Why regenerative braking belongs on the brake pedal

[roblab]

I'm currently driving a Prius, and I like how it handles the regen. Taking my foot off the gas allows some coasting, some light regen, and a chance to relax my leg. If I want a little more regen, a very light touch on the brake pedal accomplishes that, without engaging the physical brakes.

I would hope my Model 3 allows a similar setup.

It won't. Tesla has already decided that one pedal driving is superior. Those of us who live with it agree. Those who do not drive Teslas seem to be imagining something that isn't there.

As to the chance to relax your leg, that's why we have TACC. You don't need a light touch on any pedal at all to accomplish driving in traffic.

I owned a Prius. When we got the Tesla, we sold the Prius, because it was inferior in every way. No one wanted to drive it. Some day maybe you will see how this works.

 

[Red Sage]

I owned a Prius. When we got the Tesla, we sold the Prius, because it was inferior in every way. No one wanted to drive it.

Heh. This reminds me of an old joke that goes...

"There once was a very smart man who lived in our town. He moved away."​

 

[deonb]

the car reaches terminal velocity rather early in the descent and from there on all the potential energy gained is being dissipated as friction of various types, dominantly aerodynamic drag at higher speeds.

That's not what you said. You said:

When you fall at terminal velocity, all the energy you are gaining is going into drag

Very different things. If you said the first thing from the beginning, I wouldn't have argued with it.

Well... apart maybe from "dominantly", but that you might or might not be right on. Bearing frictions also increase at higher speed. Either way, it's plausible. But 75mph terminal velocity from drag alone is not.

 

[bhzmark]

Tesla is smart enough not to do many of the things other companies do. But hey, I conceded up front this is a matter of taste. I like Tesla's taste, so far...

Tesla should also know that if they can eventually make electricity instead of brake dust, the car will be better. I don't understand the fetish for making brake dust and brake heat. I'd prefer the brakes to make electricity instead.

 

[ohmman]

Tesla should also know that if they can eventually make electricity instead of brake dust, the car will be better. I don't understand the fetish for making brake dust and brake heat. I'd prefer the brakes to make electricity instead.

Agree, but there are limits to the effectiveness of regen for safety braking. You need to make brake dust and waste heat when you need to stop quickly and safely. Generally, the design should be made to limit that waste heat. I think Tesla mostly does a good job of this without overcomplicating it.

 

[CarlitoDoc]

Cool, just finished reading all the posts, and in doing so I earned a PhD in Physics. Thank you all for the volumes of literature. I guess you may now call me Dr.Dr

 

[GoTslaGo]

This thread could get hot fast, look out.

So the soothsayer award goes to @int32_t

If I had a rep point, you definitely earned one from me!

 

[shokunin]

I am blown away buy the amount of arrogant and willfully ignorant hate over a guy pointing out the practical effects of regen on the throttle. If your "rebuttal" doesn't include an empirical rebuke of the science at hand, the it holds no relevance but feel free to exercise your freedom of speech...if you live in the USA...because Canada doesn't have that.

Really? empirical rebuke of the science? The OP is preaching to us ignorant folks about basic vehicle dynamics 101 on throttle response, weight transfer and loss of traction, specifically to the rear wheels and oversteer. The OP fails to provide any empirical evidence regarding said dynamic vehicle response on a Model S or X.

The OP's essay is very much correct on what can cause oversteer and understeer. However, the Model S and X have a huge amount of weight below the axles and centered between them. The weight transfer from regen is not the same as say tapping the brakes on a RWD Ford F150 on icy pavement. The regen is nearly the same as driving a manual transmission and lifting your foot of the gas or downshifting on an auto.

Unless you know how to heel toe, most drivers in an emergency will hover over the brakes first, but there may be situations where you'd need to accelerate out of a situation. In a Tesla, you have very fine control of both regen braking and if you need to accelerate out, there is less of a need shift between the brake and the accelerator.

 

[bhzmark]

there are limits to the effectiveness of X=[regen for safety braking]. You need to Y=[make brake dust and waste heat] when you need to Z=[stop quickly and safely].

Luckily Tesla has the balls to test and engineer and design around the limitations that some people feel bound by. A few years ago you could have said many statements of the form

"there are limits to the effectiveness of X so we need to Y when we want to Z."

And then tesla would have proved you wrong.
E.g.., X=battery range, Y=use ICE, Z=travel long distances

And by the way TACC and AEB already seemlessly blend hard braking making brake dust with slower braking making elec. The iBooster does that already. So problem is solved. The current limit is just on the battery receiving end.

 

[Az_Rael]

As to the chance to relax your leg, that's why we have TACC. You don't need a light touch on any pedal at all to accomplish driving in traffic.

TACC is an option, though, and not everyone will choose to get it. So regular cruise control would have to be used to briefly rest a foot in highway traffic driving.

The other scenario I get into is when I have placed my foot on the pedal awkwardly for some reason and I have to lift and adjust. I will just have to click on cruise, lift and adjust, then click cruise back off.


You guys are winning me over, though. I have been driving my Volt in high regen for a couple weeks now, and I just got behind the wheel of my husbands S4. I was annoyed at the lack of friction when taking my foot off the gas.

I still have the automatic quick "cover the brake" reaction when I see something fishy happening ahead of me though. That seems to be my only issue with smooth regen driving right now. I suspect that habit will take a while to break (and better I break it now with the Volt's much less severe regen lift off)

 

[Xminus6]

I don't understand the idea that modulating the throttle is somehow physically harder than switching your foot back and forth from pedal to pedal. In stop-and-go traffic, my leg gets much more tired in a car with weak regen. In the Model S I can deal with it 95% with one pedal (and no, I don't have TACC or AP). It's made my commute through heavy traffic much easier and relaxing compared to our previous Nissan Leaf or our other EV, the Toyota RAV4 EV.

Also, when going down long steep declines it's much more controllable than the Leaf was. The previous discussion about the trade-off of allowing the car to gain speed from coating vs. maintaining speed from regen is not applicable at all in my situation because there's rarely a long decline on a highway that doesn't include hundreds of other cars disrupting my flow of driving. So I end up maintaining speed regardless.

 

[Ciaopec]

Tesla got it wrong when they put heavy regen on the throttle. It's one of several things they got wrong, but probably the most serious one. It's not stopping me for buying a Tesla or two, but worth pointing out. When I test drove a Model S, I liked it much better with Low Regen. I realize I'm probably in the minority on that, but I also realize most people are very likely ignorant about the reasons why.
.

Flames to /dev/null

I had posted earlier about regen braking on a Lexus GS450h hybrid. I awoke this morning with a thought about this whole notion.
Is this whole thread just an academic discussion? Since I am not an automotive engineer and only have a passing understanding of transmissions my question is this: Does the Tesla drive train (direct gear) even lend itself to anything other than regen on throttle off?

 

[Zoomit]

Does the Tesla drive train (direct gear) even lend itself to anything other than regen on throttle off?

Software controls the level of energy recuperation from the motors. The drive train hardware does not dictate regen on throttle lift.

 

[Xminus6]

I had posted earlier about regen braking on a Lexus GS450h hybrid. I awoke this morning with a thought about this whole notion.
Is this whole thread just an academic discussion? Since I am not an automotive engineer and only have a passing understanding of transmissions my question is this: Does the Tesla drive train (direct gear) even lend itself to anything other than regen on throttle off?

I assume that Tesla engineers could have done it either way as Musk has previously been quoted as saying that he chose this method because blended braking was not going to be easy to accomplish well and in the time frame needed to ship with the Model S. Whether those were the main reasons or not, they got it right. It's much easier to drive a Model S than my other EVs or an ICE.

 

[Ciaopec]

Software controls the level of energy recuperation from the motors. The drive train hardware does not dictate regen on throttle lift.

That part I understand, I think. But on a more basic level, if regen was not a goal, would the car not stop itself once the accelerator was lifted?
And, if that is the case, a regen on braking only, would be cumbersome (an extra step) and would force the brake lights on (I hate brakes unless absolutely necessary, e.g., slowing in a controlled manner on a freeway). So it just seems logical and appropriate to regen on throttle off, but increase regen with brake application.

 

[Ciaopec]

I assume that Tesla engineers could have done it either way as Musk has previously been quoted as saying that he chose this method because blended braking was not going to be easy to accomplish well and in the time frame needed to ship with the Model S. Whether those were the main reasons or not, they got it right. It's much easier to drive a Model S than my other EVs or an ICE.

Thanks. You must have composed and posted about the time I posted #255

 

[Red Sage]

That part I understand, I think. But on a more basic level, if regen was not a goal, would the car not stop itself once the accelerator was lifted?
And, if that is the case, a regen on braking only, would be cumbersome (an extra step) and would force the brake lights on (I hate brakes unless absolutely necessary, e.g., slowing in a controlled manner on a freeway). So it just seems logical and appropriate to regen on throttle off, but increase regen with brake application.

I believe the point made earlier is that there is nothing to 'increase' with regen by pressing the brake pedal. 100% of regen is on the GO pedal. You would have to redistribute the amount of regen to do it the other way. Possibly by reducing the maximum lift throttle regen to only the 20%-to-40% range. It would satisfy a few people, perhaps -- but only at the expense of the current majority -- who feel Tesla Motors 'got it right' already.

 

[Ciaopec]

I believe the point made earlier is that there is nothing to 'increase' with regen by pressing the brake pedal. 100% of regen is on the GO pedal. You would have to redistribute the amount of regen to do it the other way. Possibly by reducing the maximum lift throttle regen to only the 20%-to-40% range. It would satisfy a few people, perhaps -- but only at the expense of the current majority -- who feel Tesla Motors 'got it right' already.

Great! I'm finally part of the majority. Just took a while to make sure. ;-)

 

[Dan Detweiler]

TACC is an option, though, and not everyone will choose to get it. So regular cruise control would have to be used to briefly rest a foot in highway traffic driving.

The other scenario I get into is when I have placed my foot on the pedal awkwardly for some reason and I have to lift and adjust. I will just have to click on cruise, lift and adjust, then click cruise back off.


You guys are winning me over, though. I have been driving my Volt in high regen for a couple weeks now, and I just got behind the wheel of my husbands S4. I was annoyed at the lack of friction when taking my foot off the gas.

I still have the automatic quick "cover the brake" reaction when I see something fishy happening ahead of me though. That seems to be my only issue with smooth regen driving right now. I suspect that habit will take a while to break (and better I break it now with the Volt's much less severe regen lift off)

Just an FYI, if you have been driving a Volt in L I can tell you that the regen in a Tesla is much more aggressive than even that. That was the first thing I noticed when test driving a Model S. I have been driving my Volt in L for four years now. I am sure I will get used to it though...can't wait!

Dan

 

[Az_Rael]

Just an FYI, if you have been driving a Volt in L I can tell you that the regen in a Tesla is much more aggressive than even that. That was the first thing I noticed when test driving a Model S. I have been driving my Volt in L for four years now. I am sure I will get used to it though...can't wait!

Dan

I have been told that Volt L is somewhere between Tesla Low and Standard regen. I was not a L driver (didn't like it), so once I found out Tesla doesn't give you the option for regen on the brakes at all, I decided to start "training" so that I will hopefully have a smoother transition.