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Regen Braking for Beginners.... I have questions

thrill

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I regularly drive different vehicles. I have occasionally reached for the non-existent regen paddle when driving my camaro with a stick, but in an emergency situation I've never not moved my foot to the brake pedal. Regen will probably never match how fast you can fully stop by stabbing the brake pedal. As long as you maintain that muscle memory, IMO it doesn't matter what you're driving.

I'm actually more thrown off when I drive my wife's Volt because when the battery is nearly full, it doesn't offer any hints on how much total regen you have available. It's also not nearly as powerful as the regen in my Bolt. I often end up overshooting stops and needing to additionally use the brake pedal way more often. The Volt also seems to be able to come to a complete stop occasionally but then creep mode kicks in and I have to quickly jump to the brake pedal.

I was pretty interested in the Taycan until I found out Porsche decided they didn't want a one-pedal driving mode.
Hmm, it seems it'd be nice to offer a pseudo-regen mode, where the vehicle would offer to use the disc brakes just enough to not "lose that regen feeling" (sorry, read the other thread first) when releasing the teleportation pedal even though the vehicle is not performing regen, so as to maintain a consistent feel.
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ajdelange

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Bottom line is that Rivian offers 4 levels of regen.
Those that want one pedal driving have that option. Those that want a different experience have that choice.
Removing the option just because Tesla did would be as silly as redesigning the R1S to have falcon wing doors and only two motors because that's what Tesla did on the Model X.
Read his post carefully. The truck he drove offers no option other than 1 pedal. But it offers one pedal with reduced gain (3 levels of reduced gain in fact). Telsa used to do that and found it brought nothing to the party. I have always assumed Rivian to be at least as smart as Tesla (pinched enough of their engineers) and thus think it quite reasonable to assume that they will come to the same conclusion. I'm not suggesting that they will in fact come to that conclusion nor indeed that they should. Just thinking that they probably will.

It appears your family members are going to be lead to the water and forced to drink it too or forego the benefits of regen altogether. They may be unhappy at first but I am guessing that like most everyone else who has experienced one pedal they will soon come to appreciate it.
 

DucRider

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Read his post carefully. The truck he drove offers no option other than 1 pedal. But it offers one pedal with reduced gain (3 levels of reduced gain in fact). Telsa used to do that and found it brought nothing to the party. I have always assumed Rivian to be at least as smart as Tesla (pinched enough of their engineers) and thus think it quite reasonable to assume that they will come to the same conclusion. I'm not suggesting that they will in fact come to that conclusion nor indeed that they should. Just thinking that they probably will.

It appears your family members are going to be lead to the water and forced to drink it too or forego the benefits of regen altogether. They may be unhappy at first but I am guessing that like most everyone else who has experienced one pedal they will soon come to appreciate it.
You are privy to information that Rivian does not trigger regen thru the brake pedal? Care to share a link? Only Tesla has chosen to go this route, and I find it unlikely that Rivian has followed that path.

A bit confused as to why my family members (and everyone else for that matter) that drive EVs with blended braking are foregoing the benefits of regen. They just use a different pedal and/or paddles to modulate it.
 

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First many thanks for posting this (and the other things too)

Relieved to hear that but didn't doubt it.

You'll get used to it and come to love it.

A little (very little physics). The acceleration, a, experienced by a vehicle of mass m is a = P/(m*v) where P is the power delivered to or taken from the motors and v is the velocity in the forward direction (for this discussion). At slow speed for a given amount of power a is large because v is small. That's why it feels as if it is really grabbing at low speed and feels more like ICE engine decelleration at higher speed. By limiting the amount of P taken (lower levels of regen) you can clearly limit a. And, this won't cost you a joule if you manage it in such way that you don't have to use the friction brakes (see hypermiling comment below). I don't see the necessity to have 4 gain settings as the pedal is a continuous gain control. Perhaps Rivian will learn this as Tesla did and remove it via OTA update as Tesla did. Or perhaps they won't.


I believe that is required by law.


No, that's because of a = P/(m*v). There is a limit as to how fast Rivian wants to charge the battery. That sets an upper limit on P which in turn limits a. [Note: g = a/9.8]


Is that referring to regen braking or the friction brakes?

Theoretically yes but there are going to be practical limitations and there will probably be some software choices as in do we want "creep" or "hold" when coming to a stop.

I think it will too to the point that my guess would be that Rivian will remove the other levels.

Remember the fuel crisis of 1973 and how we learned to "hypermile"? Part of that was knowing when to take your foot off the gas pedal so that you came to a stop right at the line at a stop sign or light. Exactly the same skill is involved here.
AJ,

As always, thanks for your thorough input. I love hearing the science behind what I experience in the world.

To your question about whether I was referring to the braking or regen, it was the braking, which I found to be very smooth, predictable, and linear, if that helps. Even so, the regen in level 4 was also stout, but I'm comparing it to what I've been told is only .2g's of regen slowing in my ELR. Level 4 in the Rivian felt at least double that. It feels very firm and comes on immediately, especially noticeable at slow speeds. At higher speeds, it seems to ramp up quickly, but a little more gradually than at low-speeds. Oddly, most of my experience with it included onset at speeds below 30 or over 120. I don't recall full right-pedal lifts at more normal, everyday speeds, at least while on the pavement. Regardless, it felt solid and predictable every time I did use it.

As I believe you pointed out, that is what one-pedal driving is all about. When it comes to a written instruction manual:

"Push to go, lift to slow"

is about all I'd need to see in any directions. Once you get used to it, it becomes intuitive. Sure, the brakes still get used when they're needed, but I sure love my ELR in "Low", which is GM's way of labeling one-pedal driving. Having multiple options and learning when to use each will be part of getting to know our Rivians. I'm looking forward to hearing from you and the other Tesla drivers here as to how the two systems compare.

Thanks again for the details, and also for the earlier laughs. I can't tell you how many times I've tried to lighten the mood when I've told someone that someone else was off to the hospital (only appropriate when it's nothing life-threatening), and they ask, with concern for the individual, "What is it?". Of course, you know the response. It's something along the lines of: "It's a big building full of doctors and patients, but that's not important now."

I can't help myself....64 going on 15.
 

ajdelange

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Well you got me snd the Mrs reminiscing about the Zucker bros. and Leslie Neilson for much of the afternoon.
 

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ajdelange

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You are privy to information that Rivian does not trigger regen thru the brake pedal? Care to share a link?
Only going by what the man who has driven one has reported. Read his post again and see if you find any suggestion in there that blended braking is available. Then considering what I have discussed this afternoon use Occam's razor to see if you really think Rivian will have unnecessarily complicated their braking system in order to provide blended braking. You still haven't given me an answer as to why they should do that.

Only Tesla has chosen to go this route, and I find it unlikely that Rivian has followed that path.
This is just one of many ways in which Tesla has led the development of BEV technology. I think it very unlikely that Rivian would not follow their lead unless there is some reason why they shouldn't and I have asked you about 5 or 6 times to enlighten me as to what that might be and so far you haven't. Thus I am still flying on common sense.

A bit confused as to why my family members (and everyone else for that matter) that drive EVs with blended braking are foregoing the benefits of regen. They just use a different pedal and/or paddles to modulate it.
I don't think people that drive cars that require brake pedal pressure to invoke regen are wasting regen. I think that given the evidence from our correspondent they will only be able to get it from Rivian via the skinny pedal. It just doesn't make sense from an engineering point of view to provide rejen through two pedals when as duck has faithfully reported it is completely available from the one and Occam's razor suggests the same. But Occam's razor is not always right. It is just right so often that engineers and scientists invoke it often. Perhaps you are right.

Who really cares? The majority of us have what we want (one pedal).
 

DuckTruck

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Well you got me snd the Mrs reminiscing about the Zucker bros. and Leslie Neilson for much of the afternoon.
You got me going first by throwing in the Airplane tie-in with Julie and Robert. The Zuckers put out some fun stuff and also let the world know that Leslie Nielson and Peter Graves had some pretty good comedic chops. They even showed us the funny side of Kareem. I never saw that during his playing days.

Thanks again!
 

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As long as you maintain that muscle memory, IMO it doesn't matter what you're driving.
Exactly, and that first part is what I’ve been writing about. If I get used to one pedal driving as the norm, will my reaction time suffer because I’ve lost my muscle memory for driving a traditional setup?

@ajdelange hasn’t responded to that concern. I assume it’s because he understands that even if HE has maintained the muscle memory with no loss in reaction time at all, not even a tenth of a second, he can’t guarantee that OTHER PEOPLE won’t because of the human factor.

At 65 miles per hour, even if I only lose 1/10th of a second response time mentally processing that the vehicle I’m in needs more than just rapid accelerator lift to start braking, I’ve traveled just over 9 feet and 6 inches. There are a number of times I’ve had to make a panic stop where if I’d traveled just over 9.5 feet I would‘ve hit something or someone.

For me, I’m unwilling to jeopardize that ~9.5 feet for one pedal driving until I’m satisfied it’s not as big an issue as I fear or it is no longer an issue because all my cars support one pedal driving.

I’m not saying one pedal driving is bad, I’m not saying anybody with a mix of cars shouldn’t use one pedal, and I’m not saying that I won’t switch to one pedal, I’m only saying that I’ve considered the benefits versus the risks and with my current experience and capabilities it doesn’t make sense for me.

edited: typo
 

DucRider

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I think it very unlikely that Rivian would not follow their lead unless there is some reason why they shouldn't and I have asked you about 5 or 6 times to enlighten me as to what that might be and so far you haven't.
Adjustable regen fits a wider range of customer needs/expectations and offers more flexibility in a variety of driving conditions (off road in particular). Not allowing the brake pedal to be used to recapture energy is only efficient if max regen is dialed into the throttle lift, otherwise energy that could be put back into the battery is turned into waste heat thru the friction pads.

Less regen wanted in some off road conditions:

In this particular case, Emme was still using "one pedal driving", but with lowered regen capability.


When my wife test drove the Model Y at the Tesla dealer, the salesman's explanation of the removal of lower regen options was that "customers were burning up brake pads". I didn't ask him to elaborate on that nonsense.

Tesla has chosen to essentially force customers into one pedal driving.

We know that Rivian is most definitely offering varying levels of regen thru the right pedal.
They can either:
1) Recapture additional energy when using the brake pedal
or
2) Turn that energy into heat

I doubt they chose the latter.
 

SoCal Rob

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Adjustable regen fits a wider range of customer needs/expectations and offers more flexibility in a variety of driving conditions (off road in particular).
I appreciate Rivian giving us regen options so drivers can choose what is best for them given conditions, preferences, etc.
 

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ajdelange

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Exactly, and that first part is what I’ve been writing about. If I get used to one pedal driving as the norm, will my reaction time suffer because I’ve lost my muscle memory for driving a traditional setup?

@ajdelange hasn’t responded to that concern. I assume it’s because he understands that even if HE has maintained the muscle memory with no loss in reaction time at all, not even a tenth of a second, he can’t guarantee that OTHER PEOPLE won’t because of the human factor.
I think you are saying that if you get trained up to brake by releasing the skinny pedal only you may lose your reflexive skill at slamming on the brake pedal as you would in an ICE car. Is that right? If so I couldn't comment because I don't know. Experiments would have to be done to determine whether your thesis is valid or not and if it is whether it represents a safety threat. I am not qualified to do either of those things. As mentioned earlier I'll drive a couple of hundred miles without ever touching the brake pedal. So far whenever it has been necessary the instinct has been there. Odds are that my reflex time is appreciably longer than yours as you start losing that at about 30 apparently and 30 was a long time ago for me.

I guess we could look into the accident history with Teslas to see if they have more accidents from slow braking reaction times than other cars. Were anyone else sharing your concern I would assume someone would be looking into this. The fact that some purveyor of FUD hasn't unearthed anything like this leads me to believe that this is not a factor. The fact that both Tesla and Rivian offer one pedal driving leads me to believe that they have not found this to be a factor. But I won't dismiss it out of hand either.

For me, I’m unwilling to jeopardize that ~9.5 feet for one pedal driving until I’m satisfied it’s not as big an issue as I fear or it is no longer an issue because all my cars support one pedal driving
If you are uncomfortable with it, don't use it.
 

ajdelange

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Adjustable regen fits a wider range of customer needs/expectations and offers more flexibility in a variety of driving conditions (off road in particular). Not allowing the brake pedal to be used to recapture energy is only efficient if max regen is dialed into the throttle lift, otherwise energy that could be put back into the battery is turned into waste heat thru the friction pads.
It is becoming clear that, despite multiple explanations, you still don't understand how 1 pedal regen works so go back and have a look at the earlier posts that explain it. In particular reread (or, I suspect, read for the first time) #66 where it is explained how the skinny pedal, by itself, controls acceleration and decelleration.

Less regen wanted in some off road conditions:
I don't think you are getting that single pedal driving allows the driver to obtain as much acceleration as he wants (subject to the limitations of battery discharge current and the motor's limitations) in either the forward (accelerate) or reverse direction (decelleration).

In this particular case, Emme was still using "one pedal driving", but with lowered regen capability.
She needs to learn how to drive a BEV in sand (not saying I'm qualified to be the instructor). You don't need regen (or brake) to stop in sand. Rolling resistance will do that for you. Same as with an ICE vehicle. The exception is, of course, if a kid or dog runs right in front of the truck. Then you slam on the brake or come off the skinny pedal. The front end goes into the sand if you do that, of course. The way to stop in sand is watch the power meter which will be indicating something like 30 kW at 10 mph (Cr = 0.3, 2500 kg vehicle) and ride the skinny pedal back to bring the power consumption smoothly down to 0. The vehicle will slow at about -0.28 g.
She can get as little or as much regen as she wants with the 4 setting as described by duck.

When my wife test drove the Model Y at the Tesla dealer, the salesman's explanation of the removal of lower regen options was that "customers were burning up brake pads". I didn't ask him to elaborate on that nonsense.
If you had done you might understand this better. What the guy was trying to tell you is that if you need to absorb x Wh to bring the car to a stop and you select a reduced gain regen mode such that it can only remove x/2 Wh in the available distance then the other x/2 have to be removed by the friction brake. Which, of course, causes them to wear. That's true but I think the better explanation is that there is no need for the reduced gain mode.

Tesla has chosen to essentially force customers into one pedal driving.
Yes. Why wouldn't they?


We know that Rivian is most definitely offering varying levels of regen thru the right pedal.
They can either:
1) Recapture additional energy when using the brake pedal
or
2) Turn that energy into heat
I doubt they chose the latter.
Or the savvy driver can simply select mode 4 and capture all the energy. We note that duck, even in his brief encounter with the truck, was able to perceive that modes 2 and 3 aren't worth much. Why would a driver want any mode except 4. What advantage do they give the driver?

Adjustable regen fits a wider range of customer needs/expectations and offers more flexibility in a variety of driving conditions (off road in particular). What need or expectation do I get from lower gain regen? I don't have any expectations as to benefit from lower gain settings. What expectations do you have? How does a lower gain give me more flexibility off road? That's what I am trying to understand. Of course the other question that I can't get an answer to is why, given that I have complete control from one pedal, would I want to have duplicate control in another pedal or a set of paddles or whatever. Frankly the answer "because it isn't what Tesla does" is not very satisfying.
 

DucRider

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It is becoming clear that, despite multiple explanations, you still don't understand how 1 pedal regen works so go back and have a look at the earlier posts that explain it. In particular reread (or, I suspect, read for the first time) #66 where it is explained how the skinny pedal, by itself, controls acceleration and decelleration.

I don't think you are getting that single pedal driving allows the driver to obtain as much acceleration as he wants (subject to the limitations of battery discharge current and the motor's limitations) in either the forward (accelerate) or reverse direction (decelleration).

She needs to learn how to drive a BEV in sand (not saying I'm qualified to be the instructor). You don't need regen (or brake) to stop in sand. Rolling resistance will do that for you. Same as with an ICE vehicle. The exception is, of course, if a kid or dog runs right in front of the truck. Then you slam on the brake or come off the skinny pedal. The front end goes into the sand if you do that, of course. The way to stop in sand is watch the power meter which will be indicating something like 30 kW at 10 mph (Cr = 0.3, 2500 kg vehicle) and ride the skinny pedal back to bring the power consumption smoothly down to 0. The vehicle will slow at about -0.28 g.
She can get as little or as much regen as she wants with the 4 setting as described by duck.

If you had done you might understand this better. What the guy was trying to tell you is that if you need to absorb x Wh to bring the car to a stop and you select a reduced gain regen mode such that it can only remove x/2 Wh in the available distance then the other x/2 have to be removed by the friction brake. Which, of course, causes them to wear. That's true but I think the better explanation is that there is no need for the reduced gain mode.

Yes. Why wouldn't they?



Or the savvy driver can simply select mode 4 and capture all the energy. We note that duck, even in his brief encounter with the truck, was able to perceive that modes 2 and 3 aren't worth much. Why would a driver want any mode except 4. What advantage do they give the driver?
I'm not the one with the comprehension problem.
I've driven probably 20 times more EV models than you have and experienced more than a single way to handle regen.
Some people, as idiotic, backwards and poor drivers as they are, prefer lower deceleration from the right pedal. Rivian has acknowledged this and will make it available. I personally much prefer one pedal driving with as much regen as the vehicle is willing to dish out and invariably set it that way. But I am not egotistical enough to insist that what I like is the only way it should be done and that anyone with a different preference is less intelligent, lacks common sense or is unskilled.

Which is the better choice given (as idiotic as it is) that Rivian is making modes available less than the full amount of regen from the "skinny pedal"?
1) have the brake pedal add in more regen before engaging the friction pads
or
2) use only the friction pads

The only logical choice that anyone with any semblance of intelligence would choose of not allowing a mode with reduced regen to begin with is apparently off the table. We can't change the fact that Rivian has royally screwed up by offering this choice to their customers, so we are left with the above choices. So which makes more sense?

Your obsession with one pedal driving being (or that should be) the only option for EVs is simply absurd. If people are more comfortable with more traditional controls, who are you to declare them incompetent and clueless drivers? And the companies like Porsche and Audi that eschew one pedal driving to be as clueless as their target customers? Come down off your high horse and Elon worship long enough to recognize that sometimes choice is good - provide the options for using your product in a variety of ways and let the customer to decide what fits them best.
Tesla historically has been able to dictate certain things in their products simply because there really wasn't much competition. That is becoming less true every month. Want a real steering wheel instead of a yoke? You actually don't. Want a stalk for your turn signal? Wrong again! Have people adapted to some of the Tesla oddities? Yep. Is the driving experience universally improved? Not even close.
 

ajdelange

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It's part of Tesla's job to educate the public and they are doing that. Nevertheless it is such a privilege to dialogue here with someone who knows so much more about automobile technology than Elon Musk!

I guess my remaining question is "In denying me the modality for regen that you have decided I should have what is it I can't do that drivers of properly designed cars can?" Still trying to get the answer to that one.

Hinc equitavit!
 

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Adjustable regen fits a wider range of customer needs/expectations and offers more flexibility in a variety of driving conditions (off road in particular). Not allowing the brake pedal to be used to recapture energy is only efficient if max regen is dialed into the throttle lift, otherwise energy that could be put back into the battery is turned into waste heat thru the friction pads.

Less regen wanted in some off road conditions:

In this particular case, Emme was still using "one pedal driving", but with lowered regen capability.


When my wife test drove the Model Y at the Tesla dealer, the salesman's explanation of the removal of lower regen options was that "customers were burning up brake pads". I didn't ask him to elaborate on that nonsense.

Tesla has chosen to essentially force customers into one pedal driving.

We know that Rivian is most definitely offering varying levels of regen thru the right pedal.
They can either:
1) Recapture additional energy when using the brake pedal
or
2) Turn that energy into heat

I doubt they chose the latter.
BTW, Emme should be participating in the R1T this year too, so we should get a good idea of the production range off road.
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