Regenerative Braking Safety Issue

[Pollux]

Point taken.

I confess one of the things I loved about my Audi A4 Quattro was the ability to handle ice and snow via brakes, engine braking, popping the clutch into neutral, downshifting.

While I lean towards being able to completely disable regen, as I think most major features should have a way to be disabled by someone who knows (or at least thinks s/he knows) what s/he's doing, you might consider whether there is a way to get the behavior even faster. What I'm thinking about is the time it takes to navigate the UI to find the option and turn it off. Compared, say, to popping a clutch into neutral or even shifting into neutral. One hand on the stick, one on the wheel, one foot on the accelerator/brake, one foot on the clutch... lots of control. "One hand on the center console" seems like bad news to me in a challenging driving situation.

I get it that you could turn off regen for a period of time. But even that first interaction to disable regen requires forethought; otherwise, you're turning it off *after* you've encountered the first challenge that makes you think, "whoa! better turn off that regen!".

As I go further down that path, I wind up inventing a clutch for a Tesla, which is just plain silly. I don't know what it would look like to be able to get the car to give you finer control without sacrificing a hand to the center console. If anything, the trend is towards less human control and more automation.

Alan

Hi Alan,

For the winter I use the 19" wheels and Pirelli winter tires. They grip very well. Except on ice

Jonathan

 

[mknox]

While I lean towards being able to completely disable regen, as I think most major features should have a way to be disabled by someone who knows (or at least thinks s/he knows) what s/he's doing, you might consider whether there is a way to get the behavior even faster. What I'm thinking about is the time it takes to navigate the UI to find the option and turn it off. Compared, say, to popping a clutch into neutral or even shifting into neutral. One hand on the stick, one on the wheel, one foot on the accelerator/brake, one foot on the clutch... lots of control. "One hand on the center console" seems like bad news to me in a challenging driving situation.

Except that technically, all you have to do is flick the gear stalk into Neutral, then back into Drive. The stalk is right there by the steering wheel, and you don't even have to press a clutch to do it. Having said that, I've never had the need in the past 3 winters.

 

[Pollux]

I yield to the gentleman from Toronto.

The "neutral" option on the gear stalk lives in one of my many mental blind spots. I just never ever shift an automatic into neutral; I only do that with a manual. I should convince myself to do use Neutral in the S. I'll practice doing just that in the snow and ice this winter.

Thank you, @mknox.

Except that technically, all you have to do is flick the gear stalk into Neutral, then back into Drive. The stalk is right there by the steering wheel, and you don't even have to press a clutch to do it. Having said that, I've never had the need in the past 3 winters.

 

[mknox]

The "neutral" option on the gear stalk lives in one of my many mental blind spots. I just never ever shift an automatic into neutral; I only do that with a manual. I should convince myself to do use Neutral in the S. I'll practice doing just that in the snow and ice this winter.

Yeah, I believe you have to think of the Model S as not even having a "transmission", automatic or otherwise... because it really doesn't. Even "neutral" is probably not the right term and is just carried over from ICE car vernacular. (I'll often tell people my Model S doesn't have a "reverse gear" which will raise some eyebrows until I explain it just spins the electric motor in the opposite direction).

What I believe you'll find is that you get really good at modulating the gas pedal (whoops... accelerator pedal) to control the amount of re-gen specific to the circumstances, eliminating any need for touching the stalk.

 

[st50maint]

Yeah, I believe you have to think of the Model S as not even having a "transmission", automatic or otherwise... because it really doesn't. Even "neutral" is probably not the right term and is just carried over from ICE car vernacular. (I'll often tell people my Model S doesn't have a "reverse gear" which will raise some eyebrows until I explain it just spins the electric motor in the opposite direction).

Exactly what happens in neutral? Is the drivetrain still moving normally but just not regenerating power?
What happens in park? Is it more than just the mechanical brakes being applied?

 

[3mp_kwh]

Exactly what happens in neutral? Is the drivetrain still moving normally but just not regenerating power?
What happens in park? Is it more than just the mechanical brakes being applied?

I don't think there's any clutches, so yes, still connected w/o power. You have to feather back into "D", if in snow for instance. Of the electrics I've tried, MS seems to have a really smooth transition, but one that falls over a narrow amount of pedal travel. So, it can be hard to avoid "transmission braking". This is where the i3 seems especially finicky, IMO. Since it is also rear drive, on 155mm tires, I bet the OP would favor their MS.

What's wrong with a little lift-throttle over steer, anyway

 

[spottyq]

Exactly what happens in neutral? Is the drivetrain still moving normally but just not regenerating power?
What happens in park? Is it more than just the mechanical brakes being applied?

There is no way to disengage the motor from the wheels (since there is no clutch.) If the wheels rotate one turn forward, the motor will rotate 9,7 (don't remember the exact number, but it is fixed) turns forward. Same thing in reverse. You can't make the motor turn without turning the wheels or vice versa.*

When in neutral, the motor is rotating freely. (Neither producing nor consuming electricity.)
Same thing in park. The car will then also apply the parking brakes (If I remember correctly, these are separate brake callipers on the rear wheels.)

*Well actually it is a bit more complicated than that, since there is a differential, but the basic principle is there.

[Edit :] Dang, 3mp_kwh beats me to it !

 

[Pollux]

What I believe you'll find is that you get really good at modulating the gas pedal (whoops... accelerator pedal) to control the amount of re-gen specific to the circumstances, eliminating any need for touching the stalk.

Yes, that's what has served me well over the past two winters. Well, except for the me getting really good at it part.

 

[AWDtsla]

What's wrong with a little lift-throttle over steer, anyway

Good point, what happens in a Model S when you do this? I assume regenerative braking will cease, because it's too late for differential braking to do anything.

 

[mknox]

Good point, what happens in a Model S when you do this? I assume regenerative braking will cease, because it's too late for differential braking to do anything.

In my experience over 3 winters... very little. The Traction Control and Stability Control seem to jump right in and do their thing pretty quickly. Not that I tried to lose control of my car or anything. Maybe next winter I'll do some aggressive maneuvers in an empty parking lot and see if I can force it.

 

[AWDtsla]

In my experience over 3 winters... very little. The Traction Control and Stability Control seem to jump right in and do their thing pretty quickly. Not that I tried to lose control of my car or anything. Maybe next winter I'll do some aggressive maneuvers in an empty parking lot and see if I can force it.

lift-off oversteer is not really a winter thing, since you need adequate traction to be able to shift the weight of the car. You would have to push it to the limits of dry cornering traction under power then suddenly lift off while still turning.

 

[LoL Rick]

One other point about shifting to neutral and the concern about engaging reverse. You can also press the stalk down to select neutral. Then if you overshoot, you hit drive again. Try it!

 

[mknox]

lift-off oversteer is not really a winter thing, since you need adequate traction to be able to shift the weight of the car. You would have to push it to the limits of dry cornering traction under power then suddenly lift off while still turning.

Very true. I was thinking in the context of winter driving.

 

[Skotty]

How many of you discussing this problem like the idea of self driving cars, believe it will make cars safer, and think they will happen in the near future? Reason I ask is that hybrid anti-lock braking systems are designed to stop the car as best as possible even with regenerative braking, and many of you are advocating ways to turn off these systems so that you can control it yourself, thinking that if would be safer under your own control.

So what's going on here? Do you believe the braking control systems are poorly implemented? And if so, why be so optimistic about self driving cars in the near future if they can't even get stopping done right after decades of hybrid cars with regenerative braking systems?

 

[mknox]

How many of you discussing this problem like the idea of self driving cars, believe it will make cars safer, and think they will happen in the near future?

Honestly, I remain a bit skeptical. In sunny, dry, clear California maybe. But in northern states and Canada with snow covered, potholed roads, frozen over cameras and sensors on the car along with a boatload of other variables I just don't know.

 

[AWDtsla]

How many of you discussing this problem like the idea of self driving cars, believe it will make cars safer, and think they will happen in the near future? Reason I ask is that hybrid anti-lock braking systems are designed to stop the car as best as possible even with regenerative braking, and many of you are advocating ways to turn off these systems so that you can control it yourself, thinking that if would be safer under your own control.

No, ABS is not about stopping the car "as best as possible", its about keeping driver control in hard braking situations by allows the wheels to spin, thereby allowing some static coefficient of friction which can be directional in the case of the front wheels.

So what's going on here? Do you believe the braking control systems are poorly implemented? And if so, why be so optimistic about self driving cars in the near future if they can't even get stopping done right after decades of hybrid cars with regenerative braking systems?

Yes they are. I've had plenty of situations on loose surfaces where ABS is just annoying, deceleration forces drop off the second ABS engages, lets say in loosely packed snow or sand or gravel. But for an average/below average driver in the same situation ABS may have saved them from sliding into some object.

The point is not just to aim at a 5th grade level because that's the average, you let people that can or want to handle it have the control they need.

 

[hickin]

Has there been update on this topic? I recently drove my all wheel drive model s in winter conditions for the first time, and while the car performed quite well in snowy/slushy road conditions, my wife had a minor incident where the car went off the road in black ice conditions. (Fortunately there was no damage to both car and wife). This seems like such a simple issue to resolve.

 

[jerry33]

Has there been update on this topic? I recently drove my all wheel drive model s in winter conditions for the first time, and while the car performed quite well in snowy/slushy road conditions, my wife had a minor incident where the car went off the road in black ice conditions. (Fortunately there was no damage to both car and wife). This seems like such a simple issue to resolve.

Most of the vehicles I see in the ditch are all wheel drive. My opinion is that this is because drivers don't really realize that braking is the same whether two wheel or four wheel drive. There are a few other reasons too, like tires, but that would apply to all vehicles.

 

[AWDtsla]

Most of the vehicles I see in the ditch are all wheel drive. My opinion is that this is because drivers don't really realize that braking is the same whether two wheel or four wheel drive. There are a few other reasons too, like tires, but that would apply to all vehicles.

I haven't seen a Subaru in a ditch yet. Most cars I see in a ditch are trucks or SUV's which probably didn't even have the AWD option. Of course there is no better way to announce to the world "I don't know anything about cars or how to drive" than to get a big lumbering SUV. When they're flipped over be sure to check for AWD transmission. Also, those cars don't tend of have AWD, but 4WD, which is different. They will spin you at any rate of speed, they're only meant for very low speed traction.

Like this guy

 

[Stiction]

Most of the vehicles I see in the ditch are all wheel drive. My opinion is that this is because drivers don't really realize that braking is the same whether two wheel or four wheel drive. There are a few other reasons too, like tires, but that would apply to all vehicles.

THIS.

I've seen the same thing over and over.

Just because you can GO doesn't mean you can STOP.