Does Chill mode increase efficiency? Surprisingly, Tesla says yes

Does Chill mode increase efficiency?

This question seems to come up in Tesla circles every so often, and the conventional answer is "no, if you drive exactly the same speeds then acceleration mode does not impact efficiency".

But Tesla has some interesting notes in the manual:

If your vehicle is equipped with a heat pump (to determine if your vehicle has a heat pump, touch Controls > Software > Additional Vehicle Information), you can improve the efficiency of the cabin heating by reducing your selected acceleration mode. This allows the heat pump system to take more heat from the Battery to efficiently heat the cabin, instead of maintaining the Battery's ability to provide peak acceleration performance.

So in weather cold enough to use cabin heating apparently yes it can improve efficiency.

Link to the section for Model 3 (it also exists for S and presumably any heat bump vehicle).

"Tesla Model 3 | E-Cannonball 2018" by JayUny is licensed under CC BY-SA 2.0.
Admin note: Image added for Blog Feed thumbnail

 

[DB288]

but you no empirical proof of that…

this statement is not necessary true:

“This is talking about accelerating to the same speed (for example at an on-ramp). If the average speed about that same, that largely reduces that contribution.”

you do not know if this multi system car that includes mechanical, electrical, chemical and computer elements not to mention a unique heat distribution system has a linear response where all accelerations are equal and scale linearly…

you do not know if tesla has engineered the software and the hardware to be optimal for certain use cases and less than optimal for others…

i can definitely take the same driving route and achieve measurable non trivial differences in energy use by using autopilot or not…

to say i drive like a wild person when not on autopilot can’t explain it all…

and even it did…then wouldn’t that mean that chill and autopilot in fact have a significant impact…

 

[BitJam]

but as a theoretical physicist (you brought it up not me) you know that real world non-thought experiment empirical measurements need to be modeled using the actual system one is studying…

My goodness! This is remarkably similar to previous incorrect criticism of my post. Again, I was responding to someone who incorrectly claimed it was a law of physics that doing work faster requires more total energy than doing the same work more slowly.

1. we do not live in that perfect frictionless F=ma world

Nowhere do I say, assume, or imply that we live in a perfect frictionless world. I even talked about various losses in the post you quoted! And in my sig I say that we are imperfect beings in an imperfect world which seems to be especially true in this thread.

2. the battery connected to motor with computer control does not have to be linear with respect to energy usage…you used no parameters of the battery; motor; system that drives the wheels; wheels moving on pavement; suspension system to model your assertions

I honestly cannot understand what you are trying to say or how it would pertain to my post. I did mention heat losses which cover most of the points seem to imply I omitted. In addition, the power output from the motor and the heat losses in the wiring scale together over a large range of currents. I avoided saying they were "linear" because power and losses scale as the current squared and I didn't want to give some smart alec ammunition for further ridiculous nitpicking.

My only assertion (that you seem to have read or take issue with) is there is no fundamental law of physics that says doing work faster must be inherently less efficient. Having parameters for various parts of the car have nothing to do with this simple fact.

As I said before: if my balance between being clear and being pedantic didn't suit you, I apologize.

antecdotally:
1. clearly driving fast with friction/wind mf resistance lowers efficiency

I totally agree. I even alluded to this in my post saying that one of the reasons faster acceleration slightly reduces efficiency is because you spend slightly more time at higher speeds.

2. i believe rapid acceleration def uses more energy than slow stead acceleration..,

I agree. This is what I said in the part of my quoted post that seems to be invisible to critics. I gave several reasons why in the real world faster acceleration will result in slightly lower efficiency.

i have ben using autopilot a lot and watching my Wh/mile

autopilot/chill accelerates slowly (sometimes embarrassing slow for cars behind me) and i get <215 Wh/mi through a range of conditions (no a/c or heat) and around town at 35mph autopilot i have gotten <200 wh/mi

but it a punch it and have a high rate of acceleration …260 wh/mi

i def think chill + autopilot/slow acceleration enhances range

Thanks for doing this research! I and others have given numerous reasons why this would be true. Even Tesla says there are some circumstances where using Chill Mode increases efficiency, which is why this thread was started. However my main point is, was, and will continue to be that there is no fundamental law of physics that says it must be this way.

As I said before: Believe it or not, even real physicists make mistakes. So I appreciate corrections. But I think the post you quoted is both correct and clear.

Finally, your post reminded me of another one of my favorite quotes. Thank you for that!

In theory there is no difference between theory and practice while in practice there is.​

 

[drtimhill]

Yes driving fast does, but this is not talking about driving fast. This is talking about accelerating to the same speed (for example at an on-ramp). If the average speed about that same, that largely reduces that contribution.

Was mentioned in the other thread years ago, this is mostly the case because most people when doing rapid acceleration overshoot the target speed and then will waste more energy slowing back down. The main energy lost there is from going a higher speed and wasting energy slowing back down, not necessarily from the acceleration. It largely depends on what assumptions you make.

AP vs manual driving has the same issue as mentioned above. Most people have a harder time manually staying below a set speed and maintaining it with little variation (that's what cruise control is generally good at). So when driving manually, people tend to go faster than necessary, then slow down too much, then need to speed up again. So there are major differences from that, vs necessarily that it has to do with chill.
If you want a test solely about chill vs normal, then only do that. For example, manual driving chill vs regular. AP chill vs AP regular. Not having two different variables being changed.

But in fact there IS an energy difference .. in the reduced efficiency of the motors. High torque dramatically reduces the motor efficiency causing a much larger percentage if the energy entering the motor to be lost as heat. If you get more heat from the motors (and other components) then by definition you have used more energy to get to the same velocity since, as noted, the eventual kinetic energy of the car will be the same once it has reached the target speed.

 

[sidewinder]

Sorry, am I missing an important point in this discussion - what does the Tesla SOFTWARE do when the car is in chill vs standard mode? It might have been programmed to (let's say) maintain 20 degrees C in chill mode and 35 in standard mode, and just THIS could be the main efficiency difference while changing the driving mode?

this is precisely the point of op. in standard/sport mode, battery has to be heated to a higher temp and that temp maintained regardless of how you drive. this is so the battery can deliver the boost if/when it's called for. in chill mode, there is no need to provide this instant boost. so heating system can now take battery heat without much impact to performance. this means that standard/sport mode drains more battery (even without heavy acceleration) and the effect will be more pronounced on longer distances especially during cold weather.

however, agree with the majority of posters that within the same mode, difference in battery usage would be little if not negligible regardless of acceleration. in an ice car it would be different story.

 

[stopcrazypp]

But in fact there IS an energy difference .. in the reduced efficiency of the motors. High torque dramatically reduces the motor efficiency causing a much larger percentage if the energy entering the motor to be lost as heat. If you get more heat from the motors (and other components) then by definition you have used more energy to get to the same velocity since, as noted, the eventual kinetic energy of the car will be the same once it has reached the target speed.

Actually this is not true. Here's an example of an efficiency map of a switched reluctance motor (Model 3 is said to use a variant). You will notice there are large regions where the efficiency is the same or better even with the drastically more torque, and the peak efficiency is at higher rpms (which a faster acceleration might get you into quicker, plus it corresponds with a higher power region). Yes, applying more power will use more energy for a given time (note the time applied is shorter), but that doesn't mean it necessarily is less efficient (power out vs power in). The estimates done upthread try to figure IR losses, but a motor does to follow such a simple equation.

https://www.semanticscholar.org/pap...niak/524fc7add6618c11ced58ff4e0120fa46d75f37a

The LRs have a front induction motor. Induction motors also do not follow the simple IR losses equation (where more power applied is less efficient). There is a peak efficiency point with partial load, and actually applying less load is less efficient.

Three Phase Induction Motor Performance | Electrical Academia

This is why motors have to be selected to be optimized to the given load, and you can't just buy a overpowered motor and just run it at very low load and expect it to be efficient.

 

[DB288]

Actually this is not true. Here's an example of an efficiency map of a switched reluctance motor (Model 3 is said to use a variant). You will notice there are large regions where the efficiency is the same or better even with the drastically more torque, and the peak efficiency is at higher rpms (which a faster acceleration might get you into quicker, plus it corresponds with a higher power region). Yes, applying more power will use more energy for a given time (note the time applied is shorter), but that doesn't mean it necessarily is less efficient (power out vs power in). The estimates done upthread try to figure IR losses, but a motor does to follow such a simple equation.

https://www.semanticscholar.org/pap...niak/524fc7add6618c11ced58ff4e0120fa46d75f37a

The LRs have a front induction motor. Induction motors also do not follow the simple IR losses equation (where more power applied is less efficient). There is a peak efficiency point with partial load, and actually applying less load is less efficient.

Three Phase Induction Motor Performance | Electrical Academia

This is why motors have to be selected to be optimized to the given load, and you can't just buy an overpowered motor and just run it at very low load and expect it to be efficient.

i not an expert at these graphs but it doesn’t seem like a fixed efficiency at all operating points, eg it’s not a perfect system with a linear response to the demanded acceleration…

and the motor is a relatively simple device whose efficiency is best generalized and characterized in the literature …

i guess i’m a curmudgeon…but i think it’s really hard to take idealized physics equations or lab graphs about 1 component of the system and make detailed statements about a car actually functions in the real world…

i think a car’s performance could (and is) be modeled but only with detailed knowledge of the whole system

 

[sleepydoc]

i not an expert at these graphs but it doesn’t seem like a fixed efficiency at all operating points, eg it’s not a perfect system with a linear response to the demanded acceleration…

and the motor is a relatively simple device whose efficiency is best generalized and characterized in the literature …

i guess i’m a curmudgeon…but i think it’s really hard to take idealized physics equations or lab graphs about 1 component of the system and make detailed statements about a car actually functions in the real world…

i think a car’s performance could (and is) be modeled but only with detailed knowledge of the whole system

You’re correct - you can’t take one part of a complex system and extrapolate it to the whole, it that’s also the point of this entire thread and also a point @drtimhill was making. An EV is a complex system with many components that behave differently under different circumstances. Energy use is not necessarily linear or conserved. Even heat generation which is typically considered waste can be beneficial if it’s used for optimizing battery performance (or heating the cabin on a cold day.)

In the end, all the specific examples simply show the potential variables involved and how you can’t make assumptions with a complex system.

I’ll go back to my previous post where I described as controlled a test as possible (for me) where I drove an identical loop twice. The first time with hard acceleration and the second time with conservative acceleration. Weather, traffic, wind, etc we’re all identical. In the end, the hard acceleration used a small but measurable extra amount of energy.

 

[briank9]

Chill mode reduces the target temperature of the battery and uses any heat generated from driving is put into HVAC instead of maintaining temps for max performance. Ie Driving my MYP in the cold on chill mode and was power limited the entire time because the battery was taking heat from it and putting it into HVAC.

 

[voldar]

the hard acceleration used a small but measurable extra amount of energy.

Which doesn’t say if normal mode vs chill mode is a thing, if you can accelerate in Normal mode as in Chill mode.
In my Volt, accelerating hard to a set speed or accelerating gradually to the same speed, in the end, ended up to use about the same energy. The same was the case of my Bolt. For the time being, the same is for my Tesla. I used once Chill mode and I found it no different than my Normal mode driving. I wish Elon would show numbers of the instant power used under acceleration/deceleration instead a black line or green one for the negatives ones. If Tesla is more efficient in Chill mode, definitely is not because acceleration/deceleration but how the heat is scavenged between the two modes. In Normal, the heat is kept in the battery, in Chill mode the heat is used for HVAC.

 

[voldar]

If Tesla is more efficient in Chill mode, definitely is not because acceleration/deceleration but how the heat is scavenged between the two modes. In Normal, the heat is kept in the battery, in Chill mode the heat is used for HVAC.

From the owners manual :
>> If your vehicle is equipped with a heat pump (to determine if your vehicle has a heat pump, touch Controls > Software > Additional Vehicle Information), you can improve the efficiency of the cabin heating by reducing your selected acceleration mode (see Acceleration Modes). This allows the heat pump system to take more heat from the Battery to efficiently heat the cabin, instead of maintaining the Battery's ability to provide peak acceleration performance. This helps to maximize driving efficiency in colder weather. Note that when subsequently increasing the acceleration mode, the Battery requires time to warm up before the increased level of acceleration is available.

 

[rjpjnk]

I wish Elon would show numbers of the instant power used under acceleration/deceleration instead a black line or green one for the negatives ones. If Tesla is more efficient in Chill mode, definitely is not because acceleration/deceleration..

If I remember correctly you can read actual current and voltage from some of the apps with the installation of the OBD2 dongle. If you log these quantities you could get a definitive answer as to which maneuvers use the most energy.

 

[voldar]

If I remember correctly you can read actual current and voltage from some of the apps with the installation of the OBD2 dongle. If you log these quantities you could get a definitive answer as to which maneuvers use the most energy.

I had a Volt for 4.5 years then a Bolt EV for other 4.5 years and the instant power was shown in numbers in the DIC. I already know that going from A to B it isn't that different in energy consumption (used in both cases) to write home about. The energy needed to go from 30 mph to 60 mph is a constant at a given time and driving conditions. That you get to this number by hard acceleration or slow acceleration, it doesn't matter much, you'll use the same amount of energy to get there.

 

[rjpjnk]

I understand the basic physics says only the change in velocity matters for textbook objects with no limitations but it would be interesting to see how a real world vehicle with its various frictions, air resistance and motor efficiencies impacts this. My guess is that would will find the higher acceleration case more costly due to these imperfections.

 

[DrChaos]

Chill mode improves efficiency for me, and I'm sure 99% of it is changing human behavior.

 

[voldar]

Chill mode improves efficiency for me, and I'm sure 99% of it is changing human behavior.

Interesting, for me the Chill mode seems to be worse than Normal mode. Maybe because I expect Chill mode to behave as Normal mode so I press more the pedal to get the same feeling.

 

[Spinkick]

I get that chill mode doesnt improve efficiency, but is it true in the manual

"You can improve efficiency of the cabin heating by reducing your selected acceleration mode, allowing the heat pump to take more heat from the battery to efficiently heat the cabin instead of maintaining the battery’s ability to provide peak acceleration performance. ‘Chill’ is the most energy efficient mode, especially in cold weather. To adjust your acceleration mode, tap ‘Controls’ > ‘Pedals & Steering’ > ‘Acceleration’ from the vehicle touchscreen to adjust the amount of acceleration you experience when driving. Select from one of the following modes:

• ‘Chill’ limits acceleration for a gentle ride and optimizing cabin heating in cold weather.
  Note: When Chill is selected, Chill displays on the touchscreen above the driving speed.
• ‘Standard’ provides the normal level of acceleration on non-Performance vehicles.
• ‘Sport’ provides the normal level of acceleration on Performance vehicles.

Does this actually work, or is this meant for plaid cars that actively heat the battery?

Has anyone tried scanmytesla and see if the battery temp is lower on a cold day in chill mode than in performance mode (modelyp, heat pump)? I'd be interested to see if there is a difference.

 

[Spinkick]

Some data in another thread. Cold weather drivers probably do see some improvement from chill mode as the battery is allowed to get cooler and the heat pump is allowed to take heat from the batteries in exchange for not as high acceleration:

TIL: Plaid acceleration mode continually conditions battery and affects HVAC?

Well, the data is in, and I don't see any real difference. My numbers for the month of testing actually came out a bit higher but I'll chalk that up to the hotter weather and more AC usage. I ended up at 336 wh/m in Sport mode vs 330 the prior month and half in Plaid. I do wonder if this...

teslamotorsclub.com

 

[David99]

Has anyone tried scanmytesla and see if the battery temp is lower on a cold day in chill mode than in performance mode (modelyp, heat pump)? I'd be interested to see if there is a difference.

I have a MYP and done my daily drive in chill and normal (sport) mode. (The YP doesn't have normal mode, only chill and sport). I watched the battery temperature closely and to my surprise there is basically no difference. If the battery is cold (10 C), the car will not actively warm up the battery as you drive. No difference weather in chill or sport. Eventually it will warm up naturally drom driving, but again, it seems the same in both modes.

After I supercharge, the battery is very hot. Often around 60 C. Again, it makes no difference if you drive in chill or sport mode. The battery temperature drops the same as you continue to drive. So the car doesn't seem to try to keep the battery temperature at a higher level than in chill mode in any scenario.

IOW, I can't see any evidence of the statement that in chill mode the car will use more heat energy from the battery to warm the cabin. Looking at the numbers, it behaves the same in both modes. Maybe that was the case in an earlier software version, where in sport mode, the car would keep the battery temperature higher. I certainly can't see any evidence of this with the current software.

 

[DrGriz]

I have a MYP and done my daily drive in chill and normal (sport) mode. (The YP doesn't have normal mode, only chill and sport). I watched the battery temperature closely and to my surprise there is basically no difference. If the battery is cold (10 C), the car will not actively warm up the battery as you drive. No difference weather in chill or sport. Eventually it will warm up naturally drom driving, but again, it seems the same in both modes.

After I supercharge, the battery is very hot. Often around 60 C. Again, it makes no difference if you drive in chill or sport mode. The battery temperature drops the same as you continue to drive. So the car doesn't seem to try to keep the battery temperature at a higher level than in chill mode in any scenario.

IOW, I can't see any evidence of the statement that in chill mode the car will use more heat energy from the battery to warm the cabin. Looking at the numbers, it behaves the same in both modes. Maybe that was the case in an earlier software version, where in sport mode, the car would keep the battery temperature higher. I certainly can't see any evidence of this with the current software.

10°C is not cold. If you think so, "you haven't driven very far."

 

[David99]

10°C is not cold. If you think so, "you haven't driven very far."

That is completely irrelevant to the discussion of how chill mode or sport mode behave.