This is perhaps a follow up with another thread about using the proper regenerative braking for the right road conditions. However, this thread is about the safety of Regenerative Braking on EV especially on the EQS.

I noticed that there were several incidents in which I saw people braking and swerving to the left or right behind me. I had on strong regen, and I thought, "Are people just memorized by the awesomeness of the rear end of my EQS that they forget to brake? Kidding aside, I decide to research and found several articles like this:
https://www.carscoops.com/2023/06/hy...ative-braking/
and this
https://www.consumerreports.org/cars...s-a9533519285/

Sure thing, when I let off the accelerator pedal with strong regen. there's no brake lights until about the low teens mph. So heads up guys/gals, don't use strong regen unless you are in heavy stop and go traffic. Use normal or intel regenerative braking.

On another note about Intelligent regenerative braking, I don't know what is the detection distances limit of the system in mode. It's safe to say that it CANNOT see as far as your eyes can see. Therefore, even with Intelligent regen., you HAVE to brake first unless the car in front has been there only a car lengths ahead for some time. If a stationary car is 1000ft away and you barrowing 60 mph at it, do not expect the intelligent regen. to slow you down. I'm still looking to see if there's any technical document on the limit of distance detection. I suspect that it is only about as far as the adaptive cruise detection.

 

Yup, it is something MB can address in a software update but they claim it is working as designed and meets regulations. Quotation from your article: “The brake lamp control is not a design element. It functions in compliance with regulations. Brake lamps are not required to illuminate while the vehicle is stationary and the brake pedal is not depressed.”

 

Spot on @MB37 . I had strong regen on, joined highway traffic and moved to the left lane of three. Traffic was moving at ~30 mph and the car ahead stopped at the brow of the road. Took my foot off the accelerator and was slowing with plenty of space to stop. Looked in the rear view mirror and saw that the guy behind was still approaching quite fast, so I accelerated then braked hard. He swerved to the left at the last second and stopped on the paved side of the road with the front of his car in line with my seating position. My short acceleration saved our bacon. If I had been in a lane where there was no space to the left or right it would have been a bad scene.

The brake light operation can be seen using the Assistance mode of the drivers display. At one point when regen is braking the brake light comes on then as the vehicle stops it goes off for between 10 to 20 seconds. This may meet regulations but is very dangerous. Yes, it could easily, and should be, addressed by a software change.

 

I would send this into NHTSA since this poses a real safety hazard. It takes only a few minutes:
https://www.nhtsa.gov/report-a-safet...le-information

 

THIS NOT TRUE!

You guys should refrain from posting false information. Those articles are about HYUNDAI.
Please for the love of god, do not equate a Mercedes to a freaking Hyundai/Kia.
Mercedes brake lights with regen work just fine. I assure you that people swerving around you is due to your bad driving or theirs.

Mercedes brakes lights operate by the brake pedal or a sensor that detects the rate of deceleration. (Normal regen is not enough and Strong regen is more than enough.)
This is the ONLY problem with MB implementation. Once the vehicle stops and is no longer decelerating,
If your foot is not on the brake pedal the brake lights will turn off until the car automatically applies the physical brakes after a few seconds.

We have discussed this here before and there is a video that clearly explains this. https://mbworld.org/forums/eqs/86665...uperation.html
See post 11 for how MB brake lights work.

When it comes to safety… Do not post false information as fact!

 

FYI, if you show the "Assistance" display on the driver's screen (i.e., the left-hand screen for most of us), then you can see the rear brake light of 'your' car in the display - so you can know when the rear brake light is (and isn't) on.

 

Excuse me, not false information. Do some driving with Strong Reg and even DISTRONIC. There is a short period just before the car stops and when it stops that the brake light was on, is then turned off, and then comes on again.

 

This is simply not true. I use strong regen all the time, have had my wife follow me to ensure that the brake lights come on, and they do. Now, When I get to the speed where creep mode takes over, they go off, and come on again if I hit the brakes. But they definitely come on when I ease the accelerator on my 450+, I see the reflection all the time in the grills of the cars behind me, and have never experienced an event such as is being described here. This is false information.

 

You have not stated your experience using the Assistance mode driver display. Please do that and report back.

All other aspects of this display, like left/right proximity sensor, simulated vehicles on either side, etc. all seem to be accurate. This leads me to believe that the brake light display is also correct.

I have no reason to provide false information, and would frankly like to hear that the assistance display is incorrect. The YouTube video, post #11, in the other thread explicitly describes what is should in the Assistance mode driver display.

 

Correction: My statement about the strong gen not displaying brake lights is inaccurate. Sorry for the oversight late at night / early morning. Let me elaborate. With my own testing under normal regen., the brake lights DOES NOT come ON with the EQS without actual brake pedaling. Under strong regen. at about 50 mph, the regen. kicks in and for after about a second and a half, the brake lights will come on until the accelerator pedal is pressed again or when it comes to a complete stop. Then it turns off. For that brief moment, the strong regen slows the car down about 5-7 mph from about 50 mph, and then the brake lights comes on (as seen from the assistance display). I am confident that CR's reporting of .15g brake light trigger is about right (I can't display the assistance and g force meter at the same time to verify, but my butt dyno is confident). However, in the real world of .15g deceleration and a delayed brake light, there's still a strong case for safety issue in the EQS. Allow me to explain:

I was driving about 55 mph on the freeway (traffic somewhat congested) with strong regen. A car was following me about 1 to 1.5 car length. I noticed an almost complete stop again. So I reacted with releasing the accelerator pedal, and the strong regen kicked in. After a quick realization that I still have room in the front, I lightly press on the accelerator pedal to cancel the strong regen. Within this 1 to 1.5 seconds saga, the car decelerated about 10 mph and I would estimate that the driver behind me only saw a tap of my brake light due to the delayed brake lights of the strong regen. To make the case worse, the driver may or may not have seen the split second brake light, but a huge decrease in speed was achieved due from the strong regen. and me light pedal the accelerator.

This type of incident happened to me 2 times within 2 days. I jokingly chalked it up to the mesmerizing rear end of an EQS. Perhaps it was some of that and some of it due to the delayed brake lights coming on in strong regen. Either way, I think if strong regen. is to be used, the brake light should come on IMMEDIATELY as soon as regen kick in. This is probably another reason why (aside from efficiency) we shouldn't use strong regen. in the EQS on the freeway.

 

I am in agreement with you regarding the assistance display. We probably need someone to do actual testing because it may come on as shown on the assistance display, but it is quite a delay. To decelerate at .15g and the brake lights not coming on immediately is just sloppy programming and frankly, as some of us have experienced, it's real safety issue.

 

Agree. On the conservative and safe side the brake light should come on with a couple of seconds of lifting off the accelerator, when in strong regen, AND should not turn off until the pedal is pressed again.

This turning off of the brake lights for a short time also happens when the car is stopped when using DISTRONIC.

 

Wow, you two are stubborn. I did actually make a video of this when we discussed it last in that thread but post 11 with that video cleared up the discussion so there no longer a need for my video.

The brake lights come on IMMEDIATELY after I take my foot off the go pedal.
​​​​​​​

 

This is like two ships passing in the night, we seems to be focused on different things.

Your video clearly shows the brake lights turning off just before the car comes to a complete stop, and seconds after coming back on. That is the issue!!!!! It should stay on.

It is my recollection, but I could be wrong, that in some situations the brake light does not come on immediately after lifting off the accelerator, but very shortly after. I really don't care if this is immediate or a couple of seconds later as it is not a safety issue unlike the first item. I previously said that it should and if it does then that is great. Will test this later today and post my experiences.

 

Yes, that is well established and a known fact.
As mentioned several times before, it’s based on deceleration. Once the vehicle stops decelerating, if the foot is not on the brake pedal, the lights will turn off.
YOU ARE WRONG!!

 

Lol, this guy busts out a drone in follow-mode hah. This forum is awesome. It looks like upon deceleration (with regeneration) the brake lights activate as we would all want/expect.

But, I also see something I wasn't expecting... which is once the car comes to a halt... then brake lights actually stop illuminating even though the vehicle is stationary. But at the 50-seconds mark, the brake lights turn back on while the vehicle is stationary. Is this because you purposely stepped on the brake pedal at the 50 second mark?

I guess this is one of the things where Tesla seems to have set a precedent that has become the norm even if its not intuitive. Tesla (and their proponents) swoon over the one pedal driving. This means an operator who lifts off the accelerator will cause the vehicle to begin slowing down (through regeneration) and the brake lights turn on. And also, once the vehicle comes to rest, Teslas will activate disc brakes to hold the vehicle stationary. This activation of the brake booster will cause the brake lights to remain illuminated once the vehicle is at rest, even if the brake pedal is not depressed.

However, Mercedes does not tout a "one pedal" driving mode. So, what I think Mercedes does is use regeneration to bring the vehicle to a halt, but then expect the operator to step on the brake pedal to activate the disc brakes and the brake lights. I can see why some people may feel this is an issue, since the Tesla status quo is that a strong regeneration/recuperation driving experience is now "one pedal" where touching the brake isn't necessary. Personally, since our previous two vehicles were Teslas, I habitually do not touch the brake pedal when I'm in Strong Recuperation and the vehicle is stationary. I can see this as a possible safety concern since now my brake lights aren't illuminated even if the vehicle is at rest.

 

Brake lights not being illuminated when vehicle is at rest and foot is not on brake is also the case on many ICE cars.

 

The green ready thing was bugging me initially -- like does MB think I'm so fookin' stoopid I don't know I'm driving right now and not parked at a red light? -- but I guess they're mimicking the hold function of a gas car. The power meter on mine even goes down when I depress the brake pedal a little further, like activating hold. It'll hover around 7% or so otherwise, even though I've completely stopped (creep mode off).

I guess I'm lucky this is my first EV in a way as I have no clue what real one pedal driving is like so that hasn't been an issue for me.

 

And I bet most of these people did not go through driver-ed in high school ;-)

 

ICE cars creep forward if the vehicle is in gear. So operators of ICE will hit the brakes to hold the vehicle at a standstill. Even people who put a ICE car in neutral, clutch in, or park at a red light will usually have their foot on the brake as well.

The Mercedes EQ holding steady without the brake lights being illuminated is a more recent thing. Personally I am surprised the EQ doesn't just activate the hydraulic brake booster when the vehicle is at rest and no pedal is depressed. Would solve for all scenarios one way or another.

But maybe the concern is that by default the EQ settings enable a forward creep; so Mercedes assumes the EV operator is driving the vehicle like ICE? I turn off forward creep in the EQS via settings and BMW i4 via the gear selector. And I just naturally assumed the vehicle applied the brake lights when stationary because I was used to what Tesla does.

 

Hope you have had a coffee and have settled down by this. No need for shouting.

I did some tests with my EQE SUV. Maybe it operates differently from the EQS, but I am not wrong about what I recall happening and what is displayed in the Assistance mode on my car.
1. The brake light comes on about 1 second after completely lifting off of the accelerator pedal, either at low speed of high speed.
2. I can crawl in traffic, lift off the accelerator pedal for a short while and then gently pressing it again and the brake light never comes on.

Neither of these two operations bother me. Is the operation in the EQS really different to the EQE? I really don't care.

What does bother me is the other situation that has been hotly discussed and we all seem to be in agreement about.

 

Thats what I thought. Mercedes was not mentioned. I believe Hyundai already resolved it too.

 

I have explained this several times. My car has creep mode enabled. Once the regen braking slows the car to the speed when creep mode takes over, the brake light goes out (what, 5mph?). Then you hit the brakes if you have to come to a complete stop, and the brake lights come back on. Or, you can turn off creep mode, and this will not happen until you come to a complete stop and put your foot on the brake. This is not rocket science. But, I can assure you that in strong regen, the brake lights come on as soon as the car starts braking when I back off the accelerator. My wife has followed me to ensure that this happens. There is no question about it. I have done this every day for two years in traffic. Ya'll have a good day.

 

I would advice not to come too quick to a conclusion about someone's experience.

I, too, have done testing on my EQS AMG. I picked an empty road, set my HUD to power, the driver display to assistance display, and the center console to the IWC stop watch. In strong regen, I drove 55 mph. I released the accelerator pedal at the same time I press the start button on the IWC. As soon as the brake light came on in the assist display, I press the stop button. On 3+ trials, I got a time delay of 1.64, 1.87, and 1.76 seconds and etc.. Nothing under 1.5 seconds. My fingers was no more than a few centimeters from the button. Even if you account for my delay reaction, which is .07 to .14 of a second, the brake lights are delayed on average 1.5+ seconds AFTER the release of the accelerator pedal (which is the immediate start of the strong regen.) to the time the brake lights come on. The assumption is that a strong regen produces -.15g.

In that 1.5 seconds timeframe, the car behind you has travelled 120 feet (55mph) before it sees the brake lights come on. Fortunately, your 55 mph has slowed to a 50 mph when the brake lights comes on. That puts a closer gap of 11 ft before the person behind sees your brake lights. Below is the calculation, but because I'm not a physicist by trade or mathematician, please check my calculation.

55 mph = 80.66 ft/sec
50 mph = 73.33 ft/sec
5 mph delta =7.33 ft/sec; *1.5 = 10.995 ft travelled
Using an online linear motion calculator, a -.15g deceleration for 1.5 seconds at 55 mph will result in 50.1 or 50 mph (assuming that a strong regen produce a .-15g deceleration.).

If you want to test this for yourself, have a blind test with a friend following you at 55 mph at about 1.5 car length and post a video of his/her reaction. I'm interested to know.

 

I agree that brake lights come on on strong regen. but the ~1.5 seconds delay at 55 mph is my issue. Why not have it come on as soon as you release the accelerator pedal in strong. regen? I also did further test on the intel. regen., but the algorithm on when the brakes are applied/brake lights come on, the speed of travel, and the distance of the car in front comes into play which as a result, sometimes the green pedal icon comes on but the brake lights are delay anywhere between 1 seconds to 3-5 seconds.