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another regen/brake light discussion

Discussion in 'Roadster: Technical' started by walk_n_wind, Jun 27, 2010.

  1. walk_n_wind

    walk_n_wind Member

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    #1 walk_n_wind, Jun 27, 2010
    Last edited by a moderator: Jun 29, 2010
    Did you mean you hate the brake lights not coming on? Or does the roadster fire the reds on throttle-off?
     
  2. Kevin Harney

    Kevin Harney Active Member

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    Yes the Roadster fires the reds on throttle off. Regen is strong on the Roadster and IMHO the reds are necessary when the throttle is released.
     
  3. walk_n_wind

    walk_n_wind Member

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    *speechless*
     
  4. vfx

    vfx Well-Known Member

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    Brake Lights on During Regen

    I have been a stick-shift ICE down-shifter for years. Engine braking has the same result as motor/generator braking but does not light the reds. Every time I let off the Roadster accelerator on the freeway the car behind me brakes as does the one behind him and so on and so on.

    People who are cautious might see the three Roadster tail lights come on from 6 car lengths back and slow in anticipation of some event that is never going to happen. This type of false clue I believe at best, terrible for traffic flow, at worst dangerous because someone might overreact and cause a pileup.

    Try driving behind a Roadster sometime. It's maddening how much the lights go on. I would hate to be behind one all the time in traffic. As an owner, the idea of someone cursing me because of something that is largely out of my control bothers me every day in LA traffic.

    Two compromises I might consider.
    1. Have the brake lights come on exactly 1 second after full throttle-lift. That delay would give the driver time to reapply pedal pressure without giving false signals and messing with the heads of drivers behind them.

    2. Maybe just the third light comes on but only half bright.
     
  5. walk_n_wind

    walk_n_wind Member

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    Has anyone had a dialog with Tesla about this...functionality? Just curious what their explanation was.

    I don't want to belittle the amount of thought Tesla put into this, but they've basically decided they can redefine what a brake light means. Anyone who drives a high-revving engine with a manual transmission (and some modern automatics) slows down considerably without applying the brakes, so it's not like the Roadster is unusual in that way.

    I'll be sure to share my concerns with Tesla. Because like VFX, this would affect my peace-of-mind while driving. The last thing I want to do is send mixed-messages to other drivers.
     
  6. ChargeIt!

    ChargeIt! Member

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    VFX,
    Do you do complete lift-off frequently, and for what reason ?
    If you anticipace the traffic movement ahead you can do partial lift-off and the reds would not light. If you do full-lift off because of misjudging traffic ahead, then IMHO the reds SHOULD light as a warning. If you do full lift-off to get more regen ... then the 1 second solution would also not help.

    Not trying to criticize, only wanting to understand more about the reasons. ( I fully understand not wanting to confuse drivers behind you. )
     
  7. vfx

    vfx Well-Known Member

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    Racing is about smoothness but also about getting from one place like a corner to the next as quick as possible. The Roadster changes lanes and comes up to other cars driving slow and at stop lights as fast as thought. This is where max regen comes in and really not necessary to telegraph to drivers far back behind the Tesla that it's motor braking. Again, next time you drive in traffic behind a Roadster watch the tailights coming on far more than a normal car.
     
  8. AnOutsider

    AnOutsider S532 # XS27

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    Interesting, I wouldn't have thought they'd do that (fire the reds on coasting), but I suppose if it's a full lift off and not on a half/casual lift, it makes sense.

    I wonder if my car does it and if I drive folks behind me insane haha
     
  9. walk_n_wind

    walk_n_wind Member

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    There should be a negative acceleration that qualifies as significant deceleration, and the accelerometer that measures it should turn the brake light on/off.

    Add that and keep the fact that the brake pedal actuates the brake lights, and we've got a system I'd be happy to use.

    Of course, all that along with some wicked-violent regen. Yeah!
     
  10. Doug_G

    Doug_G Lead Moderator

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    Do the lights illuminate as soon as the amps go negative, or turn on at -20kW, or what? (My Roadster arrives on Saturday, so I don't know the answer to this yet!)

    Personally, I think having them turn on is a good idea, but I'd prefer that they go on only for heavy regen, e.g. at least half power.
     
  11. SByer

    SByer '08 #383

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    The lights light up during regen based on the deceleration g-force. I think Tesla has the algorithm right, just not the particular threshold.

    Though after the northern road rally, it's not nearly as annoying as I feared, and it's a HELL of a lot less annoying than the brake lights on an automatic in traffic, which are darned near useless.
     
  12. ChargeIt!

    ChargeIt! Member

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    I also think Tesla has it right (in the USA). (In Europe existing (?old) laws require brake lights to be activate only upon pressing of the brake pedal, which IMHO is dangerous, given the (new technology) strong regen (deceleration) the Roadster produces.)

    Shall we compromise ?

    How about a dashboard indicator that lights in sync with the brake lights to tell the <insert adjective here: {concerned, compassionate, paranoid, careful, courteous, mindful, altruistic, safe, defensive}> driver, allowing driver to adjust right-foot "go pedal" behaviour ?
     
  13. doug

    doug Administrator / Head Moderator

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    #13 doug, Jun 29, 2010
    Last edited: Jun 29, 2010
    How about the simply curious? :smile:
    Though isn't there enough light scattered from the CHMSL to tell whether or not your brake lights are on via the rear view mirror?




    .
     
  14. chronopublish

    chronopublish 2008 Roadster #VP27

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    I'm a little confused - do other Roadster drivers often lift off the throttle while on the freeway? My driving habits naturally adapted to keep on the accelerator at all times unless my intent is to slow down quickly, in which case the red tail lights seem appropriate.
     
  15. ChargeIt!

    ChargeIt! Member

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    Yes, add {curious} to those adjectives. :smile:

    As to mirror: No or at minimum very difficult (easier at night). And it would be unsafe to continually keep checking the rear-view mirror -- too much time spent in focal distance adjustment and taking eyes off the road (it takes a while to identify the back-scattered red light). Especially bad for "older" (over 40+) drivers. The blinking lights on the dash are more easily noticed in your peripheral vision without much effort (e.g. the signal or T/C blinking).
     
  16. AnOutsider

    AnOutsider S532 # XS27

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    I don't know about roadster owners, but I drive an R8 and most of my (light, at-speed) braking is done by lifting off the accelerator. Same effect as a light tap on the brake really -- if you downshift, even bigger effect
     
  17. ChargeIt!

    ChargeIt! Member

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    Never driven an R8, but I'll assume it's basically same as any luxury sports car. Thus the lift off you are doing generates some, but not a lot of decel. This amount (in a Roadster) would NOT light the brake lights on a Roadster. Your downshifting would come close or cause sufficient decel (depending on conditions) that would trigger the reds.
     
  18. shark2k

    shark2k Member

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    Out of curiosity have you ever driven a stick shift (not trying to be a jerk, just trying to find out). When driving a stick shift down shifting helps to slow down really quick, especially when used in conjuction with the brakes. But just downshifting by itself, you can get a good amount of deceleration and no brake lights come on at all and I haven't heard of anybody getting rear ended because of that. The other drivers are supposed to be paying attention to the cars in front of them so if they see themselves coming up quickly they should get on their brakes to slow down. Considering people rear end people with their brake lights on I'm inclined to agree with VFX.

    Note: I've only driven a Roadster once and it was at max speeds of 30 mph. My car is a stick shift so I do have experience with downshifting.

    -Shark2k
     
  19. Tdave

    Tdave Member

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    Roadster regen braking is considerably stronger than any engine braking in an ICE car. Roadster regen can exceed -0.2 g's. That's a lot. I would be scared if the brake lights didn't come on with throttle lift, and I'm really glad they do.

    Another reason it's safer is in a panic situation. With the Roadster the brake lights come on as you're lifting the accelerator and before you make it to the brake. The car behind probably sees your brake lights a half second sooner than the same situation with an ICE car. He is alerted, and in combination with other visual cues of the emergency, will react faster.

    No doubt in my mind the brake lights need to come on with throttle lift. As someone else has mentioned, maybe the threshold could be adjusted, but only slightly.
     
  20. Doug_G

    Doug_G Lead Moderator

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    The regen is MUCH stronger than downshifting a standard.
     

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