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Tesla's 18650s versus larger format automotive cells

Discussion in 'Battery Discussion' started by JRP3, Jan 12, 2011.

  1. JRP3

    JRP3 Hyperactive Member

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    #1 JRP3, Jan 12, 2011
    Last edited by a moderator: Jan 17, 2011
    The problem with that is commodity cells have been in development for years and further price reductions are probably going to be smaller than the new larger automotive cells that are just starting to be built in volume and might have greater cost reduction potential. With easier assembly and management the larger cells don't have to be as cheap as the smaller cells to make assembled pack costs competitive.
     
  2. doug

    doug Administrator / Head Moderator

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    #2 doug, Jan 12, 2011
    Last edited: Jan 12, 2011
    It's true that commodity cells already benefit from economies of scale, and thus the price per cell is not likely to drop dramatically. However commodity cells also benefit from regular rolled-out improvements due the the rapid product cycles of consumer electronics. Will larger format automotive cells improve at a similar rate? (an honest question) It will be interesting to see how the $/kWh of assembled packs of both types track over time.
     
  3. JRP3

    JRP3 Hyperactive Member

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    Not so sure about that, I think it's the other way around, unless I'm not understanding your point. Products benefit from improved cells, and cell improvements are limited by the technology used to make them. There is certainly demand for improved Automotive cells as well, and they are about to grow in usage from basically zero into millions of units.
     
  4. vfx

    vfx Well-Known Member

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    But if many different manufactures of different consumer products all demand the same battery in the billions for portable drills, laptops, and sports cars, won't that create/demand more improvement iterations on that form?
    What it looks like (for now) individual car makers each have their own proprietary cellpack and their supplier only has one customer to answer to.
     
  5. doug

    doug Administrator / Head Moderator

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    What I mean is that new commodity cells are getting used in new products all the time, so the rate of iteration is high. Incremental improvements get implemented quickly. (Lotta polysyllabic "i" words there!)

    Hmm... Although, given the nature of many consumer electronics, pressure is likely on higher energy capacity rather than longevity.
     
  6. TEG

    TEG TMC Moderator

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    #6 TEG, Jan 12, 2011
    Last edited: Jan 12, 2011
    This_Video points out that the economy of scale benefits of mass manufacturing for 18650 cells keep costs down regardless of which chemicals you put inside. So when Panasonic started working with Tesla on new automotive specific chemistry for next generation cells, it seems they decided that 18650 was still the best way to package them.

    I don't think we have heard Tesla mention of the Daimler "pouch cell" in a long time.
    http://cleantech.com/news/4475/daimler-takes-10-percent-stake-tesla
     
  7. JRP3

    JRP3 Hyperactive Member

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    My point is these cells have been in development for so long the easy improvements have already been done. Demand can't trump physics.
    To some extent that's true but each supplier is also competing with the entire market. If one makes an improvement others must follow or be left behind.
     
  8. EVNow

    EVNow Active Member

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    But the important point (from Tesla POV) is that the improvements are "free". They don't have to pump in a lot of money like Nissan has to do, for eg. They also don't need to depend on a single source like Ford or GM.

    But the downside is the complicated BMS.
     
  9. JRP3

    JRP3 Hyperactive Member

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    And pack assembly time, complexity, more aggressive temperature management and higher energy use. Possibly shorter cycle life as well. Other than that.....
     
  10. doug

    doug Administrator / Head Moderator

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    #10 doug, Jan 12, 2011
    Last edited: Jan 12, 2011
    pack assembly time
    Probably doesn't take that long for a robot. Tesla seems to have simplified their packs into modules of 500 or so cells. I doubt pack assembly is a manufacturing bottle neck.

    complexity
    I'm not sure it's really that complicated. There is certainly high redundancy, but that's the sort of thing a computer is good at dealing with. There may be complicated cell balancing algorithms, but I suspect once figured out, it's not too hard to implement, again with a computer. Tesla should have a lot of experience by now with the Roadster.

    temperature management, energy use, cycle life

    these are more chemistry issues, somewhat independent of cell form factor (as TEG alluded to above). Your current argument seems to be one of packaging.

    Again, it will be interesting to see how the pack $/kwh track for the two approaches. I'm sure Tesla will do/is doing whatever makes the most sense for them.
     
  11. qwk

    qwk Model S P2681

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    Tesla wins either way. They have the lowest cost NOW, and can switch to a better chemistry later if need be.
    This is really a no brainer.
     
  12. JRP3

    JRP3 Hyperactive Member

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    I'd say it takes about 68 times as long to assemble 6831 cells as a 100, even for a robot. As for chemistry constraints, the form factor means Tesla is stuck with what the manufacturers are building in volume for that form factor, which for now at least seems to be LiCo cells that need more baby sitting. Certainly this could change in the future.
     
  13. stopcrazypp

    stopcrazypp Well-Known Member

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    That's probably balanced by assembly time/cost for individual cells, assuming the overall assembly time is the same for smaller cells vs larger cells. There's probably extra time spend to assemble the module, but once a modules are made, the rest of the assembly should be very similar to large format cells.

    a123 makes 18650s too, so that's at least one alternative.
     
  14. vfx

    vfx Well-Known Member

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    I like to step in and say I really enjoy JR3P's take on all things electric. A good challenge makes me think.
     
  15. Cobos

    Cobos S60 owner since 2013

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    #15 Cobos, Jan 12, 2011
    Last edited: Jan 13, 2011
    Well if the robot can make 40000 Model S battery packs a year it doesn't matter that it works more or longer.
    Also keep in mind I did some back of the envelope calculations in another post where Tesla will be the around the 3rd largest user of 18650 cells. Ignoring Tesla will for the producers almost be as bad as ignoring Dell. Hence at that point Tesla got huge purchasing power.

    Cobos
     
  16. JRP3

    JRP3 Hyperactive Member

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    Thanks for the props. I feel the same way, challenge makes me did deeper into the issue and question what I know.
     
  17. EVNow

    EVNow Active Member

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    Whatever high density battery comes out in prismatic format is likely to find its way into consumer formats as well. Manufacturers are always looking for longer lasting Laptops. So, I expect NMC to come to laptops the same time (or earlier) it comes in Nissan Leaf.

    I doubt, though, Tesla will ever become a mass market auto major. They will likely be bought out by someone and continue as a luxury EV niche.
     
  18. JRP3

    JRP3 Hyperactive Member

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    But the price per wh has to be lower for the commodity cells to make sense in the laptop/Tesla model than it has to be for the large scale prismatic model. Now if the NMC allows easier management and temperature control that might help the efficiency of the Tesla system but unless it eliminates the need for active liquid cooling it probably won't lower pack costs.
     
  19. theBike45

    theBike45 Banned

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    There's simply no way any new battery technology will not end up in laptops and Teslas. Nor does the Tesla's cooling system
    figure more than incidentally in its cost at this point or any likely point in the future. The Volt's cooling system is quite elaborate
    as well, and it uses large format batteries. Mass production and competition is the key, and only LG is making Volt batteries. As to
    the matter of 6800 cells, just look at the number of cells in the Volt's paltry 16 kWhr battery pack.
     
  20. EVNow

    EVNow Active Member

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    NMC doubles the density with little additional cost. So it will be cheaper when mass produced.
     

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