How does Preconditioning work?

[dho112]

Can someone explain exactly how Preconditioning works?

Specifically, once you select a Supercharger in Nav and the battery begins heating; How is that heat generated?

The entirety of the descriptions I’ve been able to find consist of this ambiguous, “They run the motors inefficiently” And I’m assuming they scavenge that motor heat and transport it to the battery, but how exactly is an electric motor “run inefficiently”, and Does this mean the car preconditions much faster if you’re actually driving? (using the motors) because I know you can heat the batteries while stationary, or does it not matter moving or not?

And I guess the biggest question; Does excessive “preconditioning” in any way cause accelerated degradation/fatigue with any motor parts? Even ridiculously insignificantly? (i.e. MAYBE causing “potential” trouble after 750,000 miles instead of a million miles 😛)

Thanks in advance!

 

[beatle]

Lots here Tesla New Patent To Use Electric Motor Waste Heat Mode To Heat Battery including this quote:

In a waste heat mode, the drive motor electronics power the stator without causing rotation of the rotor. Further, in the waste heat mode, the drive motor fluid pump at least partially fills the hollow cylindrical body with the fluid to force the fluid from the hollow cylindrical body via the fluid exit ports to spray upon the stator end-windings and to extract heat from the stator end-windings. Still further, the drive motor fluid pump circulates the fluid to a heat exchanger for heating a battery.​

​

There will be waste heat generated from pulling energy out of the battery as well, and that is retained in the battery, so yes, the battery will heat faster if you're driving the car. Maybe this wears the motor insignificantly, but it's still insignificant wear, if at all.

 

[GtiMart]

I believe there's a difference between the single and dual motor versions. While the rear motor is driving the car forward, I don't think it can also be "driven without causing rotation"... but I don't know if that generates less heat or just as much. Clearly a dual motor will generate more overall heat than a single motor.
@beatle, do you know if the heatpump is also used to heat the battery on 2021+ cars? I'm under the impression that it is used but have no proof.

 

[beatle]

Short answer, "yes, I think so."

Long answer: Can heat pump on newer M3/MY heat traction battery?

 

[archae86]

I run Scan My Tesla on my 2023 model 3. One of the few parameters I observe all the time is motor stator temperature. If I hop in my model 3 after it has done the ordinary sort of scheduled departure preconditioning (not the "I'm navigating to a SuperCharger kind) the stator is noticeably hotter than my garage ambient. Not a lot, but I consider that evidence that some way of wasting power in the motor when everything is standing stock-still exists and gets used.

 

[drtimhill]

The entirety of the descriptions I’ve been able to find consist of this ambiguous, “They run the motors inefficiently” And I’m assuming they scavenge that motor heat and transport it to the battery, but how exactly is an electric motor “run inefficiently”, and Does this mean the car preconditions much faster if you’re actually driving? (using the motors) because I know you can heat the batteries while stationary, or does it not matter moving or not?

On the model S/X there is a dedicated heater for the battery. On the model 3/Y there is no heater. Instead, as you note and rather ingeniously, the motors are run in such a way that they generate excess heat (it's basically a phase thing from the alternator, but the details dont matter really). You can actually hear it if you know your car sounds well, there will be a slight whine coming from the motors. I'm not certain what the mapping is between speed and efficiency of this process, it's probably pretty independent of speed. Overall though, the batteries will heat somewhat faster at higher speeds simply because any power draw from the battery always results in SOME heating of the battery (basic chemistry).

Once this is done, the car changes the flow of coolant to pump the excess heat from the motors into the battery pack (the coolant system is pretty flexible in how it can move heat around, this is one of several different modes the car uses for heat management).

 

[Supcom]

On the model S/X there is a dedicated heater for the battery. On the model 3/Y there is no heater. Instead, as you note and rather ingeniously, the motors are run in such a way that they generate excess heat (it's basically a phase thing from the alternator, but the details dont matter really). You can actually hear it if you know your car sounds well, there will be a slight whine coming from the motors. I'm not certain what the mapping is between speed and efficiency of this process, it's probably pretty independent of speed. Overall though, the batteries will heat somewhat faster at higher speeds simply because any power draw from the battery always results in SOME heating of the battery (basic chemistry).

Once this is done, the car changes the flow of coolant to pump the excess heat from the motors into the battery pack (the coolant system is pretty flexible in how it can move heat around, this is one of several different modes the car uses for heat management).

If you are preheating while driving to a supercharger, it may be that the motors do not need to be fiddled with to generate the required heat. There will, of course, be waste heat from the motors. If this warms the cooling fluid sufficiently, it may be enough to simply pump it through the battery with no additional energy expenditure required.

 

[drtimhill]

If you are preheating while driving to a supercharger, it may be that the motors do not need to be fiddled with to generate the required heat. There will, of course, be waste heat from the motors. If this warms the cooling fluid sufficiently, it may be enough to simply pump it through the battery with no additional energy expenditure required.

Possibly but that's not what the car does .. it determines the time/distance to the SC and heats the battery accordingly .. it has to be pretty hot for optimal SC charge rates.

 

[SageBrush]

In a waste heat mode, the drive motor electronics power the stator without causing rotation of the rotor.

I have no idea how it is possible to run current through the stator and *not* spin the rotor, but that no doubt explains why I do not work at Tesla.

By the way, I've read that this trick provides 83% of the heat obtained by resistance heating for the same power

 

[Nubo]

The term "pre-conditioning" really bugs me on the way to the supercharger. I'm not "pre" conditioning the battery. I'm conditioning it. If we must have the term "pre" involved here, then it's pre-charge conditioning.

 

[dho112]

The term "pre-conditioning" really bugs me on the way to the supercharger. I'm not "pre" conditioning the battery. I'm conditioning it. If we must have the term "pre" involved here, then it's pre-charge conditioning.

Unless the battery actually “conditions” normally during a supercharging session; Which I think it does when the battery is not at optimum temperature (i.e. the message you sometimes get where it says, “battery is warming for better charging” WHILE it’s actually plugged in and charging…

In that instance “pre-conditioning” (before you get to the suupercharger) IS technically correct

Now what really drives me nuts is the term “Near-miss”. When two planes ALMOST collide, that’s a “near-hit” a near-miss means they almost missed, and actually collided… ☺️

 

[Supcom]

I have no idea how it is possible to run current through the stator and *not* spin the rotor, but that no doubt explains why I do not work at Tesla.

By the way, I've read that this trick provides 83% of the heat obtained by resistance heating for the same power

There are multiple stator windings that are fed AC currents with different phases, normally 120 degrees apart. By modifying the phase relationships, the motor controller can make a bad motor, but good heating element. Since the AC current for the stator windings must be made by the motor controller from the high voltage DC, creative programming should allow the motor controller to create the three phases with any arbitrary phase relationships.

 

[SageBrush]

In that instance “pre-conditioning” (before you get to the suupercharger) IS technically correct

Yah. The 'pre' refers to something other than the conditioning.
Similar to conditioning the cabin before you get in the car. 'Pre' in the sense of occurring before you get in the car.

 

[Nubo]

Unless the battery actually “conditions” normally during a supercharging session; Which I think it does when the battery is not at optimum temperature (i.e. the message you sometimes get where it says, “battery is warming for better charging” WHILE it’s actually plugged in and charging…

In that instance “pre-conditioning” (before you get to the suupercharger) IS technically correct

Now what really drives me nuts is the term “Near-miss”. When two planes ALMOST collide, that’s a “near-hit” a near-miss means they almost missed, and actually collided… ☺️

Nah, it's either conditioning or it isn't. Pre-conditioning would be something you're doing to get the battery ready to be conditioned. In other words, it would be "conditioning". It's just language inflation. George Carlin explained it best (also describing the "near-hit") but I decided to remove the link to that video because of language

 

[Nubo]

Yah. The 'pre' refers to something other than the conditioning.
Similar to conditioning the cabin before you get in the car. 'Pre' in the sense of occurring before you get in the car.

Lol. It's a prefix, not a milieu.

 

[drtimhill]

Unless the battery actually “conditions” normally during a supercharging session; Which I think it does when the battery is not at optimum temperature (i.e. the message you sometimes get where it says, “battery is warming for better charging” WHILE it’s actually plugged in and charging…

In that instance “pre-conditioning” (before you get to the suupercharger) IS technically correct

Now what really drives me nuts is the term “Near-miss”. When two planes ALMOST collide, that’s a “near-hit” a near-miss means they almost missed, and actually collided… ☺️

Probably a better cover-all word would be "preparing" ... avoids specifying what it is doing, but informs the driver that its doing whatever is necessary.

 

[theothertom]

There are multiple stator windings that are fed AC currents with different phases, normally 120 degrees apart. By modifying the phase relationships, the motor controller can make a bad motor, but good heating element. Since the AC current for the stator windings must be made by the motor controller from the high voltage DC, creative programming should allow the motor controller to create the three phases with any arbitrary phase relationships.

So the motor isn't as efficient during the preconditioning cycle as it normally would be? Wh/mile goes up?

 

[drtimhill]

So the motor isn't as efficient during the preconditioning cycle as it normally would be? Wh/mile goes up?

kinda has to, since the heat has to come from somewhere. That's true even MS/X where there is a dedicated battery heater (dont know if the newer ones now use the same trick as the 3/Y).

I've never bothered, but it you are very careful about steady driving you might even be able to see the change on the energy screen, though I doubt it will be much of a difference. (Remember that the motors are always generating some heat even when normal.)

 

[STS-134]

kinda has to, since the heat has to come from somewhere. That's true even MS/X where there is a dedicated battery heater (dont know if the newer ones now use the same trick as the 3/Y).

The newer ones use the heat pump when it's possible to do so and take heat from the atmosphere. When I navigate to a supercharger, the radiator fans turn on and I can feel cold air coming out of the radiator.

 

[drtimhill]

The newer ones use the heat pump when it's possible to do so and take heat from the atmosphere. When I navigate to a supercharger, the radiator fans turn on and I can feel cold air coming out of the radiator.

So, ultimately, they are pumping heat from your body into the battery