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Dangers of rapid regenerative braking?

Discussion in 'Model S: Driving Dynamics' started by chuckb, Jul 11, 2014.

  1. chuckb

    chuckb New Member

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    my sister test drove a tesla last week - she said when she let off the accelerator the car almost stopped - has anyone ever been rear ended because of the abrupt slowdown ? thanks
     
  2. dsm363

    dsm363 Roadster + Sig Model S

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    How fast was she going? If she was going 20mph the car would slow down quickly but nothing like slamming on the breaks. It is an unusual feeling with regenerative breaking at first. She likely just wasn't used to it and it isn't a problem. The accelerometer in the car senses this and turns on break lights at a certain rate of deceleration (believe I have that correct).
     
  3. ecarfan

    ecarfan Well-Known Member

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    "Almost stopped" is an exaggeration. It slows down gradually but if you are not used to the feeling of regen braking it can seem rather dramatic.
     
  4. NigelM

    NigelM Recovering Member

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    I don't recall anyone being rear-ended because of regen braking; the regen slowdown isn't that abrupt. Possibly your sister was surprised at the regen braking, the car does slow down faster than if you simply lifted your foot in an ICE car.
     
  5. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    From a high speed the rate of slowdown is likely less than what you would normally do with the brake. From 20 mph it's more rapid, but it's not like hard braking. I'm guessing NigelM is correct and she was surprised that it really does slow down. After a few minutes of driving you learn to modulate your foot and after a day or two you'll wonder why you ever did it any other way.
     
  6. flashflood

    flashflood Member

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    Yeah, it's mostly a matter of what you're accustomed to. With a manual transmission, the car will lurch a bit if you take your foot off the gas abruptly. With an automatic, the car will just coast, i.e. no rapid change in speed. In general, I find that the Model S feels more like a manual because there's no slip and no delay. I drove manual years ago, but spent the last 15 in an automatic, so it was a bit of an adjustment. But once you get used to it, the regen braking is actually fantastic because you almost never have to move your foot off the accelerator.
     
  7. Vger

    Vger Active Member

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    And recall that if this behaviour does not work for her, at least at first, she always click the "low regeneration" mode in the preferences on the touch screen.
     
  8. igotzzoom

    igotzzoom Member

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    That's the one thing I noticed when I drove my friend's car. The regenerative braking is much more aggressive than coasting with a conventional automatic, but feels similar to lifting off the throttle in a manual in a lower gear.
     
  9. caddieo

    caddieo Member

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    It also depends on how fast you're going when you lift off. At very slow speeds, the effect is more abrupt and noticeable.
     
  10. snellenr

    snellenr Member

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    Yes, that was my biggest driving adjustment when I got the car, coming from my manual-shift Sentra - turning corners. I'd gotten used to coasting into the corner and then accelerating through the turn, and the regen threw off my timing pretty badly. It doesn't take long to get used to it and adapt your style, though.
     
  11. pgiralt

    pgiralt Active Member

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    The most important thing to remember is that the brake lights will turn on with reven which actually makes it safer than a manual transmission downshifting which would not turn on the brake lights.
     
  12. invisik

    invisik Member

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    I think they should initially put the regen in reduced for test drives. It is really freaky when you've never experienced it before.

    the brake lights do come on when you are slowing at a significant enough rate. I personally think they don't come on soon enough as I regularly notice people in my rear view mirror doing surprise braking when I've been regening for a bit but not the full let off the pedal regen. I sometimes tap the brake to get the lights to come on sooner. And I'm not talking people talking on cell phones or twirling their hair while driving, these people are usually paying attention and it happens at multiple stop lights in a row....

    -m
     
  13. seanahan

    seanahan Member

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    At my test drive in Dallas they turned regen on low to start. At the end of the drive, on an open stretch of road, they put it back up to show me how it worked.
     
  14. Zythryn

    Zythryn MS 70D, MX 90D

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    I've given test drives where the first time driver was more impressed with the regenerative breaking than the acceleration:biggrin:

    However, before any test drive I warn people about the strength of the regen.

    Personally, I haven't had people creeping up on me when regenning any more than in any other vehicle.
     
  15. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    I've had no issue with this either. Perhaps I'm used to it as most of the cars I've driven have been manual, semi-automatic, or had regen.
     
  16. FLDarren

    FLDarren Member

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    I disagree. I initially thought is was weird. After about a mile of driving I realized the benefits of one pedal driving. Now I wouldn't have it any other way. Just another marvelous feature of Model S.

    I have noticed during regen that once you hit about 20mph, the regen does push you forward a little more until you get to about 10mph.
     
  17. artsci

    artsci Sponsor

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    Regen has not been much of a problem for me with tailgaters. I commute 15 miles each way every day on a busy interstate which is often bumper to bumper. I watch my rear view mirror incessantly for people following too close, especially in regen. It really hasn't been a problem. When the occasional moron follows too close I just switch lanes so the fool can rear-end someone else. When the path ahead opens up sometimes I just sprint away and leave the tailgater in the dust.
     
  18. chuckb

    chuckb New Member

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    thanks to you all
     
  19. UberEV1

    UberEV1 Member

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    +1 for one pedal driving. It takes a bit getting used to, but gives better ultimate control. I've driven hybrids with regen on the brake pedal and much prefer it the other way around.

    As I recall, brake lights are triggered when regen rate exceeds 15kW, which is a relatively low rate of deceleration. So, drivers behind you should get the signal even in cases of minor deceleration.
     
  20. invisik

    invisik Member

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    I think that's part of it.. the rate of deceleration is not consistent at different speeds. Pressing the brake at different speeds is consistent.

    Being a former owner of a few Lincoln Town Cars, I've gotten used to driving very smoothly. Slowing down gradually with regen is a struggle because 1. the brake light doesn't come on soon enough and 2. it doesn't slow the car soon enough (depending your speed and distance from stopping point) that you have to left off almost completely or completely and thus jarring the passengers a little. When I'm driving by myself, I just lift off the pedal completely so the brake light comes on, then press a little to have a more graceful slowdown.

    I changed the regen to the reduced setting once to try it... now that could be done smoothly... but I'd rather have the juice. So I keep trying. :) I know I'm a bit over the top with the smoothness, but it's really annoying to me when you get into a super nice car and the driver can't keep it in tight control.

    -m
     

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