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Tesla tech talk Boston

Discussion in 'News' started by cinergi, Feb 12, 2011.

  1. cinergi

    cinergi Active Member

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    #1 cinergi, Feb 12, 2011
    Last edited: Feb 14, 2011
    Tesla had a tech talk in Boston today, which I attended. I was there from 10am until about 4pm. About 1.5 hours of group tech talk, and the rest was chit-chat with various attendees and Tesla employees. I took copious notes, recorded the 1.5 hour session (and just listened to it again to update my notes). I won't post the recording (no permission, no video for reference of what was being pointed at, difficult to hear), but here's a quick-n-dirty dump. I left out the answers to the questions where I thought most of us here already know.

    Dan Myggen (my CA) did the talking / Q&A. He's based out of the Palo Alto headquarters. Also had some representation from the NY office.

    I'll separate these into Roadster/generic and Model S groups

    Roadster

    Front bumper is plastic -- softer, cheaper; CF cracks when hit hard enough
    Foam, followed by CF crash zone from front to fan/radiator area
    Fans/radiator for the A/C
    DC/DC converter mentioned -- I mentioned I've been told this is a DC controller, and the 12V stuff is elsewhere (and also that the small "motorcycle battery" no longer powers the contactors)
    Q: a/c affect range?
    Q: charge times
    Q: Same connector as volt?
    Adapter in the works
    Q: Air cooled only?
    Q: roadster battery capacity?
    Q: charge loss? 60-65 Kwh to charge 53Kwh (56Kwh pack, 53 usable)
    Q: charge linear? Curve is half circle, start slow if 0%, max power until near full, taper off
    Q: Roadster tells you your available range?
    Q: partial charging hurt battery? Lots of small cycles "much much better" than a few long cycles; top it off every day; LiONs don't have memory
    Q: long-term depletion higher than thought? (IPO news). 60-80% cap. After 7 years. Faster depletion up front, levels out, and increases rate again towards 6 years
    Battery in roadster is 3-4 generations old (Model S 160/230 pack is 2 gen, 300 probably 1 gen old; not available at launch)
    Cost of pack? Roadster is 30k today.
    Battery pack assembled by hand; inspect each 18650, measure voltage, etc.
    4 channel abs brake system
    Hydraulic brake booster; electric vacuum pump
    Noises - turning on. Battery coolant, brakes, clicks. Two contactor clicks in battery pack (NOTE: so yes, this means the current from battery is actually switched)
    Battery coolant -- keep pack temp even so you have even wear of the pack (solve weakest link in chain problem)
    Back of car:
    Battery pack subframe is a stress member of the frame
    Steel hoop for roll bar (under the CF) - meets NHRA roll bar rules
    Q: how much does battery weigh
    11 sheets; 99 bricks, 69 in each brick
    6831 batts
    ~400 temp sensors in the battery pack
    Lines from batt to PEM
    PEM -charge inverter, drive inverter; IGBT's
    Stator, rotor, 3 phase, 4 pole
    variable frequency drive
    Regen braking
    Single pedal driving - "defining feature" (NOTE: sweet! great to see Tesla believes in this)
    Synthetic brake pedal (a la Prius) = poor feedback on brake pedal
    Q: horsepower? Think torque instead
    Q: "Chipping" the car for more power?
    Hp and torque always cross at 5250 rpm (if not, the dyno chart in question is bogus)
    Gear reduction, input shaft, differential, etc. -- simple system; motor always connect to gears
    Instant response
    Q: Battery recycling; legally can be thrown out (not toxic enough)! Work with 2 recycling groups for pickup. They pay tesla for the used batteries
    Q: insurance cover batteries?
    Q: roadster in snow? TC very fast to respond. Allows 2% slip rear to front
    Q: impact of cold on batteries. 3 degrees C or less means no charge. What about parking lot? No regen. Tesla is thinking about it. Range impact? Heat, cold air is denser = more drag ... ; Tesla thinking about pre-trip battery warming. what to do when car isn't plugged in
    Q: Solar roof? Keep battery warm?
    Crash structure in back of car. NHTSA requires higher speed rear impact performance in EV (something like 35 vs 50) due to acid leak worries for lead-acid (yup, even though lead-acid isn't being used here)
    Transaxle designed to split and absorb energy on significant-enough rear impact
    Q: green car? Where does lithium and cobalt etc come from? Don't know but researching for model s. Are we mining from "bad countries" or devastating another? Tesla cares about this topic (limited by money and relationships to suppliers as Tesla doesn't carry enough weight with suppliers yet)
    Q: scratch in paint? Repair?
    Q: maintenance ? $600 yearly maint. 1 day routine. Clean PEM. Replace refrigerant.
    Service van -- service many things remotely
    Can download logs remotely
    SOC, temp, alerts, etc. sent to Tesla on daily basis (if you enable the modem). Dan checks report daily and emails customers if they have problems.
    example: In storage mode, lose power, go below 10% SOC, Dan emails customer
    Q: theft? Alarm, can't hot-wire. One stolen so far (key stolen from house); another attempt made (but failed)
    Better to think about battery life in terms of time spent at voltage and temperature (esp. at the extremes)

    Model S
    .25 drag coefficient for model s; .35 for roadster
    LED headlights -- supplier sourcing issue. Model S will be HID (I think I heard that right -- don't quote me)
    Q: model s charge times
    Pack swap in model s; no swap stations in US, no known plans, but it's designed for it
    Quick charging. Model s 230 mile quick charge STD mode 45 mins
    Model S info. Target under 4k pounds. Cells stand vertical in the battery pack. Stiff structure, pack's contribution to rigidity, etc. Car doesn't roll forward under heavy braking which means better regen and traction and bigger rear brakes. ~45F/55R weight distro; 97% Aluminum; boron steel reinforcements in various areas like b-pillar
    Charging maps on model s, iPhone app, etc. all big factors in the development; no firm commitments on what's going in
    Hint at API for 17" screen (developer access)
    Schedule 2nd qtr 2012 for first deliveries. 7000 in first year. Order today = 1st qtr 2013. First 1,000 (sig series) -- probably generally fall 2012
    Lineup: alpha, beta, pre-release candidate, founder, ...
    Q: Event for reservation holders? Spring? Not sure
    Alphas doing cold weather testing now. Until crash test is done, no one outside tesla can drive.
    Lojack? No, but modem/gps can be effective enough
    17" touch screen is standard feature
    No spare tire (TPMS reduces need)
    Q: Special lift for model S like Roadster? not sure
    Real production cars to be shown late this year
    17 stores now, plan for 50 at model s launch; they realize need for stores
     
  2. ckessel

    ckessel Active Member

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    #2 ckessel, Feb 12, 2011
    Last edited: Feb 12, 2011
    Great stuff. That surprised me unfortunately. I'd thought all current reservation holders were going to get the car next year. I reserved early last month, but it sounds like it'll be 2 years before I'd get the car. That's roughly forever :(. Maybe it's just perception, but I could swear when I started looking into the Model S a few months ago, it was late 2011, then became mid 2012, now it's sounding like its early 2013.
     
  3. qwk

    qwk Model S P2681

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    Thanks, some of the answers confirm rumors.
     
  4. Talkredius

    Talkredius Member

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    Thanks al lot cinergi, was any thing mentioned about a 1. gen pack for the Roadster ?
     
  5. dpeilow

    dpeilow Moderator

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    Slipping 60% in there is a bit sly.


    Useful info. That's got to be a faster rate than supported by CHAdeMO.
     
  6. dsm363

    dsm363 Roadster + Sig Model S

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    Thanks. Great info.

    I know some of this was about the Roadster but was this referring to the Roadster or the Model S?

    Q: Same connector as volt?
    Adapter in the works

    Did they say what connectors the Model S would have? J1722, what kind of DC fast charger...etc

    No LED headlights? I find this strange. It's becoming standard on the higher end luxury sedans. It looks cool so I think people will expect it too. Not a big deal of course though.
     
  7. dpeilow

    dpeilow Moderator

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    I'm not sure if we ever got "official" numbers for the packs (other than JB's quote of 85-95kWh for the 300 mile pack) but if we took the 3400mAh cell as their "1 gen old" tech, then that gives 98kWh and it works out at 290 Wh/mile from the range mode capacity. That would then give 51.5 kWh and 74 kWh pack sizes for the 160 and 230 mile cars, respectively. That roughly lines up with standard cell sizes.

    So if standard mode still means 80% of capacity, then for the 230 mile car that means ~60 kWh would have to be charged in 45 minutes. Assuming efficiency losses of 20% (tallies with other high power charging) then the charger needs to supply 100kW.

    That's quite a lot over CHAdeMO (max 125A x 500V = 62.5kW). Only J1772 DC seems to be talking about this sort of power level (200A x 600V = 120kW, here).
     
  8. Norbert

    Norbert TSLA will win

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    According to that pdf, the SAE J1772 DC Charging standard is scheduled for Aug 2011. That may be just in time for Tesla to use it as the Model S' primary connector, given that it includes J1772 Level 2 and Level 1.
     
  9. Lloyd

    Lloyd Active Member

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  10. dpeilow

    dpeilow Moderator

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  11. ckessel

    ckessel Active Member

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    Yea, that's a bit concerning unless 45 minute charge stations become very prevalent in the next 3-4 years. If depletion is fast up front, then say reduced to 85-90% in the first couple years? I regularly travel Portland, OR to Seattle, WA which is about 190 miles. I figured the 230 mile pack would be fine (since I'd stay over the weekend so recharge isn't an issue). Buying a car that wouldn't be capable of making that trip after maybe even just a year of ownership is really making me reconsider.
     
  12. cinergi

    cinergi Active Member

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    With the additional note that most people would be at 70%
     
  13. cinergi

    cinergi Active Member

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    Anything that wasn't labelled Model S or obviously Model S would be Roadster information. I'll see if I can edit it up to place things into two clear sections.

    He didn't say which connector explicitly but did say it's the new SAE standard and that electrically it's basically the same as the Roadster. I assumed that to be the J1772.

    The LED headlights isn't strange to me after I understood what Tesla's challenege is. As a small company, getting a supplier to spend the time designing an LED headlight housing to fit the Model S is very difficult (there's not enough money/incentive for the supplier). Dan mentioned that there are a couple cars that have it now -- there are only a couple of headlight housings on the market, none of which are likely to fit well with the Model S design.
     
  14. dpeilow

    dpeilow Moderator

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    Sounds like a reasonable assumption. Tomsax's work shows they are essentially electrically the same.
     
  15. dsm363

    dsm363 Roadster + Sig Model S

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    #15 dsm363, Feb 13, 2011
    Last edited: Feb 13, 2011
    Thanks. That's good news. If only the public J1772 charging stations were over 30A though.

    That makes sense. Hopefully the light output will be better than on the Roadster.

    Seems like SAE is going to be late to the party. I wonder what Tesla will choose for the Model S for DC charging then.
     
  16. Tommy

    Tommy Member

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    I have read one of the disadvantages of LED lighting for headlight use is the lack of forward radiant heat, therefore a heating system must be incorporated into the lighting system to melt any snow & ice that accumulate on the lens. I would think such a system would negate any energy efficiencies of using LED rather than a HID system. So what ever system is the most reliable and not cost big $ to replace works for me. And like you, not a deal breaker for me.
     
  17. Norbert

    Norbert TSLA will win

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  18. AndrewBissell

    AndrewBissell Member

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    Norbert - thanks for that link.

    I think it's interesting to note how the DC proposals for the "Mennekes" connector work. Because there are already more pins (due to 3-phase support) they are able to do DC fast charge up to 70kW with the same connector.

    Only to jump to 150kW do they need to add the extra heavy duty pins that the SAE J1772 DC proposal needs at the outset.

    A very interesting French article (http://www.ifri.org/downloads/actuelledeboncourtchargingstandardsev.pdf) surveys all of this (not with total accuracy) and makes a very important observation that I think we all probably agree with but that the industry seems to be forgetting - Customers need standards to feel confident. (though they also observe that technology is evolving fast and it may be too soon to impose standards).
     
  19. Doug_G

    Doug_G Lead Moderator

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    I don't care as long as the headlights are much brighter than the Roadster's.
     
  20. Norbert

    Norbert TSLA will win

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    If Mennekes fast charging will be DC as well, then this probably removes any possible cost advantage on the DC end. It would seem the US and Japan are more likely to go with 90 kW and J1772 AC Level 2 compatibility, even if additional pins are needed. (Sidestepping the CHAdeMO question for a moment.)
     

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