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Discussion Starter #1
Hello

I've had a Zoe for over four years and just realised I don't know something, and it's easier to ask here than it is to test it out for myself.

When the speed limiter is on, do the rear brake lights come on when the speed limiter causes braking? In the drivers' seat do I have any way of knowing if the limiter has turned the brake light on or not?

It's not an easy thing to work out for myself whilst driving...
 

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I would expect them to be independent.
The brake light will come on when the car is negative accelerating (slowing down) more than a certain value or the brake pedal is pressed (so the brake light may come on when you regen by just lifting your foot off the throttle). So if the limiter causes a sudden negative acceleration (so you accelerate hard to the limit speed, then it suddenly slows you down when you hit the limit) then I would expect the brake lights to come on.
 

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I don't think that Zoe will actually brake whilst using the speed limiter. I think it will just ignore how hard you are pressing on the pedal and not go any faster than the limit you have set. I think it is software driven. I think it will allow you to overspeed, but you should get a warning on the dash.

Personally I've never used it as I prefer to rely on cruise control when in those sort of situations.
 

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Co-author of CanZE. Q210 nov 2013
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TL;DR on OP's question: I am not sure.

The CC/SL only "operates" the accelerator. It will never engage the brake pedal. That does not mean it cannot decelerate, it surely can. Same as you taking your foot off. ZOE does not regen massively in that scenario, and it also depends on the temperature and SOC, but it sure does. Pressing the brake pedal does make for even more powerful regen braking (again, temp/SOC allowing), but this is not what the SL does. Ever. The consequence is that going downhill with SL can quite easily get you in overspeed. Friction braking only kicks in if regen can no longer provide the requested deceleration (and in two more edge cases).

As for the brake lights, AFAIK there is strict regulation based on deceleration. I have seen the numbers on this forum I think, but I admit I am too lazy to look it up. But as we know, almost all car related regulations have "valid starting date xxxx" clauses, so that might be an escape, see i.e. TPMS. Case in point: some drivers swear their brake lights come on in certain conditions while not touching the brake pedal. But I have never seen it on my old 2013 Q210. If that is all correct, at least in the older models non-brake-pedal regen could simply be limited to the upper bound of the then-current regulation. A mild support for that hypothesis is this: I am in the habit of when taking an exit from the highway, to simply let it coast freely, then regen without touching the brake pedal. If you know the exit well, this puts me at exactly the right speed at the traffic light or roundabout. This often puts a car right on my rear bumper.

Anyway, the speculative correct and not entirely complete answer (hehe) seems to be: brake lights depend on deceleration rate. Max deceleration rate on the SL might not ever reach the limit, by design, and dependent on model/firmware.
 

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Discussion Starter #5
Thanks yoh-there for the thorough answer, that's exactly what I was looking for.

My situation's not too dissimilar to your roundabout example. On my commute home, there's a long downhill section in a 30mph zone which I always use the speed limiter for. The angle of the hill is just perfect for the speed limiter keeping it at 30 (it occasionally rolls up to 32 and beeps, but not often). It certainly feels like there's active braking being done by the car, compared to just free rolling with no pedal press, but I wasn't sure.
 

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I have heard people say it can do on a very strong downward incline but have not seen it myself. If it's dark you can keep an eye on your rear view as the middle brake light tends to illuminate the parcel shelf a little.
 

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I don't think brake lights turn on during the day (headlights off, or headlights on but light-sensor says it's daytime). That's because 99% of the time there's an Audi 2mm behind me almost immediately.

When the light sensor tells the car it's nighttime however, the brake lights to do come on much much more often. That's because the Audi is then at 5mm distance. What I noticed is that when going uphill/downhill at night, without accelerating (mild regen), the brake lights do come on.

I don't hate Audi drivers, btw. Who am I kidding, ok, I do...
 

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Brake lights are triggered by a switch above the pedal mechanism. There's no way for the Speed Limiter to move the pedal, ergo no way for it to trigger the brake lights.
 

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Brake lights are triggered by a switch above the pedal mechanism. There's no way for the Speed Limiter to move the pedal, ergo no way for it to trigger the brake lights.
However, there is a requirement on level 3 regen and one pedal driving for the brake lights to show on deceleration.
 

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The Zoe will defo activate the brake lights under decelerations even if the brake pedal is not pressed

I have proved this

it will also keep the brake lights on after braking if the deceleration continues due to regen

JJ
 

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However, there is a requirement on level 3 regen and one pedal driving for the brake lights to show on deceleration.
We are taking about the Zoe - it doesn't have any levels or one pedal driving.

It seems the EU regulations are brake lights must be shown at -1m/s^2. My maths is rusty but i think that is slowing down ~2.2MPH per second.

Does the Zoe do that on regen without you pressing brake pedal? I had assumed it only came on with brake pedal and they selected low regen level to allow that setup and avoid complications.
 

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..Does the Zoe do that on regen without you pressing brake pedal? I had assumed it only came on with brake pedal and they selected low regen level to allow that setup and avoid complications.
yeah they defo come on

not on the flat v often but on a slight incline yes

also they defo stay on after you’ve applied the brake and released it if the car continues to slow at the specified rate

modern cars have accelerometers for many things like traction control and stability control

our mobile phones have lots too - just standard technology these days so the system knows what the system is doing

JJ
 

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I checked mine last night, after finding that if I lower the rear view mirror enough to see the "hump" where the rear wiper fits, the high level brake light reflects on the trim enough to see.

The brake light do come on under regen, but only on high deceleration. I took my foot right off suddenly (clear flat road) from about 40mph and brake lights definitely came on. Reducing speed using regen under normal conditions didn't trigger the brake lights.
 

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I did exactly want you did and could see the central brake light

sometimes the lights went off straight away, sometimes they stayed on for 3 or 4 seconds

uphill makes it easier to show but it does it on the flat as well

my only issue with this approach is that I don’t want to be seen as one of those drivers who “taps” the brake all the time when driving

JJ
 

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@Eclectic what car model is that? Just thought it would be a good idea if this is all standard or was introduced maybe later.
 

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I checked mine last night, after finding that if I lower the rear view mirror enough to see the "hump" where the rear wiper fits, the high level brake light reflects on the trim enough to see.
Funny enough I did same yesterday and can see as @Problemchild reported. Good to know 👍
 
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