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Is coasting retarded like it is on the Roadster?

I understand that on the Roadster, regenerative braking becomes active when the accelerator pedal is not pressed enough to maintain speed and that as a consequence, coasting functionality is retarded. I also understand that unlike the Toyota Prius, the regenerative braking in the Roadster is not in any way linked to the brake pedal.

Telsa has some very promising technology, but these are issues that impair the driving experience enough that every time I think about possibly getting one, I tell myself that it is not worth it because I cannot coast without having the regenerative braking activate.

Does anyone know if these issues have been fixed in the Model S or does Tesla Motor still consider them to be features? If they do consider them to be features, is it possible to turn them off?

So Mycroft, I understand you would not miss "real" coasting at all?

I coast a lot (when driving a manual shifter), typically with my foot hovering over the break pedal. For instance, as soon as I notice that I cannot make a green light, I stop accelerating and switch to coasting, but I do not want to slow down much in advance of the traffic light, either, because traffic is dense and if I slow down too much someone will make a (dangerous) attempt to pull into my lane just in front of me.

In this situation, it would be ideal to control the amount of regen with the break pedal rather than the accelerator pedal. The prerequisite for doing so is that the accelerator pedal does not apply any regen when I lift my foot completely off.

I still like that idea, but if it can be implemented with the accelerator pedal instead, all the better. (EdG)

Have you driven the Roadster? I am not entirely sure that I correctly understand your suggestion, but it seems to me that the Roadster has it implemented precisely like that.

I'm not sure if I would miss it or not, but I think I could get used to "coasting" to a stop by backing off on the pedal to a touch of regen. I'm thinking I would feel more in control.

My brakes would last a long time! My rear tires, not so much. :)

Volker, it seems like the genesis of your suggestion is that the "true coasting" on the Roadster is fine line. Isn't the obvious fix simply to create a bigger coasting zone on the accel pedal? Actually put a dead-band in the middle, where you have a few millimeters of coasting (push harder, you accelerate; push less, you regen).

Robert, thanks for your suggestion. You are an alert reader.

If I remember correctly (from a 20 minute test drive), the pedal in the Roadster is trimmed such that there is a very smooth, continuous correlation between the pedal travel and the acceleration/deceleration. Without some practice, this makes it hard to feel where the "coasting" point actually is, but I think, that's a good thing. Usually, I simply want to determine speed or acceleration/deceleration. I don't care if that propulsion or regen or coasting is necessary to achieve it -- just give me the speed/acceleration I want. The Roadster's acceleration pedal does an admirable job at this.

And then there are opportunities where the actual speed is not so important to me and I can or want to make conserving energy my top priority. In these cases I want to coast/sail, maximizing the distance traveled at max efficiency (i.e., with neither propulsion nor regen), regardless of how much or how little deceleration that implies.

Thus is different situations -- depending not only on traffic but also on time pressure, mood of the day, and the available-to-required-range-ratio -- I have different priorities. I am looking for a configuration that seamlessly and effortlessly supports both without requiring me to explicitly switch modes or configure options. I think that BMW's concept may be appropriate, a sensible extension of what Tesla already implemented in the Roadster.

As far as I understand this is all a matter of coding, which means that they could make it user adjustable on the touch screen. You set up your own personal preferences, and the car loads them every time it recognizes your key in the drivers seat.

Personally I'm sceptic to the bigger dead band on the accelerator pedal. It would make it a bit hard to keep a steady speed if the road goes up and down, cos you would need to move the foot a lot over the dead band. But this could also be user adjustable.

They could just make a coasting button on the back of the steering wheel that u push when u want to coast. If u push the break or accelerator after that, the coasting mode would end.

I think finding the coasting point of the accelerator pedal is like using a clutch. A matter of practice.

They could just make a coasting button on the back of the steering wheel that u push when u want to coast. If u push the break or accelerator after that, the coasting mode would end. (Kallisman)

I think that could work for me although I still believe that BMW's idea beats yours in simplicity and elegance.

I think finding the coasting point of the accelerator pedal is like using a clutch. A matter of practice. (Kallisman)

Except that the better you get at using the clutch, the shorter you will use it, usually only for a second or less. In contrast, when coasting you want to stay in that state as long as possible.

I'm a roadster owner, and I have to say I find much of this thread confusing and sometimes surreal. The "power control pedal" (there have been many discussions of what exactly to call this) works beautifully and smoothly; anyone who's driven a roadster for more than 10 minutes in traffic has fallen in love with it.

Coasting is a concept that is made necessary by internal combustion engines. Personally I see no reason at all to coast in a Tesla. We've all spent lots of our driving years learning to have our foot in the right position to get the desired speed or acceleration (or now braking), unconsciously moving it as we get to a slight hill or the traffic in front slows a little. Why would you, as someone above said, want to be in coast mode with your foot hovering over the brake pedal?

I agree with the people who say it is insane that lifting off the pedal entirely should cause coasting. If you look at the US NHTSA reports about braking in the Prius, there are reports that sometimes as the brake transitions between regeneration and real brakes, it stops braking momentarily! Some accidents have been caused by this. You don't want discontinuous behaviour.

Large trucks have, for many years, had pretty much the behaviour of the Tesla; when the driver backs off the throttle past the point of normal engine braking, it engages "compression braking" (mucks with the valves somehow to cause even more drag from the engine). Truck drivers love it because it is much less stressful and less work for them.

Anyway, my conclusion is simple: trust Tesla to (mostly) get it right. If the regeneration is adjustable, I for one will set it to maximum and leave it there, and trust my foot to regulate it well. I say "mostly" above because there are a couple of glitches. When you cancel cruise control with the button, you get a braking action unless you have tried to match the power pedal first, and if you hit bad bumps while decelerating sometimes the traction control cancels the regen and it can be surprising.

I'm hoping for user config. The way I look at it, is the "accelerator" is called the accelerator for a reason. It's not an "accelarator/coasting/braking pedal depending on how you twiddle it with your big toe" pedal. Right next to it is the brake pedal. I'm hoping that obvious function won't change much. If I have to shift my foot off the accelerator pedal for a moment, I don't want the car to start slowing, and I would prefer to not have to hit steering wheel buttons to overide.

I'll probably set it similar to an ice car to just give me a gentle slowdown with foot off the pedal.

And I really do hope the S regens when braking, not just when not accelerating.

ggr, thank you very much for your comment, which is worth much more than any theoretical discussion!

Coasting is a concept that is made necessary by internal combustion engines. Personally I see no reason at all to coast in a Tesla. [...] Why would you, as someone above said, want to be in coast mode with your foot hovering over the brake pedal? (ggr)

The only good reason would be to conserve energy. For me it also seems natural and convenient, but that may be a reminiscence of ICE driving which I will possibly loose once getting used to the Tesla way of driving.

And I really do hope the S regens when braking, not just when not accelerating. (jbunn)

Ditto.

Whatever regen is in place when slowing down should probably continue if you move your foot to the brake pedal. If some feature removes the regen when your foot is off the "power control pedal" then it will probably also stop regen from occurring during braking, which seems a waste and less safe (longer brake distance).

Is there a situation where regen should not be engaged during braking? Or is there a reason why regen is never engaged during braking? Otherwise it would seem a simple thing to allow the regen to continue always until you give the car more power.

Having test driven the roadster, it takes all of about 10 mins "learning curve" before you "get" it. It was one of the best features, i found, other than the massive and immediate "thrust back into the seat"!! One of the major advantages of regen as fitted to the roadster, is that your wheels will stay clean of brake dust, and you will probably never need to to change your brake pads (if you drive the car in a sane fashion). I really can't see what the controversy is in this regard. Brake lights come on so no issues there (better than in my current Merc which only has brake lights when actually braking. Guys, wait to drive the actual vehicle before getting so fired up!

I agree with @dborn. After driving a Roadster, I found the regen braking to be a huge advantage.

@dborn, @michiganmodels. Funny. In my posts above I explicitly state that I have driven the Roadster and that I like its implementation of regen. There is little to none controversy on whether or not having regen on the accelerator pedal is a good thing.

All I noted was that BMW took the same approach, and took it one step further. I still think there may be something to it, but from the discussion here I learned one thing: It (the discussion) is entirely in vain. Seems that this kind of things cannot be discussed unless you have actually experienced it in practice. So we must rely on Tesla to do the experimenting and testing for us, and hope that they come up with the best possible solution.

The Roadster is very promising, but if you think that it cannot be improved, then you are stuck.

A test drive and long-term use are different beasts. When your body picks up the automatic software adjustments to exploit the system, that's when you can judge its value.

jbunn;
In physics terms, acceleration is any change of vector (direction or speed).

Besides, it's called the "goose" pedal.
;p

@VB: "I still think there may be something to it, but from the discussion here I learned one thing: It (the discussion) is entirely in vain."

I agree that there may be something to it. I disagree that the discussion is in vain. For one thing, we have to talk about *something* while we wait for our cars to be built. For another, I hadn't thought about coasting too much with regards to the regen braking.

I'm still not sure what BMW's implementation is, but since our discussion, I've been thinking about it. I think someone might have mentioned it earlier, but I think an automatically adjusted, very slight indent in the pedal's travel might work.

So, as you're accelerating or maintaining speed, the pedal is calling forth the juice. Then you let up on the pedal and you feel a very slight indent. This indicates that you're coasting. As you let up a little more, you're out of the indent and you are regeneratively braking.

I'm thinking that that implementation would definitely work for me!

@EdG, as far as I know Tesla does regen whenever your foot is not in accelerator pedal, so in braking you are doing both, max regen and braking (otherwise that would feel really odd).

Only way to not do that is that you press accelerator at the same time you press brake.

Problem with regen is that it only affects rear tires, so it can't be extremely powerful, otherwise you might lose control of the car. You would need to have engine at the front tires too to implement so powerful regen that normal brakes do not get engaged at all.

Also normal brakes are required by law in many places, so no matter how reliable regen you could get you would still need to install those, and connect them to brake pedal.

I think Tesla implementation is about as good as it could get, especially with user adjustable regen level.

Thanks for that, Timo, simple and effective. I'm not very clear on the control system that, as little as I understand, ensures no slippage on acceleration or regen. From what I've read, the control of the wheels that gives us the equivalent of a "limited slip" system comes almost "for free" with an EV.

With that system in place, I imagine even a lot of regen on the rear wheels wouldn't cause a loss of control.

Too much braking in the rear is bad?

Not enough because the regen is strong and the driver isn't pressing down enough? Then the driver just brakes harder.

@Mycroft: I like your "indent" point better than my "deadband" idea. Perhaps this issue is completely moot, but as you point out, we need something to talk about, and Tesla doesn't through any new crumbs for us to peck over!

re: Brian H's comment

When I taught physics, I would tell my students that a car has three "accelerators." Then ask them what they were.

cerjor;
goose pedal, brake, steering wheel.
Nice!

Emergency brake, hand dangling out the window, convertible top? :-)

@cerjor,
Mary Catherine O'Malley, two swiped cans of Pabst Blue Ribbon beer from my grandpas stash, and the back seat???

Brian, I had to backspace a couple of times over "Gas Pedal". This is going to be a habit to break. A lifetime of saying things like "hit the gas" will be hard to break.

I think it's going to take even longer to get used to cerjor's "accelerator pedal", "other accelerator pedal", and "accelerator wheel".

For those of us who enjoy physics, there is an old article on the Tesla site that talks about the change in mass as you use the battery. On the roadster a few hundred miles will decreace the mass of the battery by about the mass of a grain of sand, only to be gained by recharging.

http://www.teslamotors.com/blog/weighty-matters-involving-electrons

I believe the official term for the device to increase the rate of motion is called the "torque pedal". It won't change "put the pedal on the metal", or "floor it".

Sorry, but just like I'm still dialing a phone number, I'll be hitting the gas in my electric car. :)

"Goose it!" So it's the goose pedal. "Accelerator" and "torque" pedal etc. are just to science-y. ;)

Brian H: What about calling it the power pedal? Cos it's regulating the the power, wether it goes to or from the motor. It also gives u the power to decide the speed.

My father still calls his fridge an icebox, and I'm genetically as stubborn as him, so I'm going to call it the gas pedal out of tradition. Language is oftentimes divorced from the modern functional reality.

Golf is a good example:

I still call my woods "woods" despite them having no wood in them whatsoever. I openly mock people who refer to them as "metals."

Anachronisms abound. As long as people understand what you are saying you are probably good. Creating new language is far more complex than creating new products.


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