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

 

[shahryaran]

That article says:

The attempt basically consists of driving at extremely low-speed in order to get the most efficient driving speed for the vehicle while also not using power consuming onboard features like climate control.​

​

It does not say they got better efficiency by limiting their acceleration.

That's exactly the point. Not accelerating yields better efficiency.

 

[gsmith123]

That's theoretical. The system producing 200W now likely has less efficiency than 100W

Agreed. Both @BitJam and myself have specifically mentioned how efficiency is lower at higher acceleration. That's not the point we're disagreeing with (I don't think you're quite grasping the points @BitJam has been making)

That's exactly the point. Not accelerating yields better efficiency.

That's the wrong conclusion to reach from that article. Driving slowly minimizes air drag losses, at steady state cruising. It has nothing to do with acceleration. If you drive 100 miles at 30 mph and then at 60 mph you'll use significantly more energy at 60 mph even if you only looked at consumption from the cruising at constant speed part of the test. Note in both cases you're cruising at constant speed - no acceleration.

 

[rjpjnk]

Pretty sure work done = energy spent regardless of how fast you do it.

But the original question wasn't about driving more gently, it was about trading battery temp and cabin temp. We were wondering if selecting chill mode saves energy because something doesn't get as hot. Still wondering.

 

[shahryaran]

Agreed. Both @BitJam and myself have specifically mentioned how efficiency is lower at higher acceleration. That's not the point we're disagreeing with (I don't think you're quite grasping the points @BitJam has been making)


That's the wrong conclusion to reach from that article. Driving slowly minimizes air drag losses, at steady state cruising. It has nothing to do with acceleration. If you drive 100 miles at 30 mph and then at 60 mph you'll use significantly more energy at 60 mph even if you only looked at consumption from the cruising at constant speed part of the test. Note in both cases you're cruising at constant speed - no acceleration.

Speed is different than velocity. I'm taking about when efficiency gets involved with velocity

 

[shahryaran]

Pretty sure work done = energy spent regardless of how fast you do it.

But the original question wasn't about driving more gently, it was about trading battery temp and cabin temp. We were wondering if selecting chill mode saves energy because something doesn't get as hot. Still wondering.

That's still exactly my point. Because driving in chill mode yields less intensive power delivery, thus less heat is generated.

I agree that heat pump can retrieve some of that heat made by motor and cabin. But not generating heat in the first place is a more efficient than generating heat and retrieving it.

 

[gsmith123]

Speed is different than velocity

I'm well aware. What do you think the difference is, precisely?

If your overall point is that higher acceleration increases powertrain heat losses, agreed. That's not under contention. I literally explained those in a previous post.

 

[stopcrazypp]

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:



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).

Interesting. I think Tesla is saying that the cabin will heat up faster in chill mode because it is allowing the battery to remain colder. But in what sense is this more efficient?

Tesla is using a different definition of efficiency in context. In context, they are saying the heating may be more time efficient if you use chill mode given there is more heating capacity available. This is a common way "efficiency" is used to describe a heating system (how long it takes to heat up a given space to a given temperature from a given interior/exterior temperature).

That is different from saying that it is making the car more energy efficient (amount of work done for given energy).

 

[shahryaran]

I'm well aware. What do you think the difference is, precisely?

If your overall point is that higher acceleration increases powertrain heat losses, agreed. That's not under contention. I literally explained those in a previous post.

My point is that higher acceleration (increase the rate of velocity) requires more energy (more work being done) because you are increasing the rate (work over time) in which the flow of electricity is being delivered to the motor. That's why more heat is generated.

 

[shahryaran]

Tesla is using a different definition of efficiency in context. In context, they are saying the heating may be more time efficient if you use chill mode given there is more heating capacity available. This is a common way "efficiency" is used to describe a heating system (how long it takes to heat up a given space to a given temperature from a given interior/exterior temperature).

That is different from saying that it is making the car more energy efficient (amount of work done for given energy).

That definition of efficiency at its core is the same as energy efficiency

 

[stopcrazypp]

That definition of efficiency at its core is the same as energy efficiency

No it's not. It's just saying the car heats up faster. The car still ends up using the same amount of energy to heat it up, just that it's faster. The amount of heating capacity difference isn't likely to change the COP in any appreciable way, just that the heating capacity is higher.

I'll give you an example to illustrate it.

Say you have a 1 ton/12000 BTU heat pump. It has a given energy efficiency running at full bore. I install another identical 1 ton/12000 BTU heat pump in parallel. Now the room can be heated roughly twice as fast, but the energy efficiency is the same!

 

[shahryaran]

That definition of efficiency at its core is the same as energy efficiency

Any system is less efficient at higher work load at any scale of existence. That's why a human body on a bicycle is more efficient than any electric motor ever made including Tesla
That's how an ant can carry 7 times of its weight

 

[shahryaran]

Any system is less efficient at higher work load at any scale of existence. That's why a human body on a bicycle is more efficient than any electric motor ever made including Tesla
That's how an ant can carry 7 times of its weight

All I can tell you is that my 2020 M3LR with no heat pump gets better distance traveled in chill mode

 

[gsmith123]

Tesla is using a different definition of efficiency in context. In context, they are saying the heating may be more time efficient

I wish they had just said "heats faster" so we knew exactly what they meant!

 

[stopcrazypp]

I wish they had just said "heats faster" so we knew exactly what they meant!

The problem is that the term is frequently used to describe both. When people say "this heater is heating my room more efficiently than my old one", they can mean that it's heating it faster, it is more energy efficient, or both. It's a bit ambiguous.

 

[shahryaran]

I wish they had just said "heats faster" so we knew exactly what they meant!

What Tesla means is that using your main battery to heat up the cabin is less efficient than heat pump

 

[rjpjnk]

Tesla is using a different definition of efficiency in context. In context, they are saying the heating may be more time efficient if you use chill mode given there is more heating capacity available. This is a common way "efficiency" is used to describe a heating system (how long it takes to heat up a given space to a given temperature from a given interior/exterior temperature).

This sounds right to me. I believe that is the sense in which they meant "efficient". I think they should have used the word effective instead. Efficiency tends to imply some degree of optimality or minimization of waste in science circles.

 

[rjpjnk]

All I can tell you is that my 2020 M3LR with no heat pump gets better distance traveled in chill mode

I think everyone agrees with this. In the same way a gasoline car gets better mileage if you don't floor it so much and keep it under 55. Less energy lost to heat and air resistance gives greater efficiency of fuel usage.

 

[shahryaran]

No it's not. It's just saying the car heats up faster. The car still ends up using the same amount of energy to heat it up, just that it's faster. The amount of heating capacity difference isn't likely to change the COP in any appreciable way, just that the heating capacity is higher.

I'll give you an example to illustrate it.

Say you have a 1 ton/12000 BTU heat pump. It has a given energy efficiency running at full bore. I install another identical 1 ton/12000 BTU heat pump in parallel. Now the room can be heated roughly twice as fast, but the energy efficiency is the same!

Incorrect. If you do the same job faster, your efficiency is worse because you consumed twice the energy by doubling the heat pump

 

[shahryaran]

The term "chill" in chill mode does not imply any state of lower temperature for the battery.

Chill mode refers to a mode of driving style in which the car's acceleration is less sensitive to the pedal movement. This effect in turn lowers the intensity of power delivery to the motor, which in turn generates less heat and thus (giving the heat pump at work) causes the cabin to heat faster because the heat that the car generates to keep the battery temperature for optimal operation is rerouted to the cabin instead of the battery.

 

[stopcrazypp]

Incorrect. If you do the same job faster, your efficiency is worse because you consumed twice the energy by doubling the heat pump

You are making the same mistake people tried to explain to you in terms of acceleration. You are doing the same job faster, but the total amount of energy required to do the job is still the same! So you did not consume twice the energy, you consumed the same amount.

Say for example it takes 2 hours to heat up the room with the 1kW heat pump. That means it takes 2 hours * 1kW = 2kWh.

The double heat pumps instead take 1 hour to heat up the room: 1 hour * 2 * 1kW = 2kWh.

The energy consumed is the same!