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Preconditioning Car Yield Full Regen Capability?

Discussion in 'Model 3' started by agreif, Jan 4, 2021.

  1. agreif

    agreif Member

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    Just a question out of curiosity, when you precondition the car to "depart at" a certain time (within the car scheduling interface, not the app), should the battery have full regen capability by the time you leave? I ask because I don't see that exact behavior.

    My example, I drive 15 minutes to a destination charger (48A/240V) in 20F temps (no plugged in in my garage at my house, so starting cold) and am charging at that destination charger for 2 hours, with a scheduled departure 2 hours from when I arrive. I can arrive at the charger at 50% with a charge threshold set at 80%. When I get in right around the departure time, the regen graphic will still have a half dozen or so dots on the regen bar. From a few links and from the manual, I thought that would be fully ready to go by scheduling it that way. Am I missing something or have a setting wrong to expect it to behave that way?

    As an aside, I can get to full regen capability after driving for quite a while (hr+) but was just curious about this one.

    Link 1
    Link 2
    Link 3
    Link 4

    Thanks in advance, and sorry if this is a greenhorn question. I tried the search, but maybe I missed a thread covering it.
    Andrew
     
  2. Silicon Desert

    Silicon Desert Active Member

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    A lot of reasons for that. One of the reasons depends on how cold the battery is. At home, I have never been able to get the battery warm enough to get full regen on the home charger even after a few hours. Like your area, it can get really cold up here.
     
  3. elptxjc

    elptxjc Member

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    At least our 2021 turns the battery heater on when turning HVAC on. Many folks are complaining that there should be a different button to turn battery heater on, and I agree. But after doing the cabin heating for about 3 minutes, our car has noticeable regen at about 50F. So for colder temps, it should probably run longer. The other point made was that if doing the preconditioning would hurt the battery pack in the long run, due to the strong current needed. I wonder if that's true. If not, then I'd be okay by 'wasting' a little energy to be comfortable. But if that degrades the battery pack more, then I wouldn't use it, at least not as often. Does anybody know if it affects battery life?
     
  4. Let's Drive

    Let's Drive Member

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    If I'm reading correctly, you're referring to two separate scenarios.

    Generally speaking, if I don't precondition the battery, I'll receive a notification which states regen braking will be reduced, but gradually improve (as it heats up). When I precondition, I don't receive this message.

    Independent of the above, being near the preset SOC cap or threshold (which will occur if you're near the end of a charge session) will also result in a lack of full regen on the bar, regardless of how warm the battery is. As the SOC drops (driving around normally), I see fewer dots.
     
  5. DaveRZ

    DaveRZ Member

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    The "battery heater" in a model 3 is really just the system running power through the stators in the motor(s). This heats the motors up, and the HVAC system then moves that heat into the battery. Same method (but much higher target temps) when the system preconditions for supercharging. The Model 3 (from what I've read) uses up to 7,000 watts for heating the battery - which, for non heat-pump Model 3's is also the same amount used to heat the cabin - so 14,000 watts when both are preconditioning, with everything on full blast. Since you're not in Buffalo, NY, that'll probably drop down to a reasonable power draw very quickly, and even less since your car has the new heat pump.

    14kW is a lot of power, but only a drop in the bucket when you consider what you use while normal driving. Imagine city driving where you are pulling 100kW accelerating, then letting off and regen-ing 80kW back into the pack. Do that over and over and over in traffic. The batteries are made to do this.

    While I cannot confirm this, many have said you can prevent the battery heater from turning on along with the HVAC by turning on the HVAC from inside the car (don't step on the brake and turn the car on). Using the phone app assumes you're preconditioning to go somewhere and preps the battery and the cabin.

    Finally, if you precondition while still plugged in, you'll offset a lot (or all)of the power draw. The power still comes from the battery (you want it to warm up), but it'll be simultaneously replenished up to the peak output of your charging setup.
     
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  6. Gasaraki

    Gasaraki Active Member

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    Does the scheduled departure even work when you don't plug it in? I thought the whole point of schedule departure was so the car can charge and to full and preheat before you leave so the interior and battery is warm. Without it being plugged in, preheating the battery for however amount of time it take to warm a really cold battery is just not worth the energy use.
     
  7. BeeGood

    BeeGood Member

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    I believe it would heat/cool the cabin even if it’s not plugged in.

    In terms of what it directly does with the battery...I’m not sure, but you’d get some (maybe not much?) preconditioning when the climate controls turn on.
     
  8. agreif

    agreif Member

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    Even when I precondition the battery (when plugged in, I don't do it without being plugged in), I am pretty sure I am getting that "regen reduced" message still. I'll double check that next time. With the latest update and that precondition battery toggle being present, maybe it will be different.

    I didn't realize the higher the charge, the less regen capable it is. I guess that makes sense, just never had made that jump. I think I'm usually around 80% when I am driving off but a few recent times was higher so maybe was that. I'll have to check again.

    I haven't used the precondition while unplugged.
     
  9. Gforce1

    Gforce1 Member

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    Apparently yes, it does. I’m on 2020.48.30 in my 2018 LR RWD. I was surprised yesterday when I got in the car to leave in the morning and had full regen in 20 degree weather. I went on to my TeslaFi logs and sure enough the car woke up 2 hours before I left and burned through 10% battery heating the battery and then the cabin. I charge at work and don’t plug in at home so I was surprised. I changed the scheduled departure time on the screen and checked again this morning and sure enough I had full regen when I left this morning. I had no idea the car would warm up without being plugged in until now. Not sure if it’s a bug or a feature.
     
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  10. Phlier

    Phlier Bluebird

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    I think this functionality was added in a recent firmware release. I seem to recall reading something about it when I was glancing through the Release Notes recently.
     
  11. jsmay311

    jsmay311 Active Member

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    Man, that’s a lot of wasted energy. I hope that’s not typical behavior. Preconditioning should not be designed to be so dramatically wasteful.
     
  12. Phlier

    Phlier Bluebird

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    #12 Phlier, Jan 13, 2021
    Last edited: Jan 13, 2021
    While I do agree with the sentiment, there's a different point of view, as well.

    Our cars are soooo efficient, that anytime there's an inefficiency, it really stands out. Yet ICE vehicles are so amazingly inefficient, that you'd have to let your Tesla waste warm up energy doing nothing but warming up for for a year to even waste as much energy as an ICE vehicle does in a single tank.

    We seem to be able to accept things that are just wildly inefficient as just being the way they are, yet when efficient devices are shown to have modes that aren't entirely efficient, we bring them to task.

    Sure, it would be great if our cars weren't wasting that much energy, but in the grand scheme of things, it really isn't that much.

    Edit: ICE vehicles should also be properly warmed up before driving (wasting energy), too.
     
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  13. jsmay311

    jsmay311 Active Member

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    That’s a wildly inaccurate statement.

    If my car used 10% if it’s battery every day of the winter prior to moving an inch, I’d be better off driving a hybrid or an efficient ICE car all winter from an environmental (carbon emissions) standpoint.
    (Of course, this depends on your local grid energy mix, driving style, and distance driven per month. But this will be true, or at least close to true, for most Americans.)

    This hasn’t been true for decades.

    https://www.washingtonpost.com/news/wonk/wp/2014/12/29/the-biggest-winter-energy-myth-that-you-need-to-idle-your-car-before-driving/
     
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  14. Phlier

    Phlier Bluebird

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    I definitely exaggerated the energy wasted, to be sure, as I can't be bothered to run the actual math, but the point itself is still valid.

    The article you linked to is only half of the picture. If it is cold enough outside that the oil in your car has increased its viscosity, you are doing your car's engine a great disservice by not allowing it to warm the oil enough to flow and lubricate your car correctly.
     
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  15. BeeGood

    BeeGood Member

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    Sure it’s not “necessary” but people still do it just to to warm the cabin and melt frost/snow on the windshield when it’s cold.

    10% sounds like a lot (I mean, in fairness it is), but from a cost perspective it’s less than a dollar’s worth of electricity (for most peoole). In that regard, it’s not materially worse than idling an ICE for 5-10 minutes.

    And the main thing here is that it’s optional. Personally, if it’s that cold outside, I’m not worrying about preconditioning the battery. Unless you have a long trip, you’re still not getting full regen for a while after you start driving.
     
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  16. Gasaraki

    Gasaraki Active Member

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    Don't spend 10% of your battery just to heat it up. You will not get that back in efficiency while driving. The only time when you should preheat is before you go supercharging. The energy used will hopefully be made back from a faster charge instead of a really cold battery "coldgating"
     
  17. agreif

    agreif Member

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    Well, I stand corrected. When I went yesterday and had it precondition before leaving, it looks like it did exactly that as I had pretty much full regen capability.

    PXL_20210113_140941001.jpg
     
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  18. Phlier

    Phlier Bluebird

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  19. variable

    variable Member

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    Even running my HVAC for an hour prior to departure hasn't gotten all regen back in 20-30F weather. It gets a good way there, but I still see dots.
     
  20. SSedan

    SSedan Active Member

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    Just drive the car, worry about warming the interior for you, let the car worry about the battery and afapt to how it drives.
     
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