Safer or better driving experience with energy recovery?

[WasserGKuehlt]

We have particularly icy conditions in Norway right now, and my view is a bit different than this. Also on ice and slippery snow I prefer coasting (=no regen-on-liftoff) as I am then 100% sure that all wheels are rolling with no attempted braking. Then I use the brake pedal (to get some regen) or acceleration when and where I think there is low risk to it.
The lift-off regen can well be so weak and controlled that the car won't start skidding, but better safe than sorry.

Agreed, one needs to find the 'safe' limit to slowing down without losing traction. With recoup on, I still control braking, but with the accelerator pedal.

Sponsored

 

[Scandinavian]

We have particularly icy conditions in Norway right now, and my view is a bit different than this. Also on ice and slippery snow I prefer coasting (=no regen-on-liftoff) as I am then 100% sure that all wheels are rolling with no attempted braking. Then I use the brake pedal (to get some regen) or acceleration when and where I think there is low risk to it.
The lift-off regen can well be so weak and controlled that the car won't start skidding, but better safe than sorry.

It must be very icy in Norway now then. When I was there over Christmas it was quite slippery with ice at round about and up to the entry of the round about. But I never had any issue at all with the regen on at lift off. Felt very stable and smooth. Gentle slowing of the car that way felt very safe.

And 4 wheel drive managed to pull us out of some tricky sitauations

 

[Avantgarde]

This part of your quote confused me. If turning it off gets better range, what's the point of having regenerative braking? I always thought the purpose of it was to return some energy (however minimal) back to the battery and hence, improving range (in whatever capacity).

I think what you're saying (and maybe I'm misunderstanding) is that the benefit of "coasting" outweighs the benefit of returning energy back to the battery? If so, has anyone ever been able to quantify the difference?

Often confused topic. Here is my take in case it helps. Start with 3 facts:

1- It is more efficient to not to brake at all if possible (regen or pads)
2- If the car needs to brake, Regen is always better than pads, because you are recouping some of the energy back (although not all the energy back)
3- In Taycan Regen can work in two ways: by moderately pressing brake pedal (even in coasting mode) or by turning on lift-off regen feature (in which case regen slows the car down every time you lift off accelerator even when you are not braking, which is the ONLY way a Tesla utilizes regen braking)

"Regen is more efficient" - by this, I believe many people seem to mean "Lift-off regen feature is more efficient": Is it true? It depends. On two critical factors:

A- Inefficiency of lift-off regen: Auto Lift-off results in unnecessary regen braking when the driver actually does not intend to slow down. In these instances, yes regen captures some of the energy back but it is not a 100% efficient system. Lets say it captures 70% of the energy back and 30% is lost due to mechanical inefficiencies. So every unnecessary slow-down results 30% of loss.

B- Efficiency benefits of lift-off regen: Lift-off regen reduces the instances of "hard braking", where braking force needed requires brake pads to engage. Every time brake pads engage it results in 100% loss of energy. So the less this happens, the higher the efficiency. Since lift-off naturally and immediately slows down the car every time the driver lifts the foot off the accelerator, it is less likely to "slam the brakes" due to last minute notice of a stopped traffic etc.

So for any given drive profile if B>A then yes "LIFT-off regen will be more efficient" if A>B then "Coasting option" will be more efficient. In reality, for most drivers A>B is a LOT more likely to be the case and that's what Porsche is referring to when they say "coasting is more efficient".

Then why did Tesla choose the "other way" only? - Cost and simplicity. Because by relying on "lift-off" for all regen braking, they dedicated brake pedal to only conventional braking, which meant they did not have to go through the mechanically complex business of blending regen with conventional braking when brake pedal is pressed. (which they would probably do a horrible job anyways). And the fact that at least some (B) exists helped them make this trade-off, even if they knew (B) is not greater than (A) for most people.

Finally, I think another downside of lift-off auto regen could be on battery longevity. Time will tell, but can't help but think, unnecessary brake/charge-acceleration episodes will inevitibly result in higher # of Battery-discharge-charge cycles in the long run.

 

[or1]

It must be very icy in Norway now then. When I was there over Christmas it was quite slippery with ice at round about and up to the entry of the round about. But I never had any issue at all with the regen on at lift off. Felt very stable and smooth. Gentle slowing of the car that way felt very safe.

And 4 wheel drive managed to pull us out of some tricky sitauations

It is extremely slippery just now around where I live, and yes roundabouts seem particularly hit. Lift-off regen may handle also this well, as per your experience. Still, I prefer that all friction that can be mustered is available for my actions and not partly being used up by automatics. Not that I think I am better than automatics, but it cannot know what I intend to or need to do in the next seconds. If I will need max for steering, I don't want to have to give a touch of "throttle" to null out the lift-off regen, or press the button suddenly to turn it off.

But that is how my brain and operator feelings work around this, others may find other ways that work as well.

 

[sufcrusher]

Excellent summary.

Then why did Tesla chose the "other way" only? - Cost and simplicity. Because by relying on "lift-off" for all regen braking, they dedicated brake pedal to only conventional braking, which meant they did not have to go through the mechanically complex business of blending regen with conventional braking when brake pedal is pressed. (which they would probably do a horrible job anyways). And the fact that at least some (B) exists helped them make this trade-off, even if they knew (B) is not greater than (A) for most people.

I do find it sad that plenty of people are blindly parroting Tesla fanboy or marketing speak on how amazing and innovative and more efficient their one-pedal-driving is. And, deliberately or not, implying that the Taycan can't do regen at all.

For example: The first thing the Lucid salesman proudly told me when I went to make a test drive: "yes, we have one pedal driving, it's so much better and more efficient, unbelievable that your Taycan doesn't have it." /facepalm

Personally I'm 100% convinced free coasting is better for efficiency.

 

[mystermykee]

I drive with both overrun recuperation on and off, mainly on for when it makes sense given the current traffic conditions (a lot of speed changes). I prefer "engine braking" instead of riding my brake pedal to control speed. As for overrun recuperation being safer with respect to braking time/distance, it's hard to definitively say.

However, what I do know is that the accelerator and brake pedal mappings are different when overrun recuperation is on compared to when it is off. When it is on, there's already some regen being applied. For example, if you depress the brake pedal two inches, you'd get more total regen than if depressing the brake pedal the same amount with recuperation off. In that sense, the brakes seem to "bite" faster. Couple that with TSB: Brake Pedal Travel Perceived as “Too Long” Just Before the Vehicle Comes to a Standstill - July 18, 2023, the Taycan brakes feel much closer to that of an ICE car. I love how Porsche decided to blend regen with mechanical brakes, it makes for a much better driving experience. It's very difficult to decel both quickly AND smoothly when regen and brakes being separate like Tesla and Lucid. Just ask your passengers.

As for efficiency, I guess I'm in a small majority and could care less about it, especially since my daily commute keeps me between 30-60% SoC before I charge again at night. I like to think of it as unlimited miles/day!

 

[OzzieT]

No, it's not.

Regenerative braking is not user-adjustable on the Taycan.

What you enabled is the lift-off-accelerator recuperation.

Thanks @DerekS for the correction. I've updated the post. For those who did not know the difference like me, the following courtesy of Copilot:

Regenerative braking and recuperative braking are two terms that are often used interchangeably, but they are not the same thing. Regenerative braking is a mechanism that allows electric vehicles and hybrids to operate more efficiently by making use of the kinetic energy created when the vehicle slows down. When you hit the brakes on a car, kinetic energy is created. Regenerative braking lets EVs and hybrid vehicles store some of that kinetic energy in the battery to use when you accelerate again.

Recuperative braking, on the other hand, is a braking system that recovers energy from the braking process and converts it into electrical energy. This energy can then be used to power the vehicle’s electrical systems or stored in the battery for later use. Recuperative braking is used in electric trains, trams, and some electric cars.

In summary, regenerative braking is a type of recuperative braking that specifically refers to the process of storing kinetic energy in the battery to use when accelerating again, while recuperative braking is a more general term that refers to any braking system that recovers energy from the braking process and converts it into electrical energy

 

[WuffvonTrips]

For those who did not know the difference like me, the following courtesy of Copilot:

I'll stick my neck out and say that I don't believe that that distinction between regeneration and recuperation is correct- some manufacturers may use distinctively different definitions of the 2 processes, but in general, they are both basically converting kinetic energy to electrical energy, resulting in the car slowing down (or not speeding up on a descent), regardless of whether triggered by the brake pedal or some automatic or default behaviour of the car (such as simulating OCE overrun, or automatically braking to some extent when the accelerator is released).

When you hit the brakes on a car, kinetic energy is created.

No, it's the opposite- KE is lost when slowing down. In the case of regen/recup, it's lost by conversion to electricity (and heat, because the conversion process is less than 100% efficient).

 

[WhydidisellmyM5]

A few weeks ago I had a very low speed, minor collision, necessitating a few weeks off the road for body shop repairs. I hit the brakes pretty hard but the Taycan is a very heavy car and no matter what the speed, it takes a bit of stopping. I 'just' hit the car in front of me and the tow bar height on the SUV was perfectly positioned to punch a hole in my lower front bumper.

Since receiving my car from the repairers, I am a little more wary of low speed collisions. Applying the brake pedal is different in the Taycan over my previous ICE vehicles. It seems the brake is not as responsive or instantaneous with a gentle push, and I don't know if that is due to the fact it is electronic, or if the car is so heavy, or both. High speed braking seems more normal, but low speed braking feels different and there have been a couple of other close shaves.

Recently I switched on energy recovery. This is different to regenerative braking, so is called energy recovery in the Taycan (except if you search for it in the online manual in the Porsche app when you need to use 'recuperation' as the search term). There is no reason why I had it switched off to begin with other than I'm new to EV's. Mine is now set to 'Auto' and it has made a profoud difference. Not so much from a battery perspective, but rather a driving experience.

When you lift your foot off the accelerator, energy recovery kicks in and immediately creates a decelaration effect. I'm now finding that reassuring from a driving perspective, especially at lower speeds. Energy recovery is commencing the braking motion before I have a chance to touch the brake, and when I do touch the brake, it seems it has more of an immediate impact. Aside from the reassurance, it does make the driving experience feel safer.

Interested in thoughts and perspectives from the EV pro's and the newbies like me.

this is a known issue that Porsche are fixing from what I’m told. I have my car going in for one small issue, I mentioned this issue and they said they are aware but it would need a rebooking as it’s not a rapid fix. I likened it to the brakes on my bike needing bleeding and not always being there when you needed it:

 

[Jhenson29]

I'll stick my neck out and say that I don't believe that that distinction between regeneration and recuperation is correct- some manufacturers may use distinctively different definitions of the 2 processes, but in general, they are both basically converting kinetic energy to electrical energy, resulting in the car slowing down (or not speeding up on a descent), regardless of whether triggered by the brake pedal or some automatic or default behaviour of the car (such as simulating OCE overrun, or automatically braking to some extent when the accelerator is released).

I basically agree, at least in the context of electric vehicles, but I’ll add some thoughts.

I’ve stated it before, but we use “regen” to refer to any negative torque at the motor. Think of “generator”. So, regen is more a property of what’s happening at the motor with no regard to where the energy is going.

“Recup” is referring to “recovering” the energy (in this case, kinetic energy returned to the battery; instead of being lost as heat).

The Taycan has no regen without recup (there’s no where else for the energy to go, like braking resistors, or another inverter on a common DC bus). So, I tend to use the terms interchangeably on the Taycan, unless I have a specific meaning where one is more applicable (e.g. I tend to use “recup” when discussing Porsche modes because that’s the term in their manuals or I use “regen” more often if discussing something specific about the motor and not the system as a whole). Edit: and often default to the term the other person is using if responding to someone.

But I don’t generally fuss about it unless a term is very wrong for the context, which isn’t typically the case in discussions about the car.

Sponsored