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Regenerative Braking - regen

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Ah, fair enough. I'm not really sensing that difference as, I must admit, I'm not paying sufficient attention to screen brake lights to make a comparison! At least it's something that should be capable of being tweaked in software so that the deceleration trigger is more appropriate. Perhaps if enough people highlight the issue with Tesla they might review that feature and incorporate a future change.

I've looked and not seen brake lights on the vehicle image even when braking!
 
I've looked and not seen brake lights on the vehicle image even when braking!

I am not 100% sure about what I have seen, but I think it is like this:

If the car image is zoomed in (it appears to zoom in and out on its own while driving), and rear lights are on, they are also turned on in the car image. When I press the brake pedal or use regen over a certain threshold, the intensity of the red lights in the image is increased.

If the car image is zoomed out, there is not the same intensity difference. The red lights in the image are turned on with the same intensity if either the brake lights are on, or the rear lights are on, or both are on.

(Of course, I can also just look in my rear view mirror. I have one of those Model 3s where the brake light leaks into the cabin.)
 
It is.

I am getting curious now, after reading all these posts. It is obvious that we think differently, but it is not exactly clear to me what is causing this difference. Since you are the first one to actually express your thinking about how you lift the accelerator pedal, I hope you don't mind that I pry into your brain a bit.

First I will describe my own thinking:
Before I test drove a Tesla for the very first time, I knew the concept of one pedal driving, but I had no idea what it would feel like. However, as soon as I tried it, my thoughts were "Okay, this is a function, which can brake the car with the accelerator pedal. So I will need to modulate my lifting of the accelerator pedal in the same way I would modulate my usage of the brake pedal."

And then it immediately became natural to do it that way.

(I had also been worried that this would not work very well with the TACC, when taking over manual control of speed after using TACC. Luckily, it turned out that TACC doesn't disable abruptly like in my other cars - it actually ramps down slowly, so I have plenty of time to catch it with the accelerator pedal and modulate the regen.)

And now back to you:
When reading your post, I get the impression that you think Tesla wants you to drive the car with a lot of regen. So when you lift the foot gradually to control your regen, you feel that you are not trusting the car.

Is this correctly understood? And how have you reached that conclusion?

HI Allan - you are free to pick my brain - I'm not sure my brain has much to offer on this one! or if there is any value to it! but sure!

I'm not using my brakes much at all really - mainly responding to pedestrians or other cars doing unexpected things, or when parking. So i feel I grasped the one pedal driving thing as a high level concept fine. I just need to finesse it, and thats been the last thing on my mind recently really - but long term I should be getting better with it. I'll never be the most efficient driver on the league table - I like to drive to just get there at a safe speed and wouldn't ever be sat at 64 on the motorway if it was the optimum speed for efficiency. I'm also fine to charge a bit longer on long trips etc its no hassle and a good time to walk/stretch/text/email/eat so I'm ok to top up twice not once on a long trip.

But I know I'm not driving in the most efficient way due to the stats on the car against what other UK, and indeed scottish drivers are achieving - so I'm keen to learn how to be better with this - so on the look out for ways, and i do think (know) the use of the regen and feathering the accelerator is a key way to do this. I'm also a bit put off by the brake lights coming on as the car slows for a round about for example looking to cars behind like I have slammed my breaks on - probably as a result of 'too much lift too soon' and the change in speed hitting a threshold someone else had identified was how the car decided to show brake lights. Just in an ICE easing off the accelerator wouldn't look like that to other road users.

I guess it boils down to me not knowing the 'stopping distance' such as - when travelling at x speed the regen will bring you to a stop in y metres? time will probably let me know that - bu the regen seems to be pretty variable due to temp, length of drive and potentially other factors.

I am easing off a bit too much too early - as I would in an ICE and thats what is slamming the brake lights on, and I probably need to lighten foot less, but earlier. thats what my slightly under pressure brain has to offer you Allan. And I bet you are sorry you asked!! it felt rude not to reply to you though!
 
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Just in an ICE easing off the accelerator wouldn't look like that to other road users.

I guess it boils down to me not knowing the 'stopping distance' such as - when travelling at x speed the regen will bring you to a stop in y metres? time will probably let me know that - bu the regen seems to be pretty variable due to temp, length of drive and potentially other factors.

The easing off in another vehicle really isn't as strong as standard regen (it can be more similar on some motorbikes) unless it's a very cold start (so little regen) and in that instance you are not worrying about the regen braking effect being too strong.

You don't need to work anything out with deceleration ... you feel it and see it, then progressively lift off more and add actual brakes if you need them. All drivers are doing the equivalent all the time in "normal" cars because the rate of deceleration varies with so many different factors ... you know if your car is not slowing down as quickly as you need and you just brake accordingly. For example in a normal car if you are driving fairly quickly down a steep gradient and you are approaching a corner that you have to slow down for: engine braking will be invisible and you will need to press the brakes harder to arrive at the corner at the speed you want than if you were driving up a similar gradient at speed and had a similar corner approaching when gravity and engine braking will be enough to slow down to the same speed. You don't need to think about it because you can feel and see the deceleration and you automatically compensate. I suppose you could therefore equate regen to driving a normal car up a very steep hill ... you automatically use less braking effort to come to a stop without consciously thinking about it.

Other things that affect braking force required in a normal car: what gear you are in .. strong winds .. water on the road surface .. tyre wear .. temperature ... the computational genius that is a human driver takes these things in their stride! They're sure to manage regen too!

... and forget about the brake lights!! They're going to do what they do ... you just need to be driving your car!
 
And I bet you are sorry you asked!! it felt rude not to reply to you though!

Thank you. And I am not at all sorry for asking. As an engineer it has always fascinated me how people think when they use a piece of technology - and how the design of that piece of technology is often expecting them to think in a whole different way. So an apparent user error may actually be a design error.
 
A lot of drivers don’t lift off (normal cars) at all. It’s one pedal or the other.

Clearly when in a situation requiring deceleration in a normal car you just lift off completely and transfer your foot to the brake (I'll not get into left foot braking ... that's a topic in itself!) Mind you, there are some rather special situations when taking your foot off the accelerator is not the best move even in a normal car. I recall a situation when driving on a country road in winter where a previous snowfall had left snow at the side of the road but the road surface was completely dry and clear ... I came round a curve at 50/60mph to discover the next section of road had a complete snow covering ... and I wasn't on winter tyres ... just taking my foot off the accelerator was too much and the car started to drift straight off the road so I had to reapply just enough pedal to keep the car pulling through (front wheel drive) and as the curve straightened was only then able to start feathering the accelerator to get the speed down to the 20mph that was needed to safely drive that snowy section. Other than a change of underpants all was well!
 
Oh, yes, there certainly is.

If I lift the foot, I get instant, full regen.

If I disengage TACC, the regen slowly ramps up over a few seconds.

You can easily test this difference for yourself.

The slow ramp-up of regen makes it very easy to seamlessly take over control with the accelerator pedal without any sudden jumps in regen.

I’m not convinced there is a difference but maybe it depends on how fast you are going and whether the road is clear ahead. On a clear flat section of the M4 I disengaged TACC at 70 mph and watched as regen went to about 75% on the bar. I repeated by lifting my foot at 70mph and the increase in regen to 75% seemed exactly the same. Neither I, nor my passenger, could spot any difference. Might try it again from different speeds if others are convinced there is a difference in the M3. I suspect the performance may be different going downhill when the car would provide more regen.
 
I did not say that the amount of regen is different. I said that the ramp speed for regen is different.

I fully accept what you said . Perhaps I should have been more precise and said that the rate of increase in regen to a maximum of around 75% seemed exactly the same. I’ve now repeated the experiment from various speeds and can still detect no difference although I haven’t been able to try it with a passenger with a stopwatch. Could there be a difference between models or software? Mine is an LR AWD. Now on 2020.44.10.1. I am set on standard, rather than low, regen.
 
ould there be a difference between models or software? Mine is an LR AWD. Now on 2020.44.10.1. I am set on standard, rather than low, regen.
Same here. LR AWD 2020.44.10.1 (now updated to .15 two days ago). Regen on standard.

How fast is your ramping? I haven't tried with a stopwatch either, but I would say that with our car it takes 5-7 seconds to ramp up regen after disabling TACC. And less than 1 second when lifting the foot from the accelerator.
 
I fully accept what you said . Perhaps I should have been more precise and said that the rate of increase in regen to a maximum of around 75% seemed exactly the same. I’ve now repeated the experiment from various speeds and can still detect no difference although I haven’t been able to try it with a passenger with a stopwatch. Could there be a difference between models or software? Mine is an LR AWD. Now on 2020.44.10.1. I am set on standard, rather than low, regen.

Same here. LR AWD 2020.44.10.1 (now updated to .15 two days ago). Regen on standard.

How fast is your ramping? I haven't tried with a stopwatch either, but I would say that with our car it takes 5-7 seconds to ramp up regen after disabling TACC. And less than 1 second when lifting the foot from the accelerator.

How are you disabling tacc? Just a thought, maybe the ramp is different if you tap the brake Vs using the stalk.
 
How are you disabling tacc? Just a thought, maybe the ramp is different if you tap the brake Vs using the stalk.

I’ve been disabling TACC by moving up the stalk. Maybe a couple of days before I get another chance to experiment but I’d say that if set in the 50-70 mph range the car takes about 3 seconds to reach whatever regen it is going to get to whether I disengage TACC or take my foot off. I suspect the regen bar may go further to the left faster when slowing from lower speeds but I haven’t looked closely at this. Does sound like AllanO may be getting much more aggressive regen when lifting off the foot than I do. I don’t think my brake lights will come on with regen braking until I’m doing less than perhaps 30mph. Presumably AllanO will have brake lights on with max regen after 1 Sec.
 
Does sound like AllanO may be getting much more aggressive regen when lifting off the foot than I do.

At least in my imagination, yes...

Today I tested it more thoroughly, and it turned out that the difference is not a result of disabling TACC vs. lifting the foot. It is a result of different initial speeds. I usually use the foot at low speeds, where the deceleration regen is much stronger.
 
At least in my imagination, yes...

Today I tested it more thoroughly, and it turned out that the difference is not a result of disabling TACC vs. lifting the foot. It is a result of different initial speeds. I usually use the foot at low speeds, where the deceleration regen is much stronger.

I was beginning to wonder whether something like this might be the issue. The Tesla is a heavy car. At 70 miles an hour regen alone does not have a huge braking effect initially regardless of how fast it comes in. The same amount of braking at a low speed will certainly slow you down quickly. Incidentally, did I see somewhere that only the rear motor, and hence the rear wheels, provide regen braking?
 
I was beginning to wonder whether something like this might be the issue. The Tesla is a heavy car. At 70 miles an hour regen alone does not have a huge braking effect initially regardless of how fast it comes in. The same amount of braking at a low speed will certainly slow you down quickly. Incidentally, did I see somewhere that only the rear motor, and hence the rear wheels, provide regen braking?
From what I can tell the rear motor on the AWD cars is preferred, after all it's the most efficient motor. But in low grip or when making turns it shifts some or all of the regen forward to the front motor. Bjorn did a video showing it quite well with scanmytesla last year.
 
From what I can tell the rear motor on the AWD cars is preferred, after all it's the most efficient motor. But in low grip or when making turns it shifts some or all of the regen forward to the front motor. Bjorn did a video showing it quite well with scanmytesla last year.
The rear motor is the one doing the regen i.e. feeding energy back to the battery, but the front motor also provides retardation. The ratio is usually around 25% front 75% rear.

This is an interesting discussion. When I was driving ICE cars, especially with high compression engines which give you lots of engine braking, there were times when that was very helpful in preventing other drivers from reacting to brake lights.

I think it's mentioned earlier, but when overtaking a line of traffic and pulling into a gap, it's preferable to slow the car back down without the brake light coming on as that tends to cause the driver you've just overtaken to react and brake for no reason.

So I can see there are good reasons to be able to use regen to declerate rapidly without it triggering the brake lights, but I think those reasons would be lost on most people and for safety's sake I guess we're stuck with it working the way it does.
 
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The rear motor is the one doing the regen i.e. feeding energy back to the battery, but the front motor also provides retardation. The ratio is usually around 25% front 75% rear.
Bjorns video certainly shows it shuffling the regen around to wherever it thinks is best depending on grip. You can see each motors torque with the scanmytesla recording, sometimes its entirely the front motor doing the regen, sometimes the rear, and sometimes a split.
4:53 in particular shows it on snow moving the regen towards the front as there's not enough grip at the rear
 
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Compared to lower regen setting (my preferred choice), when I disengage TACC it unleashes much stronger regen if I’ve done this via the stalk.

It seems to unlock the “full” regen potential as indicated by the dotted/full line when TACC is cancelled whereas obviously if you are only in the low regen setting for normal driving you only get about half of the effect.