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How to tell when the rear brake lights are on

Discussion in 'Model S: Driving Dynamics' started by gaswalla, Dec 26, 2012.

  1. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    The savvy folks on this forum probably already know this, but I couldn't find the answer when I searched. Then, today I stumbled upon the answer in my own car.

    We know that the rear brake lights come on by deceleration - usually from the regenerative brakes - in addition to the traditional method of coming on when the brake pedal is pressed. I've been curious to see when the lights are actually on. If you go to the "about" screen by pressing the big T at the top, middle of the touch screen, you will get a picture of your car, VIN#, and firmware version/release notes. Pay attention to the brake lights on that picture - now press the brakes... the picture is a real-time version of the car, with active rear brake lights. It works while driving too.. cool for a few minutes, then it's yet another distraction. Nonetheless, it allows you to understand what the guy behind you is seeing as the car slows down.
     
  2. mknox

    mknox Well-Known Member

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    Can you see any reflection from the center high mounted brake lamp in the back window? On some of my past cars, this was an easy "tell" (at least at night) to see when the brake lights are on.
     
  3. brianman

    brianman Burrito Founder

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    As mentioned previously, using the rear cam at night works pretty well for observing as well.
     
  4. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    Yes, the rear cam would work well at night. Personally, I cant see any reflection in the back window at night. The real time picture on the "about" screen works well during the daytime.
     
  5. Doug_G

    Doug_G Lead Moderator

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    I was using the "rear cam" technique last night. I noticed that at higher speeds, above 60 kph (40 mph) that the regen brake lights didn't really engage at all. Anyone else see this?
     
  6. MikeK

    MikeK R#129, TSLA shareholder

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    I also found the trick with the About screen. I want to take a co-pilot with me and have him or her tell me when they go on and off as I try out some different speeds and regen levels.
     
  7. elreydetodo

    elreydetodo #14,427

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    Does anyone know how much energy it costs to keep the HD (or SD) rear camera displaying while you drive? I'd be curious to find out if it's especially draining to use it.

    - - - Updated - - -

    Does anyone know how much energy it costs to keep the HD (or SD) rear camera displaying while you drive? I'd be curious to find out if it's especially draining to use it.
     
  8. cinergi

    cinergi Active Member

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    I don't think we can know -- but if we assume an impossible/outrageous number like 200 watts, that's still less than 1 mile of range lost per hour running it.
     
  9. byt

    byt Member

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    If you pull up the car image from the Tesla logo the brake lights illuminate on the image when engaged by the regenerative breaks.
     
  10. byt

    byt Member

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    Oops, MikeK beat me to it! :)
     
  11. AltPowr

    AltPowr Member

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    I drove around yesterday for over an hour trying all different speeds and methods of lifting off the accelerator pedal. I came to the conclusion that there are only two modes that I noticed:

    - Brake regen set to STANDARD: Every time I lift off the accelerator, no matter what speed between 10MPH and over 90MPH, the brake lights come on automatically. I tried lifting off slowly, fast, everything.
    - Brake regen set to LOW: Same tests as above, the brake lights NEVER came on automatically.

    Does anyone else see anything different? I did notice that sometimes lifting off the pedal at over 90MPH it took a drop of about 5MPH or more before the brake lights came on automatically.
     
  12. Doug_G

    Doug_G Lead Moderator

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    Yes, I have seen something different, namely not being able to get the brake lights to come on at highway speeds. I'll try it again.
     
  13. AltPowr

    AltPowr Member

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    Very interested to hear what you come up with. Make sure you are aware of the regen setting during the test - I changed mine back and forth. I would love to leave it on STANDARD regen and not have the brake lights come on at highway speeds.
     
  14. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    My car exhibits the same behavior as Doug reports: at 65mph with Standard regen selected, when I lift off the accelerator the brake lights do not come on. At some lower speed the brake lights do come on. The maximum regen is limited to 60kW, which leads to greater deceleration at slower speeds. Remember, the brake lights are tied to deceleration, and the faster the car's speed the less deceleration a given amount of regen will produce. Anybody noticed how much longer it takes to slow using regen alone from, say, 75 to 50 mph, than it does from 50 to 25?
     
  15. AnOutsider

    AnOutsider S532 # XS27

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    Which, for me is good. I'm used to engine braking and don't want to flash the people behind me unless I'm decelerating hard. Thank you to the OP for the tip. I tried the rearview cam thing, but unless there's something for the lights to reflect off, I still don't see them. Going to try this today to see in which cases it happens. It seems to be if you fully lift off the accelerator press the brakes. I notice if I lift slightly off and coast (partial regen), the lights don't SEEM to come on -- which is truer the higher my speed.

    Also, I realized for the first time the other day that when you brake, it does actually still regen. It's been so seamless I never noticed.
     
  16. kishdude

    kishdude P #130

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    I actually think that this should be an indicator on the smaller display. On a regular ICE car, you always know when your brake lights are on because your foot is on the brake. In the Tesla, this is difficult to tell. I think in a future update there should be a small indicator on the smaller display so that you can know when your brake lights are on.
     
  17. Doug_G

    Doug_G Lead Moderator

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    I've only ever used Standard regen. I think you'll find that 99% of Roadster owners leave it on Standard.
     
  18. AltPowr

    AltPowr Member

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    Then they are making the cars differently, or there is some other factor involved. I spent at least 90 minutes driving around on freeways and long roads yesterday at all different speeds. When regen was set to STANDARD, the only way I could keep the brakes lights from turning on automatically was to not let the accelerator pedal go all the way up. I would have to keep it pressed in a bit. Every time I took my foot completely off the pedal, the lights came on - whether I did it slowly or fast, and at any speed. I tested it quite a bit at speeds over 60MPH.

    I'm puzzled. Because I don't want the lights coming on unless I'm really braking, or if I let off and the car is going less than 30MPH or something coming to a stop.

    I did notice that most of the time regen would go up to 60kW in STANDARD, but it never went over 30kW in the LOW regen setting.
     
  19. AnOutsider

    AnOutsider S532 # XS27

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    If you fully release, then you start to slow hard, no? In that case, I think the brake lights are appropriate. When I want to slightly slow, I ease off the accelerator, which gives me some regen, keeps me coasting, and keeps the brake lights off.
     
  20. AltPowr

    AltPowr Member

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    It's subjective whether you want brake light on or not, but when I slow on the freeway from anything over 50MPH, I don't want brake lights coming on. Especially if I was speeding and need to slow down quickly for some particular reason - maybe a cop in another lane. At those speeds it does not slow enough for someone behind me to see brake lights. In fact, it just looks like you have no idea how to drive if you press your brakes while driving at 65MPH. That should only be needed for an emergency, not slowing down.
     

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