Regenerative braking and range

[kort6776]

I would like it if drivers had an option. I was surprised to learn this car only has two levels of regen and it cannot be turned entirely off. My other EV allows it to be turned off and coast. It also uses regen when the actual brake pedal is pressed, unlike the Lucid. That said, I have gotten used to it and drive in the high regeneration setting all the time.

agreed, not having the option to turn off the regen is a flaw, maybe a software fix could address this

 

[hmp10]

Didn't like that what about Porsche's take

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cars.usnews.com

The Porsche take makes more sense technically.

However, it is premised on the net efficiency of first deceleration followed by acceleration, noting that it is best to keep the kinetic energy in the car as much as possible instead of storing it in the battery for retrieval during reaccelerating.

The truck-passing scenario you have described is one of deceleration after the passing maneuver to a lower speed which you intend to maintain. Thus it does not involve the two-way losses Porsche seeks to address. In your scenario, all the energy is dissipated to friction and air resistance losses with none of it recovered to the battery.

 

[hmp10]

that is the theory that porsche went with for the taycan which has minimal regen . . . .

I'm not sure Porsche has minimal regen. I think the main difference is that its regen is triggered only by pressing the brake pedal, not by backing off or releasing the accelerator pedal.

 

[xponents]

I'm not sure Porsche has minimal regen. I think the main difference is that its regen is triggered only by pressing the brake pedal, not by backing off or releasing the accelerator pedal.

This is correct. Porsche does not plan to support one-pedal driving, although there is an extremely mild degree of regen when lifting off the accelerator. They say this is done to increase braking feel, which doesn't make sense to me because... the Lucid would technically have MORE feel than the Taycan when pressing the brake pedal (although obviously, the Porsche's "actual" brakes would soon engage). When was the last time somebody needed to coast on a track?

One pedal driving, in my opinion, is actually more involving regarding the driving experience. But hey, what do I know, I can't even drive

 

[hmp10]

that is the theory that porsche went with for the taycan which has minimal regen.
for me I prefer the regen that the lucid has. once mastered it works well. the minimal savings of range is not that important to me.

There are some larger points to consider here.

Lucid is absolutely obsessed with range -- which is a function of energy efficiency -- viewing it as perhaps the key feature for broadening EV adoption. And Lucid chose the approach they did to regenerative braking in pursuit of that goal. Tesla had the same goal early on of proving that EVs could have practical range, and they chose the same approach.

When the Taycan was first introduced and the auto press questioned why its regenerative braking was triggered only by application of the brake pedal, Porsche's answer at the time was that it wanted to replicate the experience its drivers were used to in operating an ICE vehicle. There was no mention of its greater range efficiency. Even in the article linked above, Porsche still makes the point that one-pedal driving can be uncomfortable for some of its customers.

I don't question the point Porsche raises about two-way losses when staying within the confines of a very specific use case: decelerating slowly by coasting to be followed shortly by return to a higher speed. But I wonder if they aren't making a lot of this limited scenario as justification for their real purpose of eschewing one-pedal driving because it is not familiar to Porsche traditionalists. Claiming it's all about engineering aligns more with the Porsche brand than saying its customers are resistant to certain aspects of technological evolution.

But over the totality of a typical trip where many episodes of speed adjustment occur in different scenarios, I cannot imagine that Lucid would have chosen an approach that would reduce range rather than enhance it.

 

[Steveinarizona]

There is another factor at work here. Lucids and Teslas don't have blended braking systems. In these cars when one steps on the brake pedal, it immediately invokes the friction brake. In a blended braking system initially pressing the brake pedal starts regen but pressing harder starts friction.

Coasting is a reasonable alternative driving strategy for a vehicle with a blended braking system and the Taycan and Genesis GV60 do have blended braking systems. So one can coast in them and step on the brake and still get regen. In my GV60P I drive with the lowest regen setting and use coasting. But in a car without a blended braking system, IMO coasting is less efficient. Because Tesla is so dominant in the field, many users simply assume that all cars work like Teslas.

 

[xponents]

There are some larger points to consider here.

Lucid is absolutely obsessed with range -- which is a function of energy efficiency -- viewing it as perhaps the key feature for broadening EV adoption. And Lucid chose the approach they did to regenerative braking in pursuit of that goal. Tesla had the same goal early on of proving that EVs could have practical range, and they chose the same approach.

When the Taycan was first introduced and the auto press questioned why its regenerative braking was triggered only by application of the brake pedal, Porsche's answer at the time was that it wanted to replicate the experience its drivers were used to in operating an ICE vehicle. There was no mention of its greater range efficiency. Even in the article linked above, Porsche still makes the point that one-pedal driving can be uncomfortable for some of its customers.

I don't question the point Porsche raises about two-way losses when staying within the confines of a very specific use case: decelerating slowly by coasting to be followed shortly by return to a higher speed. But I wonder if they aren't making a lot of this limited scenario as justification for their real purpose of eschewing one-pedal driving because it is not familiar to Porsche traditionalists. Claiming it's all about engineering aligns more with the Porsche brand than saying its customers are resistant to certain aspects of technological evolution.

But over the totality of a typical trip where many episodes of speed adjustment occur in different scenarios, I cannot imagine that Lucid would have chosen an approach that would reduce range rather than enhance it.

Something about Porsches response is not adding up. They are either straight up lying or trying to mislead the public.

The Taycan uses permanent magnet motors, as the Lucid does. It is my understanding (correct me if needed) that these motors literally cannot coast, at least naturally. To give the impression of "coasting" to the driver, they have to provide a small amount of power to the motors.

So my question is, how is this any more efficient than Lucid's implementation, which essentially does the same thing but with one pedal and manually?

 

[Adnillien]

The best estimates for round trip efficiency of regeneration back to drive power is 80% to 85%. This efficiency is consistent with what we see in charging losses (10% to 15%) and drive train losses of about 5%. Friction brakes just turn the cars kinetic energy into heat and result in 100% of the energy being lost. Pure regen or blended brakes will encounter the same round trip losses. A car like the Porsche will keep a small amount of power to the drive unit to simulate coasting. In a one pedal car like Lucid, a skilled driver will modulate power and regeneration to achieve any rate of deceleration or coasting desired. One may method may be better for some drivers while the other may be better for other drivers. If done right, it will not chance efficiency. It is really a matter of preference. The blended brakes feel more like an ICE car and that is natural for many drivers. Pure regeneration is taking advantage of something not available in ICE cars. I prefer the pure regeneration in the Lucid but I understand why a lot of people prefer the blended brakes.

The Green Car Future article is not worth the read. They do not understand basic physics like what kinetic energy is nor do they understand how regenerative braking works.

 

[scal_air]

I don’t know the physics, so I’m not going to pretend to be an expert. All I know is when I drive downhill from Nederland (8200 ft) to Boulder (5600 ft) on high regen, I end up with a few kWh MORE in my battery pack than when I started. That would not happen with coasting. I might end up using almost no energy that whole way down, but I wouldn’t be gaining energy.

That’s true but you’re not coasting the entire way down, right? If regenerative came on when you hit the brakes, you would also gain energy in that situation. I’m curious what a real comparison would show between regenerative braking without coasting (one pedal) and coasting with brakes that engage regenerative…

 

[joec]

That’s true but you’re not coasting the entire way down, right? If regenerative came on when you hit the brakes, you would also gain energy in that situation. I’m curious what a real comparison would show between regenerative braking without coasting (one pedal) and coasting with brakes that engage regenerative…

It's a windy, amazingly fun road all the way down. I don't need to tap my brakes more than once or twice the whole way in the Lucid. I just let up on the accelerator and let regen do its thing to slow down.

In my ICE car, I use brakes before almost every turn. There would be no way to simply coast down that road, no. You'd pick up way too much momentum.

My brake pedal gets less use than anything else on my Lucid.

 

[mezdon]

On my 2019 Hyundai Kona, There are paddles behind the steering wheel that allow me to set the regen level at one of 3 levels. Works great on a big downhill where I can just coast or use a bit of regen to slow down, all with a simple finger flick. I posted about my Lucid ride out of lake placid after the eclipse, where I went 40 miles in 4 hours, and with a combination of regen and coasting managed to to go the 40 miles while only using 38 miles of range. From Lake placid to Keane, about 15 miles on 3 big hills, managed to regenerate about 20 miles of energy. (but at only 10 miles/hr). On a side note, have done those same hills on my bike, and hit 47mph with people passing me. Couldn't go any faster cause ran out of big gears.

 

[terrycs]

It's a windy, amazingly fun road all the way down. I don't need to tap my brakes more than once or twice the whole way in the Lucid. I just let up on the accelerator and let regen do its thing to slow down.

In my ICE car, I use brakes before almost every turn. There would be no way to simply coast down that road, no. You'd pick up way too much momentum.

My brake pedal gets less use than anything else on my Lucid.

I use standard (minimum) regen and the brake pedal every time I wash my car ... only to wipe the rust off the rotor face.

 

[hmp10]

Regenerative braking didn't even cross my mind as a reason for buying our first Tesla in 2015. By the end of the day the car was delivered I was a total convert to regen, thinking it the best feature of the car besides the instant, prodigious torque.

At the time, I lived in a gated community with a half dozen speed bumps between the gate and our house, and I quickly learned to feather the throttle to sail serenely over them and resume speed without ever having to move my foot off the accelerator. I could control the deceleration much more precisely using regen than by trying to figure out when to start coast down in our ICE vehicles, which usually meant finally having to get on the brake pedal for more precise final control.

Soon I began to hear the phrase "one-pedal driving" and realized our Tesla didn't go quite that far with regen. When we traded it for a Model S Plaid six years later, I finally got my first taste of true one-pedal driving, and I instantly embraced it.

I keep both our Tesla and our Air set to maximum regen and would never want a car again without true one-pedal driving.

We forget that when first learning to drive we all had to learn to modulate the brake pedal to stop our ICE cars smoothly. It became such second nature to us early in our driving experience that we no longer realize it was a learned skill, not a genetically-encoded or intuitive one. It's the same with regen and one-pedal driving. To drive smoothly, you have to learn to modulate the throttle during deceleration just as you once learned to modulate a brake pedal. It' no harder to do once you open your mind to it, and it makes controlling the car all the simpler when you can do it with one pedal.

 

[Pittsburgher]

Chiming in on this thread because I have a peripheral question about coasting and neutral.

First, from my 40+ years of ICE driving experience, I have always been a fan of utilizing neutral for improved gas mileage and (theoretically) reduced wear on parts of the ICE drivetrain. Started with manual cars (remember those, ha ha) where going into neutral and releasing the clutch allowed for near frictionless coasting. Then I experimented with utilizing neutral on automatics. Works just as well, and with a little rev matching when going back into D, seems to not cause any damage to transmissions. I have never had any transmission issues on any of my (20+ ?) vehicles over the years. Seems BMW now offers this feature as "behind the scenes" activity when drivers use ECO mode . . . where the car will decouple the drivetrain (significantly reducing driveline losses) when going downhill. This to me makes WAY more sense for improving gas mileage than say, "smart" alternators, which result in an ~ $700 cost for battery replacement (because a tech has to connect a laptop and do "reset" procedures to teach the alternator that a new battery has been installed). I digress - but what a joke.

So . . . I have yet to use neutral (regularly) on my Air Touring . . . and, like HMP and many others, I have FULLY embraced one pedal driving. It's awesome (in either regen mode) and I expect to keep my Lucid for 10 years or more, and expect to never replace brake pads. That said, I do have issues with getting mild oxidation on the rotors. And I dislike the severity of deceleration required to get enough braking to actually clean the rotors, even when in low regen mode. So I recently found a nice 1/4 mile hill, and by shifting into neutral on a rolling start at the top of the hill, and using the brakes gently the whole way down the hill, was able to clean the brake rotors nicely. Worked perfectly.

This leads to the question of understanding whether operating the car in neutral on longer hills at highway speeds is harmful to the car ? More importantly, would disengaging (going from D to N) at 75 mph, or reengaging (N to D) at 65 or 70 mph (say at the bottom of a hill) be harmful to the car ?

I have no physics or mech engineering background to back this up, but I do feel like "feathering" the go pedal to try to maintain the narrow band between acceleration and regen, is not only kind of a PITA, but also intuitively seems to be less efficient than allowing the car to coast in neutral as far as it can before reengaging D (like a soap box derby car). I would only do this on specific grades where the vehicle maintains speed (+/- 5-10 mph), and engaging the friction brakes is unnecessary.

Would love to hear any thoughts (admittedly, more on the potential vehicle harm, than on the debate around efficiency) !

 

[st50maint]

For what it’s worth, coasting in neutral on a downgrade is illegal in many states.

“The driver of a motor vehicle when traveling on down grade upon any highway shall not coast with the gears of such vehicle in neutral.”

 

[joec]

Chiming in on this thread because I have a peripheral question about coasting and neutral.

First, from my 40+ years of ICE driving experience, I have always been a fan of utilizing neutral for improved gas mileage and (theoretically) reduced wear on parts of the ICE drivetrain. Started with manual cars (remember those, ha ha) where going into neutral and releasing the clutch allowed for near frictionless coasting. Then I experimented with utilizing neutral on automatics. Works just as well, and with a little rev matching when going back into D, seems to not cause any damage to transmissions. I have never had any transmission issues on any of my (20+ ?) vehicles over the years. Seems BMW now offers this feature as "behind the scenes" activity when drivers use ECO mode . . . where the car will decouple the drivetrain (significantly reducing driveline losses) when going downhill. This to me makes WAY more sense for improving gas mileage than say, "smart" alternators, which result in an ~ $700 cost for battery replacement (because a tech has to connect a laptop and do "reset" procedures to teach the alternator that a new battery has been installed). I digress - but what a joke.

So . . . I have yet to use neutral (regularly) on my Air Touring . . . and, like HMP and many others, I have FULLY embraced one pedal driving. It's awesome (in either regen mode) and I expect to keep my Lucid for 10 years or more, and expect to never replace brake pads. That said, I do have issues with getting mild oxidation on the rotors. And I dislike the severity of deceleration required to get enough braking to actually clean the rotors, even when in low regen mode. So I recently found a nice 1/4 mile hill, and by shifting into neutral on a rolling start at the top of the hill, and using the brakes gently the whole way down the hill, was able to clean the brake rotors nicely. Worked perfectly.

This leads to the question of understanding whether operating the car in neutral on longer hills at highway speeds is harmful to the car ? More importantly, would disengaging (going from D to N) at 75 mph, or reengaging (N to D) at 65 or 70 mph (say at the bottom of a hill) be harmful to the car ?

I have no physics or mech engineering background to back this up, but I do feel like "feathering" the go pedal to try to maintain the narrow band between acceleration and regen, is not only kind of a PITA, but also intuitively seems to be less efficient than allowing the car to coast in neutral as far as it can before reengaging D (like a soap box derby car). I would only do this on specific grades where the vehicle maintains speed (+/- 5-10 mph), and engaging the friction brakes is unnecessary.

Would love to hear any thoughts (admittedly, more on the potential vehicle harm, than on the debate around efficiency) !

I would not shift the Air while in motion. Neutral is sort of difficult to engage in the first place; you could easily accidentally throw it into reverse. And I don’t think there would be any benefit mechanically, anyway.

 

[hmp10]

Neutral is sort of difficult to engage in the first place; you could easily accidentally throw it into reverse.

I think Lucid's software blocks going into reverse while the car is in forward motion.

In our Honda Odyssey, the windshield wiper swipe function is engaged by pushing upward on the right-side steering wheel lever (exactly where the Air's gear shift lever is). On a couple of occasions I have absent-mindedly tried to swipe the wipers in our Air by pushing the gear lever upward. Fortunately, nothing happened.

 

[Steveinarizona]

In our Honda Odyssey, the windshield wiper swipe function is engaged by pushing upward on the right-side steering wheel lever (exactly where the Air's gear shift lever is). On a couple of occasions I have absent-mindedly tried to swipe the wipers in our Air by pushing the gear lever upward. Fortunately, nothing happened.

I find this type of problem is magnified on rental cars when one has a vehicle for the first time. I remember many years ago renting a car at the San Diego airport and getting a Chrysler PT Cruiser. I started the car and drove to the exit window where I would normally hand the paperwork to the attendant for confirmation before being allowed to drive out. Alas...I couldn't find the power window buttons. Instead of putting the buttons on the door, like every other car company at the time, Chrysler put them in the middle of the dashboard.

I am driving a Genesis now. It seems that for half of the current generation Genesis, the company has switched the steering wheel controls from side to side. I have no idea which is original nor do I care; but I do wish that it would be consistent. I used to have a BMW PHEV; the charging port was on the driver side fender. That is where I had installed my EVSE. But on the new EVs, BMW has put the port on the passenger side rear fender. These are just a few examples. There are many, many such examples from just about every car maker.

 

[hmp10]

I find this type of problem is magnified on rental cars when one has a vehicle for the first time.

It's a particular problem for Americans with things Japanese. I've owned quite a few Japanese, German, and American cars over the years. The control layouts of the German and American cars were similar, but the Japanese cars invariably reversed everything.

And it doesn't just apply to cars. I used to travel to Japan frequently on business and found everything reversed. You flip Japanese light switches down to turn them on. Hot and cold water taps are reversed, and you turn those taps in the opposite direction from Western taps. You face the wall on some toilets. You drive on the left side of the road (as in England and most of its former colonies).

One night at a dinner in Osaka I was telling one of our company's expats how odd I found this consistency of reversal. He started laughing and told me a story. He had gone for his annual physical on one of his visits back to the U.S. The doctor looked at his abdomen and asked him about a fresh surgical scar. He told the doctor he had to have an emergency appendectomy in Japan. The doctor said, "no, that's not from an appendectomy. An appendectomy scar is horizontal, not vertical." (This is actually done for anatomical reasons, based on something called the McBurney point, which makes the Japanese determination to go the opposite way seem even more perversely determined to be contrarian.)

 

[kort6776]

the range gained by trying such tricks is minimal at best and not worth the bother.