Regenerative Braking Safety Issue

[brucet999]

Note that this applies to a normal car too. Normal cars have "regen" too! Obviously it doesn't actually regen, but releasing the accelerator entirely creates drag if you're above a certain speed, and if you have RWD then you'll encounter the same trouble as described here. And the solution is the same: shift into neutral.

From this, I take it that your ICE vehicles have been manual shift. Almost all automatic transmissions in "Drive" coast when you let off the gas. To get engine braking you have to deliberately shift into lower gears.

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I've driven Model Ss through three winters. I have always left regen on "Standard" and have never had an issue as long as I was driving at an appropriate speed for the conditions.

From what you say, I would guess that you are adept at feathering the accelerator pedal such that you get regen only very gently if at all. Those who lift the right foot in order to be ready to use the brake pedal may experience abrupt application of regen.

 

[mikeash]

From this, I take it that your ICE vehicles have been manual shift. Almost all automatic transmissions in "Drive" coast when you let off the gas. To get engine braking you have to deliberately shift into lower gears.

That's not true. Engine braking in D on an automatic will be relatively minor, but it's there, and it's about as strong as a Model S's regen when set to Low. Next time you drive an automatic (if ever... may we all avoid such things from now on!) take your foot off the gas entirely, watch how it coasts, then shift to N and observe the difference.

In modern cars this actually does save a bit of fuel, because the car is able to shut off the fuel entirely and let the wheels keep the engine spinning.

 

[Odenator]

I've driven Model Ss through three winters. I have always left regen on "Standard" and have never had an issue as long as I was driving at an appropriate speed for the conditions.

I do know a number of people who state they switch regen to "low". However, I have found that unnecessary.
We drive daily in the winter and have winter tires on one, while leaving all seasons on the other car.

I have had to turn off traction control more often than switching to low regen.

I'm not saying others haven't had issues. I just wanted to make sure that any readers are aware that the OP is not a universal experience.

This has been my experience as well. I use studless snow tires during the winter and I love the smooth deceleration on snow and ice in my RWD P85. Is the OP using all seasons?

 

[mknox]

This was something I was extremely worried about prior to delivery. In fact, if you go back, you'll probably find posts of mine with all kinds of hand-wringing over what might happen. I've now driven the car through 3 winters, including the mother of all ice storms that shut down Toronto and much of Southern Ontario for days. I have found that the car's TC and stability control work extremely well and while I will get a bit of "wiggle" from the back in these conditions, the car will remain straight and true even with Regen on "Normal". I never once even felt the need to set it to "Low".

Now, what I feel is a big contributor to this is having the car equipped with proper winter tires. If anyone is sliding around on ice with summer or "all-season" tires, I have very little sympathy.

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That's not true. Engine braking in D on an automatic will be relatively minor, but it's there, and it's about as strong as a Model S's regen when set to Low.

Absolutely. This became very apparent during my first cold weather experience in the Model S back in 2013. When it's really cold, Regen will be disabled completely and the car rolls much more freely than an ICE with your foot off the gas. In fact, it's a little scary the first time you experience the Model S with 0 regen.

 

[StaceyS]

I think this issue is more descriptive of the challenge of driving a car in adverse winter conditions rather than specific behavioral issues with the Model S.

Before the Model S, I've driven only manual transmission cars, both front wheel drive and rear wheel drive, with traction control and without. I have lost traction at times under very icy conditions due to compression braking using the engine and transmission to slow down. These were situations where I was very aware of conditions, and was actively prepared for the possibility of losing traction.

The best two things I have done to counter these handling issues in every car I've ever driven:
1) Make sure the car is wearing good snow tires
2) Drive hyper-aware of the road conditions

I expect similar instances with the regen braking of the Model S, and I'm headed into my first winter with regen set to "standard".

I don't believe this is a Model S issue, or a Tesla issue. This is a "learn to drive the car you own properly under adverse conditions" issue.

 

[AWDtsla]

I don't believe this is a Model S issue, or a Tesla issue. This is a "learn to drive the car you own properly under adverse conditions" issue.

No, a manual transmission car in the same situation is clearly superior to the Model S since you can declutch. This is not a phrase anyone should be able to say, and it's quite silly because it's a simple as a one line software fix.

 

[mknox]

No, a manual transmission car in the same situation is clearly superior to the Model S since you can declutch. This is not a phrase anyone should be able to say, and it's quite silly because it's a simple as a one line software fix.

You can "declutch" a Model S with a quick flick of the gear stalk, putting the car in neutral. Tap it fully, and you're back in Drive. However, I have never found the need to do this over the course of three winters.

 

[neroden]

No, a manual transmission car in the same situation is clearly superior to the Model S since you can declutch. This is not a phrase anyone should be able to say, and it's quite silly because it's a simple as a one line software fix.

We addressed this earlier. You can switch into neutral in the Model S, and yes, you can switch back out of neutral. *I have done so*. (I see that mknox makes the same point.)

In normal icy driving (as opposed to when I was going down a hill with black ice), however, I've found that keeping an eye on the power meter is quite sufficient to keep regen/power in the "near coasting" range.

Which brings us to the topic of the dreadful proposed "7.0" update which removes the crucial power meter from the center display. The power meter is your key to safe driving on slippery roads: keep the power near the 0 level, not too high, not too much regen, and you're not likely to skid.

 

[AWDtsla]

You can "declutch" a Model S with a quick flick of the gear stalk, putting the car in neutral. Tap it fully, and you're back in Drive. However, I have never found the need to do this over the course of three winters.

How do you get back into drive at speed without upsetting the balance of the car?

 

[mknox]

How do you get back into drive at speed without upsetting the balance of the car?

No different, I suppose, than when you let the clutch out on an ICE at speed. You would put the car back in "D" and simultaneously apply some accelerator pedal. If you don't apply the accelerator, you'll get regenerative braking, but on an ICE if you don't apply some gas when you let the clutch out, you'll get engine braking too. FWIW, I have not tried this, but haven't yet run in to situation where I felt I would need to.

 

[brucet999]

That's not true. Engine braking in D on an automatic will be relatively minor, but it's there, and it's about as strong as a Model S's regen when set to Low. Next time you drive an automatic (if ever... may we all avoid such things from now on!) take your foot off the gas entirely, watch how it coasts, then shift to N and observe the difference.

I did exactly that with my wife's Lexus RX350. From 45mph I took foot off gas and felt no engine slowing and heard no engine noise (as one would do if shifting into 2nd), then I shifted to neutral and felt no difference, then back to drive and again no difference apart from a momentary engine noise as it engaged.

 

[danni]

I did exactly that with my wife's Lexus RX350. From 45mph I took foot off gas and felt no engine slowing and heard no engine noise (as one would do if shifting into 2nd), then I shifted to neutral and felt no difference, then back to drive and again no difference apart from a momentary engine noise as it engaged.

With a torque converter automatic, I believe the availability of engine braking depends on whether or not the gearbox has gone into lockup or not. In lockup, you should get engine braking just like on a manual car with the clutch engaged. Some automatics only go into lockup on the highest gear, others can do it in any gear (though as far as I know, the non-hybrid Lexuses should belong in the latter category).

 

[brucet999]

With a torque converter automatic, I believe the availability of engine braking depends on whether or not the gearbox has gone into lockup or not. In lockup, you should get engine braking just like on a manual car with the clutch engaged. Some automatics only go into lockup on the highest gear, others can do it in any gear (though as far as I know, the non-hybrid Lexuses should belong in the latter category).

If by lock-up you mean what happens when the driver moves the shift lever to the left where he can change gears up or down one gear at a time, by "jogging" the shift lever up or down, yes i have that feature, but it doesn't happen automatically.

 

[Cottonwood]

I've driven Model Ss through three winters. I have always left regen on "Standard" and have never had an issue as long as I was driving at an appropriate speed for the conditions.

I do know a number of people who state they switch regen to "low". However, I have found that unnecessary.
We drive daily in the winter and have winter tires on one, while leaving all seasons on the other car.

I have had to turn off traction control more often than switching to low regen.

I'm not saying others haven't had issues. I just wanted to make sure that any readers are aware that the OP is not a universal experience.

I have also driven through three winters in both a 2WD P85 and this last winter in an AWD P85D. I have used Nokian Hakka 7 studded winter tires and Nokian Hakka R2 studless winter tires. My driving has been in various levels of snow, slush, and ice, including slippery wet ice. Like Zythryn, I have never had a problem.

OTOH, I have driven my Roadster and my P85 in winter conditions with high performance summer tires. That is just scary and I will never do it again. Also, I did a little driving in the first winter snows here in Colorado in the P85D on Michelin Primacy all season tires; that was a little squirrelly, to say the least; it probably would have been scary on wet ice.

My strong recommendation is to get real winter tires like the Nokian Hakka R2's for winter driving.

Here are some links to my Tesla's on Nokian Hakka's in winter conditions:

• Nokian Hakkapeliitta R2 Snow Tire Report - Hakka's 2WD vs AWD on Glare Ice
• Nokian Hakkapeliitta R2 Snow Tire Report - Michelin Primacy vs Hakka R2's on Packed Powder
• Nokian Hakkapeliitta R2 Snow Tire Report - The Pagosa 16% Driveway

 

[brucet999]

My strong recommendation is to get real winter tires like the Nokian Hakka R2's for winter driving.

Living in SoCal, I only see snow when I drive a few hundred miles to the mountains, so snow tires are not a practical idea. For such trips, we've always used snow chains on the drive wheels. If I were to get a D model, would I have to have two sets of chains?

 

[danni]

If by lock-up you mean what happens when the driver moves the shift lever to the left where he can change gears up or down one gear at a time, by "jogging" the shift lever up or down, yes i have that feature, but it doesn't happen automatically.

No, that's not what I mean by lock-up. Here:

Torque converter - Wikipedia, the free encyclopedia
How lock-up torque converters works. ✔ - YouTube

 

[Pollux]

@Cottonwood,

When would you use the Hakka 7s versus the R2s?

Thanks,
Alan (a happy R2 owner)

I have also driven through three winters in both a 2WD P85 and this last winter in an AWD P85D. I have used Nokian Hakka 7 studded winter tires and Nokian Hakka R2 studless winter tires. My driving has been in various levels of snow, slush, and ice, including slippery wet ice. Like Zythryn, I have never had a problem.

OTOH, I have driven my Roadster and my P85 in winter conditions with high performance summer tires. That is just scary and I will never do it again. Also, I did a little driving in the first winter snows here in Colorado in the P85D on Michelin Primacy all season tires; that was a little squirrelly, to say the least; it probably would have been scary on wet ice.

My strong recommendation is to get real winter tires like the Nokian Hakka R2's for winter driving.

Here are some links to my Tesla's on Nokian Hakka's in winter conditions:

• Nokian Hakkapeliitta R2 Snow Tire Report - Hakka's 2WD vs AWD on Glare Ice
• Nokian Hakkapeliitta R2 Snow Tire Report - Michelin Primacy vs Hakka R2's on Packed Powder
• Nokian Hakkapeliitta R2 Snow Tire Report - The Pagosa 16% Driveway

 

[Cottonwood]

@Cottonwood,

When would you use the Hakka 7s versus the R2s?

Thanks,
Alan (a happy R2 owner)

My experience (and verified by some limited, personal testing) is that the Hakka 7's (now Hakka 8's) only beat the Hakka R2's on wet, soft, very-slippery ice. Even on the wet ice conditions, the 7's are only a little better than the R2's; the R2's "Cryo Crystals" in the rubber act as micro, silent studs. In all other snow/ice conditions, I have found the two tires to be about equal. On cold, dry pavement, the R2's win; steel on pavement is slippery. The worst part of the 7's is their noise on dry pavement compared to the quiet electric car. At neighborhood/city speeds, I called them my Rice Crispy tires, snap, crackle, pop...

I disliked the 7's so much, that I sold them for a song with 50% tread left, and replaced them with new R2's.

My most humorous episode with the 7's was when I got the P85 Sig back from an annual inspection, and the tech listed the tires as customer supplied, 3rd party tires. I pointed out that they were Tesla originals in 2012! The local service manager acknowledged that I was correct, but never sent me a new, corrected report.

Nokian Tires Web Page: Nokian Hakkapeliitta R2 - A non-studded tire that offers supreme driving comfort and safety

 

[Pollux]

Nice to get some thoughtful feedback. I have had nothing but good experiences with my R2s but lack your insight and descriptive powers. I won't spend any more time worrying about 7s or 8s.

Thanks,
Alan

My experience (and verified by some limited, personal testing) is that the Hakka 7's (now Hakka 8's) only beat the Hakka R2's on wet, soft, very-slippery ice. Even on the wet ice conditions, the 7's are only a little better than the R2's; the R2's "Cryo Crystals" in the rubber act as micro, silent studs. In all other snow/ice conditions, I have found the two tires to be about equal. On cold, dry pavement, the R2's win; steel on pavement is slippery. The worst part of the 7's is their noise on dry pavement compared to the quiet electric car. At neighborhood/city speeds, I called them my Rice Crispy tires, snap, crackle, pop...

I disliked the 7's so much, that I sold them for a song with 50% tread left, and replaced them with new R2's.

My most humorous episode with the 7's was when I got the P85 Sig back from an annual inspection, and the tech listed the tires as customer supplied, 3rd party tires. I pointed out that they were Tesla originals in 2012! The local service manager acknowledged that I was correct, but never sent me a new, corrected report.

Nokian Tires Web Page: Nokian Hakkapeliitta R2 - A non-studded tire that offers supreme driving comfort and safety

 

[jquint]

Hi Alan,

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

Jonathan