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Motor or Efficiency Loss over time

Discussion in 'Model S: Driving Dynamics' started by andyro, Dec 3, 2015.

  1. andyro

    andyro Member

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    #1 andyro, Dec 3, 2015
    Last edited: Dec 3, 2015
    I have searched the TMC forum for answers on this subject, and while I have mentioned this concern on several work orders, I have never gotten a satisfactory explanation or resolution. Here is the issue: I purchased a Signature 85, its serial S2108 for Canada - so early days. I got used to being able to carefully drive pretty close to the average of the 'rated range' line of the trip graph, in Si units: under 200Wh/km, often far less. Then my drive unit was replaced about a year ago - and ever since - my efficiency tanked. The drive unit was 'upgraded' to a P85 motor, as I was told the early S85 motors in the lower HP range were discontinued. Now I can no longer come close to the 200Wh/km number, and since the new drive unit was installed, I have gotten an average of 220Wh/km (equal to 354Wh/mi over 37,600miles) - which is on the high end I understand from reading the lifetime efficiency thread, and I live in a very flat area with moderate continental temperatures.

    On speaking with other Signature P85 owners that travel the same routes I do - we have shared stats, and mine are always higher - and this is less related to driving style, because we are often stuck in the same weekend traffic. So I was determined to get to the bottom of this. Last time I was in for service, the loaner was a P85 with the same wheels I have, same everything, just a newer car. I drove it home like a bit of an animal, lots of fast starts, I was trying to get a high number like with my sig - not even possible.

    My 71km trip consumed a total of 13.8kWh, for an average of 192Wh/km. the next night, almost identical empty road, same 22degree temperature, I drove like a little old lady in my car, and used 16.4kWh or 229Wh/km. A good 15% difference. And 15% of a 400km trip - as you all know, is the difference between arriving at your planned destination or not.

    anyP85.jpg

    Loaner P85

    myP85S.jpg

    My P85 :(

    I would like to understand what the issue could be here.

    a) driving habits - I ruled this out after I did my test with the loaner.
    b) temperatures - same - ruled out after loaner test.
    c) wind and hills - ruled out.
    d) roof rack/sunroof/windows - nope.
    e) drag in wheel bearings - Tesla service checked - nope - rolls normally
    f) tire inflation/type/wheel type - same tires, same inflation (checked w. pocket guage, 42psi & 42psi)
    g) inversion issue - maybe
    h) regen issue - maybe

    At first Tesla said it was because the motor was a higher wattage model, but W=v*a, so if I am not *making* the motor work harder, why would it use more than the current supplied - it didn't make sense. I am starting to think my inverter is not paired to the new motor - could that be the issue? Where would the lost power go? Heat? Is my inverter getting unusually hot? I have no idea. I would be very grateful for any of you technically savante owners to offer your enlightened opinion here, as I am flummoxed to say the least, and I would like my car to perform as specified - and to do so, it seems I need to explain to Tesla what is in fact going on here.

    Thanks all!
     
  2. sorka

    sorka Active Member

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    #2 sorka, Dec 3, 2015
    Last edited: Dec 3, 2015
    I've had P85 and S85 loaners without there being any major difference between them. In fact, I get about the same efficiency in those as my P85D. 280 wh / mile in 75F weather at 65-70 MPH. In 55 degree weather, I averaged 300 wh / mile yesterday getting to work.

    Your biggest culprit and the thing you didn't mention and is the alignment status after the DU replacement. Did they provide with the alignment sheet for the 4 wheel alignment they did after the DU replacement?
     
  3. Saghost

    Saghost Active Member

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    If the loaner is that much more efficient in the same conditions, I tend to think there's a problem with your car. Lots of things can produce that sort of problem - mostly classic cars things that have nothing to do with being an EV.

    Alignment?
    stuck brake pad?
    I'm not 100% sure what you meant by "same" on tire pressure - was it the same as the loaner?

    One way to differentiate between a motor issue like you're thinking and a drag/load issue like I'm suggesting would be a coast down type test - take the car up to some fairly high safe speed on a straight quiet piece of road (100 kph?) and then shift it to neutral and record how the speed drops (could take notes or use a stop watch, but a phone video of the instrument panel is probably easier, safer, and more objective.) Then do the same thing with the loaner in the same place in similar weather. If you have a mechanical issue with the car, yours will slow significantly faster.
    Walter
     
  4. andyro

    andyro Member

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    Thanks, alignment - brakes - I will ask them to check, but I've replaced my rims and tires since due to dings/rash, I figured alignment would have been part of it. In fact my rotors and shields(?) were just replaced - but I'm getting the same lousy numbers. You might both be right, mechanical drag of some variety rather than some electrical issue. Coast test - good idea thanks, will try w. a service tech.
     
  5. David99

    David99 Active Member

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    That's a great idea! That's a great way to test if there are mechanical issues with the car or not. If both cars decelerate equally, then it has to be something in the motor/inveter
     
  6. Todd Burch

    Todd Burch Electron Pilot

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    I would agree that alignment or stuck brake pad is a plausible possibility. "Higher wattage model" is complete nonsense--as you said, you're not demanding more power when driving the same way. Energy is energy, no matter how you slice it.
     
  7. apacheguy

    apacheguy Sig 255, VIN 320

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    Odd. My Sig S85 had its DU replaced in February. I got the base unit. No P upgrade.
     
  8. freeewilly

    freeewilly Member

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    Do you get P motor performance now?
     
  9. andyro

    andyro Member

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    #9 andyro, Dec 4, 2015
    Last edited: Dec 4, 2015
    Zero difference from what I could tell at the time of the swap. I never felt a huge difference from S85 to P85 to be honest. P85D hell yes. I think I recall them saying the 85kW cars got the upgrades but not the 60s, if that makes any sense? PS - the 60kW loaner I borrowed at the last service got only 178Wh/km for the same 71km trip to my house.
     
  10. SmartElectric

    SmartElectric Active Member

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    I understand that you drive with efficiency in mind, and that long distance travel may sometimes require the highest efficiency.
    We too have an early S85 (see sig below for VIN range) and the efficiency is not much different from what you report.

    Big picture though, my Smart ED is less efficient that your Tesla. Averaging more than 250 wh/km over 2 years.

    I'm not suggesting you ignore what you feel is a problem, but it might be worthwhile to balance that concern with driving enjoyment and stop looking at the efficiency.

    Story:
    When we owned a Mercedes GLK, I was constantly driving in the right lane attempting to get better than 10L/100km on the highway on long trips. It was excruciatingly frustrating driving like this, like there was an egg under the accelerator pedal.
    The first week we had our Tesla (bought CPO summer of 2015) we drove from Toronto to NY City and back. Cruised in the left lane, no one passed us on the road, and we made it to every supercharger with enough range remaining to be comfortable. It was the absolute best car road trip ever, and we thoroughly enjoyed the driving part of the trip, even though it was 20 hours in 4 days.

    Moral of the story: Enjoy what you have, it's the best car in the world.

    Peace. :wink:
     
  11. andyro

    andyro Member

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    I hear ya, but the thing is, before my drive swap I was getting 180-200Wh/km - for my first 80,000km. Then drive swap - and I can't do better than 220Wh/km. That's what bugs me the most...
    and in Winter this is so much more pronounced. With all heat off - only enough to defrost - I am going up to 270, 320Wh/km - whereas my first Winter - I'd never go over 220... same roads, same temperatures... it just seems buggy. When compared apples to apples last summer in my little test - and from everyone I've talked to, the numbers seem off for my sig.
     
  12. eye.surgeon

    eye.surgeon Member

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    Stop looking at the efficiency meter and enjoy your car. You're worried about couch-change amounts of electricity. Your mental time is worth more than that.
     
  13. apacheguy

    apacheguy Sig 255, VIN 320

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    Disagree. We are talking 10-20% efficiency drop. It is clear the OP has a valid concern. It may be indicative of a more serious problem (alignment, brakes, etc.) and it is worth getting to the bottom of.
     
  14. jpet

    jpet Jan P.

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    You did not recently change tires, did you? During the first 1000 km, new tires can consume up to 10% more energy.
     
  15. ChadFeldheimer

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    With a stuck brake caliper imposing 3 kilowatts worth of drag (30Wh/km difference at, say, 100km/hr), you'd likely see one wheel much dirtier than the others (from brake dust). The corner with the stuck brakes would also be noticeably warmer than the others after a highway drive. At least, this has been my experience with sticking brakes.

    Unless the theory is that all brakes are functioning improperly?

    Alignment is a possibility and worthwhile to check.

    I suspect (1) the swapped motor and/or inverter is somehow ~10% less efficient or (2) it's a lot more windy whenever OP is in his car (versus a loaner) =)
     
  16. jpet

    jpet Jan P.

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    With the last V7 firmware, you should see less energy consumption in stead of more so I also agree this is not normal.
    To give you some perspective, here are some statistics from quite a few users (this is from the Tesla Battery Survey sheet):

    Energy consumption stats.jpg
     
  17. andyro

    andyro Member

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    It's not the couch change I'm concerned with. We have very few superchargers and cold temperatures up here. The 10-20-30% difference is enough to not make it to our cottage, or to require not turning on heat. Which makes the spouse call this a 'stupid car' - it wouldn't be an issue with the 30-80km extra margin I became accustomed to in the first 1.5yrs. There's no way we will be buying an X or any future Tesla if I can't win these small battles. I think it must be some kind of drag. More wind when I drive the car - hehe, exactly! Thanks for the stats above jpet - handy reference. My latest tires are worn 5000km by now.
     
  18. jpet

    jpet Jan P.

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    From the stats you can see that 220 Wh/km is not an unusual figure so that's probably the reason Tesla does not really want to invest a lot of time in your "case".
    But... if you have a clear reference point from the past, something's going on if that suddenly changes by 10% IF the conditions (especially temperature!) are the same.
     
  19. andyro

    andyro Member

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    #19 andyro, Dec 4, 2015
    Last edited: Dec 4, 2015
    That's just it. My past experience, and other local drivers with sigs, and my 'test' against a identically configured P85, driven in identical circumstances and weather, indicates a minimum 15% difference, that's why I'm taking issue with it. On average, I think most people drive MS as if they are enjoying it (hence 220Wh and not 200Wh as an average) - I do too, but with lots of long distance driving, I drive to arrive. PS - Have you compared your Battery Survey with data from the US/Canada lifetime efficiency thread? I seem to recall 330Wh/mi down to 300 was a standard range for my area, flat terrain.
     
  20. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    That's what I'd think too.

    - - - Updated - - -

    It's more fun to see how efficient you can be compared to pretending you're sixteen again. And it's hardly couch change. Compare these two:
    Dec_1_2015_jerry.jpg

    Tesla Dash 12-2-15.JPG
    That's 4.2 MW difference, or over 25%.
     

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