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 or making a Paypal contribution here: paypal.me/SupportTMC

How is Tesla charging the Panasonic 18650PF at over a 1C rate?

Discussion in 'Model S: Battery & Charging' started by VRdublove, Jun 27, 2014.

  1. VRdublove

    VRdublove New Member

    Joined:
    Jun 27, 2014
    Messages:
    1
    Location:
    Fletcher, NC
    This is my first post on the forums, what a fantastic community!

    My question relates to Tesla's fast charging of Panasonic cells.

    Every spec sheet that I've seen from Panasonic lists the maximum charge rate as 0.5-0.7C. With Tesla's 120kW Superchargers, they would be charging at 1.41C. Are they accomplishing this through active thermal management? Surely you can charge a battery faster than its suggested charge rate, but I would expect reduced lifespan of the battery. Is temperature management the only thing that limits the maximum suggested charge rate of these cells?

    It's my understanding that the Model S uses the Panasonic 18650PF cell, which has an DC resistance of around 43 mOhms. Other 18650 cells in the industry with similar internal resistance numbers are rated for a 1C max charge rate. I'm wondering if Panasonic is rating their cells to a reduced charge rate in order to maximize cycle life to 80% of initial capacity.

    I expect that because Tesla is using a liquid cooling system, it can safely support a faster charge rate, with minimal added stress on the cells. I imagine that the standard 0.7C rate is with the expectation that most applications of this cell are for power tools in sealed enclosures, so the charge rate is reduced to manage temperature, and increase safety margins since cooling is only passive.

    Can any one firm up my speculations?

    Cheers,
    Tommy
     
  2. Cosmacelf

    Cosmacelf Active Member

    Joined:
    Mar 6, 2013
    Messages:
    3,399
    Location:
    San Diego
    Yes Tesla uses active liquid cooling. You especially notice it during Supercharging when the pumps and AC turn on. Also the specific cell that is used in the Model S isn't a generic Panasonic cell. It is a custom one and AFAIK, no one outside of Panasonic and Tesla knows the exact specs.
     
  3. Teo

    Teo Banned

    Joined:
    Jun 4, 2014
    Messages:
    155
    Location:
    London, UK
    #3 Teo, Jun 27, 2014
    Last edited by a moderator: Mar 13, 2016
    Besides liquid cooling, the batteries also have a custom chemistry which helps with battery life. By the way in Europe superchargers are 135 kW. The most technical video that I know of about Tesla batteries is this one:

     
  4. stopcrazypp

    stopcrazypp Well-Known Member

    Joined:
    Dec 8, 2007
    Messages:
    7,047
    Tesla's cells are custom built. They don't just use off the shelf cells. You can use the spec sheets of those type of cells as a basis for rough comparison, but can't use the exact specs and expect them to be the same.

    Also we already know that for the 85kWh pack, Tesla is using 3400mAh cells, so it can't be the 18650PF anyways (at 2900mAh).
     
  5. LMB

    LMB Member

    Joined:
    Mar 9, 2013
    Messages:
    192
    Location:
    South Shore Boston
    (LMB spouse)

    It's also true that the maximum charge rate only occurs when the battery is at less than 30% of capacity. By 50% capacity, the charge rate is less than 1C and declines steadily until the battery is as full as Tesla allows. If you've ever done a range charge at a Supercharger, you know that the last 25 miles take a *long* time.
     
  6. djp

    djp Roadster 2.0 VIN939

    Joined:
    Aug 28, 2011
    Messages:
    1,108
    Location:
    Toronto, Canada
    The cells can be charged faster at low state of charge. The SuperChargers ramp down as the battery charges, they're not charging at 1.4C all the way to the top.
     
  7. Electric700

    Electric700 Member

    Joined:
    May 21, 2013
    Messages:
    986
    Location:
    Florida, United States
    What is the C in 1.4 C? Is that related to temperature (Celsius), amps, volts or something else?

     
  8. trils0n

    trils0n 2013 P85

    Joined:
    Feb 12, 2013
    Messages:
    1,294
    Location:
    SF Bay Area
    1C = total capacity in 1hr
     
  9. UberEV1

    UberEV1 Member

    Joined:
    Mar 9, 2014
    Messages:
    258
    Location:
    San Jose, CA
    "C" = Couloumb. From Wikipedia . . .
    The coulomb (named after Charles-Augustin de Coulomb, unit symbol: C) is a fundamental unit of electrical charge, and is also the SI derived unit of electric charge (symbol: Q or q). It is equal to the charge of approximately 6.241×10[SUP]18[/SUP] electrons.
    Its SI definition is the charge transported by a constant current of one ampere in one second:
    1ba9bbd88f6e7f38ea20f9134ef7b42b.png
     
    • Dislike x 1
  10. David99

    David99 Active Member

    Joined:
    Jan 31, 2014
    Messages:
    2,054
    Location:
    Brea, Orange County
    "C" is this case stands for capacity (not 'coulomb'). A battery capacity is measured in Ampere-hours (Ah). A single AA rechargeable cell for example has 2 Ah. The charge/discharge rate is relative to the capacity. If the battery is charged at 2 Ampere, that is called 1C. If the battery is charged at 1 Ampere it would be 0.5C. If the battery is charged at 4 Ampere it is 2C. And so on. By using this value (charge/discharge current relative to capacity) it is easy to compare different size battery systems.
     
  11. N4HHE

    N4HHE Member

    Joined:
    Oct 15, 2013
    Messages:
    620
    Location:
    Madison, AL
    A modern NiMH AA cell can have a 2 Ah capacity but historically NiCAD AA was in the 300 to 600 mAh range.
     
  12. Matias

    Matias Active Member

    Joined:
    Apr 2, 2014
    Messages:
    1,590
    Location:
    Finland
    Is that enabled at the moment?

    - - - Updated - - -

    About high C rate:as many have pointed out, charging with full power is only possible, when battery is empty. Here is more info from blogger with Tesla's coments ( in red):

    http://teslaowner.wordpress.com/2014/01/01/supercharger-time-test/
     
  13. ch_model_s

    ch_model_s Member

    Joined:
    Feb 4, 2013
    Messages:
    24
    Location:
    east switzerland
    No.. we only get about 108kW in Europe right now....
     
  14. Matias

    Matias Active Member

    Joined:
    Apr 2, 2014
    Messages:
    1,590
    Location:
    Finland
    Why not 120?
     
  15. Muzzman1

    Muzzman1 Member

    Joined:
    Feb 8, 2014
    Messages:
    517
    Location:
    Los Angeles
    I can not find the thread for the life of me, but I'm fairly certain that someone on this determined that even at 135kwh the charge rate is much less that 1C.
    Anyone here know what thread I'm talking about?
     
  16. Electric700

    Electric700 Member

    Joined:
    May 21, 2013
    Messages:
    986
    Location:
    Florida, United States
    Thanks for clearing this up!

     
  17. Cosmacelf

    Cosmacelf Active Member

    Joined:
    Mar 6, 2013
    Messages:
    3,399
    Location:
    San Diego
    It can't be less. The entire battery pack contains 85 kWh of energy. So an 85 kW Supercharger would fill an empty pack in one hour. Which is 1C.

    135 kW of power would charge it at 135/85= 1.6C
     
  18. UberEV1

    UberEV1 Member

    Joined:
    Mar 9, 2014
    Messages:
    258
    Location:
    San Jose, CA
    @David99: Thank you for clarifying and introducing a concept new to me. Hard to believe after all the threads I have read here that I missed this one. Thanks!

    @trils0n: My apologies for the incorrect correction.
     
  19. jkirkebo

    jkirkebo Model S P85+ VIN 14420 EU

    Joined:
    Jun 13, 2010
    Messages:
    950
    Location:
    Fredrikstad, Norway
    At least 122kW has been reported, but only at the newer sites like those in Denmark.
     
  20. green1

    green1 Active Member

    Joined:
    Mar 25, 2014
    Messages:
    4,116
    Location:
    Calgary, Alberta, Canada
    There have been reports of many 135kW chargers, but it seems that they are being used to allow more charge to the second stall rather than the full 135kW to one vehicle. max charge rate for a single vehicle seems to be in the 120-125kW range.
     

Share This Page