles per charge.

        By 2015 (when it looks like just about everyone will be selling some sort of BEV/REEV/PHEV) it is entirely possible to have a Roadster-sized car getting 200+ mile range on somewhere around just 3,000 commodity 18650 laptop cells. 100+ mile range on somewhere around 1500 cells.

        Set your 5th cup of coffee of the day down on the table, and step away from the caffeine.
      • 4 Years Ago
      The benefit of the 18650 format battery packs is supposed to be how easy it is to upgrade the pack to more powerful commodity batteries over time.

      For example, the Tesla roadster pack uses 6,831 2.2ah cells to get a 56 kWh pack. That was 2006/7. Today the could use 3.1ah cells, and have a roughly 80 kWh pack.

      Panasonic has formally announced they will begin mass producing 4.0ah cells in 2012. That would be a roughly 100 kWh pack.

      That is nearly doubling the battery capacity in only a few years. A 100 kWh pack could reasonably be expected to deliver 400+ mile range in a roadster, just by swapping in larger capacity batteries into the same size battery pack. Now all that needs to happen is for Tesla to actually DO IT and show what is possible....
      • 4 Years Ago
      With all these battery technology break throughs I've been hearing about; they must be in theory only! None of the auto industry is reporting experimenting with or using anything near what I've heard can be done from Korea for example and others doubling lithium power with low charge times to 3 minute charge times etc. I might as well stop reading about break throughs period or if I wee managing a large auto company have the battery department fired & replaced with younger scientists! Go Zieffer!
        • 4 Years Ago
        You hear about "breakthroughs" with ICE vehicles too but it still takes a long time to see them come to a production vehicle. Take Start/Stop tech for example, we have been hearing about it for years, yet still cant get it in any car in NA.
      • 4 Years Ago
      As the price is high and the range is low (like now), the laptop cells make more sense. As the price gets lower and the energy density increases (in the future), the large format cells will become the choice.
      • 4 Years Ago
      I don't think that you can just state that large format / prismatic cells are $700-800 per kWh. Nissan can't have spent that much -- that would be half or more than half of the retail price of the Leaf!? I thought I heard that theirs costs about $350/kWh?

      Neil
        • 4 Years Ago
        So, the Volt's pack costs $8,800 by that measure, and the Leaf MSRP is about that much *less* than the Volt. Given that the Leaf battery pack is 50% bigger and it can use 95% DOD without active cooling, the Leaf battery tech seems more robust, and it's got to be less costly. At $350/kWh that totals $8400 -- about 26% of the MSRP. (Of course there is no ICE and all it's accoutrements.) The Volt battery pack is about 21% of its MSRP.

        Prismatic cells are better space packing, by definition. Cars need the capacity.

        Neil
        • 4 Years Ago
        "Are you saying that if we really want EV's to be successful, we need to find some hot porn stars and shoot some official ABG promotional videos? =)"

        Fisker's ad campaign is one strategy, Nissan's polar bear commercial is another.

        Which got your attention and held it longer? Which one is more likely to get pinned up on a young enthusiast's wall?
        • 4 Years Ago
        "Also, VHS was more successful because that is the format that pornography was distributed on. "

        Are you saying that if we really want EV's to be successful, we need to find some hot porn stars and shoot some official ABG promotional videos? =)

        • 4 Years Ago
        This reminds me of the fight over VHS versus Betamax video formats: VHS "won" the tech war because it was 1. cheaper and 2. could go longer than the "superior quality" Betamax format. We shall see a similar outcome in the "small cell versus large cell" electric storage battery war-- whichever technology is cheaper and gives the best range will "win" over the other. Or, is the words of my Army Air Corps dad, "Keep It Simple, Stupid!"
        • 4 Years Ago
        Jeff,

        Initial cost is important, for sure. But so is overall cost. If prismatic cells last 2-3X longer then that is huge.

        Neil
        • 4 Years Ago
        Yeah, these numbers are hard to deal with since they are so secret and may describe completely different things. Is the price just the raw cell price? The pack price? The pack price including a thermal management system?


        Some people have said the Volt battery is $1000 per 'useable' KWH . . . but since they are only using ~50% of the pack, didn't that just mean $500/KWH of raw cells.
        • 4 Years Ago
        "VHS "won" the tech war because it was 1. cheaper and 2. could go longer than the "superior quality" Betamax format."

        Also, VHS was more successful because that is the format that pornography was distributed on.
      • 4 Years Ago
      as others have picked up on (which is nice so I don't have to throw a tantrum to wake up the world) the price comparison is based on a flawed premise. currently the few large format cells out there might be a bit more expensive than the cheapest laptop cells (18650 format 3.6V chemistry) but it's only a bit. nissan stated their pack costs 9000$ which puts their cell cost at around 300$/kWh. cheapest laptop cells are around 250. not a huge difference. and that's what's currently available. not a fundamental difference. indeed the soft pack pouch style cells should be cheaper to make and have better specs.

      the only merit to laptop cells from what I understand is that currently there are more available of them, you can always get new ones and the tech is a bit ahead. but that is not an inherent quality. that's simply because laptops are being sold and electric cars are not and the battery fabs are not all bright enough to realize what is coming and produce a product with suitable specs and price so cars can be made. the few that do make them like LG chem for the Volt or A123 in general are douchy about selling them. it's a massive mystery what exactly malfunctions in their brains but for some reason some battery producers decide that they will only sell the batteries to a few, not anyone who wants to buy them.

      eventually and fairly soon it will all be larger cells. maybe 20Ah size and bigger and I expect it will be the pouch format.
      maybe multiple cells in one pouch so you have maybe 36V in a single cell. like a big book. that way you can skip cables and have ultimate connections.
      • 4 Years Ago
      I'd love to read the original article but I suspect it is filled with misinformation.

      The big companies are paying nowhere near $800/KWH for large format batteries. They won't give out specific numbers but they've hinted at things like ~$500/KWH.
      Listen here for that quote:
      http://www.commonwealthclub.org/archive/10/10-05electriccarspanel-audio.html

      I think small-format is dead. It made sense when they had no other option because there was nothing else available. But even Tesla has bailed on the small format for the Model S.

      The $200/KWH batteries are not going to cut it. They are going to die in 3 to 8 years. That is why the Roadster does not have a good battery warranty . . . and instead has a pre-planned battery replacement program.
        • 4 Years Ago
        Where did you hear Tesla is ditching small format batteries? The recent diagrams of the Model S pack shows slabs, but they are just a variant of the slices in the Roadster pack. From interviews, there are still 18650s inside those slabs.

        I agree small-format laptop cells are not probably not going to be used for EVs offered for sale by large automakers (it seems they are using them for trials because they don't have another decent choice yet), mainly because of life. However, for small volume makes they do make some sense, since it is harder to gain access to the larger cells (of same quality and similar price).

        Also for Tesla, who wants to build a 300 mile Model S (up to 95kWh in the pack), 18650s are the only commercially available cells that can achieve it with reasonable weight. We have heard a bit about that Audi which supposedly achieved 300+miles with some larger LMP cells, but so far there have been a lack of details and the cells are not available yet.
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