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Alarming amounts of cold weather vampire drain

Discussion in 'Model 3' started by voip-ninja, Feb 12, 2019 at 7:13 AM.

  1. Garlan Garner

    Garlan Garner Well-Known Member

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    #41 Garlan Garner, Feb 12, 2019 at 11:56 AM
    Last edited: Feb 12, 2019 at 12:02 PM
    You live in Colorado.

    I wonder if people in Hawaii would have to be presented with different drain numbers than Colorado'ans…… as opposed to Iowan's as opposed to …….

    You know what....I would LOVE for Teslas to become popular enough for range alerts to be reported during the major local network weather reports - like windchill.
     
  2. paranoidroid

    paranoidroid Member

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    The low pressure warning at 41psi is really strange. I've run my car at 40psi for weeks and no warning. I bleed them down to 36psi cold at Buttonwillow for a day on the track and no warning either.

    It does make me wonder how Tesla's warning algorithm works here.
     
  3. StellarRat

    StellarRat Member

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    So, it's reading higher up in the mountains than when you're in the low lands?
     
  4. PhaseWhite

    PhaseWhite Member

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    I think the range drop is a combination of vampire drain and a cold soaked battery. The vampire drain could be improved but the physics of lithium ion batteries will likely be the real limit to performance on the model 3 and future BMW competitors. Based on what we’ve seen from competitors recently in terms of efficiency and cold weather performance I wouldn’t get your hopes up.
     
  5. voip-ninja

    voip-ninja Give me some sugar baby

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    Yes, it is quite well documented that Tesla does not adjust for higher elevations with their TPMS sensor readings and owners have apparently been complaining about it for years.

    6,000 feet vs sea level works out to a 3 psi difference. Normally not enough to get upset about but when you're Tesla you are extra special and your tire pressure sensors go off when they are only 2-3 PSI below the door sticker recommended pressure.

    https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=167
     
  6. StellarRat

    StellarRat Member

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    I agree. There's no reason to believe that a BMW will be any better in cold weather. As far as I've read Tesla has the best batteries and battery management system in the industry.
     
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  7. voip-ninja

    voip-ninja Give me some sugar baby

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    I'm not going to argue that Tesla is ahead of the competition in the area of batteries & motors by at least 4-5 years and is continuing to innovate to maintain that lead.

    In many other areas BMW offers a superior car owning experience, at least what I've observed in my first five months of Tesla ownership.

    My comments re: BMW were not that they would be able to magically solve the issue with battery chemistry... but I can see them exceeding Tesla in many other areas, particularly vehicle service, fit/finish, cold weather experience (pretty much guaranteed they would not ship a car that had door seals freezing, charge ports freezing, inefficient resistive heater, etc.

    Time will tell I suppose, I don't expect anyone to have anything competitive until at least late next year at the earliest.
     
  8. voip-ninja

    voip-ninja Give me some sugar baby

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    It's not strange when you understand that Tesla is not adjusting for high altitudes.
     
  9. StellarRat

    StellarRat Member

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    Then they are working correctly. When you are up high you're tires are acting like they have 3 psi more in them. This is exactly how airplanes work. When you're trying to take off at high altitude you need more ground speed because the air pressure is lower. The indicated air speed gauge will show how you what your effective speed is as far as what your wings and control surfaces are seeing. I'd say the Tesla TPMS sensors are more accurate than some other sensors that "cover up" the true situation.
     
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  10. voip-ninja

    voip-ninja Give me some sugar baby

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    This is absurd. Other cars I have owned with TPMS sensors adjust for the altitude difference, the Tesla does not. If the tires are inflated using a race gauge and set at 42 PSI at 6,000 feet the Tesla thinks the tires are at 39 PSI and throws an alarm. If I try to set the tires to the "comfort" inflation level (39PSI) that Elon Musk himself recommended for the Model 3 then the TPMS sensors will read 36PSI and will be in alarm.

    I have never had disagreement between the TPMS sensors in my other cars and the gauges I use, so I have to assume that those manufacturers measure air pressure with the MAF or something else and adjust automatically. Those manufacturers also allow for a PSI variation of more than 2-3 PSI before setting off low pressure warnings in the cockpit.

    Stop being a Tesla apologist on this issue, especially when you likely live at sea level and don't have to deal with it.
     
  11. AlanSubie4Life

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    #51 AlanSubie4Life, Feb 12, 2019 at 1:23 PM
    Last edited: Feb 12, 2019 at 1:35 PM
    For tire pressures, what matters is relative pressure (that's what a tire gauge measures). Unfortunately the Tesla sensors are not being corrected for local atmospheric pressure; they are displaying what is effectively absolute pressure. Apparently most ICE cars do this correction with the intake flow/volume sensors.

    As already referenced earlier...

    Model 3 TPMS sensors are junk

    EDIT: I think this above-referenced thread title is misleading - there is nothing wrong with the sensors, it's just the way the data is reported & acted on by Tesla. END EDIT.

    This is like Deflategate all over again. (Gauge pressure vs. absolute pressure was a thing there because people were trying to calculate how much the pressure changed for a given change in temperature to see whether the "GOAT" had done something nefarious.)

    The good news is that I'm sure eventually Tesla will be able to software update this somehow. Shouldn't be that difficult...
     
  12. voip-ninja

    voip-ninja Give me some sugar baby

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    Elon tweeted yesterday that a picture of Mars was erotic enough that he felt he needed to nut, so somehow I don't think this is a priority. Honestly this problem has existed on Tesla cars since introduction, but the S and X must either have a wider margin before the low pressure warnings go on or they have a compliant enough suspension that owners don't mind over-inflating tires for it to be an issue for them.

    And yes, you are correct, Tesla is displaying absolute pressure when all that matters from the perspective of tire inflation levels is the local atmospheric pressure.... also known as the actual measurable air pressure difference between the inside of the tire and the outside atmosphere.
     
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  13. AlanSubie4Life

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    I didn't even know No Nut November was a thing until yesterday. Thanks Elon!
     
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  14. StellarRat

    StellarRat Member

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    I'm not being an "apologist". Science is science. Not the other way around. Should Tesla also not take outside temperature and tire heating into account? Those affect the pressure readings too. I'd want my tires to operate like they're supposed to at whatever altitude I filled them at. Fudging the numbers just to prevent owners from worrying is not good engineering. You have to draw the line somewhere.

    Now, that said, I agree that maybe the low pressure alarm software should take altitude into account or at least note that the problem maybe altitude related, so it doesn't bug you for a minor pressure change.
     
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  15. AlanSubie4Life

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    #55 AlanSubie4Life, Feb 12, 2019 at 1:56 PM
    Last edited: Feb 12, 2019 at 2:07 PM
    I feel like you might not be understanding the core issue here - it's that the TPMS should be corrected such that they read gauge pressure because that is what matters. As an aside: temperature increases tire pressure due to the ideal gas law, but you have to use the absolute pressure to predict that change (add 14.7PSI to the gauge pressure at sea level, a few PSI less at 5k feet, and THEN use the ideal gas law, using ratio of degrees Kelvin). Temperature definitely affects gauge pressure and the absolute pressure in the tire, but the gauge pressure is still what matters because that is what determines how much the tire deforms.

    Lets assume a perfectly calibrated tire pressure gauge.

    The problem here is that in order for the OP to actually run the CORRECT gauge pressure (let's say the target is 42PSI, as the B-pillar recommends), in Denver, he must put in less air than he would need to at sea level to get his perfectly calibrated gauge to read 42PSI (because atmospheric is lower). The TPMS measures the pressure in the tire, and reads it as about 39.3PSI (it's presumably actually reading 54PSI (which is correct with Denver atmospheric pressure of 12PSI) , and subtracting 14.7 (NOT 12PSI), then displaying this result (39.3PSI)). This is because it is reading absolute pressure and not correcting for the atmospheric pressure.

    This is the OP's (and @mongo 's) claim for how it works. I have not independently verified the behavior (I am at sea level), but it is certainly plausible.
     
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  16. StellarRat

    StellarRat Member

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    I thought he said that the pressure the TPMS was showing varied with altitude not that he couldn't put the right amount in at altitude. That's a different. In that case, I agree, it should compensate for altitude. However, the tires will read too high pressure when he moves to sea level and will actually be overinflated. There's really no easy way to fix this without cheating somehow. Unless the car stays at the same altitude always it will always vary.
     
  17. voip-ninja

    voip-ninja Give me some sugar baby

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    [​IMG]

    Yet somehow other manufacturers have managed to fix this without "cheating somehow".
     
  18. diamond.g

    diamond.g Active Member

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    Can the TPMS not be reprogrammed to send the correct reading?
     
  19. voip-ninja

    voip-ninja Give me some sugar baby

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    Find a way and I'll Paypal you $100.
     
  20. StellarRat

    StellarRat Member

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    No, they're just putting your mind at ease with the software. Your effective tire pressure IS changing with altitude. Just because it reads correctly by the software doesn't mean the tire is acting like it really has that much air in it. Anyway, I'm not going post anymore on this. It's not that big of deal to me.
     

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