High vs low level brake regen for overall range

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Joe c said:
Still confused regarding these answers, not sure if everyone is on the same page. For one, I'm sure that pressing the brake pedal also activates more regen before going into friction brakes. Bmw talks about it in their blog regarding the mini SE regen. https://www.bmwblog.com/2020/01/18/mini-cooper-se-technical-details-and-specifications/
"Regeneration always occurs during braking as well."
My question is, if I have it on low regen mode and press brakes to get into more regen (not friction) and slow the car at 0.19g, wouldn't it be equivalent to high regen mode which automatically does 0.19g of regen? I feel like I read somewhere where a YouTuber hypermiled on his SE and put it on low regen and actually got better range.
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You are misunderstanding the statement in that blog. They are not saying that the brakes add more regen, just that regen occurs during braking (because regen always occurs when your foot is off the accelerator). To reword their statement: brake application does not reduce or disable the standard regen.

To the better efficiency at lower regen:
You will be more efficient with the low regen but only if you do not use the brake pedal at all to slow down. Because of the losses in the drive system, coasting is more efficient than regen (and lower regen is closer to coasting) but coasting to a stop is not a realistic way to drive.
 
Okay, so are you saying that the brake pedal in the mini only uses friction brakes? Because that would be very different from other EVs. Like I said earlier, in my PHEV, it's very clear that even though there's some regen when coasting, it's a lot of regen when I press the brake, you can actually see how much energy is going in while pressing the brake and then you know it goes into friction brakes because you see less energy going in as you press further into the brake pedal. I would think that the mini uses a similar system when pressing the brake (first regen to max then go into friction brakes)
 
On my PHEV, for example, when I'm going down a hill, I press just enough of the brake to get max regen in the meter but without going into friction braking. I can sometimes get quite a bit back on steep hills just doing that.
 
Joe c said:
Okay, so are you saying that the brake pedal in the mini only uses friction brakes? Because that would be very different from other EVs. Like I said earlier, in my PHEV, it's very clear that even though there's some regen when coasting, it's a lot of regen when I press the brake, you can actually see how much energy is going in while pressing the brake and then you know it goes into friction brakes because you see less energy going in as you press further into the brake pedal. I would think that the mini uses a similar system when pressing the brake (first regen to max then go into friction brakes)
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OK, so some Googling reveals that the Pacifica PHEV works as you describe: "The friction material of the brake pads do not immediately contact the brake rotor when the brake pedal is depressed unless the amount of pressure you apply to the brake pedal indicates a desire to stop more quickly than the regenerative system can accomplish on its own."

However, this is actually not the way most EVs work.

As an example, for Teslas: "Brake pedal does friction brakes only. Regen is accomplished only by letting off the accelerator. 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."

It's my understanding the Mini works the same way as Teslas, as do most other EVs.
 
Joe c said:
Okay, so are you saying that the brake pedal in the mini only uses friction brakes? Because that would be very different from other EVs.
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Correct.

It is different than some EVs but not all. There's two ways automakers approach this:

The "old school" way of thinking is that only the brake pedal should be used to slow the car and the car should coast (or have minimal regen) when neither pedal is pressed. With this approach, they are trying to replicate the experience of an automatic ICE.

The "new school" thinking is the one pedal driving. The regen is controlled entirely by lifting off the accelerator pedal and the brake pedal only controls the friction brakes (when additional stopping power is necessary). Teslas, the BMW i3, and others all use this new school style of regen control so it's not something unique to the MINI.
 
Carsten Haase said:
Correct.

It is different than some EVs but not all. There's two ways automakers approach this:

The "old school" way of thinking is that only the brake pedal should be used to slow the car and the car should coast (or have minimal regen) when neither pedal is pressed. With this approach, they are trying to replicate the experience of an automatic ICE.

The "new school" thinking is the one pedal driving. The regen is controlled entirely by lifting off the accelerator pedal and the brake pedal only controls the friction brakes (when additional stopping power is necessary). Teslas, the BMW i3, and others all use this new school style of regen control so it's not something unique to the MINI.
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Exactly, well said.

It's the difference between cars with one-pedal driving and those without. Most current and new EV models offer one-pedal driving - including the latest Leaf, whereas the older model Leaf didn't.
 
Joe c said:
Okay, so are you saying that the brake pedal in the mini only uses friction brakes?
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Yes. The brake pedal only engages the friction brakes.

Regen braking happens when you let off of the gas pedal. You can see it in the gauge cluster on the "tach" and on the amount of energy going in as it shows a negative amount of energy being used. This is called "one pedal driving".

Hyundai has one pedal driving:
Kia does too:
Nissan Leaf: https://www.theguardian.com/technol...riving-mode-for-both-accelerating-and-braking

F1 cars have a complicated system of regen braking when they apply the brake pedal and they can control the bias for this as well. When it doesn't work, the friction brakes overheat and catch on fire or lock up. Failures were more common when F1 introduced the KERS system.
 
As an FYI, Tesla’s software update that is currently rolling out adds blended braking to the one pedal driving if the state of charge is so high the amount of regen (and thus braking) would be limited.
In other words, at high states of charge the system will blend in some friction brakes when you back off the accelerator so that the overall level of braking is the same as pure regen at lower states of charge, for a more consistent experience. Currently at high states of charge you get a warning on the screen that the amount of braking via regen alone is limited, which means you end up having to use the brake pedal at times. Now you can 1 pedal all the time.(well, except for in emergency or other very short notice heavy braking situations).
 
Joe c said:
On my PHEV, for example, when I'm going down a hill, I press just enough of the brake to get max regen in the meter but without going into friction braking. I can sometimes get quite a bit back on steep hills just doing that.
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I think you have gotten it by now. Hybrids all use blended breaking. EVs are all moving toward one pedal driving where the brake pedal is just for friction brakes. If you are one pedal driving by the time you remove your foot from the accelerator the regen is already maxed out. I could be proven if someone was to video the power needle of a MINI set to low regen with and without the brakes applied going downhill. Even better if they have the display set to show instantaneous power usage value.
 
AndysComputer said:
As an FYI, Tesla’s software update that is currently rolling out adds blended braking to the one pedal driving if the state of charge is so high the amount of regen (and thus braking) would be limited.
In other words, at high states of charge the system will blend in some friction brakes when you back off the accelerator so that the overall level of braking is the same as pure regen at lower states of charge, for a more consistent experience. Currently at high states of charge you get a warning on the screen that the amount of braking via regen alone is limited, which means you end up having to use the brake pedal at times. Now you can 1 pedal all the time.(well, except for in emergency or other very short notice heavy braking situations).
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Interesting, I'm surprised they didn't have that already!
 
Torrey said:
If you are one pedal driving by the time you remove your foot from the accelerator the regen is already maxed out.
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Except when the battery is already fully charged. Then lifting your foot from the accelerator must activate the SE's brakes.

I wonder how much power the motor uses to keep the SE from rolling backwards on a steep hill? Why doesn't the SE use its brakes for this task (it doesn't light the brake lights, so I assume the brakes aren't involved)?
 
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I have no expertise in this, but from personal experience, (and I've never actually driven Uncle Larry outside of high-regen mode), but with 100% charge, even IF the battery isn't gaining charge, it's still using the electric traction motor to slow the car, even though it's not storing additional energy. Yes, your generated electrons are spilling onto the street, but it doesn't have to default to the friction brakes in the absence of charging. I have truly mastered (no, I'm not gloating. Ok, I'm gloating a little) the art of one-pedal driving, and I love it. But I regen-brake the crap out of this thing, and as of 3000 miles, have zero brake dust on my sparkly little Roulettes. In our Toyota Hi-Hy, I almost never brake when coming down the hills from the Sierras, putting it on cruise when we exceed the downward acceleration I hear that little engine kick in to slow us, and am happy knowing it's not burning gas, just kicking up energy. Still no brake dust in 10k miles. FWIW
 
drdunkyn said:
I have no expertise in this, but from personal experience, (and I've never actually driven Uncle Larry outside of high-regen mode), but with 100% charge, even IF the battery isn't gaining charge, it's still using the electric traction motor to slow the car, even though it's not storing additional energy. Yes, your generated electrons are spilling onto the street, but it doesn't have to default to the friction brakes in the absence of charging. I have truly mastered (no, I'm not gloating. Ok, I'm gloating a little) the art of one-pedal driving, and I love it. But I regen-brake the crap out of this thing, and as of 3000 miles, have zero brake dust on my sparkly little Roulettes. In our Toyota Hi-Hy, I almost never brake when coming down the hills from the Sierras, putting it on cruise when we exceed the downward acceleration I hear that little engine kick in to slow us, and am happy knowing it's not burning gas, just kicking up energy. Still no brake dust in 10k miles. FWIW
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The 2022 SE must have an excess electron diverter that zaps the brake dust created when the battery is fully charged.
 
drdunkyn said:
I have no expertise in this, but from personal experience, (and I've never actually driven Uncle Larry outside of high-regen mode), but with 100% charge, even IF the battery isn't gaining charge, it's still using the electric traction motor to slow the car, even though it's not storing additional energy.
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The car absolutely blends in friction brakes at high states of charge (not just 100% but above around 95%) and in cases where the battery can't take that much power (same scenarios where power is limited like cold or too hot). Power can't just go poof, it needs to go somewhere and I'm certain the MINI doesn't have a giant resistor bank hidden away to dump the energy as heat.

MINI did a decent job of blending in the friction brakes so it's not that noticable but you can both feel it through the brake pedal (harder than normal pedal feel) and hear the brakes with the window down. With my car at least, the blended regen/brakes decelerates slightly slower than 100% regen power.
 
drdunkyn said:
with 100% charge, even IF the battery isn't gaining charge, it's still using the electric traction motor to slow the car, even though it's not storing additional energy. Yes, your generated electrons are spilling onto the street
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If this were the case, there'd have to be either recharge or motor heat. Since there's no grounding wire hanging down to drain off the electrons I think it's doubtful that the motor is used to slow the car down without regeneration because of heating issues. More likely, in my opinion, the software kicks in the friction braking (à la traction control).
 
Carsten Haase said:
To the better efficiency at lower regen:
You will be more efficient with the low regen but only if you do not use the brake pedal at all to slow down. Because of the losses in the drive system, coasting is more efficient than regen (and lower regen is closer to coasting) but coasting to a stop is not a realistic way to drive.
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I actually did the maths for this (in another thread) and it goes like this. If you can judge it perfectly, coasting to a stop is more efficient than driving at speed until the last minute and then using full regen to come to a stop. The caveat to this is that you don't turn off the car when stopping using regen until the coasting car catches up. The coasting car takes longer to get there and would use more energy running the accessories if the regen car powered down. At city speeds, there is basically no difference, however at freeway speeds there is a small benefit to coasting. The faster you go, the more energy you need to keep you at the constant speed, and the better the benefit. Below about 50kph, they are statistically the same.

The trick with low regen (or coasting) is that at city speeds, if you can come to a complete stop without using the brakes, and the full regen car doesn't power down (eg traffic lights), any difference is lost in noise after a decimal point. In the real world though, lower regen is normally not enough to slow you for a light where you couldn't plan ahead. Any use of the friction brake to aid slowing down means you are wasting energy and makes the brakeless high regen is more efficient.

So in summary, around town it is better to be in high regen so you can stop faster in unforeseen situations without using the brake. On the freeway, coasting or low regen is better so long as you don't need to use the brakes.
 
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