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Supercharger tapering visualized

Discussion in 'Model S: Battery & Charging' started by dirkhh, Sep 11, 2013.

  1. dirkhh

    dirkhh Middle-aged Member

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    I did a little 300+ miles road trip today with two quick visits to my favorite Supercharger in Centralia, WA. This is with an S60 (values would be different with an 85kWh battery as that allows higher currents). Anyway, I logged the telemetry data for today's trip and I think this results in a nice graph of the Supercharger tapering as the battery gets fuller (the graphs are created with the visualization tools in teslams). We start at 314V and 215A (SOC of 33%) and the voltage slowly goes up to 342V but the current falls to 93A (81% SOC - that's when I continued my trip).

    Screen Shot 2013-09-11 at 8.45.06 PM.png
     
  2. SFOTurtle

    SFOTurtle Active Member

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    Assume you're running 4.5 (or not running 5.0)? I think this graph is going to change substantially once 5.0 is rolled out.
     
  3. dirkhh

    dirkhh Middle-aged Member

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    I'm indeed on 4.5.
    I know that a few people with 5.0 are using teslams - but don't know if any of them have been to a supercharger.
    Alpha?
     
  4. Dreamin

    Dreamin Member

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    What is this statement based on? Just curious.
     
  5. dirkhh

    dirkhh Middle-aged Member

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    Data shown by several 85 owners. They charge with over 400V. When I asked the service manager in Portland he confirmed that 60s only charge with up to about 70kW (I've never seen more than 67kW on mine).
    No information if this will change in 5.0. He seemed to think it was a hardware limitation.
     
  6. bradc

    bradc Member

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    Charging is on a per-cell basis, so the max charging rate of the the 60 kWh will always be ~70% of the max charging rate of the 85 kWh. If Tesla figures out how to apply a higher rate of charge to an individual cell, that would apply to both the 60 and 85 kWh models.
     
  7. drees

    drees Active Member

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    Current (Amps) on the 85 kWh battery is the same as on your 60 kWh (unless you have firmware 5.0), what's different is that the voltage is significantly higher.

    Nice charts, BTW - easy to see how Tesla could push the pack harder - typical QC behavior would be to charge at constant current until pack voltage hits upper limit, then taper current to keep pack voltage from going over that max.
     
  8. dirkhh

    dirkhh Middle-aged Member

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    So you're saying that as the 85s get 90->120 kW I'll get 67-> 90kW? Cool, I'd like that.

    I noticed on my recent trips that "walk to Starbucks, have a latte, go to the bathroom, come back" takes about 30 minutes.
    And as a result on the way home I left a bit too early and arrived with 0 miles left in the battery. Oops. 30% faster charging would have given me 10 more kWh and I wouldn't have had to drive the speed limit (now writing this somehow sounds far less annoying than it felt...) :)
     
  9. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    I'm interested in resolving the apparent discrepancy between your statement "Maximum charge power: 324V/205.5 A" and what the graph shows. It looks like the end of the voltage ramp-up is a point at (~325V,~215A). Is the discrepancy in what the car reports on the display vs. what teslams logs?
     
  10. dirkhh

    dirkhh Middle-aged Member

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    The algorithm picks the point where current * voltage is the maximum and records the values. There's of course always the option that there's a bug in my code - it's open source, feel free to check :)
    (and yes, none of the data here is from the car's display - it's all from the data that teslams collects from the API)
     
  11. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    I guess that's why I'm asking the question: 325*215 is greater than 324*205.5 by a fair bit. Even if I'm reading the graph wrong, it's probably not by that much...

    ...and thanks, but I retired from reading other people's code eight years ago and don't feel the need to start in again. :biggrin:
     
  12. drees

    drees Active Member

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    In theory, anyway, yes.
     
  13. bluetinc

    bluetinc Member

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    Dirkhh,

    Very cool graphs! It would be neat to see the power (V*A) overlaid on your first graph. I think seeing that line will give a clearer indication of the taper on, taper off, and max power output limit of the Supercharger.

    It's really interesting to see your Pack charging voltages, which look a good bit different from the 85s. I've seen the 85's pack voltage when not charging, run from about 316V (6% SOC) to about 398V (100% SOC). During charging this Pack voltage is of course a bit higher by something in the order of 7-20V. I think that points to some interesting tidbits on how they stacked the batteries differently in the 60kWh batteries than in the 85kWh batteries.

    Peter
     
  14. dirkhh

    dirkhh Middle-aged Member

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    That should be easy to do. Let me add that when I have a moment :)
    I'm a strong believer that data can be better understood if it is reasonably visualized. That was my main interest when I started out on this project. Sadly not a lot of people have posted their graphs so I don't think we have a ton of data to work with. Do you have an 85 and a Supercharger in easy reach? I'd love to see similar graphs from 85s.
     
  15. dirkhh

    dirkhh Middle-aged Member

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    Is this what you had in mind? And I clearly stand corrected, my maximum charge power appears to be slightly above 68kW...
    This should also address the comment from stevezzzz - the actual max is at 322V and 212A - the old algorithm triggered on the charge rate as delivered by the API in mph and that clearly was wrong (the charge rate in the telemetry data is not tracking the actual power - strange).

    NewEnergy.png
     
  16. Musterion

    Musterion 18h 03m 37s −24° 23′ 12″

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  17. dirkhh

    dirkhh Middle-aged Member

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    Interesting use case. But looking at my data I can tell that supercharging tapers to below 60kW at around 55% SOC - yet I can also show more than 65kW regen with 87% SOC...
    My guess is that you are starting with 90% but the SOC creeps up to about 95% as you drive down hill... is that an explanation?
     

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