Regenerative Braking Capacity

SafeWill

Member
It is very interesting, and thank you for your answers.
It will certainly be a question I will ask to the person that did the conversion with Bolt components that he could possibly answer. He’s back mid November after a 2 months family trip all over USA.
I noticed in the video that ultra capacitors might be heavy for this kind of regeneration, and getting into GM technology would be easier than Tesla’s.
Food for thoughts.
 

CappyJax

Well-Known Member
I've tried to make the concept as simple as possible so people without degrees in engineering can understand at the highest level at least how regen braking works. But if you have interpreted what I said as implying that the control is simple you have misunderstood. This is not a matter of adjusting the field rheostat on a DC motor. These are three phase motors and translating driver input and car speed into proper torque and field commands is a very complicated process which must be done at a rate so high that DSP techniques are often employed. Beyond that D and Q commands must be translated, again at high speed, into current commands to the windings. These cars do what they can do not only because we have efficient motors and decent battery energy density but because of incredibly sophisticated electronics which can efficiently switch hundreds of amps at hundred of volts at sub microsecond rates.
Whatever dude. No matter how sophisticated the electronics, the way it goes from applying power to regenerative braking is by SIMPLY CHANGING THE FLOW CURRENT THROUGH THE MOTOR.

And Musk isn't a mad genius. He is intelligent with a massively over inflated ego. And no, he isn't saving the world. Electric cars will not save us. This is why having a high IQ doesn't mean someone is smart. A smart person would actually be able to see all available evidence and recognize that emissions are a small part of our problem and that destroying are carbon sinks are the biggest part of our problem. We have destroyed nearly 1/3 of the worlds forests for crop production and grazing land for people to eat meat. If all the forests that we have destroyed still existed, it would be absorbing near 100% of our global CO2 emissions. So, in terms of people who are smart and recognize the real problem we face, then the people behind companies like Beyond Meat and Impossible Foods are far smarter than Elon Musk.

And again, making money in capitalism is more about one's willingness to exploit the unethical system in which we live, and not about overall intelligence. If you think it has anything to do with intelligence, then explain Donald Trump. Luckiest idiot alive.
 

ajdelange

Well-Known Member
Do you actually have any concept of how DQ control works? Ever even heard of it?

As for the rest, thank's for the calibration point(s).
 
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SlaterGS

Active Member
I am interested in this as well because I was surprised to hear that Tesla's won't bring the car to a complete stop.
My Leaf brings me to a complete stop with the e-pedal activated similarly to the sounds of it as your Volt. All the while showing regen and recently at around 32 F no different than it was when it was 80 out.
There are no regenerative braking assist levels to choose from, it is on or off. This is one area where all EV's could benefit especially knowing everyone drives different and the strength of the e-pedal is quite surprising for first time drivers and it can actually detract from the experience because it is so different.
Correction to my previous statement.
Regenerative braking vs the e-pedal I guess are different on my Leaf?

Regardless of the temp, the e-pedal still acts the same as far as slowing down the vehicle in the same amount of time until it is stopped.
However I noticed yesterday when I first got in the car that it only showed two bars available for regen. I'm guessing there are 10-12 total.
Drove a few miles to take the kids to school and when I got back in it showed 4 bars available. It was odd as all the bars were never available for regen all of yesterday even though it went from 40's in the morning up to 70's during the day.
This morning when I backed out of the garage, it was 65 degrees and it had full regen bars available.
I'll keep watching this, but it does seem that regen is being limited at different points.
 

Hmp10

Well-Known Member
I just watched a YouTube review of the Audi E-tron. As with the Porsche Taycan, you actually have to press the brake pedal to get any regenerative braking at all. In other words, there is no one-pedal driving, which is one of the features I have most come to love on my Tesla. In fact, the most annoying thing I now find in driving my Honda minivan is how often I have to get on and off the brake pedal compared to the Tesla. It's something I never thought about before driving the Tesla, but now it is a major source of annoyance in driving an ICE.

It completely mystifies me why Porsche-Audi would not at least offer the driver a choice of using one-pedal driving.

Please, please tell me that Rivian is not going to adopt such an approach. If they do, I might reconsider my deposit.
 

EyeOnRivian

Well-Known Member
Please, please tell me that Rivian is not going to adopt such an approach. If they do, I might reconsider my deposit.
I happened to ask a Rivian platform engineer about this at the Normal event last week and he said re-gen braking would be via the brake pedal, though he also said a decision has not been made whether it will be available via the accelerator pedal. This was the first and only time I had heard this, so take it with a grain of salt. Good question to follow up on for those attending the next event Rivian will be at.
 

Hmp10

Well-Known Member
The only reason I can think of that Rivian would decide to handle regen through the brake pedal only is that they are wanting to make it feel like driving an ICE vehicle. If so, that is a very backward look at things. Regen braking and the associated one-pedal driving is just one of many inherent features of EV driving that is superior to ICE driving. I know some people don't like (or, more often, think they wouldn't like) one-pedal driving, but everyone I know who has a Tesla finds it one of the most appealing features.

I'm not clear on how regen even works only through the brake pedal. I thought that once you life off the accelerator pedal to coast speed down, the motors automatically go into generation mode. Does Porsche-Audi actually use electronics to counter or override regeneration unless the brake pedal is pressed?

Besides the power, torque, and smoothness of driving a Tesla, there are two other things that have completely spoiled me and that I will badly miss if I don't have them in another car. One is one-pedal driving. The other is the huge Google Earth screen. Being able to drive around and know what buildings and streets are on the other side of tree lines or around curves or over hills is so helpful in so many situations that I never thought about beforehand. In some photos I've seen of Rivian, it looks like it might have something similar, although smaller. I can only hope.

I'll forgo either one or the other of these features. If I have to forgo both to get a Rivian, my next EV might well be another Tesla.
 
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SlaterGS

Active Member
In fact, the most annoying thing I now find in driving my Honda minivan is how often I have to get on and off the brake pedal compared to the Tesla. It's something I never thought about before driving the Tesla, but now it is a major source of annoyance in driving an ICE.

It completely mystifies me why Porsche-Audi would not at least offer the driver a choice of using one-pedal driving.

Please, please tell me that Rivian is not going to adopt such an approach. If they do, I might reconsider my deposit.
This, this, this!
I can't stand driving our Chrysler T&C anymore and this is the main reason. The next vehicle we purchase will be to replace the minivan and it must have 1-pedal driving or it will not be considered. Hoping the R1S will have this supported.
 

Joel

Well-Known Member
I also prefer one pedal driving especially in slow traffic. I think it should be an option to engage regeneration once you lift off. I would hope the Rivian borrows from Tesla what they have done right and mostly right and improve on it. I am not looking for a ICE experience or the dealer experience.
 

ajdelange

Well-Known Member
I'm not clear on how regen even works only through the brake pedal. I thought that once you life off the accelerator pedal to coast speed down, the motors automatically go into generation mode.
No, the motor/generator is neither until it is configured to be one or the other through management of the stator currents.

Think of the system as having 4 parts:

1)A battery
2)A machine
3)A controller
4)A computer

We all know what the battery does

The machine has 3 sets of coils fixed to its frame and a rotor connected to the gearbox. Embedded in the rotor are some magnets

The controller connects the battery to the machine stator coils in different ways according to what the computer wants the machine to do. If it wants to speed up the car it closes and opens the switches in such an order at such a rate and for such a length of time that power flows from the battery to the machine. If it wants to slow down the car is turns them on in such order etc that power flows from the machine to the battery.

The computer tells the controller how much power to send to or absorb from the machine dependent on many inputs to it such as
a)Battery SoC and temperature
b)Speed of the vehicle wheels
c)Obstructions surrounding the car i.e. other cars in front
d)What the driver wants to do.

It senses what the driver wants to do by reading driver controls i.e. the pedals and any buttons or switches or user settings that may pertain. Thus if, in a Tesla, the driver has selected max regen and takes his foot completely off the pedal the computer will command the controller to signal the machine to produce as much regen power as it can given its speed and the computer's ideas as to what is a reasonable rate of decelleration. It will limit that command if the battery is nearly fully charged or if it is cold or if the user has selected mild regeneration.

The other cars work the same way except that if the design does not include one pedal driving removing one's foot from the pedal does not trigger the computer to ask for regen. In those cars some other action such as moving a paddle or depressing the brake pedal is required.


Does Porsche-Audi actually use electronics to counter or override regeneration unless the brake pedal is pressed?
No, it just doesn't issue regen commands until the brake pedal is pressed.
 
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Hmp10

Well-Known Member
I wish you had been around during an earlier hot debate about flat towing and regeneration. A couple of posters were insisting that regeneration occurred inherently without any commands being sent as soon as current flow to the motor was interrupted or reduced. I was accused of being a complete ignoramus for thinking that some sort of command signal was involved in the switchover.
 

Hmp10

Well-Known Member
I happened to ask a Rivian platform engineer about this at the Normal event last week and he said re-gen braking would be via the brake pedal, though he also said a decision has not been made whether it will be available via the accelerator pedal. This was the first and only time I had heard this, so take it with a grain of salt. Good question to follow up on for those attending the next event Rivian will be at.
I was poking around the internet to see if I could find anything more about Rivian's regenerative braking plans, and I found this post by RefugeEV on this forum from March. It cites Rivian's VP of Development & Integration in explaining how Rivian's one-pedal driving will work.

"Full-stop one-pedal regen braking
Like an increasing number of electric cars, the new Rivian vehicles can not only regenerate power back into the battery to help slow down but can quickly bring the vehicle to a full stop and hold it there without use of the traditional brake pedal — even on an incline.

The BMW i3, Chevrolet Bolt EV, 2018 Nissan LEAF, and the new Hyundai Kona Electric can all do this.

On the other hand, so far, Tesla vehicles require use of the brake pedal to quickly come to a full stop or hold the vehicle in place.

Like the Bolt EV and 2018 LEAF, Rivian supports driver configurable options to control the intensity and behavior of regenerative braking that occurs on the accelerator pedal.

Regenerative braking is ineffective at very slow speeds (the last several mph) so car makers that support full-stop one-pedal braking either blend in friction braking (in the 2018 Nissan LEAF) or they use active motor torque using a small amount of power from the battery as the Bolt EV and Rivian do. Similar strategies are used to hold a car on an incline.

Charles Sanderson, Rivian’s VP of Development & Integration, says they can hold the vehicle at up to a steep 20 percent road grade just using active motor torque.

Like almost all other electric and hybrid cars, Rivian also initially uses regenerative braking as the traditional brake pedal is pushed but transition to friction braking as the need for anti-speed increases as the driver pushes down farther on the brake pedal.

Like many other car makers, Rivian is using Bosch’s iBooster brake system. Even Tesla has used this system since they introduced partially-automated driving features into the Model S although Tesla has programmed it to use only friction braking when the driver steps on the pedal, presumably to guarantee the highest level of consistent braking feel."

It's not unusual for find two people from the same firm giving different answers to the same question. I guess we'll just have to wait for more information. I agree that someone should ask the question at the next Rivian event.
 

EyeOnRivian

Well-Known Member
Nice find @Hmp10 . It would seem RefugeEV's source to that March post was from an Electric Revs article dated Nov 29, 2018 - "Rivian: the powertrain details you won't read about elsewhere." That's nearly a year ago and a lot can change in that time especially for a start-up like Rivian.

The only thing clear here is that it's unclear what Rivian will do. Definitely need to corner one of the engineers, preferably one that worked (still working?) on the regen brake function, at the next Rivian attended event.
 
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