TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

Battery Format for Model 3 - 18650 commodity cells or large format batteries

Discussion in 'Model 3' started by Reeler, Mar 12, 2016.

?

What cell format will Tesla use for the Model 3?

Poll closed Mar 30, 2016.
  1. Commodity 18650 cells tuned for auto applications just like all their other cars

    50.0%
  2. Large format cells just like all other auto manufacturers with their own battery factory

    50.0%
  1. Reeler

    Reeler 7th Year of Pure EV

    Joined:
    Oct 14, 2015
    Messages:
    890
    Location:
    Mountain West
    Thus far, the Roadster, Model S and Model X have used commodity 18650 format cells. Other manufacturers with their own factories have instead gone for large format cells. Tesla's decision was pragmatic in that economies of scale kept costs low, but that much wiring is complex and has other issues.

    Now that Tesla will have their own battery factory, I don't personally see any reason not to follow what everyone else has done--large format batteries. I predict that this will happen with the Model 3 release and completion of the Gigafactory. What do you think?
     
    • Funny x 1
  2. Jason S

    Jason S Model S Sig Perf (P85)

    Joined:
    Apr 20, 2012
    Messages:
    1,410
    Location:
    Rocklin, CA
    Something in between. I recall seeing mention of a little bit larger cell than the 18650 -- but I don't recall the name of them.
     
  3. Johan

    Johan Took a TSLA bear test. Came back negative.

    Joined:
    Feb 9, 2012
    Messages:
    6,906
    Location:
    Drammen, Norway
  4. aronth5

    aronth5 Long Time Follower

    Joined:
    May 8, 2010
    Messages:
    1,594
    Location:
    Boston Suburb
    This or something very similar in size.
     
  5. Lex

    Lex Member

    Joined:
    Apr 23, 2015
    Messages:
    711
    Location:
    Toronto, Canada
    This is really interesting stuff. Are we sure they're still going to use a similarly sized cylindrical cell, in general ? The Lithium Ion packs in my cellphones are not cylinders. The one in my old Motorola Razr (the rebooted one) was even highly soft and bendable.

    What about the GM cells, are they cylindrical inside the "packs" ?

    I watched a pile of Elon Musk interviews this weekend and one "a-ha" moment he shared was the team asking what the "ingredients" were in a battery, and what the commodity market costs were, to start with a base input cost. And then later, they.... :cool:
     
    • Love x 1
  6. Crankstart

    Crankstart Member

    Joined:
    Feb 4, 2016
    Messages:
    8
    Location:
    Kansas City
    GM uses LG Chem flat battery cells in the Volt. Not sure about the Bolt, but expect same/similar
     
    • Informative x 1
  7. Saghost

    Saghost Active Member

    Joined:
    Oct 9, 2013
    Messages:
    4,478
    Location:
    Delaware
    GM uses LG Chem Prismatic (rectangular) cells for all of their EVs to date - a smaller number of much larger, much more powerful cells. - the original Volt has only 288 cells (a 96 group series string of parallel triplets,) and the new Volt and Spark are actually even fewer despite the larger capacity - 192 cells arranged in pairs.

    This approach makes manufacturing simpler, but the failure of a single cell has significant consequences for the car as a whole, so the battery supplier has to have extreme quality control in place (and mostly seems to - the Volt has been putting up a pretty impressive reliability history.)

    Tesla took a RAID approach instead - they have 74 cells in parallel in each of their 96 series groups (6 groups in each of the 16 modules,) each individually fused and isolated in intumescent goo (in the original 85 kWh packs, anyway - the others are similar in concept.) This increases the odds of failure, but it allows a cell to fail without having significant impact on the car as a whole - the fuse pops, but as long as the coolant and goo are enough to stop a thermal runaway, the event ends there - and the car lost 1.4% of its range, with the odds strongly against the next failure costing any additional range.

    It'll be interesting to see which approach ends up dominent in the industry...
    Walter
     
    • Informative x 3
    • Like x 2
  8. Jeff N

    Jeff N Active Member

    Joined:
    Oct 31, 2011
    Messages:
    1,570
    The Bolt uses 96 groups of 3 cells for 288 total (same count as the 1st gen Volt). The flat cells are about 3.9 inches high and 13.1 inches long.
     
    • Informative x 1
  9. macpacheco

    macpacheco Member

    Joined:
    Feb 13, 2014
    Messages:
    419
    Location:
    Brazil
    • Informative x 1
    • Like x 1
  10. Garlan Garner

    Garlan Garner Active Member

    Joined:
    Mar 31, 2016
    Messages:
    4,815
    Location:
    Chicagoland
    Its too bad that GM can't sell great cars with those great batteries.
     
  11. Swampgator

    Swampgator Member

    Joined:
    Apr 27, 2016
    Messages:
    139
    Location:
    Florida
    What is it about the "commodity" cells that you think is better? They are known to have lower energy density and a higher cost/kwH than the existing 18650.
    The 2170 batteries will be 40% better on both metrics than the 18650s.

    Pouch cells are used by legacy automakers in compliance cars, period.
    Lucid and Faraday are not using them, because they are not designing compliance cars.
     
    • Like x 1
  12. Garlan Garner

    Garlan Garner Active Member

    Joined:
    Mar 31, 2016
    Messages:
    4,815
    Location:
    Chicagoland
    Me? I was being ficesous.
     
    • Like x 1
  13. Swampgator

    Swampgator Member

    Joined:
    Apr 27, 2016
    Messages:
    139
    Location:
    Florida
    No, sorry I was asking the OP.
    Should have made that clear.
     
    • Like x 1
  14. macpacheco

    macpacheco Member

    Joined:
    Feb 13, 2014
    Messages:
    419
    Location:
    Brazil
    The "commodity" factor was useful when Tesla was a tiny/small/medium consumer of Li Ion cells.
    In 2017 Tesla will consume upwards of 10 GWh worth of cells. That's over a billion cells in a year.
    And of course they have their own factory not far from beginning their own cell manufacturing.
    And whatever Tesla does, a few EV manufacturers will follow. Tesla is the leader.
    The game has changed.
    The only disadvantage of 2170 over 18650 is you get less total voltage (with the whole pack in series) cause large packs pack higher amps-hour but same voltage. Hence another doubt is will Tesla use 2170 cells for 75kWh packs ? If they moved 100kWh packs to 2170, would it reduce acceleration/top speed ?
     
  15. Reeler

    Reeler 7th Year of Pure EV

    Joined:
    Oct 14, 2015
    Messages:
    890
    Location:
    Mountain West
    My Bolt is being shipped from the factory right now. I am hoping to get it prior to the end of the year.
     
    • Love x 1
  16. JRP3

    JRP3 Hyperactive Member

    Joined:
    Aug 20, 2007
    Messages:
    11,322
    Location:
    Central New York
    No that's not true. Series connections make voltage additive, they can just connect the same number of the larger 2170 cells in series to have the same voltage. The larger cells means they can connect fewer cells in parallel to get the same total amp hour capacity, volts x amp hour = kWh.
     
    • Helpful x 1
    • Like x 1
  17. macpacheco

    macpacheco Member

    Joined:
    Feb 13, 2014
    Messages:
    419
    Location:
    Brazil
    JRP3, the assumption is if you migrate from 18650 to 2170 keeping the same total capacity, you would get less cells hence less voltage. If the current 100kWh pack is using 18650, migrating it to 2170 would generate less voltage.
    Since Tesla increased performance everytime they increase the MS/MX pack, I would assume going to 2170 would rollback unless they make it a 125kWh pack or something. But I'm really asking.
     
  18. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    3,081
    Location:
    Oregon
    You wouldn't have to get less voltage. You switch some cells from being in parallel to being in series to get to the voltage you want/need. (And that wouldn't change your overall kWh of the pack, it just puts more stress on the individual cells.)

    In theory you could put 96 cells in series and give someone a ~400 volt pack. Of course it wouldn't last very long...
     
    • Like x 1
  19. Saghost

    Saghost Active Member

    Joined:
    Oct 9, 2013
    Messages:
    4,478
    Location:
    Delaware
    You seem to be thinking that every cell in a Tesla pack is connected in series. If that were true, you'd have a point.

    However, all the recent packs except the 100 have had groups of 74 cells in parallel in each of the six sets hooked up in series in each of the 14 or 16 modules connected in series (thus a total of 96 groups of 74 cells in the 85 and 95, and 84 groups in series of 74 cells in parallel in the 70 and 75.)

    I don't think we have an exact cell count for the 100 yet, but it has to have upwards of 80 cells in parallel in each module from the limited guidance we've been given.

    Replacing the 18650 cells with higher capacity 2170 cells would allow you to reduce the number in parallel while keeping the same number of series strings and the same total voltage and capacity. (Or they could put the same number of cells in and get a bigger battery - assuming the new cooling system can make that fit.)
     
    • Informative x 3
  20. JRP3

    JRP3 Hyperactive Member

    Joined:
    Aug 20, 2007
    Messages:
    11,322
    Location:
    Central New York
    Saghost is correct. Simple example, I can make a 12V battery with 100 amp hour capacity for a total of 1.2kWh with different cell configurations and sizes:
    10 parallel 3 volt 10 amp hour cells create a 3 volt 100 amp hour group, 4 of those groups in series makes a 12V 100ah battery
    or
    5 parallel 3 volt 20 amp hour cells also create a 3 volt 100 amp hour group and 4 of those groups in series makes a 12V 100ah battery. Both batteries have the same 1.2kWh capacity and potential peak power output.
     

Share This Page