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Roadster Sport RED vs WHITE Performance modes

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scott451

KWH-PWR#1349Sprt,S Sig#96
Apr 2, 2009
258
3
Palo Alto
I've received a number of PM/emails about the performance of the roadster Sport and recent firmware changes. I did some data collecting on a friends sport and here's what I found:

Do I have to be in performance mode to get the max out of my Roadster Sport?
Yes. The torque in Standard mode is limited to 265 ft-lbs vs 295 ft-lbs in performance. (see plot below)

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What does it mean when the 'Performance' on the VDS changes from white to red? Do I lose power?
Yes. When VDS 'Performance' turns red, the PEM temp is >= 45C and the max torque is limited to 273 ft-lbs. When 'Performance' is white, the max torque is 295 ft-lbs. The good news is that the PEM fan is very powerful and it cools the PEM down in about 30 seconds. (@26C ambient. YMMV)

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When the PEM temperature reaches 45C, the max torque will be limited to 273 ft-lbs

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VDS 'Performance' is red, but the PEM temp is only on the last blue bar.
In the new firmware, the last blue bar is on for PEM temps 43C to 60C.

I recently got a firmware upgrade. The bars on the VDS temperature screen seem to act differently.
This screen has changed how the battery temperature is displayed. Attached is the data from my 2008 roadster. (I have also checked it against a recent roadster sport VDS )

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Disclaimer: My conclusions & data could be wrong. I don't work for Tesla nor have any friends that do. I'm just passionate about Tesla's products and understanding how they work. The data is the result of my own analysis of my roadster and discussions with (and log data from) other owners.
 

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Scott, thanks for the info! I've actually been looking around for these figure quite a while hoping Tesla would provide these one day.
Now about performance mode: firrst I thought it would simple dial in higher limits for e.g. motor current, but later I heard that charging in performance mode pre-heats the batteries. Does this mean that warm batteries have a higher power discharge (at the cost of shorter life span)? If so, you would need to select performance mode some times before you actually get maximum performance.
Any thoughts on this?
 
What instrumentation did you use to get that data?

I'd love to see comparable graphs for the other Roadster models (2008, 2010 non-Sport, Roadster 2.5 if it's any different from 2.0; I just heard that the 2.5 PEM has hi-temp chips that allow it to run much hotter).

It's also interesting that a hot PEM is limiting torque rather than power. My experience with getting Roadsters toasty is that when the motor is hot it limits torque but the PEM limits power. Maybe it's different for the lower temps you're dealing with; I'm thinking of when you get all the way to red and the warning comes up on the VDS.
 
Scott- This is awesome! You have answered so many questions and so succinctly! I don't doubt your data crunching ability at all, but one thing I know for sure... I validate what you said: "I'm just passionate about Tesla's products and understanding how they work." Thank YOU! :)
 
Now about performance mode: first I thought it would simple dial in higher limits for e.g. motor current, but later I heard that charging in performance mode pre-heats the batteries.
I don't think that the battery is "heated" in performance mode. The only time I have seen a heat record in a logfile is during charging when the battery very cold. In performance mode, the battery is allowed to run hotter. [update 11/2010] It appears that cooling is reduced when charging in "performance" mode. So the battery will be hotter when fully charged.

Does this mean that warm batteries have a higher power [output] (at the cost of shorter life span)? If so, you would need to select performance mode some times before you actually get maximum performance?
Yes (see graph below). The curve shows that for the same current, at a higher temp, the output voltage is higher so the total output power is higher. For max power, you get diminishing returns for temperatures over 45*C. And No, I haven't noticed any delay selecting performance.

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It's also interesting that a hot PEM is limiting torque rather than power.
Actually, it's the motor current that matters. I didn't plot it, because the motor current is correlated to the torque (and it's easier to get torque from the VDS). It really comes down to how much current you can pump out of the PEM without overheating it.

My experience with getting Roadsters toasty is that when the motor is hot it limits torque but the PEM limits power. Maybe it's different for the lower temps you're dealing with; I'm thinking of when you get all the way to red and the warning comes up on the VDS.
I would describe it as a "warm" PEM is limiting peak power by 7.5%. A hot PEM limits the power a lot more. Tesla is taking advantage of the thermal mass (WattSecond/degC) of the PEM heatsink to dump peak power into a warm/cool heatskink, which would normally overheat a hot heatsink. It's a brilliant move on Tesla's part because it gives you a burst of power when you need it (E.g. to beat a corvette off the line.) :cool: As a comparison, it acts a like a burst of Nitrox in an ICE, more power, but you can't use it all the time.
 
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Just curious... I have a question for people living in hot locales.

This is my first summer with my roadster. I live in Texas. The temperature during the day can frequently get above 100F and the thermometer in the vehicle frequently measures the outside temp (near the asphalt/concrete) as 115F or higher. As you can imagine, I need to use the wimpy A/C. As the weather was getting hotter and hotter, I noticed that my performance mode spent more and more time in the red. The other day, I was trying to give someone the Tesla grin, and the car was not "performing." So I put it into performance mode, and it would not switch out of "red." I turned off the A/C and waited, and still "red."

I mentioned to my Tesla Ranger that my vehicle was spending more time in performance limited mode rather than white performance mode, he said that I was using performance mode too much and that it would wear out my battery.

What is everyone else's experience? Do people in hot climates just have to suck it up and deal with a slower roadster in the summer?
 
What is everyone else's experience? Do people in hot climates just have to suck it up and deal with a slower roadster in the summer?
I wouldn't say that it's 'slower' - every Tesla Roadster is limited to 125 mph due to the single-speed gear box.

Basically, Performance Mode is more than a 10% increase in torque compared to Standard Mode, but at least Performance Mode in red is still 3% more torque than Standard Mode.

Personally, I stay away from Performance Mode, and the few times I've used it I've been able to get into the red fairly quickly. Road racing is illegal, ya know.
 
Just curious... I have a question for people living in hot locales.

This is my first summer with my roadster. I live in Texas. The temperature during the day can frequently get above 100F and the thermometer in the vehicle frequently measures the outside temp (near the asphalt/concrete) as 115F or higher. As you can imagine, I need to use the wimpy A/C. As the weather was getting hotter and hotter, I noticed that my performance mode spent more and more time in the red. The other day, I was trying to give someone the Tesla grin, and the car was not "performing." So I put it into performance mode, and it would not switch out of "red." I turned off the A/C and waited, and still "red."
If the air temp at the PEM fan intake is 115F (46C) "performance" will always be red. The A/C does not cool the PEM. If the fourth blue bar is on for the PEM in the VDS temp screen, performance will always be "red"

I mentioned to my Tesla Ranger that my vehicle was spending more time in performance limited mode rather than white performance mode, he said that I was using performance mode too much and that it would wear out my battery.
Huh? When you are in "red" performance, you draw less current from the battery. So being forced into "red" by the air temp would be easier on the battery.

Do people in hot climates just have to suck it up and deal with a slower roadster [sport] in the summer?
Yes.
 
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I'm approaching one month with the Roadster; and 2,000 miles. I'm also learning that the RED Performance Mode comes way too fast, even in the cool Pacific Northwest weather. I've had the thing turn red after only a single, full-throttle acceleration. Thankfully, it does cool down to white fairly quickly, but Performance Mode doesn't seem to be a feature that you can rely upon being there any significant amount of time.

In other words, I'm not surprised to hear that the speed can be limited. Hopefully, I'll never know.
 
spending more time in performance limited mode...I was using performance mode too much and that it would wear out my battery.
First, let me say that when you get advice from scott451, you are getting about the most accurate info from our non-Tesla sanctioned tech guru! Take his word to the bank!
Definitions are the lynch-pin on which answers are derived so allow me to better characterize the issue as I SUFFER frequently from it as well.

Last issue, first. I constantly use performance mode & I know that it will decrease my battery life. Using the car probably also decreases battery life (this is a metaphor so no tangent threads needed) as does hard acceleration wear down tire life (tangent thread already started elsewhere) but it is what speaks to MY soul, so keep on using "Performance" mode if it also speaks to you!

In "Performance" mode you can have the white letters which is normal, & per scott451, "If the air temp at the PEM fan intake is 115F (46C) "performance" will always be red." but that is not limiting your performance, however it is informing you that the PEM is getting quite hot and will soon get to the next threshold (scott451 will tell you what that is) where the car will LIMIT your performance and the acceleration becomes sluggish. A beep-beep is audible and I believe you will get a "power limit" come up in red on your right side of your dash board. Honestly, this is the Achilles Heel of the car and what I heard they were working on for future Teslas. How do they keep the batteries cool in extreme temperatures, either ambient or because of extreme demands on the performance. Still love the car; have had two Roadsters (tangent thread already started elsewhere) and had the same problem in each though in the 2008 they only had one PEM fan and in the 2010/11s they had 2 fans which helps the situation a bit.

kgb... welcome to the club! Membership still has its privileges!
 
Oddly enough, I don't get to use it in hot weather. Case in point: 31C (88F) here, sunny, and humid... wife takes one look in the garage and says she wants the soft top and A/C.

Was 96F here this afternoon, but went with the top off anyway. So long as I keep moving the air keeps me cool enough. A baseball cap is important to avoid sunburn; long waits at stop lights are miserable tho...
 
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Um, isn't 96C about 205F?

It was about 98-102F here (Carson City, Nv) and we took a nice long drive down to Bridgeport, Ca (395 south) and back via Markleeville (Highway 89 to Highway 88 to 395). We have the Taylor Mesh Top (thank you Eric! It worked fantastically) and we were very comfortable.