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Discussion Starter · #1 ·
I asked this question before in another thread, and one member suggested I should try engaging the regen in an alley to see if I can see the reflection of the brake lights. Unfortunately, I don't have any alleys handy nearby, and even if I did, I would have to be driving pretty swiftly for an alley since the regen won't even work under 7mph.

So I thought I'd ask again if anyone knows this, since I've had the car for the better part of a year and have always been curious about this. Part of me thinks they should come on for safety's sake, but another part of me doesn't want people to think I'm a horrible driver riding the brakes constantly down a hill. I also don't know if the brake lights come on in other EVs/PHEVs when using regen.

Thanks in advance!
 

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another part of me doesn't want people to think I'm a horrible driver riding the brakes constantly down a hill.
Edit - my comments below are about regen as used by ACC. I now realize that you might be referring to just using the paddles. Using the paddles for regen does not turn on the brake lights in my experience. One person claimed that they do sometimes come on when using the paddles, but I would think that is rare because I have never seen it.

(my original comment about ACC)

I was really happy with ACC (radar cruise control) and used it all the time, until I discovered that the brake lights often flash which is embarrassing, and also annoying to other drivers. The terrain where I live is I guess what you would call gently rolling hills, some of it is flat but most of the time I am going either slightly uphill or slightly downhill. After the car passes the "peak" of a particular rise the descent starts, causing the speed to slightly increase. ACC overreacts, instead of just backing off the throttle it momentarily does some heavy regen which causes the brake lights to come on. A fraction of a second later it seems to realize that the slope isn't that steep and it reduces the regen to normal level, unfortunately by then the brake lights have already flashed, and I often notice the car behind me starts to go around me, not because I have slowed down because I haven't, but because of the brake lights flashing. There are often no cars in front of me when this happens, so the driver behind me must think I am drunk or something for hitting the brakes for no reason.

This can also happen on flat ground if I am following another car and if they start to slow down a little, again ACC overreacts to the situation, even though I have plenty of distance between the car in front of me, and even though the car in front only slightly slowed down, there is a momentary heavy regen and flash of the brake lights.

It is the single most disappointing thing about my Clarity. I have tried all the different settings but nothing changes this behavior, so if I want to use ACC I have to accept that the people around me think that I am either drunk or an idiot. I guess the only positive is that people behind me don't follow as close, or they go around me, as most people seem to get nervous if the car in front of them is hitting the brakes for no reason.

Just to note that the overall operation of ACC is smooth, I don't actually feel these momentary overreaction slowdowns as they are so brief, which is why for the first two years I drove in ignorant bliss and was very happy with ACC. Until I started noticing this very unfortunate brake light behavior. I still use ACC but not as often.
 

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Discussion Starter · #3 ·
Edit - my comments below are about regen as used by ACC. I now realize that you might be referring to just using the paddles. Using the paddles for regen does not turn on the brake lights in my experience. One person claimed that they do sometimes come on when using the paddles, but I would think that is rare because I have never seen it.

(my original comment about ACC)

I was really happy with ACC (radar cruise control) and used it all the time, until I discovered that the brake lights often flash which is embarrassing, and also annoying to other drivers. The terrain where I live is I guess what you would call gently rolling hills, some of it is flat but most of the time I am going either slightly uphill or slightly downhill. After the car passes the "peak" of a particular rise the descent starts, causing the speed to slightly increase. ACC overreacts, instead of just backing off the throttle it momentarily does some heavy regen which causes the brake lights to come on. A fraction of a second later it seems to realize that the slope isn't that steep and it reduces the regen to normal level, unfortunately by then the brake lights have already flashed, and I often notice the car behind me starts to go around me, not because I have slowed down because I haven't, but because of the brake lights flashing. There are often no cars in front of me when this happens, so the driver behind me must think I am drunk or something for hitting the brakes for no reason.

This can also happen on flat ground if I am following another car and if they start to slow down a little, again ACC overreacts to the situation, even though I have plenty of distance between the car in front of me, and even though the car in front only slightly slowed down, there is a momentary heavy regen and flash of the brake lights.

It is the single most disappointing thing about my Clarity. I have tried all the different settings but nothing changes this behavior, so if I want to use ACC I have to accept that the people around me think that I am either drunk or an idiot. I guess the only positive is that people behind me don't follow as close, or they go around me, as most people seem to get nervous if the car in front of them is hitting the brakes for no reason.

Just to note that the overall operation of ACC is smooth, I don't actually feel these momentary overreaction slowdowns as they are so brief, which is why for the first two years I drove in ignorant bliss and was very happy with ACC. Until I started noticing this very unfortunate brake light behavior. I still use ACC but not as often.
That's unfortunate about ACC, but yes, I was referring to the paddles. It seems odd that ACC would engage the brake lights but not the paddles, since 4 chevrons-worth of regen can be pretty severe (though not nearly as much so as some EVs I hear).

It seems to me that brake lights should engage based on a certain g-force, rather than any amount of slowdown from regen, but that may have cost a lot more to engineer.
 

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ACC should engage the brake lights when it's maintaining speed downhills. Far too many people speed up going downhill and the brake lights alert them to the fact that you're not speeding up.
 

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That's unfortunate about ACC, but yes, I was referring to the paddles. It seems odd that ACC would engage the brake lights but not the paddles, since 4 chevrons-worth of regen can be pretty severe (though not nearly as much so as some EVs I hear).

It seems to me that brake lights should engage based on a certain g-force, rather than any amount of slowdown from regen, but that may have cost a lot more to engineer.
"It seems to me that brake lights should engage based on a certain g-force, rather than any amount of slowdown from regen..."

This is exactly how the brake lights work in our Chevy Bolt. I would not be surprised if it's also how the Clarity works, but I've not "run the experiment".

The regen on the Bolt is far more aggressive than on the Clarity. You can literally drive around town without using the brake pedal at all, while in "L" mode.
 

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That's unfortunate about ACC, but yes, I was referring to the paddles. It seems odd that ACC would engage the brake lights but not the paddles, since 4 chevrons-worth of regen can be pretty severe (though not nearly as much so as some EVs I hear).

It seems to me that brake lights should engage based on a certain g-force, rather than any amount of slowdown from regen, but that may have cost a lot more to engineer.
ACC is capable of much stronger regen than the maximum 4 chevrons using the paddles. You can see this by watching the power meter. It is understandable, expected, and desirable that the brake lights are activated when ACC uses stronger regen.

The issue is that ACC uses more regen than is needed for a fraction of a second in the situations that I describe. During that fraction of a second regen reaches a level that activates the brake lights, then quickly subsides. It happen so fast that you normally don't even feel it.

What I suspect happens is that when the computer detects that the car is speeding up because of a downhill, or the car in front of you is slowing down, it takes some number of milliseconds for the system to process the change in speed, and calculate whether it needs to use regen or merely back off the throttle. My guess is that in the first few milliseconds while it is deciding what to do, it proactively starts initiating hard regen just to be safe, then a few milliseconds later the calculations complete and it decides it can back off on regen. But by this time it's too late because the brake lights have already activated. And it seems they don't flash, they stay on for about a second or so even after regen has backed off. Apparently they programmed in a minimum time that the brake lights will display whenever activated by ACC.

In my opinion, during that fraction of a second while it is still evaluating the situation it should simply pull the throttle all the way back while it waits for the calculations to complete. None of these are anywhere near dire situations. When you start a gradual downhill (and I mean very gradual you actually still need some throttle) what happens is the car doesn't realize that you are starting to head downhill (apparently it does not have accelerometers programmed to detect this). So it blunders along for a few seconds at the same throttle setting so naturally the speed starts to slightly increase. It seems to catch it off guard as it suddenly realizes that the speed is increasing and this is what causes it to overreact briefly with regen while it evaluates what is going on. Same thing on level ground when there is plenty of space in front of you, then the car in front slows down slightly. Pulling back slightly on the throttle is all that is needed, but again it overreacts for a fraction of a second by using regen.

Theoretically it can be argued that they are doing it the safest way. But in my experience many software programmers (or whoever it is who makes the decisions) are afraid of using their judgment and just go with what is theoretically the safest because they feel they don't have any risk of criticism choosing what is theoretically the safest approach, even if it may not be the best. Sort of like the old adage, "Nobody ever gets fired for buying IBM". The typical attitude is that maybe it's one in a million there would be a problem, but let's just go ahead and do it this way and remove that one in a million chance. If I was in the discussion I would point out that activating the brake lights for no reason adds its own risk of causing an accident, if someone is on a straight road in clear weather and for no reason activates their brake lights, this can surprise the car behind them and possibly cause them to overreact and hit their brakes.

This seems to be a Honda quirk, or at least a Clarity quirk. I sometimes see other cars brake lights flash for no reason, which I assume is caused by their cruise control. But it's fairly rare. Whereas it typically happens multiple times per drive for me.
 

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It seems to me that brake lights should engage based on a certain g-force, rather than any amount of slowdown from regen
Here is the law on it for electric vehicles using regen:

"Electric regenerative braking systems as defined in paragraph 2.17., which produce a retarding force upon release of the accelerator control, shall generate the signal mentioned above according to the following provisions:

Less than or equal to 0.7 m/s² The signal shall not be generated

Greater than 0.7 m/s² and less than 1.3 m/s² The signal may be generated.

Greater than 1.3 m/s² The signal shall be generated"

Meters per second squared is a little hard to relate to, so I converted it to the change in mph per second which is more relatable.

Less than or equal to 1.5 MPH deceleration per second - The signal must not be generated

Greater than 1.5 MPH deceleration per second - The signal may be generated

Greater than 3.0 MPH deceleration per second - The signal must be generated

I'm not sure where Clarity falls in this but it's somewhere between 1.5 and 3.0 mph per second.
 

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Discussion Starter · #8 ·
ACC is capable of much stronger regen than the maximum 4 chevrons using the paddles. You can see this by watching the power meter. It is understandable, expected, and desirable that the brake lights are activated when ACC uses stronger regen.
I have only used ACC sparingly, and I have never experienced aggressive regen using it, just a light slowdown when vehicles in front of me are moving slower than my set speed. Such a system is new and scary to me (to paraphrase Phil Hartman's Unfrozen Caveman Lawyer), so I haven't put my life in its hands to the fullest extent of its capabilities. ACC wouldn't aggressively brake if a car in front of me came to a sudden stop, would it?
 

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I have only used ACC sparingly, and I have never experienced aggressive regen using it, just a light slowdown when vehicles in front of me are moving slower than my set speed. Such a system is new and scary to me (to paraphrase Phil Hartman's Unfrozen Caveman Lawyer), so I haven't put my life in its hands to the fullest extent of its capabilities. ACC wouldn't aggressively brake if a car in front of me came to a sudden stop, would it?
"ACC wouldn't aggressively brake if a car in front of me came to a sudden stop, would it?"

ACC absolutely does brake very aggressively, if necessary. I play with it in traffic, to see how effective it is. As long as the Clarity doesn't stop entirely for more than about three seconds, ACC can drive the propulsion aspect of the car entirely by itself. It's fascinating to watch/experience.

It makes driving in stop-and-go traffic far less fatiguing.
 

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"ACC wouldn't aggressively brake if a car in front of me came to a sudden stop, would it?"

ACC absolutely does brake very aggressively, if necessary. I play with it in traffic, to see how effective it is. As long as the Clarity doesn't stop entirely for more than about three seconds, ACC can drive the propulsion aspect of the car entirely by itself. It's fascinating to watch/experience.

It makes driving in stop-and-go traffic far less fatiguing.
In winter slick conditions I set ACC's following distance to one of the two longer distances and put the car in Eco mode. This allows it to restart smoothly on slick roads as well as stop smoothly. As EV Nerd says, it's amazing to watch and makes driving far easier.
 

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In winter slick conditions I set ACC's following distance to one of the two longer distances and put the car in Eco mode. This allows it to restart smoothly on slick roads as well as stop smoothly. As EV Nerd says, it's amazing to watch and makes driving far easier.
I really like ACC other than the fact that it makes other drivers think I'm intoxicated for flashing the brake lights for no apparent reason.

One way I know they are flashing besides seeing the reflection sometimes at night in my rear view mirror, is that I can hear it. Sometimes while driving in ACC I noticed a faint click sound coming from the driver's footwell. Then I began to realize that I also hear the same sound whenever I press the brake pedal. I soon figured out that it's a switch of some type that controls the brake lights, which I confirmed by looking in the rearview mirror and seeing that the click sound corresponds to brake light activation. I can make it click (and activate the brake lights) with an extremely light press of the brake pedal, not pressing hard enough to actually slow the car. I assume that's following a regulation that any press of the brake pedal, no matter how light, must activate the brake lights. Whereas regen mode has to follow the separate guidelines based on deceleration rate.

In ACC when regen is strong enough I hear the click, and if it's dark enough outside I see the brake lights. This is when I began to realize that it does it way more often than I thought, and often at times that are completely unnecessary. I don't know if my brake light switch is extra noisy, or if I have bionic hearing, or if other people are better at tuning out weird little click sounds than I am. But next time you are driving try lightly pressing the brake pedal and see if you hear the click, ideally when you are somewhere where you can see if the brake lights are being activated simultaneous with the click. Actually the garage would be a good place to try it.
 

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just as an ICE car doesn't turn on the brake lights when you downshift a manual tranny (which could possibly be a stronger speed brake than the lvl four Clarity regen!)... there's never been a need for brake lights for Clarity regen

on the other hand, full regen on my ioniq 5 will stand that effer on it's nose!

first level ioniq 5 is the equivalent to lvl three Clarity regen, and it adds up exponentially
 

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there's never been a need for brake lights for Clarity regen
If you are talking only about using the paddles I agree. But ACC is capable of much stronger regen.

just as an ICE car doesn't turn on the brake lights when you downshift a manual tranny (which could possibly be a stronger speed brake than the lvl four Clarity regen!)
Yes there is some inconsistently in how brake lights are activated, and always has been, but that's understandable since until fairly recently the technology didn't exist to have anything beyond a simple switch that activates the brake lights whenever you press the brake pedal. This however means that the brake lights come on even with a very light tap of the brakes, meanwhile heavy downshifting does not activate the brake lights at all.

With the rules for regen it seems like they are trying to correct this by basing it on the amount of deceleration. However for some reason they still mix in the old method of activating the brake lights with just a light tap of the brake pedal.

And there is still inconsistency between EV cars and gasoline cars. And even within EV they give the car makers the choice to select the deceleration level when the brake lights activate, within a certain range.

In my opinion there should be one standard for all cars, both EV and gasoline. What I would like to see is that the brake lights never activate below 1.5 mph/sec, even if you tap the brake pedal. 1.5 mph/sec and above the brake lights are on. And above 3.0 mph/sec the brake lights should flash. Obviously this would apply only to new cars as there is no practical way to retrofit old cars, but that's okay, just like when third brake lights became mandatory it only applied to new cars.
 

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If you are talking only about using the paddles I agree. But ACC is capable of much stronger regen.


Yes there is some inconsistently in how brake lights are activated, and always has been, but that's understandable since until fairly recently the technology didn't exist to have anything beyond a simple switch that activates the brake lights whenever you press the brake pedal. This however means that the brake lights come on even with a very light tap of the brakes, meanwhile heavy downshifting does not activate the brake lights at all.

With the rules for regen it seems like they are trying to correct this by basing it on the amount of deceleration. However for some reason they still mix in the old method of activating the brake lights with just a light tap of the brake pedal.

And there is still inconsistency between EV cars and gasoline cars. And even within EV they give the car makers the choice to select the deceleration level when the brake lights activate, within a certain range.

In my opinion there should be one standard for all cars, both EV and gasoline. What I would like to see is that the brake lights never activate below 1.5 mph/sec, even if you tap the brake pedal. 1.5 mph/sec and above the brake lights are on. And above 3.0 mph/sec the brake lights should flash. Obviously this would apply only to new cars as there is no practical way to retrofit old cars, but that's okay, just like when third brake lights became mandatory it only applied to new cars.
I could see an aftermarket module that goes in series with the existing brake light circuit. Three wires in, one wire out. Existing brake light feed wire is an input and functionally passed through, with the addition of an accelerometer-driven brake light signal included in the output wire. It would also require an ignition-switched power source and ground lead.

It would be a relatively simple electronic design, with regulatory approval problems written all over it.:oops:
 

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I could see an aftermarket module that goes in series with the existing brake light circuit. Three wires in, one wire out. Existing brake light feed wire is an input and functionally passed through, with the addition of an accelerometer-driven brake light signal included in the output wire. It would also require an ignition-switched power source and ground lead.

It would be a relatively simple electronic design, with regulatory approval problems written all over it.:oops:
That's why I don't think retrofit is practical. Setting new standards for car makers is one thing, but requiring retrofit of all existing vehicles is too problematic, not just the logistics but also since it's a critical safety function.

But retrofit isn't really necessary anyway, just like with third brake lights, over time the vast majority of cars on the road will meet the new standards. In the meantime, while it's not ideal to have different methods in place at the same time, that's no different than it is today with gas cars working one way, EV's working another way, and even EV's not all working exactly the same way. Setting a new standard now will not immediately improve that situation, but within a few years there would be begin to be more and more consistency as new vehicles replace old ones.
 

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I, too, have been bugged/wondering. I end up toggling between the cancel button and resume button. I touch cancel when I think I’ll be flashing my lights and then touch resume as soon as it’s clear and/or I know I’ll accelerate a little to keep up. Not ideal, but works for me.
 

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Discussion Starter · #17 ·
I don't know if my brake light switch is extra noisy, or if I have bionic hearing, or if other people are better at tuning out weird little click sounds than I am. But next time you are driving try lightly pressing the brake pedal and see if you hear the click, ideally when you are somewhere where you can see if the brake lights are being activated simultaneous with the click. Actually the garage would be a good place to try it.
I've been meaning to do this and finally remembered to give it a try in my garage just now.

I can hear the click, so it's not just you! It comes on after applying the brake pedal ever so slightly, BUT it does not activate the brake lights simultaneously. It would seem to at first, but if you have the right amount of finesse, you'll notice that the brake lights don't come on until after depressing the brake pedal just a tiny bit more after hearing the click.

So, not really sure what the click is about since it doesn't seem to be about the brake lights.
 

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I've been meaning to do this and finally remembered to give it a try in my garage just now.

I can hear the click, so it's not just you! It comes on after applying the brake pedal ever so slightly, BUT it does not activate the brake lights simultaneously. It would seem to at first, but if you have the right amount of finesse, you'll notice that the brake lights don't come on until after depressing the brake pedal just a tiny bit more after hearing the click.

So, not really sure what the click is about since it doesn't seem to be about the brake lights.
Engaging regen circuits?
 

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I, too, have been bugged/wondering. I end up toggling between the cancel button and resume button. I touch cancel when I think I’ll be flashing my lights and then touch resume as soon as it’s clear and/or I know I’ll accelerate a little to keep up. Not ideal, but works for me.
I don’t know if this has been pointed out because I haven’t read the entire thread (I don’t have the patience to read interminably long posts). But the answer is in the owner’s manual.
Organism Rectangle Font Circle Number
 

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I've been meaning to do this and finally remembered to give it a try in my garage just now.

I can hear the click, so it's not just you! It comes on after applying the brake pedal ever so slightly, BUT it does not activate the brake lights simultaneously. It would seem to at first, but if you have the right amount of finesse, you'll notice that the brake lights don't come on until after depressing the brake pedal just a tiny bit more after hearing the click.

So, not really sure what the click is about since it doesn't seem to be about the brake lights.
It's been a while but I remember now there was that tiny discrepancy, but I just tried it again and in my car even with a very light press of the pedal the click and the brake lights are simultaneous. Only if I press the pedal very, very, very lightly I can sometimes get the click to occur without the brake lights, then if I press a tiny bit more the brake lights comes on. Sort of the opposite of your experience, but either way it would be extremely rare if ever in real world driving that someone would press the pedal that lightly. So for practical purposes the click and the brake lights seems to be simultaneous.

Thanks for checking, I'm glad I'm not the only one who hears the click.


Engaging regen circuits?
I'm thinking maybe the friction brakes. Which would be consistent with the theory that anytime you press the brake pedal it mixes in a small amount of friction brake with the regen, unlike ACC and the paddles which it is believed only uses regen. Although if my theory about the switch is correct, then even ACC uses at least some amount of friction brake in harder slowing situations.
 
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