Regenerative braking and degenerate tailgaters

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#1
Alright, so I've never driven a Tesla, but I just know and decided I'm gonna go with it.

Also, I've been rear-ended twice in my life from complete stops; one of those times being potentially life/death to my and their passengers if it wasn't for seatbelts (some dumbie tourists at a drawbridge).

I've been able to observe some Model S's and X's on the road, and haven't found anything exact, but my question is:

When do the brake lights come on when regen decelerating?

I'd presume they would naturally come on at some point without touching the brake pedal for the 3, right? I felt a bit nervous seeing one Model S in particular in traffic with minimal brake lightings, and general Florida drivers behind him..
 

SoFlaModel3

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#2
Alright, so I've never driven a Tesla, but I just know and decided I'm gonna go with it.

Also, I've been rear-ended twice in my life from complete stops; one of those times being potentially life/death to my and their passengers if it wasn't for seatbelts (some dumbie tourists at a drawbridge).

I've been able to observe some Model S's and X's on the road, and haven't found anything exact, but my question is:

When do the brake lights come on when regen decelerating?

I'd presume they would naturally come on at some point without touching the brake pedal for the 3, right? I felt a bit nervous seeing one Model S in particular in traffic with minimal brake lightings, and general Florida drivers behind him..
I would be under the impression (read as I don’t know for sure) that the brake lights only come on if you step on the brake pedal.

If I think back my days of driving manual transmission vehicles. The brakes lights never came on as I rowed through the gears to slow down without touching the brake pedal.

Curious to see if there is a definitive confirmed answer here...

Side note my dad instantly put his car into Creep Mode :(
 
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#3
It seemed that way with an older (2013ish? yet very clean) Model S that the brake light only ever came on when he was going 10mph to 0mph...

Definitely a design flaw if they haven't fixed it in my opinion, because... damn son... We still have the potential for human error on these streets.
 

Bokonon

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#5
EDIT: Petra beat me to it!

The car has an accelerometer that triggers the brake lights to illuminate if the force of deceleration exceeds a certain number of Gs. Most EVs with a strong regen mode work this way, and Tesla's vehicles are no exception.

(Oddly, the first-generation Volt I used to drive was an exception... and driving in L mode almost got me into trouble a couple of times...)

EDIT 2: My parents are Tesla owners, and I think I remember my dad pointing out that you can tap on the T button on the touchscreen to see a real-time rendering of your car (including the current state of the headlights, brake lights, etc.). Presumably, if you were to open this screen while driving, you could get a sense for the level of deceleration required to illuminate the brake lights... Can any of you Model S/X owners confirm whether this is still possible?
 
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Petra

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#6
EDIT: Petra beat me to it!

The car has an accelerometer that triggers the brake lights to illuminate if the force of deceleration exceeds a certain number of Gs. Most EVs with a strong regen mode work this way, and Tesla's vehicles are no exception.

(Oddly, the first-generation Volt I used to drive was an exception... and driving in L mode almost got me into trouble a couple of times...)

EDIT 2: My parents are Tesla owners, and I think I remember my dad pointing out that you can tap on the T button on the touchscreen to see a real-time rendering of your car (including the current state of the headlights, brake lights, etc.). Presumably, if you were to open this screen while driving, you could get a sense for the level of deceleration required to illuminate the brake lights... Can any of you Model S/X owners confirm whether this is still possible?
The toy car graphic that first showed up in the instrument cluster display in software v7.0 shows brake light activation in real time.
 

3V Pilot

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#7
I've driven a couple of Model S/X and one lucky drive in the 3. I can confirm that the display shows the brake light activating without touching the pedal in the S and X. I didn't happen to look for it in the Model 3 but I'd be surprised if it didn't happen that way. They really did think of everything when they built this car and you can feel that in every detail.
 

MelindaV

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#8
would be under the impression (read as I don’t know for sure) that the brake lights only come on if you step on the brake pedal.
The regen does turn on the brake lights. I’d seen something before that it will depend on the rate of deceleration. If anything I’ve seen posts from tesla owners who feel the car will switch on he brake lights too early, making it appear they are riding the brakes.
 

SoFlaModel3

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#9
The regen does turn on the brake lights. I’d seen something before that it will depend on the rate of deceleration. If anything I’ve seen posts from tesla owners who feel the car will switch on he brake lights too early, making it appear they are riding the brakes.
Very interesting ... time to play with my dad’s car next time I take it out (possibly tomorrow night!)
 
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#11
The brake lights come on during regenerative braking once the rate of deceleration crosses a certain threshold, it's not speed driven. It is possible to modulate the accelerator pedal in such a way as to slow without activating the brake lights.
This is awesome to hear. :D

I looked at a model S manual on it, and it's not specific, but would anyone know by any chance or rough guess more specificly when they would kick on? Like say a 15 mph drop within a certain time frame from a faster speed, to maybe 10 mph drop within that time at a more moderate speed, or some way like this?

Either way, that's quite the relief! I suppose my brief experiences of noticing them not come on was more due to the slower speeds and traffic. But to this day I still can't help but cringe when looking at a guy behind me in the rearview slowing down a little too late for my tastes :eek:
 

3V Pilot

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#13
This is awesome to hear. :D

I looked at a model S manual on it, and it's not specific, but would anyone know by any chance or rough guess more specificly when they would kick on? Like say a 15 mph drop within a certain time frame from a faster speed, to maybe 10 mph drop within that time at a more moderate speed, or some way like this?

Either way, that's quite the relief! I suppose my brief experiences of noticing them not come on was more due to the slower speeds and traffic. But to this day I still can't help but cringe when looking at a guy behind me in the rearview slowing down a little too late for my tastes :eek:
I can't give exact deceleration rates when they activate but I can tell you that when I have driven a Tesla and came fully off the gas pedal from even 35 mph the brake lights came on immediately. I'm sure that I couldn't of activated them quicker by attempting to get to the brake pedal. They are very responsive at speed. I imagine if your driving slower and the rate of decel is less then maybe they would not activate as quickly but I haven't played with the enough to know how slow you'd have to go.

I'm with you on the concern of a rear-end collision though, many years ago I was rear-ended in a police car no less from a guy who was passed out at the wheel. I saw him coming, saw the guy behind me get out of his way and figured I'd "take one for the team"....you know, protect and serve all...lol. Anyway one great things about a Tesla is it's ability to avoid things due to instant torque, like this:

https://techcrunch.com/2016/11/18/w...t-speed-avoid-a-potential-rear-end-collision/
 
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#14
I can't give exact deceleration rates when they activate but I can tell you that when I have driven a Tesla and came fully off the gas pedal from even 35 mph the brake lights came on immediately. I'm sure that I couldn't of activated them quicker by attempting to get to the brake pedal. They are very responsive at speed. I imagine if your driving slower and the rate of decel is less then maybe they would not activate as quickly but I haven't played with the enough to know how slow you'd have to go.

I'm with you on the concern of a rear-end collision though, many years ago I was rear-ended in a police car no less from a guy who was passed out at the wheel. I saw him coming, saw the guy behind me get out of his way and figured I'd "take one for the team"....you know, protect and serve all...lol. Anyway one great things about a Tesla is it's ability to avoid things due to instant torque, like this:

https://techcrunch.com/2016/11/18/w...t-speed-avoid-a-potential-rear-end-collision/
Thanks a lot man, all around! And damn is that a legit video!
 

3V Pilot

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Thanks a lot man, all around! And damn is that a legit video!
When that video first came out some articles made it sound like the Tesla Autopilot saved the day but I believe in the end the driver got the credit for quick reaction. With only ultrasonic sensors at the rear of the car I don't think it could of avoided this on it's own. Someday when we all have self driving cars and they all talk to each other then rear-end collisions (and almost all others) will be a thing of the past!
 

MelindaV

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#16
this post on reddit notes the Model S manual used to state the lights would come on when Regen was at 40kW or greater. Others responded saying it activates the brake lights at slow speed with less than 40kW as well... but for generalizations, that is probably a good starting point.
 

SoFlaModel3

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#19
Took out my dad’s Model S for date night tonight with my wife and we tested some things...

1) My profile no longer has creep — love this! Makes me feel like I’m driving a stick again

2) Regenerative braking from low to standard. Awesome! Note the brakes lights come on pretty quick but it seemed like it was well timed.

3) We finally figured out “More Cow Bell”. That sheer joy makes me want EAP now