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Exactly How Strong is the Regen?

Discussion in 'Model 3' started by ZeApelido, Jan 6, 2018.

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  1. ZeApelido

    ZeApelido Member

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    One way to better quantify regen strength is at what downhill gradients (and speed if going fast) does the model 3 decelerate / keep same speed / accelerate when you take your foot off the pedal?

    For instance, if go down CA-84 from Skyline to Woodside (~5-6% grade), if you let off the pedal, what happens to the car?

    And for comparison's sake, how does the Model S behave on different known gradients?

    There are plenty of hills in California, so surely someone here has gone down a few in their Model 3 already...

    ???
     
  2. Zoomit

    Zoomit Member

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  3. ZeApelido

    ZeApelido Member

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    Thanks! So if I interpret this correctly, so get a 0.16 gravitational force (assuming all other forces are null), the car would be going down a ~ 9 degree slope, or a 15.8% gradient for the regen force to balance out (no speed change).

    Or conversely, the regen force acts similarly as if the car suddenly went up a 15.8% incline road. Is that accurate?
     
  4. TJtv

    TJtv Member

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  5. dgpcolorado

    dgpcolorado high altitude member

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    I can't speak to the 3 but my Model S will easily decelerate on regen going down a 14% grade unless the regen is limited due to a cold battery (which happens a lot this time of the year). I will point out that the regen amount — 0 to 60 kW — is speed dependent, with higher regen available at higher speeds. FWIW.
     
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  6. Zoomit

    Zoomit Member

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    That sounds right.

    I don't know how it compares to the S/X, but I should add that the Motor Trend graph for the Bolt EV is actually incorrect. They mislabeled the 3 modes (and left out one). Here's a correct chart, which is based a model a created from the second speed-dependent graph. Notice that the Drive mode in the Bolt EV is the same as the Low mode in Model 3.

    [​IMG]

    [​IMG]

    The second graph was derived from a GM press conference presentation here: https://youtu.be/yQ8P7Ooo-7w?t=24m13s
     
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  7. EV-lutioin

    EV-lutioin Active Member

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    Does anyone know why Tesla chooses less regen? It seems like it is intentional, because they could certainly have more if they wanted. Especially considering that the Bolt with full regen came out a year before the M3.
     
  8. Zoomit

    Zoomit Member

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    Great question. I can't reasonably speculate why. I know it would not require a higher peak regen power. The Bolt EV maxes at 70kW regen but that's only at higher speeds. The regen power during peak *deceleration* is 20 to 50kW. That's in Low mode and using the Regen on Demand paddle between 12 and 26 mph.

    Personally, I would like to see a "high regen" mode in Model 3 that decelerates around 0.22-0.25g on average.
     
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  9. insaneoctane

    insaneoctane Active Member

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    I agree 100%. Give me more max regen and let me choose my preference from GUI.
     
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  10. scottf200

    scottf200 Active Member

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    I would guess they were trying to find a good middle ground for the "mass market" people transitioning. Seems like with OTA they could add a higher regen option as the market demands/adjust.
     
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  11. insaneoctane

    insaneoctane Active Member

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    Unfortunately I think it is limited by the rate that Tesla conservatively is willing to charge the battery pack. For the S/X line that is 60kW. I don't know if we know what it is for the Model 3. Tesla has shown excellent battery pack longevity, so who am I to question the necessity of their choice? I will just say that if it didn't jeopardize battery life, I would prefer some higher regenerative braking options in the GUI....
     
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  12. Zoomit

    Zoomit Member

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    I don't think the max regen power is the limiting factor. As I tried to explain upthread, the Bolt EV regens up to 70kW, but the strongest deceleration happens from 26 down to 12 mph when it's creating between only 50 and 20kW of regen power.

    So I suspect it would be possible to have a "high regen" profile in Model 3 that creates stronger deceleration, but that wouldn't necessarily require higher max regen power.
     
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  13. insaneoctane

    insaneoctane Active Member

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    The graph that you posted directly contradicts MT graph which shows constant deceleration like the other EVs.... Which one is correct?
     
  14. Zoomit

    Zoomit Member

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    I made that first graph about year ago based on the second graph (coastdown deceleration), which is data presented at a GM press conference. As soon as I saw the MT graph, I immediately recognized the similar lines but I figure they messed up the labeling and dropped the Drive mode line.

    I haven’t done any specific testing to confirm the GM deceleration data, however our Bolt EV certain feels like it responds similarly. The regen modes are NOT like the MT data in my experience. In particular, the Drive mode, which has the least regen, feels significantly less powerful than the other three.
     
  15. Zoomit

    Zoomit Member

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    One other point, from my seat of the pants experience, is that the deceleration is obviously not constant. I have no reason to question the GM data because it’s similar to what I’ve felt.
     
  16. DarthPierce

    DarthPierce Member

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    Constant-power regen would be incredibly strong at low speeds (technically going to infinity), that's why it's closer to a constant G for moderate speeds.

    All the systems are likely to have a (regen) power limit instead of G limit at higher speeds. If they did the test from max speed, it would have an exponential area (power limited) and a linear region (G limited). The crossover is likely in the neighborhood of 50-60mph which is why it's not apparent in their data.

    This is also for safety in that we humans have a much better instinctive understanding of G than power: constant G is like driving up a (constant) hill - constant power would be analogous to a hill that keeps getting steeper and steeper until it's somehow steeper even than vertical
     
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  17. shokunin

    shokunin P85 & M3

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    Compared to my 2012 P85 the Model 3 seems to have stronger regen. My P85 used to have much stronger regen, but through several software releases it has been getting weaker over time.
     
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  18. eMotionRentals

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    As some of the other commenters noted, I think it's marketing, primarily. I think Tesla is trying to make a car that many ICE owners will find comfortable and familiar. If every time you lift your foot of the accelerator, the vehicle "brakes" hard through regen, some are going to hate it and will be turned off. Many of my renters set my vehicles on low regen and turn on creep. Why? Because it's familiar to them. Most like their automatic transmission ICE vehicle. Yeah, they get less range and need to keep their foot on the brake. But change is hard, even if it's change for the better.

    I remember taking my neighbor for a ride in my brand-new Model X. He constantly kept taking his foot completely off the accelerator in a a quick movement, thus jerking the car into slowing down. He hated it and could never stop doing it. It was not only an unpleasant ride for both of us, he will never buy a Tesla after that experience, I can assure you. He did NOT like it.

    With that said, it seem that Tesla could offer vehicles with three settings: No Regen, Medium Regen, Heavy Regen. They could ship all vehicles with the middle setting activated. For people like my neighbor, they could choose No Regen with a warning that it will reduce their range. For people like us who want one-foot driving, we could all turn Heavy Regen on.

    Just my two pennies....
     
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  19. electracity

    electracity Active Member

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    Or, for your neighbor, regen on the brake pedal. Light braking would be regen only.

    Although I think very few people could not learn to do one pedal driving. Manual transmission is a higher skill level than one pedal.
     
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  20. electracity

    electracity Active Member

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    Power limited indicates the dual motor M3 won't be better at regen. Perhaps it electronic rather than cell limited on the M3, as I doubt the small battery M3 has an even weaker regen curve compared to the LR car.
     

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