Alarming amounts of cold weather vampire drain

[AlanSubie4Life]

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

This is what he said. It seems like exactly what one would expect if the TPMS thought it was at sea level (it has no idea where it is or what the atmospheric pressure is).

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

I am not sure what that means, exactly. It's a confusing issue to talk about, I understand, and in Deflategate it even tripped up some pretty accomplished scientists. It might trip me up here; it's pretty easy to get things backwards. I am not sure what "the pressure the TPMS was showing varied with altitude" means. If the claims are correct, the way it will behave if you magically transport a wheel instantly from Denver to sea level, is that the TPMS will NOT display a change in pressure in the car. That is because there is the same amount (number of molecules) of air in the tire as when you started, and it (the car computer) is subtracting a constant 14.7PSI from the absolute pressure, so it will display the same number in the car (39PSI according to my earlier example).

However, the tires will read too high pressure when he moves to sea level and will actually be overinflated.

NO. The tires have less air in them, so the gauge pressure will read lower at sea level than in Denver (for the above magically transported tire). Think of transporting an empty water bottle to sea level - it gets crushed under the weight of the air. Similarly the tire will become flatter. (As you would expect for a tire that is at 39PSI according to the TPMS at sea level.)

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

If you're talking about gauge pressure changes with elevation, nobody has fixed that. If you want the TPMS to report the approximately correct gauge pressure, yes, the other manufacturers have figured that out.

 

[StellarRat]

NO. The tires have less air in them, so the gauge pressure will read lower at sea level than in Denver. Think of transporting an empty water bottle to sea level - it gets crushed under the weight of the air. Similarly the tire will become flatter. (As you would expect for a tire that is at 39PSI according to the TPMS at sea level.)

Yes, I had it backwards. Anyway, I think you get my point about the effective air pressure vs. what the software is telling you.

 

[AlanSubie4Life]

Anyway, I think you get my point about the effective air pressure vs. what the software is telling you.

I think I do. I think the software should tell you the gauge pressure, not the absolute pressure minus a constant. Which is not (allegedly) currently the case.

 

[StellarRat]

I think I do. I think the software should tell you the gauge pressure, not the absolute pressure minus a constant. Which is not (allegedly) currently the case.

Yes. I think we're on the same track.

 

[chronopc]

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.

I notice my tire pressure changes as I drive. When the TPMS first gives a reading, it shows 45 psi which is what I pumped my tires to. But as I drive I see readings as higher as 49 psi.

 

[StellarRat]

I notice my tire pressure changes as I drive. When the TPMS first gives a reading, it shows 45 psi which is what I pumped my tires to. But as I drive I see readings as higher as 49 psi.

Because the air in your tires is heating up and that increases the pressure. That's normal, but I don't think you'd want the software to report 45 psi because it would be lying to you. This my whole point. How much do you want the the software to overlook just so you don't worry?

 

[AlanSubie4Life]

I notice my tire pressure changes as I drive. When the TPMS first gives a reading, it shows 45 psi which is what I pumped my tires to. But as I drive I see readings as higher as 49 psi.

That is because the temperature in your tires has increased by about 20 degrees C (assuming they started at 0 degrees C and you are at sea level).

PV = nRT, n and R are constant, V approximately constant

So P2/P1 = T2/T1

(49+14.7)/(45+14.7) = 1.067 = T2/T1

Where T2 is final temp and T1 is initial temp, in Kelvin (0C = 273.15K).

(So if T1 is 273.15K, T2 = 291.45K)

 

[StellarRat]

That is because the temperature in your tires has increased by about 20 degrees C (assuming they started at 0 degrees C and you are at sea level).

(49+14.7)/(45+14.7) = 1.067 = T2/T1

Where T2 is final temp and T1 is initial temp, in Kelvin (0C = 273.15K).

(So if T1 is 273.15K, T2 = 291.45K)

I remember the gas laws from chemistry. That was so long ago now.

 

[McFlurri]

Figured I would share my experience in this thread too.

My personal experience with long distance (338km round trip with 111km left after a 100% charge - preheated while plugged in at about -4C), is MUCH better than the ~41% range loss that AAA is mentioning. EV's can be still quite efficient for long distance I AGREE WITH YOU.

I'm just pointing out that there are situations where the AAA report IS accurate.

Example from today for me;
Charged to 90% (447km) completed at 2:30am
Began preheating car to 20.5C at 1:27pm and car showed 421km (car is parked outside and was still plugged in even after 2:30am)
Left with 415km at 1:35pm
Work is 7km away round trip (chill mode on and temp at 20.5C) outside temp around -5C (arrived at work at 1:45pm) - wife shuttling me
Finished work and car drove 8.6km round trip (again wife shuttle service) and arrived home with 360km of range.

So my car physically drove 15.6km today, but the car used/ lost 87km worth of range.

Am I concerned.. no, because I still have ample range to do this for several more days. But here is my personal experience. Car was left alone to go to sleep. no one logged into the app to keep the car awake, I don't have that keep climate on setting turn on...

 

[Hoosier]

I drove my car home yesterday afternoon and parked it in the garage with 49% battery at about 445pm. Outside temps were 38F. The garage is unheated but is attached to the home on two sides and doesn't typically dip below freezing (garage floor will have water puddled but no ice).

Last night it got down to 20F outside. When I turned the car on this morning at 645AM to heat the cabin the battery was down to 44%.

So my car lost 5% battery in a little over 12 hours in an unheated garage where the temps hovered close to freezing but didn't go below freezing that I am aware of.

I don't plug my car in at home because I get free charging at work.

I am a bit concerned about the amount of vampire loss I am seeing with my vehicle.

 

[Hoosier]

I'm

now my third midwestern winter with my X. It lives in a heated garage where the temperature in the garage on cold nights may be mid 30's at worst. Last week the outside temp was -11F one day. Doors and mirrors froze and car became essentially inoperable after i drove to work and parked outside. Same experience today with outside temp of 20F. Energy consumption enormous even with heat off (seats, steering wheel, and wipers). When battery finally heats up things don't improve much on the mileage front. Attached is a pic of consumption recently on a cold day after commuting to work in normal urban traffic.

 

[Garlan Garner]

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

Tesla doesn't adjust...….?

Who does?

 

[voip-ninja]

Tesla doesn't adjust...….?

Who does?

The TPMS on my Acura, BMW, Mini all agree with what a gauge shows, so I assume they use some sensor in the car to adjust for elevation change offset that are applied to what TPMS reports.

I don't even care if Tesla adjusts for altitude if they would increase the warning threshold so that I can inflate the tires to Elon's recommended 39 PSI (which the TPMS will read as 34 psi) to make the car more comfortable to drive over potholed streets.

 

[diamond.g]

The TPMS on my Acura, BMW, Mini all agree with what a gauge shows, so I assume they use some sensor in the car to adjust for elevation change offset that are applied to what TPMS reports.

I don't even care if Tesla adjusts for altitude if they would increase the warning threshold so that I can inflate the tires to Elon's recommended 39 PSI (which the TPMS will read as 34 psi) to make the car more comfortable to drive over potholed streets.

Did you buy those vehicles from a dealer at that altitude? It is probable the dealer updated the TPMS (which goes back to why Tesla won't do the same to be honest, lol). I know that GM has to reprogram TPMS when changing altitudes.

 

[voip-ninja]

Did you buy those vehicles from a dealer at that altitude? It is probable the dealer updated the TPMS (which goes back to why Tesla won't do the same to be honest, lol). I know that GM has to reprogram TPMS when changing altitudes.

Yes those cars were all purchased here. I have no idea what the dealer might do pre-delivery. Keep in mind that with the exception of the Acura that was built in Canada all of the cars mentioned were built outside the US and shipped into US ports.

I still think it's possible that those cars are adjusting their TPMS offset for altitude automatically as all newer generation EFI cars would have ways of deducing the altitude or air pressure through sensors they already have.

 

[chronopc]

Because the air in your tires is heating up and that increases the pressure. That's normal, but I don't think you'd want the software to report 45 psi because it would be lying to you. This my whole point. How much do you want the the software to overlook just so you don't worry?

I am fine with the way the software works. The first time I saw 49 psi I thought I had put too much air in my tires, but I checked once the tires were cold and nope I didn't.

 

[MorrisonHiker]

Did you buy those vehicles from a dealer at that altitude? It is probable the dealer updated the TPMS (which goes back to why Tesla won't do the same to be honest, lol). I know that GM has to reprogram TPMS when changing altitudes.

I would hope they could have the TPMS adjust automatically based on the elevation instead of requiring one to "take it to the dealership" to have the TPMS adjusted.

I live at 6,000 feet and regularly drive to towns at over 10,000 feet in elevation. There are some mountain roads that I drive on which have an elevation of 12,000 feet to over 14,000 feet. Usually when driving at higher elevations, we get the warning about low tire pressure. Fortunately the TPMS doesn't have any issues when descending from 6,000 feet down to 1,000 feet when I drive to visit family in Kansas.

 

[Big Earl]

I think I do. I think the software should tell you the gauge pressure, not the absolute pressure minus a constant. Which is not (allegedly) currently the case.

I think that would require a barometric pressure sensor on the car. Most ICE cars have one for engine management, but I'm not sure if one exists on a Tesla. They could certainly calculate it based on GPS elevation.

 

[voip-ninja]

I think that would require a barometric pressure sensor on the car. Most ICE cars have one for engine management, but I'm not sure if one exists on a Tesla. They could certainly calculate it based on GPS elevation.

Yes, using the GPS to fetch the current altitude and use that as a TPMS offset is trivial but Tesla probably doesn't even have it on the radar scope.

 

[Big Earl]

Yes, using the GPS to fetch the current altitude and use that as a TPMS offset is trivial but Tesla probably doesn't even have it on the radar scope.

I'd recommend submitting a feature request by email, tweet and www.moretesla.com