Why regenerative braking belongs on the brake pedal

[Jeff N]

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 suspect that regen only on the accelerator was initially chosen by Tesla in order to avoid the complexities of blending regen and friction braking with a high quality brake pedal feel. Blended braking systems at the time of the Roadster and Model S design were available but were not highly refined.

I don't know the exact power levels, but roughly speaking, driving the Volt in 'L' splits the available regen between the accelerator and the blended brake pedal. So, maybe up to 30 kW of regen is available using the accelerator pedal and a further 30 kW is available by using the brake pedal. The total regen is thus about 60 kW on both the Tesla models and the Volt.

I suspect the Volt was designed to reach the maximum accelerator pedal regen that would avoid the need to turn on the brake lights in order to simplify that aspect of the design. Additionally, GM already had experience with blended regen on the brake pedal in their earlier Two-Mode hybrid vehicles and they weren't trying to implement $100,000 sports car level brake pedal feel.

The newest generation of blended brakes in the 2016+ Volt (and probably the 2016 Malibu hybrid) is said to have improved blended brake feel although I haven't spent enough time driving it myself to have an opinion. The Volt and Bolt EV also now have a regen brake paddle on the steering wheel (adopted from the ELR) which can engage the full 60 kW of regen braking (and turn on the brake lights) while guaranteeing no friction braking.

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.

Is the S85D or S90D with 200+ kW motor(s) still limited to roughly 60 kW of regen braking?

I'm guessing yes and it's probably because stronger braking based on releasing the accelerator pedal is judged to be too jarring and is judged to be a bad driving experience. It should be possible to do stronger additional hard regen using a blended brake pedal and that would allow more efficient driving for owners that choose to drive with the weaker regen option. It may be that greater than 60 kW regen when the stronger default Tesla regen option is enabled may not recapture that much more total energy for typical drivers making it not worth the effort to implement.

In the Model S I can deal with it 95% with one pedal....

The Bolt EV is said to allow 100% one pedal driving in many situations (in 'L') in that it will bring the car to a complete stop and will apparently automatically hold the car even on a modest incline (presumably using automatically actuated friction brakes). Pressing on the brakes or accelerator will release the automated vehicle hold. I'm looking forward to seeing how well it is implemented.

 

[gregincal]

It may be that greater than 60 kW regen when the stronger default Tesla regen option is enabled may not recapture that much more total energy for typical drivers making it not worth the effort to implement.

That's my belief, based on the fact that I rarely use the friction brakes, and generally not for very long. The small extra amount of energy I would regain would definitely not be worth the complexities of implementing blended brakes.

 

[deonb]

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This thread needs a 'Jeff' mutex.

My head hurts.

 

[Johan]

As I've stayed before I disagree with the premise of the original post food several reasons. Here's one more reason: the friction brakes are already seeing low usage with typical driving, to the point of rust build up, the hydraulics not getting worked out enough etc. which can lead to poor braking in emergencysituations. With regen on the brake pedal and with even more regen braking in general this problem would be accentuated.

 

[newtman]

This thread needs a 'Jeff' mutex.

My head hurts.

Apparently Jeffs are not very imaginative.

 

[JeffK]

We use a semaphore.

 

[Xminus6]

Apparently Jeffs are not very imaginative.

Well, my name is also Jeff. And my last initial is N. Luckily I avoided the mass of Jeffs with my screen name.

 

[pedriscoll]

In the 11 months and 18000 miles I have driven my 85D, I have thoroughly enjoyed the regenerative braking tied to the throttle. It does remind me of driving a manual and IMO, gives me far more precise control over the car. I have driven in all conditions and have never had any loss of traction due to the regen. I think it took me about 2 days to master it and I would not want to drive any other way now.

 

[Tiberius]

 

[Mark Z]

If just one accident is avoided by the extra slowing that occurs from the time the foot is released from the accelerator and moved to the brake pedal, the present engineering decision is worth it.

For those who don't agree, push for Tesla to make it user selectable, just like Creep.

 

[TES-E]

It already is selectable... put it in low regen. You can use the mechanical brakes all you want.

 

[Volare3]

...In case you do not know, yes the brake lights come on when you are in regen.

Thank you for this tidbit. I've been slowly making my way thru this entire thread and have been wondering about this.

 

[proven]

Thank you for this tidbit. I've been slowly making my way thru this entire thread and have been wondering about this.

Another thing to note.. they don't come on if you are barely in regen. The brake lights are tied to how quickly you are decelerating.

 

[eisbock]

Most Americans you mean... You're forgetting the rest of the world where manual transmission is still king. There are many who say that Americans can't drive.

I may be 15 pages behind, but this mindset is ridiculous and pretentious. I'd argue that Americans are better at driving because they found and embraced a simpler, easier, and more fuel-efficient way to drive.

You could make the same argument for doing derivatives in math: "I'm better at calculus because I do derivatives the long way!" No, that doesn't make you better, it makes you an idiot.

Like the old adage... "Work smarter, not harder."

 

[JeffK]

I may be 15 pages behind, but this mindset is ridiculous and pretentious. I'd argue that Americans are better at driving because they found and embraced a simpler, easier, and more fuel-efficient way to drive.

You could make the same argument for doing derivatives in math: "I'm better at calculus because I do derivatives the long way!" No, that doesn't make you better, it makes you an idiot.

Like the old adage... "Work smarter, not harder."

You can think what you want, I'm just stating what the world thinks of us. Also there are a great many people who still feel that when using an ICE, a manual is superior to an automatic (depending on the implementation).

I've never had to replace a clutch or gearbox on a 25 year old manual but I've replaced an automatic transmission twice in a two year period with a crappy four year old Chevy. Manuals tend to last longer and are more reliable. As far as mechanical complexity they are simpler as well.

Automatics have only recently gained ground as far as fuel economy goes, previously manual was always more fuel efficient so your argument doesn't really hold water.

Even ask a high end sports car owner if their car is automatic or stick and what they think of those who drive the automatic versions of those same cars.

If we consider that the average American can't drive stick in this day and age, it's no wonder the world thinks we can't drive. When we travel to countries that aren't the US (yes, there are other countries in the world) many times manual cars are the only option. If someone can't drive manual and manuals are the only option, then I ask can they drive or not?

Of course, I'm from the US, but I know how to look in the mirror. We aren't perfect.

 

[eisbock]

You can think what you want, I'm just stating what the world thinks of us. Also there are a great many people who still feel that when using an ICE, a manual is superior to an automatic (depending on the implementation).

I've never had to replace a clutch or gearbox on a 25 year old manual but I've replaced an automatic transmission twice in a two year period with a crappy four year old Chevy. Manuals tend to last longer and are more reliable. As far as mechanical complexity they are simpler as well.

Automatics have only recently gained ground as far as fuel economy goes, previously manual was always more fuel efficient so your argument doesn't really hold water.

Even ask a high end sports car owner if their car is automatic or stick and what they think of those who drive the automatic versions of those same cars.

If we consider that the average American can't drive stick in this day and age, it's no wonder the world thinks we can't drive. When we travel to countries that aren't the US (yes, there are other countries in the world) many times manual cars are the only option. If someone can't drive manual and manuals are the only option, then I ask can they drive or not?

Of course, I'm from the US, but I know how to look in the mirror. We aren't perfect.

I will agree that manuals are "better" in some ways, but for 99% of the population, automatics are far superior. They are more fuel-efficient today, as you already mentioned. They take out the complexity of driving; I no longer see idiots rolling backward down hills, accelerating erratically causing the guy behind him to lose his *sugar*, sudden and erratic changes in speed which generally make everybody nervous. Maybe those are just the bad stick drivers, but you can't really drive an automatic badly, right? You can drive like a loon, but at least you're not manually controlling your car poorly while doing that. There are two ways to drive like an idiot, and automatic eliminates one of those.

High end sports car drivers don't really count. If you're a pro or serious car geek, you're kinda disqualified from the conversation because the overwhelmingly vast majority of people aren't. And I bet a lot of those people will swear to the grave that the manual version of their brand new car is better because they want the world to know they still drive stick even when the automatic version likely performs better.

As far as reliability.. kinda hard to gauge. Automatics have come a long way in the few short years they've been around, and are still continually improving. Manuals? Hah. I've driven three different 20+ year old automatics (hell, one was even a Dodge!) and all still shift fine.

The only part of your argument that holds water is the foreign travel thing. If you must have an automatic, it can be tough to find one, but there is no first world area that manuals are your only choice. And if you know you're gonna be travelling somewhere where you'll be driving stick? Learn. Pick up an old beater and figure it out. Not that hard, people have been doing it for a century now.

Eventually the whole world will drive automatic because there is literally zero reason for your average Joe to have a manual. There will still be manuals for the enthusiasts, but that's about it.

Claiming somebody doesn't know how to drive because they can't drive stick is like saying somebody doesn't know how to use a computer because they can't use DOS. It's ridiculous because DOS is obsolete. Manuals will be soon. They already are in the states.

 

[deonb]

If you must have an automatic, it can be tough to find one, but there is no first world area that manuals are your only choice.

In the last 3 years, for me, both in downtown Paris and Johannesburg it was impossible for me to find an automatic - manual was the only choice. I tried multiple rental companies.

You'd have to restrict 'first world' to US and Canada only if you want to be assured an automatic.


Anyway, coming back to the topic, don't forget SMG in this discussion. With SMG the performance advantage of the manual is pretty much gone. All my performance driving training was also done on SMG's - you get all the benefits of a manual without actually having to drive a manual. And to shift from automatic to SMG is much simpler than to manual.

The whole "if you can drive a manual you're a better driver" argument makes as much sense as "if you use a crank lever instead of a starter motor you're a better driver".

 

[JeffK]

like saying somebody doesn't know how to use a computer because they can't use DOS. It's ridiculous because DOS is obsolete.

While I agree that DOS is obsolete, I might actually use the same argument when referring to Windows vs Unix/Linux since the Unix-like operating systems are on the majority of devices worldwide. I would say a user of Linux/Unix is statistically more likely to know how a computer functions like an Manual driver with how an ICE car functions. (there are, of course, exceptions). In the computer world, command line is still king.

...and yes, I agree, there are some very nice new automatics or automatic manuals out there nowadays.

 

[ModelNforNerd]

Let's go ahead and steer this back on track somewhat.

Your manual transmission driving skills are irrelevant in a Tesla.

Should you ever encounter a situation in which you need to drive stick, you will be well prepared for said contingency, but the skill is no longer germane to what we are discussing here.

 

[ThosEM]

The only thing Tesla could do to improve regen would be to add more gradations of regen control to suit different tastes. Cadillac did this on their ELR using flippers on the steering wheel, though I'm not sure that's a great idea given the importance of muscle memory. It may be better to make it more difficult to change, so it won't be fiddled with as much.

I would even grudgingly concede that they could and maybe should provide those gradations of regen on either pedal, to suit the tastes of the owner. But I personally won't care how well they succeed at making it smooth and seamless on the brake pedal, because I won't be using it there now that I'm so accustomed to single pedal driving. I have ended up feeling strongly that I want to know when I'm being energy efficient and when I'm depending too much on friction braking. A seamless transition on a single pedal would only serve to smokescreen that distinction.