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Sr+ charged to 70% at pickup. Regen dots

Discussion in 'Model 3' started by Darthbenji, Sep 28, 2019.

  1. Jffurlan

    Jffurlan Member

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    My SR+ always has dots when I first leave regardless of my charge level, temperature, or if I just finished charging. Rarely do I get rid of them. Thought this was normal until a coworker with LR was shocked I ever had limited regen.

    That being said, even if I have 40-50% regen, the green bar rarely fills completely up when slowing down. So perhaps the SR+ just can’t capture as much during regen as the LR. I wonder if it has anything to do with the lower amperage on board charger, or battery capacity.
     
  2. newtonfb

    newtonfb Member

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    I have had my SR+ since March. My regen dots only show up when I charge to 100%(which is rare) and when the temperature is cold outside (below 60F) and its been sitting for awhile. Other than that, I dont get regen dots much. I always charge to 80% everyday. If I schedule charge it to 80% when its cold out and have it finish charging before I leave for work, I dont have any dots as my battery is warm.
     
  3. Darthbenji

    Darthbenji Member

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    Ok so what’s going on with the cars showing them vs the ones that don’t?
     
  4. novox77

    novox77 1.21 Gigawatts

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    I've been through 2 winters with my Model 3.

    The dotted line means some amount of regen is being limited. It can be due to cold temperature (of the battery), or it can be due to an almost fully-charged battery. Or both.

    We're at that time of year where temps dip at night that can trigger the car to reduce regen. This is to prevent damage to the battery, as charging it hard while cold can significantly reduce the longevity of the battery. Likewise if your battery is almost full, charging it hard (like strong regen) will damage it, so Tesla reduces the regen to prevent that.

    In the middle of winter where I am (New England), temps might not go above 20F on many days. If the battery is cold soaked at those temperatures, you will not have any regen. You will see dotted line all the way to the point where the bar turns black when you step on the accelerator.

    When you charge the battery, you're also warming it. So typically if you've been charging the car for a while, the battery is warm, and you will have most if not all of your regen available (little to no dots showing). I actually schedule my charging during the winter to occur 3-4 hours before I will wake up and use the car. That way I start my commute with a warm battery and full regen. If I charge the evening/night before, that heat will dissipate overnight. Why let it go to waste.
     
  5. novox77

    novox77 1.21 Gigawatts

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    Rather than trying to decrypt how Tesla is trying to manage charging (regen is another form of charging) via SoC between SR and LR, just try to understand the physics of lithium batteries. Certain environmental conditions cause an unfavorable chemical reaction in the battery that reduces the amount of free-flowing lithium ions, which means reduced capacity over time. This chemical reaction is what renders smartphone and laptop batteries useless after a few years. The environmental conditions that cause this unfavorable reaction are:

    1) high temperatures
    2) high voltage (high state-of-charge)
    3) applying charge to a hot battery
    4) applying charge to a cold battery

    42C ambient is quite hot. A smaller pack will be affected sooner than a larger pack. This could explain why you see some regen limiting on a hot day on an SR vs LR.

    A smaller pack also means the charge rate needs to be reduced in order to keep the per-cell charge rate the same as a larger pack. This means you'll see more regen dots earlier on the SR than the LR when SoC is high.
     
  6. Darthbenji

    Darthbenji Member

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    Ok. What I’m trying to understand is why two identical cars don’t both exhibit the same characteristics.
    This isn’t some Sasquatch sighting where we all write things off to lighting and ripple effect.

    Simply repeating temperature and soc to already knowledgeable owners doesn’t help. It simply illustrates that those stating the usual suspect problems don’t understand a novel one. It was the same thing last year with the limited regen when switching to winter tires. Man there were so many ‘it’s cold’ posts. It was a legitimate problem that Tesla fixed.

    Anyway, I and many other owners know how to warm a battery to rule that issue out. We have people that never have those dots go away. We don’t all live in the arctic!
     
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  7. Darthbenji

    Darthbenji Member

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    Yes. We know all that. We’ve accounted for the usual causes and they don’t exist. Still the dots appear on some cars.
     
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  8. novox77

    novox77 1.21 Gigawatts

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    I re-read this whole thread and nowhere do I see you talking about 2 identical cars. What 2 identical cars are you referring to? I see comparison only between SR vs LR. Which are hardly identical.

    Did you see my followup response to @Dante?

    It might also help if you were a bit more coherent in your ask. Your OP refers to "pickup". What does that even mean? In my response to Dante, I proposed some reasoning via first principles around lithium battery physics that could account for:

    - seeing dots on a 42C day (charging a hot battery is bad)
    - seeing dots at a lower SoC than a LR (smaller pack means higher per-cell charge rate, which is bad)

    both of which has to do with the difference in battery capacity between SR and LR, cars which it seems like you're calling "identical", but I can't say for sure because nowhere in this post do you clarify which identical cars you're referencing.

    My suspicion is that the max regen kW on the LR is higher than what Tesla deems healthy for the SR pack in most environmental situations. If this is true, then there will be dots on the SR for a lot of conditions that would not affect the LR.
     
  9. vickh

    vickh Active Member

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    I'm sure Tesla's BMS is smarter than my laptop or phone. RE: charging a hot battery is bad. What's considered hot and does it damage the battery permanently or only affect it while hot? I only recently noticed the dots on a SR and it's starting to cool down in AZ (still in the 90s) I don't care if it limits my regen during hot days, but about permanent damage to battery.

    SC vs 24A charging ok?
     
  10. novox77

    novox77 1.21 Gigawatts

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    There isn't a hard threshold of temperature where it's suddenly bad to charge the battery. And you are right; Tesla's battery management is the best there is right now. Seeing dots in more situations in an SR does not surprise me at all. It's a smaller battery pack, which means it's more susceptible to extreme ambient temps, and it cannot charge as fast as a larger pack, so strong regen is likely limited except in the most optimal environmental conditions.

    The damage is permanent. This is what causes batteries to lose capacity over time. Tesla is trying to slow that degradation as much as possible.

    In phones, there is no active cooling mechanism for the battery. At least in a laptop, it can circulate a fan to try to keep temps down. But the problem with laptops is that frequently they are plugged in constantly, so the battery is constantly charged at 100%. Phone batteries tend to degrade due to heat and frequent charge cycles. Laptop batteries tend to degrade due to be held at 100% too much.

    When supercharging, the car is running the battery cooling system to prevent temps from rising too high. The supercharger also will regulate charge kW to make sure the voltage pressures are minimized.

    24A charging is very gentle on the battery when looking at it from a per-cell perspective. However, 24A is a tad more stressful on the SR pack than LR because there are fewer cells to distribute that charge, so the per-cell charge is higher. Not enough to be of concern in terms of long-term degradation.
     
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  11. Darthbenji

    Darthbenji Member

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    Let’s just assume you have two SR+ cars side by side. They’ve both just charged for two hours to 70% state of charge. It’s 18c. Then they both drive 30 minutes. One displays regen dots and the other doesn’t. Now also assume this occurs repeatedly. Would you find that odd?

    It will be 25c here tomorrow. I’ll have regen dots all day regardless of my soc. I’m saying that isn’t normal.
     
  12. novox77

    novox77 1.21 Gigawatts

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    I might find it odd if one of those cars has almost no regen available, as opposed to one of those cars having a tiny bit of regen reduced. However your hypothetical comparison just talks about the presence of dots and not how much of the regen bar is showing as dotted.

    it's either a defect, or there are variations between "identical" cars that are within manufacturer-accepted ranges. Much like how each electric motor has varying level of performance despite being "identical."

    If you believe there to be a defect in your car, then have it checked out by service. They have more details on what's going on with your battery than anyone on these forums.
     
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  13. Wennfred

    Wennfred Supporting Member

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    #33 Wennfred, Sep 30, 2019
    Last edited: Sep 30, 2019
    Never noticed that, thanks for posting this info, I will be charging to 100% on Friday .. trip to Vegas, will look for the Dots or Dashed Lines.

    Fred
     
  14. Wennfred

    Wennfred Supporting Member

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    4BF98678-7071-4DA4-BB01-8B2A6089AFDB.jpeg
     
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  15. Dante

    Dante Member

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    Again, just reiterating that your wealth of experience using your LR does not translate to the SR+. I have both cars. What you have said above is absolutely true/useful/observable for LR owners. SR+ behaves differently (and maybe only some SR+ behave this way). People are trying to figure out if this is normal and may be curious why it happens with the SR. Like several SR+ owners have posted here, we have some amount of limited regen most of the time when there are:
    1) NO extremes of temperature
    2) NO high state of charge (unless you consider 60% high)
    3) NOT trying to charge the battery

    Also I didn't say that 42 degrees caused limited regen in my SR+, I said it did NOT cause limited regen on my LR. The SR+ has limited regen constantly (but only a little bit, unless the extremes of temperature/charge are present, then there is more limited regen).
     
  16. novox77

    novox77 1.21 Gigawatts

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    In my post to you I accounted for a situation that does not require extremes in temp and SoC that causes dots to show up for SR.

    Let's agree that for any fixed C-rate, the max charge for an LR is higher than an SR simply because there are more cells to divide the charge coming into the car.

    If there are times where you see no dots on the regen bar, this means that the conditions are ideal such that the SR is able to take its max charge rate. If the max regen on the SR is only barely lower than this max charge rate, whereas the max regen on the LR is much lower than its max charge rate, then that means that any adverse change to the environment is going to affect the SR before the LR. This is because you are hitting the C-rate limit that Tesla has deemed safe for the SR's pack size, taking into account current conditions.

    In DarthBenji's example, if 25C is considered ideal temps that allow for the SR's max regen, 18C might already be considered too cold to allow max regen, so dots appear. For an LR, its max charge rate is likely also reduced, but since that rate is larger than max regen rate, it takes more extremes in temp or high SoC to trigger regen nerf.

    If there are night-and-day differences in regen behavior between SRs, then something else is going on. Maybe some people have SRs with larger packs that are software-nerfed? Didn't they do that to a bunch of inventory MR cars? I can't remember. If this is the case, I would expect the MR pack to be more resilient, and you'd see less regen nerfing.
     
  17. Darthbenji

    Darthbenji Member

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    Even if 18c is too cold, after an hour of driveway that temperature issue is mitigated. Same with charging it at that temperature. A friend of mine hasn’t had dots below 90% yet. I can’t get rid of them. Period.
     
  18. CharleyBC

    CharleyBC Active Member

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    Guilty as charged, your honor. I did not know that the SR+ behaves differently. My apologies. I am indeed writing from my LR experience.
     
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  19. diamond.g

    diamond.g Active Member

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    Do your dots stay after supercharging for a while?

    It would be interesting to pull CAN data from the to SR's and look at ID 252 to see if they are the same. That ID is supposed to show regen and power limits from the pack. If the settings match (or are really close) for the two vehicles, but the display shows more regen on one than the other it would indicate a MCU logic issue of some sort.
     
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  20. SigNC

    SigNC Active Member

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    regen dots come up easier in a SR or SR+ because it's easier to where the battery will not accept the max regen level. Think of how the SR doesn't charge as fast as the LR, regen is charging and if the battery is in a state, due to level of charge or battery temp where it can't take the max regen rate you will get dots.
     
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