Regen brake lights....

Discussion in 'Gen 3 Prius Main Forum' started by ChipL, May 14, 2012.

  1. Danny Hamilton

    Danny Hamilton Active Member

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    I'm pretty sure that I read somewhere that the Prius uses regen braking down to about 7 MPH or so. Unless you are stomping on the brakes for an "emergency stop" (or encounter a significant loss in traction that triggers an immediate switch to friction), almost all of the Prius braking is regen braking, isn't it?
     
  2. xs650

    xs650 Senior Member

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    Max regen braking isn't very strong. Braking way, way short of an emergency stop uses the friction brakes.
     
  3. Danny Hamilton

    Danny Hamilton Active Member

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    Perhaps you and I have different concepts of "very strong" and "way, way short of". In my opinion 100 amp braking is significant braking. Certainly there are other conditions that can trigger the use of friction brakes (full traction battery, loss of traction, braking exceeding 100 amps, emergency stop) but in general it is my understanding that most of the braking done
    by the Prius is regenerative braking. If this is not true, do you have some source you can refer me to where I can read up on this?
     
  4. vanbran

    vanbran Hmm....

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    Everyone keeps saying the Prius uses brake lights just like any other vehicle, which is true, but again, a lot of us aren't driving like any other vehicle. Our brake lights are on a lot more than anyone else for those long slow regen brakes.

    I don't think we should have no lights in regen, because you can bring the car to almost a complete stop, but it would be nice to have some way to let people know when we are braking hard. As it is I'm sure most people think I'm a granny driving with both feet...
     
  5. Danny Hamilton

    Danny Hamilton Active Member

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    The Prius is designed to be driven just like any other vehicle. You can hyper-mile any vehicle, it doesn't have to be a Prius, but automobile manufacturers are not designing and building their vehicles to address the whims of the small group of hypermilers out there. They design and build them for the general public.
     
  6. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Try this mental exercize: Visualize how many years you would need to get new rules passed the United States Department of Transportation, the National Highway Traffic Safety Administration, 50 State Departments of Transportation, the safety bureaucrats of every other nation on earth, and realize that the Prius has only been made for 10 years, perhaps it is still in committee. Meanwhile Toyota is following the same laws every other car does.

    This NHSTA document is on the lights and is had to argue with:

    FMVSS No. 108 Full Text
     
  7. dhanson865

    dhanson865 Expert and Devil's advocate

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    I want every car to have a change in rear lights not just the prius.

    Why? How about the "they love to tailgate a prius" thread? The reality is with hybrids and EVs we are driving our cars differently now than than when cars were IC only.

    See My Nissan Leaf Forum • View topic - Green light on rear bumper to show when you gain energy for a discussion on this

     
  8. dhanson865

    dhanson865 Expert and Devil's advocate

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    What that means is that the low brake lights can be on for multiple reasons but the high brake light (3rd brake light) can only be on when the brakes are on.

    But regen braking is considered service brakes so there is no problem with a hybrid doing either:

    A. show low brakes only if braking with no pedal input and all brake lights if braking while pedal is depressed

    B. show all brake lights if braking with no pedal input just as it does with pedal depression.

    And A has subsets because it's still legal to use multiple intensities on the lower brake light.

    I don't care who makes the rule change, just make it near enough to the top so it applies to all 50 states and screw the local ordinances. They can adjust to meet the new federal standard.
     
  9. qbee42

    qbee42 My other car is a boat

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    If you want this rule change, you need to do it for downshifting as well. It will be hard to decide where to draw the new line.

    The existing law is good enough. What we need is drivers who actually drive, instead of talking on cell phones and texting.

    Tom
     
  10. qbee42

    qbee42 My other car is a boat

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    100 amp braking is pretty significant at 10 mph. At highway speeds it's close to nothing. Speed makes a huge difference.

    Tom
     
  11. Danny Hamilton

    Danny Hamilton Active Member

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    True. Wasn't really thinking about high speed braking I guess. Still I was responding to xs650 saying that "Regen doesn't slow the car anymore than gearing down on a normal car so no need for brake lights when only using regen". If friction brakes are used with minimal brake pedal input at high speeds, then triggering on friction brakes really isn't going to address his concern anyhow. If friction brakes aren't used until significant pedal input at slower speeds, then triggering on friction brakes becomes a hazard. Either way using friction braking as the indicator for brake lights is a bad idea.
     
  12. qbee42

    qbee42 My other car is a boat

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    Agreed. The method of slowing is irrelevant; only the magnitude is significant. For the sake of simplicity, brake pedal application has been used for decades as an indication of driver's intent. It's not the best system, as can be seen in the posts on this thread, but it was the only practical method of automatically activating brake lights.

    With modern electronics, we could switch to accelerometer based brake lights, which activate with any significant deceleration. This would work with friction brakes, regenerative braking, engine braking, or any other method of slowing.

    Furthermore, if desired, accelerometer based brake lights could give an indication of the amount of braking. Brake light flash rate or pulse width could be modulated to indicate the amount of deceleration. For example, gentle slowing could produce quick, brief flashes of the brake lights, while a panic stop would be indicated by solid red.

    Accelerometer based brake lights would not show brake lights for a stationary vehicle. A vehicle not moving is not slowing, so no brake lights should be shown. However, and this is a big however, most of us expect to see brake lights when a vehicle is stationary in the road. Perhaps we also need a speed input to the brake light system.

    While this system could be an improvement, it is also a change. Changing anything in a safety system has its own set of risks as operators learn the new system, especially during the overlap period when the old and new must coexist on the same roadways.

    Tom
     
  13. dhanson865

    dhanson865 Expert and Devil's advocate

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    Don't eliminate the existing triggers. Make the change additive.

    That way you still have brake light on if someone has their foot on the pedal and you have brake light on if car is slowing due to any reason.

    Just because you add a speed based trigger doesn't mean you have to remove the other trigger(s)
     
  14. qbee42

    qbee42 My other car is a boat

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    You would still have false indications from brake riders. This includes the light regen group that posted in this thread.

    It would make sense to keep the existing trigger, but the logic might need to be a touch more complex.

    Tom
     
  15. vanbran

    vanbran Hmm....

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    I don't think you need sophisticated accelerometers, I think it's as simple as putting in something so that when the brake pedal is depressed hard the lights pulse or do something to draw attention.

    I see so many rear end collisions because someone decides to slam on the brakes when you don't expect it (ie. seeing a light turn yellow and panicking about being caught by the red light camera). I think a "I'm flooring my breaks now" light might help.
     
  16. dkelly

    dkelly Member

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    This simply isn't true if you have DRCC. It will brake (all the way down to 23 mph) with the brake lights a-glowin'.
     
  17. LTZR1

    LTZR1 Member

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    Then you're following too close ! The "system" is just fine as it is.
    No need to louse it up with totally unecessary complicatiions because of the incompetents behind the wheel. What needs modification is driver licensing comparable to what exists in Germany. They don't issue driver licenses out of Cracker Jack boxes there like they do here.
     
  18. dustoff003

    dustoff003 Blizzard Brigade #003

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    IDK about the options and packages up there in Canada, but if your car has DRCC when it brakes it will illuminate the brake lights. I have and use my DRCC daily rarely do I disengage it and use standard CC. I don't think standard CC will turn on illuminate the brake lights when it decelerates, I will check though.

    See my post above and dkelly's quote below.

    You are correct sir, thank you!
     
  19. vanbran

    vanbran Hmm....

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    Exactly! This whole brake lights thing is because getting in the Prius and seeing just how much people tailgate ME because they don't like the hybrid. I wont be stupid enough to run into the back of someone else, but if all it would take is a $5 switch that flashes my brake lights to tell that idiot behind me that I really am stopping and not to crash into the back of me then I'm all for it!
     
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