Regenerative braking vs brake pedal

[StealthP3D]

No. Brake pedal does friction brakes only. Regen is accomplished only by letting off the accelerator.

Newbies could find that misleading (although it's correct). It should be noted that when you lift off the accelerator and apply the brakes, you are getting full regen as soon as you lift off the accelerator and this regen is blended in with whatever friction braking you chose to add with the brake pedal. In practice, I find I never use the brake pedal unless it's an emergency. So it's basically 99.5% regen, 0.5% friction braking. Most of the time my foot never completely leaves the accelerator.

In milder winter weather down to around 25F, I may find the cold battery will cause regen to be limited but, even then, I generally have enough regen to not need to make use of the friction brakes when driving in normal, smooth traffic. When it gets frantic, all bets are off and the friction brakes are occasionally used here and there.

Ooops! I just noticed this is a Model S forum. I have two Model 3's.

 

[StealthP3D]

Agreed on all of the above. I find it amusing that occasionally people will complain about the feel of the regen. I actually get slightly annoyed when I have to push the brake. It's become a challenge to see if I can make one set of pads last forever. I find myself often debating if I should turn off 'creep' to get even just a little more regen when slowing.

You have "Creep" enabled? And you admit it?

 

[Jughead135]

So, one poster has stated 60kW of regen available, another has said 75kW. Since I don’t have any feel at all for what that means in terms of stopping power, the number doesn’t matter to me.

Question, though: when I’m using regen for the max stopping it will give me (ie, foot completely off the pedal), is that the maximum regen the car is capable of? Put another way, in TACC or higher levels of AP, can HAL decide to use more regen than than available in manual mode? Or is it all wheel brakes once that same maximum level of regen is reached?

 

[StealthP3D]

So, one poster has stated 60kW of regen available, another has said 75kW. Since I don’t have any feel at all for what that means in terms of stopping power, the number doesn’t matter to me.

Question, though: when I’m using regen for the max stopping it will give me (ie, foot completely off the pedal), is that the maximum regen the car is capable of? Put another way, in TACC or higher levels of AP, can HAL decide to use more regen than than available in manual mode? Or is it all wheel brakes once that same maximum level of regen is reached?

While using Traffic Aware Cruise Control, if the system requires more braking than the maximum regen available, it will blend in an appropriate amount of friction braking rather than increase regen past the programmed limit.

 

[dark cloud]

I am at 126,000 miles and nowhere near ready. I am a big regen fan and avoid brakes whenever feasible.
Which, I guess for me, is almost always.

If all goes well, you are about half the way there. David99 just did one set at 260,000 miles.

 

[dark cloud]

So, one poster has stated 60kW of regen available, another has said 75kW. Since I don’t have any feel at all for what that means in terms of stopping power, the number doesn’t matter to me.

Question, though: when I’m using regen for the max stopping it will give me (ie, foot completely off the pedal), is that the maximum regen the car is capable of? Put another way, in TACC or higher levels of AP, can HAL decide to use more regen than than available in manual mode? Or is it all wheel brakes once that same maximum level of regen is reached?

From what I have read, no, the motors in the car are capable of more, but that is all Tesla is allowing the battery to receive whether no brakes or panic stop.

The rear wheel drive cars were first limited to 60 kW regen, because I assume in their testing any more would increase the likelihood of the back end locking up and we know that would not be good.

Once they brought out dual motor (AWD) the regen could be balanced between the 2 motors and there is some evidence from those with Canbus readers that they are receiving 77 kW of regen energy charging. More is possible but I assume that is the limit due to battery longevity.

Of course if you need more energy in the form of deceleration or stopping power than the excess is absorbed (used) by the friction brakes and the energy is dissipated as heat, like an ICE, whether you are using TACC, AP or stopping the car without driver assistance. In the truck example above that energy is dissipated as heat, but through gearing through the compression of the engine. Truckers use a "Jake brake" using the same principle.

Having said that there was an energy graph from the Plaid at Nurburgring I saw and the regen looked like upwards of 90-100 kW, but racing or testing in attempting a one-off short lap time is not at all concerned with battery longevity. (obviously during racing the battery was warm enough to accept those high short bursts of charging)

 

[MXLRplus]

My Model X sometimes adds friction braking when I lift the throttle especially at higher speeds, SOC >80%, or temps <60°F. It also uses them at <2 mph best I can tell It bottoms out at maybe 70kW which is not a lot. You can sometimes see it bottom out the power meter but continue to add more retard force. I do wish Tesla would incorporate a numeric kW meter for us Hypermilers and EV geeks. Using a numeric meter can 'educate' your foot better for maximum range.

But with 351 miles of Monroney range, it's mostly a game for me, not a necessity like some of my other EVs.

 

[David29]

I have been interested to notice that reviews of the Porsche Taycan have complained about how Porsche implemented the regen braking on that car, only through the brake pedal. reviewers who were accustomed to other EVs did not find the "blended" braking on the Taycan to be very smooth, and that the lack of one-pedal driving reduced the car's efficiency. I guess that Porsche preferred the more traditional notion that one pedal was strictly to "go" and the other one was for slowing and stopping.

 

[2101Guy]

There is a road outside of Yosemite National Park called Old Priest Grade that I've read to be 18-20% grade in parts. I've lost brakes in older cars coming down it. In my '05 Prius, I would lose regen part way down as the battery became fully charged. I've recently taken my M3P+ down it and could control the speed to down to a CRAWL if I wanted using only accelerator pedal. No brake pedal at all. Surreal...I only had to use brakes in the last 15' coming to the stop sign. Is this really ONLY regen? So, it doesn't use friction brakes at all on aggressive decel? Very hard for me to get my mind around slowing a 4100lb vehicle to 15mph coming down a cliff...I did not smell any brakes at any point. I was beside myself as we came down it, bugging my wife because I was like a little kid. "DO YOU REALIZE WHAT'S HAPPENING RIGHT NOW??? I'M NOT USING ANY BRAKE AT ALL!!!" I was blown away... So, really? It doesn't use brakes at all during regen? Love this car...

There is even a poster on here (cant recall the name..and probably more than one) who was/is able to modify the software to get as much or as little, regen as he wants. I think I recall reading on a post here that he had to back it down a bit due to wheels locking up due to excess regen.

 

[Magiken]

My wife's first Model S (2013) went around 185,000 before trading in.

But her last service check revealed the brake pads had used less than 1 m/m. We were told a million miles would have been achievable.

Wow!

 

[Magiken]

You have "Creep" enabled? And you admit it?

Yup. I'm creepy.

 

[Ciaopec]

My Model X sometimes adds friction braking when I lift the throttle especially at higher speeds, SOC >80%, or temps <60°F. .

How did you determine that friction brakes are used at that point ? Or, are you assuming, since the brake lights come on as a result of high deceleration, that the vehicle is using friction brakes?

 

[dark cloud]

I have been interested to notice that reviews of the Porsche Taycan have complained about how Porsche implemented the regen braking on that car, only through the brake pedal. reviewers who were accustomed to other EVs did not find the "blended" braking on the Taycan to be very smooth, and that the lack of one-pedal driving reduced the car's efficiency. I guess that Porsche preferred the more traditional notion that one pedal was strictly to "go" and the other one was for slowing and stopping.

I didn't know that! Wow. That one decision would prevent from ever owning that car.

 

[MXLRplus]

How did you determine that friction brakes are used at that point ? Or, are you assuming, since the brake lights come on as a result of high deceleration, that the vehicle is using friction brakes?

Without a real gauge, it's tough. I'll admit I'm basing that post on 8 years of experience driving numerous EVs. You know that dashed yellow line that appears on the regen side of the analog kW gauge? That is not full story. That comes on when your regen is capped at ~45 kW or lower. But you will see the needle bottom out at 55-50 a lot when the line is not present. You really have drive a car with massive regen to get a good 'feel' for what is occurring. Some cars regen at over 200 kW. The Tesla has a similar amount of retard but doesn't have that 200+ kW of regen occurring.

The way to test it would be with a laser pyrometer (cheap). Accelerate to 80, then lift, and allow the car to stop on it's own. Now check the rotors with the pyro.

 

[Ciaopec]

Without a real gauge, it's tough.

<SNIP>

The way to test it would be with a laser pyrometer (cheap). Accelerate to 80, then lift, and allow the car to stop on it's own. Now check the rotors with the pyro.

This is where I get my idea of how the system works: Page,67 of the Owner's Manual.

 

[Saguarojoe]

The parking brake engages automatically for us, too ("hold mode" / ((H)) is the same physical braking mechanism as the parking brake, yes?).

Re "how hard" the regen can brake: I have no idea of the physics behind it--I guess it's a design decision to limit it...?

Hold mode is a fantastic feature. It kicks in as soon as the car stops and will prevent roll back or forward under any circumstances that I’ve experienced so far.

 

[maximnl]

Without being able to get into technicalities, I feel like I understand regen braking when I let up on the accelerator.

What about the brake pedal? Is it purely traditional friction braking? Or is a certain percentage (or perhaps "initial stages") of braking achieved via regen through the pedal, too?

Prior to my MS, my only experience with regen braking was in my aunt & uncle's Prius. The brake pedal on that car blends regen & friction braking. Different car, obviously, and the hybrid vs all-electric is only the most obvious difference. But, such a "blended" system is out there....

Is there any such mixture going on in our cars?

regen braking is not that nice as you think. Most of the time you brake too fast but you loose energy when kinetic energy is converted to electric. For highways you make most miles if it is off. I switched to middle option from aggressive regeneration and make more miles in mixed city -highway cycle. I wish tesla made middle option even softer as the car brakes too fast instead of naturally braking due to air resistance and friction.

 

[Saguarojoe]

There is a road outside of Yosemite National Park called Old Priest Grade that I've read to be 18-20% grade in parts. I've lost brakes in older cars coming down it. In my '05 Prius, I would lose regen part way down as the battery became fully charged. I've recently taken my M3P+ down it and could control the speed to down to a CRAWL if I wanted using only accelerator pedal. No brake pedal at all. Surreal...I only had to use brakes in the last 15' coming to the stop sign. Is this really ONLY regen? So, it doesn't use friction brakes at all on aggressive decel? Very hard for me to get my mind around slowing a 4100lb vehicle to 15mph coming down a cliff...I did not smell any brakes at any point. I was beside myself as we came down it, bugging my wife because I was like a little kid. "DO YOU REALIZE WHAT'S HAPPENING RIGHT NOW??? I'M NOT USING ANY BRAKE AT ALL!!!" I was blown away... So, really? It doesn't use brakes at all during regen? Love this car...

if you saw the green line and no dotted line and no warning message then my guess is yes. Regren.

 

[Jughead135]

regen braking is not that nice as you think. Most of the time you brake too fast but you loose energy when kinetic energy is converted to electric. For highways you make most miles if it is off. I switched to middle option from aggressive regeneration and make more miles in mixed city -highway cycle. I wish tesla made middle option even softer as the car brakes too fast instead of naturally braking due to air resistance and friction.

I don't understand what you're saying. Once you get used to the one-pedal driving, you just put the pedal "where it needs to be" in order to give you whatever amount of speed maintenance and/or acceleration and/or deceleration you want. If/when you get to the maximum decel that the regen will give you, then you need the wheel brakes.

It is an adjustment, to be sure, but one I'm glad I made!

 

[MXLRplus]

Your best range will be achieved with no regen and no braking, but that is impractical. One of the joys of Tesla ownership is the one-foot or no foot driving experience. With the Tesla's range, hypermiling is a choice, not a requirement.