Why regenerative braking belongs on the brake pedal

[nvx1977]

I love the one pedal driving, but Teslas are wasting energy by not capturing energy back during braking.

Actually the Tesla is capturing that energy when you do one-pedal driving. If you're saying that Tesla is wasting the opportunity during a hard brake (when you actually need to use the brake pedal), actually the Tesla is still regenning while you press the brake pedal. It just means you don't need to press the brake as hard because some of the stopping power is still coming from regen.

The key ergonomic difference between regen on brake vs regen on accelerator is that in the latter, you know exactly when you're getting energy back and when you're losing some to friction braking. This is why one-pedal driving is so satisfying. You know that you maxed out your regen efficiency by how little you need to engage the real brake pedal. You have no way of knowing this if regen was tied to the brake, though it shouldn't be hard for a manufacturer to provide either a tactile or visual cue when you've hit the friction brake threshold.

 

[EV-lutioin]

Stumbling through this thread .....

Regen has Nothing to do with the brakes.

It’s a function of the transmission.

Yes the car slows but not because of the brakes. It’s slowing..... so it’s called braking.

When you step on the brakes, the calipers hydraulically pinch the discs attached to the wheels to slow the car down. Nothing about stepping on the brake pedal gives you any regerative energy or..... regen!

Well, there are some cars that use the brake pedal to engage regen. At least that is how the Prius used to work, I'm not sure which other cars use the brake pedal to engage regen.... Accord hybrid perhaps.

 

[alevek]

Looks like the Bolt got it right then. In D it coasts when lifting the throttle just like in an ICE where throttle position as no bearing on the speed of the car. In L it regens for true one-pedal driving to a full stop. So everyone can have it as they like it. For me, once you try one-pedal driving you can never go back, I can't imagine it anyone wanting otherwise (well maybe except for my mother-in-law). The level of precision in speed and position control is amazing.

 

[scaesare]

Coming from a Leaf I miss, the regen on brakes. Leaf does both.

I love the one pedal driving, but Teslas are wasting energy by not capturing energy back during braking.

Regen doesn't turn off simply because you press on the brakes.

Obviously you don't capture all of the kinetic energy during deceleration if you also engage the friction brakes, but that's true if you initiate the friction brakes using a Tesla brake pedal or a Leaf brake pedal.

 

[Skotty]

Regen doesn't turn off simply because you press on the brakes.

Obviously you don't capture all of the kinetic energy during deceleration if you also engage the friction brakes, but that's true if you initiate the friction brakes using a Tesla brake pedal or a Leaf brake pedal.

Well, there is one scenario where you could argue it's wasting energy, but it's tied to a user choice, so it's avoidable. When you choose the option in the menu to allow coasting. Can't remember exactly what the option is called, but it reduces regen, which wouldn't have to be the case if it could regen on braking.

 

[scaesare]

There's standard and low. No "coasting" option.

If you want to minimize energy lost to regen, not sure why you'd want to choose lesser strength options. Doing that and then complaining about losing regen energy to the friction brakes would seem a bit silly.

 

[Twiglett]

Regen doesn't turn off simply because you press on the brakes.

Obviously you don't capture all of the kinetic energy during deceleration if you also engage the friction brakes, but that's true if you initiate the friction brakes using a Tesla brake pedal or a Leaf brake pedal.

actually that isn't accurate for the Leaf. Nissan use a blended brake/regen, I can feel the transition in the pedal. You can also see the increased regen when using the brake pedal.
This whole thing is a none argument though and entirely personal preference.
Personally I prefer the Tesla method and even with the Leaf find single pedal driving the most sensible and relaxing driving style, especially for driving smoothly.

 

[scaesare]

actually that isn't accurate for the Leaf. Nissan use a blended brake/regen, I can feel the transition in the pedal. You can also see the increased regen when using the brake pedal.
This whole thing is a none argument though and entirely personal preference.
Personally I prefer the Tesla method and even with the Leaf find single pedal driving the most sensible and relaxing driving style, especially for driving smoothly.

I was responding specifically @mkjayakumar who was making that claim about Tesla's implementation:

Teslas are wasting energy by not capturing energy back during braking

My subsequent point about the Leaf (or any other EV) holds true: "you don't capture all of the kinetic energy during deceleration if you also engage the friction brakes"

 

[McRat]

To clarify things about Chevrolet electric drives:

• Lifting the throttle does Regen, but at a rate similar to the decel of a 3600lb automatic transmission ICE car in Drive when you lift.
• There is a high regen position called L, so when you lift, it decels like lifting the throttle of a manual transmission V8 car.
• There is a coast position with no regen called N.
• There is a paddle that will boost the regen to near maximum (max = 60kW for Volt, 70kW for Bolts).
• Then there is also regen via brake pedal.
• Volt will slow to 1-2 mph with regen only. Bolt will stop.

So it will emulate an Automatic Trans, a Manual Trans, or an EV depending what you desire.
Best range will be achieved by running in D and avoiding cruise control. Just try to avoid exceeding the regen limit (60 or 70kW) or you will be wasting range by braking with the discs. In these cases, the paddle is really handy. If you use the paddle when you need to stop, you know you are getting close to max regen, and need to increase your following distance accordingly. This saves you from taking your eyes off the road during a braking event.

 

[Twiglett]

I was responding specifically @mkjayakumar who was making that claim about Tesla's implementation:


My subsequent point about the Leaf (or any other EV) holds true: "you don't capture all of the kinetic energy during deceleration if you also engage the friction brakes"

I see what you mean

 

[JPWhite]

I suppose we've had automatic transmissions for so long folks have forgotten what it was like to drive back in the day of manual transmissions.

Approaching a roundabout it was common practice to drop the car into a lower gear. The engine would "brake" the car and you could use the accelerator to feather the level of deceleration and if stopping wasn't necessary adjust speed using the accelerator around and out of the roundabout.

Engine braking has existed for decades, the idea that slowing a car down with any method other than the brake pedal as 'wrong' shows a lack of driving experience/knowledge.

EV's bring back the ability to 'engine brake' effortlessly and much more easily than using a gear selector. As a bonus you get some energy back, which in city driving environments can be significant.

 

[BioSehnsucht]

As someone who enjoyed driving a *standard* transmission with a high compression motor, I look forward to a car with regen on the accelerator. By all reports, I'll wish it was more aggressive, even ...

 

[mspohr]

Coming from a Leaf I miss, the regen on brakes. Leaf does both.

I love the one pedal driving, but Teslas are wasting energy by not capturing energy back during braking.

By the time you press the brake pedal, you're already at max regen so no possibility to get more by pressing the brake.

 

[Fusion]

Nope.. Tesla got it right. I wish it was more aggressive also.

 

[daniel]

My car before the Roadster was the Zap Xebra. That car had no regen at all. If you were not pressing on either the accelerator or the brake, the car would coast. When stopped it did not creep. I got used to that and I liked it. When I got the Roadster (2011) I hated having regen on the accelerator pedal... for about five minutes! Then I started to get used to it. And within about 15 minutes of driving the car, I decided it was the only way to go.

I prefer the more aggressive regen on the Roadster, compared to my new Model 3, but the 3 is still good. The Roadster has creep, so in Drive you need to keep a foot on the brake to remain stopped. I have not yet decided if I like that or if I'd prefer Creep Off, but right now I'm staying with Creep On.

 

[david_42]

As several Model S owners have reported, once you're used to one-pedal driving, losing regen completely due to a cold or hot battery can be a real shock. (NPI) If regen is on the brake, this wouldn't be noticeable.

 

[Skotty]

As several Model S owners have reported, once you're used to one-pedal driving, losing regen completely due to a cold or hot battery can be a real shock. (NPI) If regen is on the brake, this wouldn't be noticeable.

That's actually a very good point for what one advantage of regen on brake is. Appropriately engineered, it can handle the necessity for reduced regen transparently. A minor quibble, but valid.

 

[DR61]

EV's bring back the ability to 'engine brake' effortlessly and much more easily than using a gear selector.

Interestingly, when I sell our current 6-speed manual Mini and get the Model 3, it will be the first time in 56 years of driving that I will not have a manual car. My wife similarly has long been a manual driver. We did have a plug-in hybrid as a second vehicle which had mild regen on the accelerator and brake pedal regen (which diminished brake feel). So I hope we will adapt to full regen on the accelerator pedal quickly. I think I will try to test drive an S before we get our configure notice.

 

[mblakele]

Interestingly, when I sell our current 6-speed manual Mini and get the Model 3, it will be the first time in 56 years of driving that I will not have a manual car. My wife similarly has long been a manual driver. We did have a plug-in hybrid as a second vehicle which had mild regen on the accelerator and brake pedal regen (which diminished brake feel). So I hope we will adapt to full regen on the accelerator pedal quickly. I think I will try to test drive an S before we get our configure notice.

I think you'll be happy with it. Regen on the Model S feels to me much like engine braking with a stick-shift. As I ease off the pedal, the car slows down. I felt at home with that right away, because I've always driven without touching the brakes much. For me the main learning process was to go easy on the go pedal, so that regen and acceleration aren't too abrupt.

 

[daniel]

As several Model S owners have reported, once you're used to one-pedal driving, losing regen completely due to a cold or hot battery can be a real shock. (NPI) If regen is on the brake, this wouldn't be noticeable.

That's why they put up a message on the screen, to let you know. I agree that losing regen is a shock, and feels all wrong. But solving that issue by taking regen off the go-pedal is like curing a headache by intentionally stubbing your toe.