additional regen braking from the brake pedal finally?

[bhzmark]

The last part of that statement is wrong. THERE IS NO SUCH THING AS UNTAPPED REGEN IN A TESLA. Tesla has defined maximum regen as 60kW. Many factors went into that decision like ability of the pack to accept charge, traction, passenger comfort, etc. Tesla then decided to apply 100% of regen on the accelerator and 0% on the brake pedal.

Can anyone prove that ibooster cars don't use add'l regen from the brakes with the ibooster?

IF THE BATTERIES CAN TAKE ADD'L REGEN THEN THERE IS UNTAPPED REGEN. that is true whether I type it an all caps or not.

using the ibooster to get add'l regen from the brakes instead of making brake dust would be be very wise. Why waste the opportunity to be more efficient?

 

[woof]

Can anyone prove that ibooster cars don't use add'l regen from the brakes with the ibooster?

Hard to prove a negative.

Easy for you to make the case however:

1. Go down a big hill at high speed.
2. Let off the accelerator, see how many kWh are being regened. (Assuming this is max regen, about 60 kWh)
3. Lightly press the brakes, see how many kWh are being regened.

If the kWh at step 3 are larger than step 2, you are correct!
However, if the kWh at step 3 are less than or equal to step 2, you are not.

Take a video and post it here.

 

[strider]

Can anyone prove that ibooster cars don't use add'l regen from the brakes with the ibooster?

IF THE BATTERIES CAN TAKE ADD'L REGEN THEN THERE IS UNTAPPED REGEN. that is true whether I type it an all caps or not.

using the ibooster to get add'l regen from the brakes instead of making brake dust would be be very wise. Why waste the opportunity to be more efficient?

Your first statement doesn't make any sense. By definition, if the car is being slowed via regen then it is not using the brakes, regardless of which pedal instructs the car to regen. My point stands. Tesla designed the car to have 60kW of regen. Only they know all of the reasons why they did this and it has nothing to do with which pedal applies the regen.

If the batteries (and all other systems, and traction, and....) can take additional regen Tesla can simply add more regen to lifting off of the accelerator. There's nothing magical about the ibooster - during regen it is simply sending messages to the EV drivetrain to tell it how much regen to apply (on a 0-100% of the manufacturer's max regen amount) and if you keep pressing the brake pedal blends in friction brakes.

 

[martinwinlow]

I think everyone who has an interest in this thread (and the head of Tesla engineering) should have a go in an i-MiEV - or at least the Peugeot/Citroen badged ones (I have the Peugeot). The implementation of the regen on this car is, IMO, simply perfect. It is quite possible with the use of good forward vision and a reasonably light right foot, to drive entirely on the accelerate except for the very last few feet (esp if you are stopping on an incline). The function of acceleration and deceleration by accelerator pedal only is flawless and totally smooth. I am looking forward to seeing how the MS compares but from what I have read here it looks like I will be missing my iOn for this aspect of its amazing engineering accomplishment, at least.

 

[glhs272]

One thing that seems to be lost in this discussion is what would be the effect to the existing braking system with increased regen? Currently, in the winter rain/snow do hell on my rotors. I have to make a point of using the real brakes every time I drive to keep them functional. When they get too corroded they don't work effectively. Unlike a ICE car where you use your brakes all the time, the model S brakes rarely get hot during normal driving. So the rotors don't bake off the moisture like they do on a ICE car. This probem has been the biggest disappointment with the Model S brakes. I would have preffered that Tesla used speacial corrosion resistant alloys in the rotors to prevent this issue.

 

[green1]

IF THE BATTERIES CAN TAKE ADD'L REGEN THEN THERE IS UNTAPPED REGEN.

except that we pretty much know that the batteries can not take any additional regen. There are supercharger taper rate graphs posted in other threads that show that by a 50% charge the rate is down to about 60kw or less. This taper rate is generally seen as being as aggressive as Tesla dared to attempt. If the car could safely put more than 60kw in to the battery at a wide range of charging states they could do a more aggressive regen, but if that were the case we'd also see less taper on the superchargers. Sure you could adapt the regen so is stronger when charge state is low and weaker when the charge state is high, but that inconsistency would be a nightmare for the driver, just look at all the posts we already see about regen limited when the pack is cold or full.

 

[ratsbew]

I definitely prefer 100% of regen to be on the accelerator. If I press the brake pedal I want to know that I'm using the friction brakes. I don't want to press the brake pedal and wonder if I'm using 95% of regen or only 80%. In other words...I want to always use 100% regen and use the friction brakes as close to never as possible. I see friction brakes as a complete waste of kWh.

 

[bhzmark]

The last part of that statement is wrong. THERE IS NO SUCH THING AS UNTAPPED REGEN IN A TESLA. Tesla has defined maximum regen as 60kW. Many factors went into that decision like ability of the pack to accept charge, traction, passenger comfort, etc.

If by "UNTAPPED REGEN" you mean the full amount of regen that is currently designed into the accel lift off deceleration curve, then yes you are correct.

But a more interesting concept is the maximum regen possibly available to recharge the existing battery pack -- not limited by "passenger comfort."

That additional regen would be the full potential of the electric motors to convert even more energy into electricity which could be obtained by allowing a stronger braking effect and more powerful regen.

Why didn't they do that with the 2WD S? Two likely reasons: 1) the braking effect would be too strong -- it would be like applying a moderate (not just minor) force on the brake and the car would decel too quickly; 2) creating braking resistance with only the rear wheels is not desirable (this is demonstrated in a video clip in an earlier thread posted on this same topic that shows a decelling S fishtailing on a slick service because of the strong braking effect applied only to the rear wheels).

# 2 can be fixed with the current addition of the front motor to use the front wheels to apply the braking power. # 1 can be fixed by using the brake pedal to capture that currently unavailable (but potentially available) additional regen from a stronger braking effect.

If you still don't understand and you think that the maximum braking effect that Tesla designers thought was an acceptable driver experience from the accel lift off just happened to coincide exactly with the maximum possible regen that was possible from the rear motor and rear wheel in full regen mode, then consider: now that we have the front wheels and the front motor to create even more than twice the regen, shouldn't the accel lift off now be much stronger and slow the car much quicker on mere accel lift off?

Can't you see how the potential regen from all four wheels and two motors might be too much to have with just accel lift off and so some of that regen would be left untapped unless it could be responsive to the appropriate driver input of, say, the application of the brake pedal?

If Toyota can do it, I"ll bet Tesla can (is?) do it even better. As they did with adaptive cruise.

For all I know, they already do it and the people arguing to NEVER EVER trigger regen from the brake pedal will be surprised to learn that the ibooster equiped Tesla's are already making add'l regen from brake pedal application! Horrors and blasphemy if that were the case!

 

[jerry33]

But a more interesting concept is the maximum regen possibly available to recharge the existing battery pack -- not limited by "passenger comfort."

I'm more concerned with the person who is too close behind me. The amount of regen braking there is now is just about right to prevent them from crashing into me. Be real careful about what you ask for.

That additional regen would be the full potential of the electric motors to convert even more energy into electricity which could be obtained by allowing a stronger braking effect and more powerful regen.

The only time a stronger braking effect would be in an emergency, and then you're going to mash the brake pedal regardless. With luck, this is an infrequent occurrence.

If you still don't understand and you think that the maximum braking effect that Tesla designers thought was an acceptable driver experience from the accel lift off just happened to coincide exactly with the maximum possible regen that was possible from the rear motor and rear wheel in full regen mode,

About all this will do is to make the regen line stay on longer in cold weather. It will also change the braking feel when the SOC is over 50%.

then consider: now that we have the front wheels and the front motor to create even more than twice the regen, shouldn't the accel lift off now be much stronger and slow the car much quicker on mere accel lift off?

Well, that's what we want to avoid to keep the guy behind us from slamming into us. To me it seems about perfect the way it is. As for the new ibooster, well maybe that's why the brakes were so grabby on the last loaner car I had.

 

[billarnett]

"[with more regen] the car would decel too quickly"

"The only time a stronger braking effect would be in an emergency"

?? Are either of you suggesting that the current amount of regen deceleration is the most you would ever use except in an emergency? I must be getting into "emergencies" every day then.

I'm more persuaded by the argument that having more than 60kW of regen might damage the battery. But though a higher rate, say 120kW, might be damaging for extended periods (as in supercharging) I wonder if it would be ok for a few seconds now and then. After all, regen braking at that rate can last for only a very short time before the car stops.

 

[jerry33]

"[with more regen] the car would decel too quickly"

"The only time a stronger braking effect would be in an emergency"

?? Are either of you suggesting that the current amount of regen deceleration is the most you would ever use except in an emergency? I must be getting into "emergencies" every day then.

I'm more persuaded by the argument that having more than 60kW of regen might damage the battery. But though a higher rate, say 120kW, might be damaging for extended periods (as in supercharging) I wonder if it would be ok for a few seconds now and then. After all, regen braking at that rate can last for only a very short time before the car stops.

When coming to a normal stop, the amount of regen is what I would use (or if there were no regen, it's about the same amount of deceleration I'd typically do). Even on the crowded freeway I seldom have to press the brake pedal. Emergency probably isn't the best term. Let's say faster than I would normally brake due to interaction with other drivers or traffic signals.

 

[NielsChr]

It would be great if this feature was active (or at least available as an option) when using the low regen setting. On long road trips, coasting can reduce leg fatigue.

Agree - should work (only) when car is set in low regen mode.

 

[strider]

That additional regen would be the full potential of the electric motors to convert even more energy into electricity which could be obtained by allowing a stronger braking effect and more powerful regen.

No. The energy from the "additional regen" of which you speak has to GO somewhere. The battery pack and other electrical components have to be able to accept that energy. The D models still use the same battery pack so if that was the limiting factor it doesn't matter how many motors or how much traction you have the car still only regen an 60kW.

Can't you see how the potential regen from all four wheels and two motors might be too much to have with just accel lift off and so some of that regen would be left untapped unless it could be responsive to the appropriate driver input of, say, the application of the brake pedal?

Lifting off the accelerator IS an appropriate driver input. It's much better and safer for a driver to keep their foot on the accelerator and modulate from zero to full regen rather than dancing their foot back and forth between pedals.

For whatever reason, 60kW is full regen in all current Tesla Model S's. That could certainly change in the future. Future packs and electronics may be able to accept higher rates of charge. They could add capacitors that could accept higher charge rates for short periods and then bleed that into the battery at a lower rate. Heck they could strap a big 'ole space heater to the roof. Then if/when the car can accept a higher regen level it is then a completely separate discussion as to whether that regen should be on one pedal or split between two.

Bottom line is that your premise that adding the ibooster allows for more regen is just simply wrong for the reasons I stated.

- - - Updated - - -

I think everyone who has an interest in this thread (and the head of Tesla engineering) should have a go in an i-MiEV - or at least the Peugeot/Citroen badged ones (I have the Peugeot). The implementation of the regen on this car is, IMO, simply perfect. It is quite possible with the use of good forward vision and a reasonably light right foot, to drive entirely on the accelerate except for the very last few feet (esp if you are stopping on an incline). The function of acceleration and deceleration by accelerator pedal only is flawless and totally smooth. I am looking forward to seeing how the MS compares but from what I have read here it looks like I will be missing my iOn for this aspect of its amazing engineering accomplishment, at least.

That is exactly how the Tesla works and is exactly how I drive. Typically I only touch the brakes at stoplights and if my timing is good I only touch the brake pedal when I rock into a parking space. All regen is on the accelerator. The Model S is a much heavier car than an iOn and so the rate of deceleration may be lower (I don't know the max regen rate of an iOn) but it's still creating a heck of a lot of energy (60kW) and adding that into the pack. bhzmark is arguing to make Tesla's work like a Prius, Volt, or Leaf where the regen is split between the accelerator and brake. The Tesla Roadster was out and tearing up the roads long before the iOn was a sketch.

 

[billarnett]

When coming to a normal stop, the amount of regen is what I would use (or if there were no regen, it's about the same amount of deceleration I'd typically do). Even on the crowded freeway I seldom have to press the brake pedal. Emergency probably isn't the best term. Let's say faster than I would normally brake due to interaction with other drivers or traffic signals.

Well, not all drivers are equal. My habit is to decelerate somewhat more rapidly than regen allows so I find myself using the friction brakes quite frequently. All I'm suggesting is that we have an OPTION for stronger regen so that folks like me can have one-foot driving without being forced to drive more "conservatively". Everyone else can simply choose one of the current options.

If the only way to implement that option was to add a few kilobucks worth of capacitors I would gladly pay. Especially if those capacitors, once charged up on the entrance to a corner could be dumped into the motors on the following straightaway

 

[bhzmark]

Wow. It is really extraordinary how confusing this topic is. I see three different concepts: Driver Input, Rate of Decel, Method of Decel

I: Driver input
IA: Driver back off the accel pedal
IB: Driver depress the brake pedal

R: Rate of Decel
RA: Holding speed
RB: Coasting and speed decreasing only from aero or other drag
RC: Gentle decel: < ~.1g (the gentle slowing effect that isn't abrupt and handles about 80-90% of your slowing needs -- as long as you plan ahead and don't race up to a redlight)
RD: Medium decel: ~.1-.3g (still not abrupt but slowing down v fast)
RE: Strong decel: ~.3 -.7g (full on hard stop)
RF: Full stopping power: ~.7-1.0g (panic stop at limit of car tires vs road)

M: Method of creating decel / drag (> aero):
MA: making electricity by using the motors to regen
MB: making heat and brake dust by using the mechanical brakes to press the pads to the rotors.

Do not confuse MA with IA.

Let's assume, what I think is true, that RE & RF requires MB. (The iboosters always engage the mechanical brakes for over .3g see: Green Car Congress: New Bosch iBooster for improved braking control, more complete capture of braking energy in hybrids and EVs)

Let's also assume that RC is and that be done with MA.

The issue is: can RD be obtained with MA? It could if the electricity generated was within the charging limits of the battery.

If so, shouldn't it be input with IB? Since RD would be too strong to apply every time you lifted off the accel pedal e.g., when coming off cruise.

 

[billarnett]

Wow. It is really extraordinary how confusing this topic is. I see three different concepts: Driver Input, Rate of Decel, Method of Decel

I: Driver input
IA: Driver back off the accel pedal
IB: Driver depress the brake pedal

R: Rate of Decel
RA: Holding speed
RB: Coasting and speed decreasing only from aero or other drag
RC: Gentle decel: < ~.1g (the gentle slowing effect that isn't abrupt and handles about 80-90% of your slowing needs -- as long as you plan ahead and don't race up to a redlight)
RD: Medium decel: ~.1-.3g (still not abrupt but slowing down v fast)
RE: Strong decel: ~.3 -.7g (full on hard stop)
RF: Full stopping power: ~.7-1.0g (panic stop at limit of car tires vs road)

M: Method of creating decel / drag (> aero):
MA: making electricity by using the motors to regen
MB: making heat and brake dust by using the mechanical brakes to press the pads to the rotors.

Good, now we can all talk the same language I'm not sure I agree with your characterization of the various levels but the numbers are clear.

Do not confuse MA with IA.

OK, but many of us believe that they should always coincide.

Let's assume, what I think is true, that RE & RF requires MB. (The iboosters always engage the mechanical brakes for over .3g see: Green Car Congress: New Bosch iBooster for improved braking control, more complete capture of braking energy in hybrids and EVs)

Let's not confuse what Bosch has implemented with what's technically possible. The motors can produce 515kW in reverse if necessary. It is certainly possible to make an EV with no friction brakes at all (except for legal/regulatory issues).

Let's also assume that RC is and that be done with MA.

Roger.

The issue is: can RD be obtained with MA? It could if the electricity generated was within the charging limits of the battery.

Of course those limits are somewhat arbitrary. I might decide I would rather burn up my battery a little faster rather than change my driving style. Or not. It's MY decision, not the manufacturer's.

If so, shouldn't it be input with IB? Since RD would be too strong to apply every time you lifted off the accel pedal e.g., when coming off cruise.

Not necessarily. RD would only happen if I lift my foot entirely off the access pedal. Intermediate positions are possible. I find it 100% natural and easy to regulate my speed with the one pedal even when approaching a stop. Perhaps others might have a different habit. I would be happy to have an OPTION to engage some of the potential regen on IB for those who want it. I would not choose that option.

Some seem to think that too much regen from IA is dangerous or inconvenient. I claim the opposite. One foot driving is much easier once you get used to it. And in a panic stop situation do you really want to have to move your foot to the other pedal before beginning to slow down? IIRC, it takes about 1/4 to 1/2 second for the average driver to apply the brakes after he makes the decision to do so. At 60mph the car 20 or 30 feet in that time. With RF on IA that time would be cut in half or more. That 10 or 15 feet might save a life. (Left foot braking can help here but it's still not as good as RF from IA.)

 

[Danal]

I drive a Leaf until I get my Model S (any day now, but that is another story). These cars RC and MA* by IA; a gentle IB will get more MA and more RC possibly becoming RD before any MB occurs. A harder press of IB engages MB and keeps making R stronger, up to RE/RF.

Being very accustomed to this, it is quite easy to lift IA and get a certain "feel" of RC and some MA. With good driving and mild traffic, this works great for lots of things. Traffic or other circumstance often causes me to IB lightly, getting the next "notch" of RD and MA (visible only in the gauge). I only MB the last few feet to a stop. Not saying this is good or bad... it just "is" the way the Leaf works. I do sort of like having two rates of MA/RC, more MA/RD, and having them clearly separated (by switching to the other pedal).

My other daily driver is a 400 Horse SSR with a Six Speed Manual. Depending on gear, it RCs pretty solidly when you just lift off that expensive pedal. Obviously no regen; but the pedal results are not that different.

When I test-drove a P85D, I had a VERY hard time transitioning to "single pedal" driving. This was around mid-December, so probably 6.1 but no dot releases. Again, not saying good or bad, just hard to make the transition. I didn't worry about this too much, other than trying not to wreck the test drive. I figured I'd get used to it after driving my Model S for a day or two.

The problem is: We are keeping the Leaf. It will be my wife's daily driver. I am a little concerned about how well she will transition if she only drives the S occasionally. Also, I understand from other posts that "Creep" mode is NOT part of driver profile, and this may complicate it even more. Same thing applies to ICE drivers.

So... maybe some very clear configuration options? As part of driver profile? "Regular Car" mode and "Tesla" mode?




*For those who have never driven one, the leaf has a large power display at the very top arc in the drivers view. Shows power consumed/re-genned. Not as nifty as the Tesla way of showing this; but absolutely "in your face", so if you are looking at all, you know how much Accel Lift vs. Brake Push regens.

 

[strider]

Not necessarily. RD would only happen if I lift my foot entirely off the access pedal. Intermediate positions are possible. I find it 100% natural and easy to regulate my speed with the one pedal even when approaching a stop. Perhaps others might have a different habit. I would be happy to have an OPTION to engage some of the potential regen on IB for those who want it. I would not choose that option.

Some seem to think that too much regen from IA is dangerous or inconvenient. I claim the opposite. One foot driving is much easier once you get used to it. And in a panic stop situation do you really want to have to move your foot to the other pedal before beginning to slow down? IIRC, it takes about 1/4 to 1/2 second for the average driver to apply the brakes after he makes the decision to do so. At 60mph the car 20 or 30 feet in that time. With RF on IA that time would be cut in half or more. That 10 or 15 feet might save a life. (Left foot braking can help here but it's still not as good as RF from IA.)

Could not have said it better myself.

The problem is: We are keeping the Leaf. It will be my wife's daily driver. I am a little concerned about how well she will transition if she only drives the S occasionally. Also, I understand from other posts that "Creep" mode is NOT part of driver profile, and this may complicate it even more. Same thing applies to ICE drivers.

So... maybe some very clear configuration options? As part of driver profile? "Regular Car" mode and "Tesla" mode?

Well, the car already has "regular" and "low" regen modes and that setting is part of the driver profile. Not sure why creep isn't other than you can change profiles while the car is in gear but you can only change the creep setting when the car is in Park so maybe there was some complication there.

People have been transitioning between auto and manual cars and it's doable. Though I did have a hysterical moment when I was a teenager and my Dad borrowed my (auto xmission) pickup and just after he made the turn near our house I heard the tires squeal - he normally drives a manual xmission car, had gone for the clutch, and hit the extra wide brake pedal. But anyone changing cars regardless of motive force should be ready for the car to handle differently.

 

[billarnett]

maybe some very clear configuration options? As part of driver profile? "Regular Car" mode and "Tesla" mode?

Options good, modes bad. I'm all in favor of having lots of options that let the driver control the way his car works. But collecting a set of options into a few modes just makes for frustration and confusion. Keep them independent unless there is some reason why each setting of option A requires a particular setting of option B. There are of course defaults for everything; I don't mind if they're all set in the way that most drivers want or the way that is most familiar to most drivers who are not used to EVs. But let me set up my car the way *I* want it! If there is a style of driving that is best done with a particular set of option settings then make that very clear IN THE DOCUMENTATION. And by all means make ALL such settings part of the driver profile.

 

[WarpedOne]

For whatever reason, 60kW is full regen in all current Tesla Model S's.

No, P85Ds have stronger regen, around 80kW: