Brake lights during recuperation?

[Tooney]

At high speeds, when Taycan is suddenly decelerated by adaptive cruse control when vehicle ahead crosses into lane, do the brake lights come on?

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[WuffvonTrips]

I doubt that any brake lights will come on by lifting off even at very high speeds without any regen. And the deceleration is not high at that stage.

I tried Vmax on the German Autobahn and just let the car coast from 255 km/h and did not feel anything different from rolling along in an ICE car in Neutral.

We need a test- reset the inbuilt g-meter, regen set to "on", lift off accelerator at around 70mph and see what the highest deceleration g force is reported. The regs mandate that the brake lights must come on when 0.13 g's are reached (converting from the m/s^2 values in the regs), and must not come on below 0.07 g's.

 

[WuffvonTrips]

I've now found this video review that does the test I suggested- unfortunately without the g-meter displayed, but it shows deceleration from 69 to 63 mph in 4 seconds (taken from the YouTube timestamp, which isn't the best chronometer), which is 1.5 mph per second, or 0.67 metres per second per second- which is below the brake light threshold of the regulations.

It might be that this regen setting would give enough deceleration to trigger the lights from a much higher speed.

IIRC from videos of auto-regen driving, that can cause enough deceleration to trigger the brake lights even from lower speeds.

(The section starts at 6:24 in the video)

 

[W1NGE]

At high speeds, when Taycan is suddenly decelerated by adaptive cruse control when vehicle ahead crosses into lane, do the brake lights come on?

I would expect so.

 

[mjw930]

At high speeds, when Taycan is suddenly decelerated by adaptive cruse control when vehicle ahead crosses into lane, do the brake lights come on?

Yes, they do as do all cars with adaptive cruise whenever the deceleration exceeds a programmed threshold that we should assume is based on regulations.

 

[Scandinavian]

At high speeds, when Taycan is suddenly decelerated by adaptive cruse control when vehicle ahead crosses into lane, do the brake lights come on?

Yes absolutely. That is the same as putting your foot on the brake!

 

[xyeahtony]

I would wager it doesn't, but i have no idea what i'm talking about. Do post some real world answers.

I'd imagine it be just like driving a car with a manual transmission. When you let off the gas while in gear, the car will also slow down from engine braking and the brake lights never turn on then.

 

[WasserGKuehlt]

I'd imagine it be just like driving a car with a manual transmission. When you let off the gas while in gear, the car will also slow down from engine braking and the brake lights never turn on then.

It's slightly different, as that is deceleration induced by compression (a purely mechanical phenomenon), which you'd only be able to detect with an accelerometer. The regen braking is software-controlled, which would have to account for the possibility of exceeding the federally-mandated threshold for triggering a braking signal. Note that throughout here, we should assume it's the 'auto' regen type - as based on my observations the deceleration caused by static regen is far below the min threshold.

Unfortunately finding that federal standard proves to be non trivial. I've found many references to a set of thresholds (see @WuffvonTrips post earlier) but not from an authoritative (in US) source.

 

[Archimedes]

I’m talking about standard regen, not auto regen or actual brake pedal use.

When I lift, I’ve always assumed that the brake lights don’t illuminate.

 

[Tooney]

I just read the posts related to this in the other thread. Thanks to @WasserGKuehlt and @WuffvonTrips.
My takeaway from what I read so far:
If Taycan complies with UN regs, brake/stop lights should be activated without the driver pressing the brake pedal when an automatic system such as auto regen, or adaptive cruise control, causes the car to decelerate over a certain rate.
Has anyone here confirmed this brake/stop light activation is what happens?

 

[WasserGKuehlt]

Has anyone here confirmed this brake/stop light activation is what happens?

This is what @Archimedes is trying to do; the theory here being that (constant) regen should not, but auto regen might. Popcorn at the ready..

 

[Archimedes]

This is what @Archimedes is trying to do; the theory here being that (constant) regen should not, but auto regen might. Popcorn at the ready..

Actually, I don’t care about auto regen or ACC. Just want to confirm that when I lift off under standard regen, my brake lights don’t illuminate.

 

[Tomato]

I have my rear dash cam pointed down where I can see the red glow from the brake light and can confirm that the brake light doesn't come on when you lift off the acceleration in recuperation ON mode.

It also doesn't light up when you have it in AUTO mode even when it slows down from 80mph to 60mph. I tried accelerating to 80mph behind a car going 60-65mph on the freeway and let the auto recup slowed the car down.

However, brake light will light up when the car is slowed down with ACC even if the rate of deceleration is lower than with recuperation in auto mode.

 

[WasserGKuehlt]

Actually, I don’t care about auto regen or ACC. Just want to confirm that when I lift off under standard regen, my brake lights don’t illuminate.

I didn’t say that was your theory ? - it was mine, and was hoping your observations would (dis)prove it. Looks like @Tomato settled it, though.

 

[whitex]

Actually, I don’t care about auto regen or ACC. Just want to confirm that when I lift off under standard regen, my brake lights don’t illuminate.

I just confirmed that few minutes ago. Lifting off at ~55-60mph, brake lights don’t go on with regen (Sport Mode). I was able to observe some lane divider reflectors in the rear view mirror which clearly lit up when I hit the brake pedal.

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