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Discussion Starter #1
I know with my MS taking your foot off the accelerator and letting the regen kick in would trigger the brake lights. On the Tesla it was easy to see since the instrument panel would show a depiction of your car with the brake lights on.

I‘m assuming this is how the I-Pace works, but since I haven’t driven in the dark yet, I haven’t been able to confirm that. Obviously this is the desired behavior to avoid being rear-ended.
 

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I had my wife follow me in our other car while testing when the brake lights turn on. In high regen the lights came on as soon as my foot lifted off the accelerator. In low regen the lights came on either when I applied the brakes or when the car decelerated to 4 or 5 MPH.
 

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Discussion Starter #5
I had my wife follow me in our other car while testing when the brake lights turn on. In high regen the lights came on as soon as my foot lifted off the accelerator. In low regen the lights came on either when I applied the brakes or when the car decelerated to 4 or 5 MPH.
This is what I would have assumed. I have my regen on high for one pedal driving, and as I lift my foot off the accelerator, braking is quite strong (assuming there isn’t a full charge). Now obviously you can gently ease up on the accelerator to come to a smooth stop and there the lights might not come on immediately.

This brings up an interesting question. Has anyone tried measuring range running the same course with regen set to high and then to low? I never tried that on the Tesla. It would be interesting to see if the added coast in low ups the range more than the additional energy recapture of high. Or it might be the other way around. The differences may be negligible, but who knows? I don’t recall this ever being addressed in BEV reviews.
 

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I've been using regenerative braking from the start as the first car I test drove had it setup (altho that salesperson didn't mention it at all and the one I bought from had no idea what I was referring to). One of the first things I did after getting my car (where regen was set to low) was to change to high and set vehicle creep to off, then test the brake lights after a friend asked me specifically how these were related. On a residential street one of us drove, the other watched and vice versa, to actually check that the brake lights did indeed come on- which they did- when removing ones foot from the pedal (accelerator seems somehow inappropriate now with one pedal driving).

After driving on a road yesterday with a 55mph limit (so 70+mph) with a stretch of stop lights, I was definitely curious as to when the brake lights were actually coming on and for what duration- intermittent? Continuous?. I watched the drivers behind me who seemed to be reacting normally to my car except for one who seemed stand-offish after the first light, perhaps due to the brakes only coming on when the pedal was more quickly removed? I need to have someone follow me while on the phone so that I can understand this in real time. I'd hate to be rear ended as that's my favorite part of the car. I always put my foot on the brake at stop lights just to be sure I am seen...early owner nerves. I'll have to also check if the brake lights stay on when stopped after stopping at a light to my test.
 

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2019 I-Pace HSE - Borasco Grey
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So having some spare time around home these days, I made a simple experiment rig for this anyone can easily duplicate. A good thing at the moment is traffic around my area is really light for such an experiment.

It turns out that the brakes light up pretty far around the side part of the brake light, and that part of the brake light isn't very far out of the mirror's view. So here's how to see when your brake lights come on:
  1. Take a cheap L bracket and tape a simple sturdy white extension to it... I used a folded business card and clear packaging tape.
  2. Put a masking tape base layer over the tail light in the area you see below to prevent the bracket from scratching the tail light
  3. On top of that base layer, using a stronger masking tape, firmly tape down the base of the bracket to the tail light, leaving the forward-most brake light LED uncovered so it can illuminate the card on the bracket. Place the white tab right behind the front-most brake LED as shown in the photo. Use your emergency flashers to verify its position if needed.
  4. Go for a drive in the dark, taking care to keep an eye on where you're going and not fixating on the mirror too much... or put the rig on the passenger side and have them call it out.
  5. The white card will glow somewhat dimly from the normal taillight (unless you tape over it in the area in front the card), but in either case, when the brakes lights come on the card will get clearly brighter as viewed from the mirror.
See photos at the end below.

For those not wanting to hack something like this themselves, the results were:
  • In Low Regen, letting off the pedal never triggered the brake lights at any speed regardless of how quickly or fully you let of the accelerator pedal (tested as high as 80mph), even as you rolled to a full stop
  • In High Regen
    • Letting off the pedal modestly does not trigger the brake lights until you are about halfway off the pedal. The point at which they turned on actually felt pretty correct to me. Looking at the speedo at the point they triggered seem to show a deceleration of roughly 2 mph per second at freeway speed and felt about half of what you get when all of the way off the pedal.
    • Letting off the pedal fully the brake lights pop on within a second and will stay on until the car rolls down to about 1 mph. Then they turn off unless you touch the brake to hold the car.
    • When using adaptive cruise on the freeway and normally approaching a slower car, deceleration is gentle enough that the brake lights do not come on (I tested with a "2-bar" following distance). I didn't test someone changing lanes in front of you causing a quick slowdown, but I'm pretty certain the lights would show if significant slowing occurred based upon observations from the G's I felt decelerating in high regeneration and were they caused the lights to come on.
4148


During this day picture it is hard to see in this photo, but just make sure you can see the taped-on tab from the mirror when sitting in a safe driving position.
4146


In a night time view, the red illuminated tab is very clear now. That's not an edited-in indicator in the center of the image, that's the real glow reflected from the tab.
(The orange light in the image is the mirror's blind-sport warning dot that shows when the car is still)
4147
 

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So having some spare time around home these days, I made a simple experiment rig for this anyone can easily duplicate. A good thing at the moment is traffic around my area is really light for such an experiment.

It turns out that the brakes light up pretty far around the side part of the brake light, and that part of the brake light isn't very far out of the mirror's view. So here's how to see when your brake lights come on:
  1. Take a cheap L bracket and tape a simple sturdy white extension to it... I used a folded business card and clear packaging tape.
  2. Put a masking tape base layer over the tail light in the area you see below to prevent the bracket from scratching the tail light
  3. On top of that base layer, using a stronger masking tape, firmly tape down the base of the bracket to the tail light, leaving the forward-most brake light LED uncovered so it can illuminate the card on the bracket. Place the white tab right behind the front-most brake LED as shown in the photo. Use your emergency flashers to verify its position if needed.
  4. Go for a drive in the dark, taking care to keep an eye on where you're going and not fixating on the mirror too much... or put the rig on the passenger side and have them call it out.
  5. The white card will glow somewhat dimly from the normal taillight (unless you tape over it in the area in front the card), but in either case, when the brakes lights come on the card will get clearly brighter as viewed from the mirror.
See photos at the end below.

For those not wanting to hack something like this themselves, the results were:
  • In Low Regen, letting off the pedal never triggered the brake lights at any speed regardless of how quickly or fully you let of the accelerator pedal (tested as high as 80mph), even as you rolled to a full stop
  • In High Regen
    • Letting off the pedal modestly does not trigger the brake lights until you are about halfway off the pedal. The point at which they turned on actually felt pretty correct to me. Looking at the speedo at the point they triggered seem to show a deceleration of roughly 2 mph per second at freeway speed and felt about half of what you get when all of the way off the pedal.
    • Letting off the pedal fully the brake lights pop on within a second and will stay on until the car rolls down to about 1 mph. Then they turn off unless you touch the brake to hold the car.
    • When using adaptive cruise on the freeway and normally approaching a slower car, deceleration is gentle enough that the brake lights do not come on (I tested with a "2-bar" following distance). I didn't test someone changing lanes in front of you causing a quick slowdown, but I'm pretty certain the lights would show if significant slowing occurred based upon observations from the G's I felt decelerating in high regeneration and were they caused the lights to come on.
View attachment 4148

During this day picture it is hard to see in this photo, but just make sure you can see the taped-on tab from the mirror when sitting in a safe driving position.
View attachment 4146

In a night time view, the red illuminated tab is very clear now. That's not an edited-in indicator in the center of the image, that's the real glow reflected from the tab.
(The orange light in the image is the mirror's blind-sport warning dot that shows when the car is still)
View attachment 4147
Thank you soooo much for the test and definitely the detail. I had my husband follow me (posted in another post) while we were both on the phone to each other. He indicated when my brake lights went on, which was never, as I was one-pedal driving and stopping. The only time they came on was when I pressed the brake pedal. Armed with your info, I need to a) test myself - or - b) get a new husband!! Just kidding!!! IF the brake lights still don't come on, then it is back to the dealer, who btw, told me they DO NOT come on unless I depress the brake pedal. Ever. This question was specifically asked when I bought the car. The salesman told me they DO come on when slowing down.
 

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Hey sis, make sure to go fast enough so that there's enough deceleration when you pull back on the gas pedal. Try 40 or 50 mph. Maybe you did that, in which case something's not right.
 

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Along with what sciencegeek said, keep in mind that in cold temperatures and/or high state of charge the regeneration is limited and might not decelerate enough to illuminate the brake lights similar to low regen setting.
 

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Also, you probably don’t want your brake lights coming on every time you lift off the accelerator, because it will drive the driver behind you crazy and possibly piss the person off. This happened to me when I first drove the IPace on the freeway. I didn’t realize lifting off illuminated the brake lights, which ultimately pissed off a Model S driver behind me. He decided to pass me and cut back in front of me forcing me to hit the brakes. Also, his tires kicked up a stone that left a permanent impact on my windshield.
 

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2019 I-Pace HSE - Borasco Grey
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Thank you soooo much for the test and definitely the detail. I had my husband follow me (posted in another post) while we were both on the phone to each other. He indicated when my brake lights went on, which was never, as I was one-pedal driving and stopping. The only time they came on was when I pressed the brake pedal. Armed with your info, I need to a) test myself - or - b) get a new husband!! Just kidding!!! IF the brake lights still don't come on, then it is back to the dealer, who btw, told me they DO NOT come on unless I depress the brake pedal. Ever. This question was specifically asked when I bought the car. The salesman told me they DO come on when slowing down.
I read back over your messages and don't see that you have confirmed that the car is set for high regeneration. On low regeneration the brake lights never come on. Just thought it would be worth double-checking in case you haven't already.
 
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