Model 3

Tesla heat pump explanation

Since the 3 now has a heat pump, assuming it's designed similarly to the Y these 3 animations of how it all works may be useful:

Part 1: https://www.youtube.com/watch?v=rgmBpEQtJ1s

Part 2: https://www.youtube.com/watch?v=kJJBmQ-5bNs

Part 3: https://www.youtube.com/watch?v=g0Ss5m2ksVY
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Comments

  • Here's a good article on it with drawings.

    https://insideevs.com/news/328782/tesla-patent-outlines-sensible-approach-to-cabin-heating/
  • I'm not going to pretend I understood all of what was said or even shown in the animation, knowing zilch about thermal dynamics, but it looks to be a very ingenious system. I also watched his video on the Model 3's "super bottle".

    One of the things that bug me about the Model 3 is that it doesn't allow me to set the air intake mode (fresh air from outside or recirculate) unless the system is on, unlike every other car I've ever owned. In cooler weather simply setting it to fresh air with the system off will greatly minimize windshield fogging, like I could with every other car. In the Model 3, with the system off I'll never know whether the car set itself to fresh air or recirculate - sometimes I feel outside air coming in, other times it feels suffocating. To get around that, I'd turn the fan on 1 and set temp to LO as not to waste battery power if I don't need heating, in order to force it on fresh air.

    Perhaps those videos explain why it is the way it is.
  • We're missing 8-balls cold box in the corner of the room's genius debunk
  • Gmr6415, outstanding videos!

    Fishy, what was the point of your link after looking at gmr's referenced videos? Your reference isn't very friendly and it isn't nearly as expansive.
  • @h2ev, I too wish there was a fresh air setting. The work around I use is with the HVAC on turn off AC, turn off recirculate, set the temperature as low as it will go and set the fan like you want it.

    Unfortunately here in Central FL it's generally so humid it fogs the windows more often than it clears them and it's rarely cool enough to get cool air coming in.
  • @FISH, Those drawings are from the patent application. Patents are generally broad in scope and often things in the final product are left out even though they are a part of the patent.

    For example the patent speaks of in the text and shows in the illustrations (if you download the patent application and look at them all) a HV (high voltage) back up heat source as well as a LV (low voltage) back up heat source, and in one diagram it shows the use of both.

    If the diagrams used in the animations are accurate, in the end Tesla only used the LV back up heat source.
  • gmr6415 is right. I am intimately antiquated with a patent expert and they indicate that patents are rarely if ever implemented in exactly the way they are described in the patent. Patents are written to satisfy a particular set of parameters with the patent office and are not intended to be production or engineering diagrams.
  • GHammer- Thanks for the clarification and very funny autocorrect of aquatinted. Had to read that 3 times!
  • Oh geez, better not tell my intimate acquaintance they are antiquated, I might be sleeping on the couch tonight.
  • > @gmr6415 said: > If the diagrams used in the animations are accurate, in the end Tesla only used the LV back up heat source."

    Correct. It takes a while to heat up the motor to heat up the coolant to heat up the heat ex coils. The resistive booster heater provides the instant heat while that happens (20 minutes) and when in cold ambient there's just not enough heat from running. No point in inducing inefficiency in the motor to generate heat when the resistive heater can provide it.
  • @FISHEV, Whether they are using it or not the patent does describe electronically altering the slip angle on the compressor motor as well as fan motors in the system to purposely make them slightly less efficient and produce more heat. If that is incorporated in the final design they can fairly rapidly produce heat for the cabin with minimal power usage as compared to resistive heat.

    The compressor motor and fans are going to naturally produce waste heat regardless and that's almost instantaneous. That heat along with the additional heat from altering the slip angle of all motors in the system can be sent to the cabin quickly. I seriously doubt the resistive heat is on or fully on for the 20 minutes you are implying. That's just an assumption though.
  • > @gmr6415 said:
    > @FISHEV, Whether they are using it or not the patent does describe electronically altering the slip angle on the compressor motor as well as fan motors in the system to purposely make them slightly less efficient and produce more heat. If that is incorporated in the final design they can fairly rapidly produce heat for the cabin with minimal power usage as compared to resistive heat.
    >

    I have to question that. All else being equal, it will require a fixed amount of heat (energy) to raise the cabin temperature a given amount. Whether that energy is sucked off the drive motors or whether it is piped through a resistor is immaterial assuming each have the same delivery method to the cabin.

    The heat pump advantage is that it can pull existing heat with minimal energy input.
  • > @gmr6415 said:
    > @FISHEV, Whether they are using it or not the patent does describe electronically altering the slip angle on the compressor motor as well as fan motors in the system to purposely make them slightly less efficient and produce more heat. If that is incorporated in the final design they can fairly rapidly produce heat for the cabin with minimal power usage as compared to resistive heat.
    >
    > The compressor motor and fans are going to naturally produce waste heat regardless and that's almost instantaneous. That heat along with the additional heat from altering the slip angle of all motors in the system can be sent to the cabin quickly. I seriously doubt the resistive heat is on or fully on for the 20 minutes you are implying. That's just an assumption though.

    While you are correct in that the compressor motor and fans, and motor stator will all heat up rater quickly, you still have to get that heat transferred. If your coolant is cold, it will still take a bit for that liquid to heat up. It's not like its a heat pipe that can transfer heat a bit faster. Now, if the car went ahead and ONLY routed that heat into the coolant and then up to the cabin it would be faster, but there is no way the car isn't going to simultaneously send the heating coolant to the also cold battery.
  • > @M-A-B-MCMLXXX said: > The heat pump advantage is that it can pull existing heat with minimal energy input."

    No free lunch, either the excess heat is there to heat the car cabin or not. Generating heat by making motor inefficient causes as much parasitic loss as the resistive heat pump on start up so until and unless the regular driving heats up the motor enough to have too much heat, it all comes out of car's range.

    Hyundai has the most advanced EV heat pump system and the Norwegian independent tests showed a 10% loss due to cold vs. the 25% of the Tesla without a heat pump. So Winter deration would be cut from 25% to 10% which is excellent.

    "A recent test of 20 EVs by the Norwegian Automotive Federation (NAF) appeared to prove Hyundai and Kia's point. In that test, a European-spec Hyundai Kona Electric not only recorded the longest range in cold weather, it also came closest to its European WLTP range rating, achieving 91% of that figure."

    https://www.greencarreports.com/news/1128440_hyundai-and-kia-honing-heat-pump-tech-for-next-generation-evs
  • “ No free lunch, either the excess heat is there to heat the car cabin or not. Generating heat by making motor inefficient causes as much parasitic loss as the resistive heat pump on start up so until and unless the regular driving heats up the motor enough to have too much heat, it all comes out of car's range.”

    Not so.

    There is no free lunch between intentionally generating heat at the motor vs with generating heat with a resistive element, which I stated above.

    However, a heat pump can pull heat from areas, including the ambient environment. It doesn’t need to come from stored electrical energy.
  • But using the resistive element would be more efficient than using the motor and cooling loop to heat the cabin.
  • > @derotam said:
    > But using the resistive element would be more efficient than using the motor and cooling loop to heat the cabin.

    Does it not depend on how it is integrated? Perhaps the resistive heater could be implemented in a less loss way (blow air over it directly into the cabin rather than losing it along the entire loop).
  • > > @derotam said: > But using the resistive element would be more efficient than using the motor and cooling loop to heat the cabin."

    How do you know that?
  • "How do you know that?"

    because you told us
  • @derotam: When one takes Thermo 201, one of the amazing things one discovers is that using a heat pump, whether one calls it a refrigerator or not, can be _much_ more efficient at heating or cooling something than using a resistive heater. Over the operating range of a heat pump, the power required to move so many joules per second of heat from point A to point B can be much less than heat energy per second so moved.
    Interestingly, in SI units, this makes more than the usual amount of sense: If one moves a joule of energy per second, that's a rate of energy usage.. and the unit is in Watts.
    So, if one uses 100 W of energy per second to move 300 W of heat per second (and that's typical for a heat pump) into a car, one expends 100W to get 300W of heating. If instead one is using the battery for resistive heating follies, 300W of heating is achieved with 300W from the battery, period.
    There are, of course, limits to this kind of thing. If one has an air conditioner (read: heat pump) on the house, if it's Death Valley outside, you're simply not going to get 40F air coming out of the air conditioner, no matter how much one plays with the thermostat. Likewise, if one has a commercial heat pump on one's house and it's Nome, Alaska in the dead of winter outside, one might not be getting, say, 90F air coming out of the vents. But within the design range of a heat pump/refrigerator system, one can and does get that 3:1 ratio between heat movement vs. energy to run the system.
    In which case, in that range, it's _less_ efficient to use a resistive heater. And that's the point.
  • > @Tronguy said: If one has an air conditioner (read: heat pump) on the house, if it's Death Valley outside, you're simply not going to get 40F air coming out of the air conditioner, no matter how much one plays with the thermostat."

    Comparing it to ambient air heat pumps is not useful

    It is really a heat exchanger. It has no independent air radiator. It takes waste heat from other systems in the car and pumps to the cabin temp radiator to raise cabin temp.

    We know the resistive heater is 4kW. The phase shifting on the motor has power draws of 1200+ Wh/mile per the 5 minute, Energy/Consumption graph. I've had battery preconditioning using that eat up 10 miles of range in a run to the charger.

    To figure out which has greater power draw, the phase shifting on the motor or the resistive heater would take some controlled comparisons.

    Since people are going to have to run the resistive heater to get heat in the first 20(?) minutes, I'd guess Tesla lets the motor et all heat up from usage naturally and then uses that heat (if any) to reduce the load on the resistive heater.
  • @FISHEV: You have got to be kidding. You, who wouldn't know a Joule from a Watt from a kW-hr are lecturing somebody on thermodynamics? You clearly don't know electrical engineering, don't know thermo, and are putting out word salad. Phase shifting, indeed: You wouldn't know a phase from a hole in the wall.
    Nor do you know multiple-stage heat pumps, the math, and how to make that all work.
    Go back to bed, troll.
    People: Public Service Announcement:
    FISHEV is a known troll of several years standing and several user
    names who pushes an anti Tesla narrative. Please
    take his opinions with a grain of salt, avoid any advice he may
    suggest, and do not let him implant any Fear, Uncertainty, or Doubt
    about Tesla or your car into your own opinion.
    He's especially bad on technical topics. He puts out blabber that's disguised as actual technical information and is blatantly wrong, as in the above. A _brief_ skim of the above only killed a few brain cells; no worries, I'll generate replacements. It's not worth anybody's time trying to parse the above; you'll have to take the word of a practicing engineer that, not only is all of his stuff wrong, it's maliciously so. Not worth anybody's time to parse.
  • Mab, I was responding to the narrow statement of

    "There is no free lunch between intentionally generating heat at the motor vs with generating heat with a resistive element"

    With the specificity of not talking about the heat pump as well as previous statements of a long time( "20 minutes").

    If we are just taking about the difference between the resistive element(not heat pump) and inducing inefficiencies in the motor to create heat that would have to be carried via the coolant, there is going to be a time hit to get that heat to the cabin especially IF the battery is also receiving that motor warmed coolant.

    Actually, even if we are talking heat pump that is ONLY moving waste heat from various car components, there is still going to be a time hit, again because the battery will probably be taking that initial heat as well. I don't see Tesla prioritizing heating the cabin over heating the cold battery.
  • edited October 23
    @derotam fair enough. My post was really in response to @gmr6415 ’s suggesting that running the engines with less efficiency in order to produce heat will do so with minimal power versus a resistive heater.

    Time to heat may certainly differ depending on how the car prioritizes things, but the same total heat will be required to raise the temperature equally. The energy advantage of the heat pump is that it can pull it from sources other than the battery, and potentially using less to move it than the amount moved.
  • Sorry MAB, I think my above post is more directed toward Tronguy. To you, the current resistive heater is air blown across the elements.

    Tronguy, I do understand that heat pumps are more efficient than the resistive heater. Had a big discussion with Magic way back because he didn't know how they worked either.
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