High vs low level brake regen for overall range

[Joe c]

Still confused about brake regen on the mini SE (really any car with brake regen). I get that high regen means when I let go of the gas there's more energy going into the battery than with low regen, but that's only with letting go of the accelerator. Don't I get regen with the brake pedal too? So wouldn't I get the equivalent amount of regen in low regen mode if I slowed down with the brake pedal at the same speed as high regen mode? If that's the case, then high regen mode doesn't really get more energy into the battery since I'm going to slow down anyways in low regen mode with the brake which gives me equivalent energy back.

Sorry if this is confusing, but I'm just trying to figure out if you actually get more overall range with high regen vs low regen mode, or is high regen mode only a way to get more of a one pedal driving experience and the range is the same regardless of which mode you choose?

 

[zellsun]

From my understanding, high regen vs low regen means quickly slowing down vs smoothly slowing down when releasing the throttle pedal. It has nothing to do with brake pedal. I’m a little doubtful that regen happens when brake pedal takes action.

 

[Jim Matthews]

I did a test using heavier regeneration settings on my KIA Niro EV.

In driving around town the combined range (over a week) was unchanged. My efficiency (miles per kWH) was no different.

Only ambient temperature made a significant difference.

This is at Sea level, both in Winter with snow on the ground and in our Mild Summer. I drove 18000 miles last year - all within 60 miles of home.

Heavier regen constantly cycles between acceleration and deceleration. It made my passengers car sick. It's the rapid changes that trigger episodes, like a novice driver at the wheel.

https://getjerry.com/questions/can-electric-cars-make-you-sick

 

[Torrey]

I got the impression that in the MINI the brake pedal is not connected to the regen system, but I don’t recall seeing a specific statement from the manufacturer one way or the other. Perhaps it is somewhere in the manual. Hybrids are known for having break pedals that start with regen and blend in friction breaks as needed.

 

[FrankinCarp]

It is an interesting question but for my part, logically, I don’t think that braking when using low regeneration returns as much energy to the battery.
The Law of Conservation of Mass and Energy applies.
The kinetic energy of the vehicle’s motion as it comes to a stop is being converted to heat and electrical energy returned to the battery.
The regeneration (high or low level) used to slow the vehicle recaptures a significant amount of the kinetic energy as power to the battery.
The braking system uses the friction of the brake pads to convert kinetic energy to heat. This heat is not going to benefit the charge level of the battery.
The regeneration system method of converting the kinetic energy back into potential energy (in the battery) is far more efficient than braking as the brake heat is simply dumped into the atmosphere.

The question really becomes one of how effectively one can modulate the accelerator pedal vs the brake pedal for best possible energy efficiency. If you can master the relatively easy “one pedal driving”, you will be rewarded with greater overall range from the kWh you lovingly add to your MINI SE from that socket in the garage.


Mike Wazowski [emoji1063]
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[MichaelC]

The question really becomes one of how effectively one can modulate the accelerator pedal vs the brake pedal for best possible energy efficiency. If you can master the relatively easy “one pedal driving”, you will be rewarded with greater overall range from the kWh you lovingly add to your MINI SE from that socket in the garage.

This right here. If you seek maximum efficiency and/or a smoother ride for yourself and your passengers, focus on how you modulate the accelerator pedal.

The sloppy drivetrains in ICE cars allows the driver to apply binary on/off inputs (or possibly encourages it). But in an EV with regenerative braking, quickly lifting off the accelerator pedal causes the car to slow down immediately in accordance with the regen level setting. Stop thinking of that pedal as a "I want to go" button, and start thinking of it as a "this is how much I want to go" control.

Want to slow down a little bit? Apply a little less pressure to the accelerator. Want to slow down faster? Lift off a bit more. With practice, you can learn to adjust how quickly or how slowly you decelerate by modulating the accelerator pedal. This includes finding that sweet spot between E-Power and Charge so you can coast--even when in high regen mode.

 

[AndysComputer]

If you use low regen and then add braking to the mix because the car is t slowing quickly enough you are wasting energy as it is converted to heat by the brakes.
Low regen recovers less energy and does not slow the car as much, requiring some use of the brake pedal in more situations. However it is closer to the feel of a traditional gas car.
If you learn to have fiber control over your right foot you can use high regen which recovers more energy as it requires less use if the brake pedal. However some drivers have trouble with the fine pedal control required and that causes the regen to come on when they do r want it, or with too much force which is jarring to passengers. It’s all about practice, much like good clutch control,

 

[insightman]

Many forum members who slow down almost exclusively using regen braking note the presence of brake-pad dust on their wheels. When the MINI Cooper SE is fully charged, no matter what the regen-braking setting, there is nowhere to put the energy from regen braking. However, the designers of the MINI Cooper SE didn't want the battery's state of charge to affect the driving experience so they implemented a way to use the friction brakes that feels exactly like regen braking. So the discussion about how much energy regen braking is returning to the battery applies only when the SE is not fully charged.

Based on this level of sophistication, I believe the MINI Cooper SE activates regen braking when the brake pedal is used (assuming the battery is not fully charged), and uses the friction brakes to accomplish a quicker stop than regen braking alone could perform. The power/charge gauge appears to back up this assumption.

The Owners Manual does not distinguish between accelerator-pedal lift-off and brake-pedal use when it says:
– On the go, the energy recovery ensures that only little energy is lost when braking.
– When the vehicle decelerates, the electric motor acts as a generator and converts the kinetic energy released into electric current.
– As a result the high-voltage battery is partially recharged in order to reach maximum range

 

[teslarati97]

Once you get used to high regen, it's much more efficient for 1 pedal driving compared to low regen. If you come from 3 pedal driving, low regen feels similar to engine braking when the clutch is engaged with no throttle input.

There is much more granular adjustments available through high regen compared to low if you can modulate the throttle appropriately (1/3 to 1/4 pedal travel).

 

[AndysComputer]

I believe the MINI Cooper SE activates regen braking when the brake pedal is used (assuming the battery is not fully charged), and uses the friction brakes to accomplish a quicker stop than regen braking alone could perform. The power/charge gauge appears to back up this assumption.

Because you take your foot off the "gas" pedal to press the brake pedal hence regen is activated so a blend/mix of the two is going on but I'm not convinced the brake pedal itself mixes anything, however I suspect that its use does not cancel the regen either, it simply wastes some of the kinetic energy as heat.

I do suspect that some kind of mix or blending is going on somewhere due the brake dust on the wheels, which I suspect is happening at near full charge as there is a delay in the vehicle slowing down when you back off which suggests to me that it's using the brakes, not regen, which makes sense if the battery is full. Poorly implemented "feel" wise though.

 

[Carsten Haase]

Because you take your foot off the "gas" pedal to press the brake pedal hence regen is activated so a blend/mix of the two is going on but I'm not convinced the brake pedal itself mixes anything, however I suspect that its use does not cancel the regen either, it simply wastes some of the kinetic energy as heat.

Definitely agree with this. If you try driving with two feet, you can hold the power meter in the "ready" zone (coasting) then apply the brakes without the gauge moving which should indicate no additional regen from the brake pedal. I believe using the brake pedal with regen in low also does not move the gauge into the second regen bar.

I do suspect that some kind of mix or blending is going on somewhere due the brake dust on the wheels, which I suspect is happening at near full charge as there is a delay in the vehicle slowing down when you back off which suggests to me that it's using the brakes, not regen, which makes sense if the battery is full. Poorly implemented "feel" wise though.

Based on the hardness of the brake pedal, you can feel when the car is using the brakes instead of regen (the pedal is hard and doesn't have the typical squishy zone).

I'm mostly convinced the stability control is overly sensitive and is activating during my regular spirited driving which could be causing some of the brake dust (in addition to BMW/MINI using notoriously dusty brake pads). This is just marketing so I don't fully trust it but does agree with my subjective opinion

 

[tesrivmini]

In regards to the OP's original question. I can't speak to the Mini as I don't have it yet. However, when I first got my Model 3 Performance, I did some testing between the two regen settings it has, as initially my wife *hated* the high setting, so I wanted to have some quantitative data to convince her to try it on high.

At the time (pre-pandemic), my daughter's school run was a 25 mile round trip (so I did that twice per school day). Over a period of a couple of weeks I tested it using the two regen settings. So as many of the variables were as close as is possible in real world scenarios - times of day, traffic, temperatures (roughly so).

I found that in the low regen setting, it used about 20% more power (total kWh used) for the trip than the high setting. However, that result is specific to that route, at those times of day, at that time of year, my driving style (hint: I didn't choose the Performance model at that time for no reason!), that specific vehicle, etc, etc. So, literally YMMV!

 

[Puppethead]

I got the impression that in the MINI the brake pedal is not connected to the regen system, but I don’t recall seeing a specific statement from the manufacturer one way or the other.

The friction brakes (brake pedal) are separate from the regen braking on the SE, due to being the exact same brake components as in the ICE models. The SE gets "blended" braking simply because regen is automatic once the accelerator is released, so when you brake with your foot you've taken it off the accelerator and thus are getting full regen as well.

The friction brakes are also activated automatically for traction control, again because of the shared ICE implementation.

 

[Puppethead]

Regarding efficiency, I recently learned on the SE low regen is 0.11 g of deceleration, and high regen is 0.19 g. Higher regen will slow down in a shorter distance, so technically it should be more efficient due to less overall drag and friction from speed=X to speed=0, but I don't think efficiency is going to be much of a factor between the two modes if you can roll to a complete stop due to how short the actual distance is in either mode. Stepping on the friction brakes will rob you of regenerative energy, so avoid using them as much as possible. Also I found driving with cruise control as much as possible minimizes unnecessary acceleration, thus improving efficiency.

 

[Joe c]

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.

 

[tesrivmini]

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.

In terms of electrical energy returned to the battery: 0.19g of regen > 0.11g of regen + 0.08g friction brakes

Friction brakes don't create electrical energy to return to the battery (i.e. regen), as mentioned earlier they just create heat.

I've seen that video, and he did, but again, it's all about the specifics of that particular drive/test he did, it will not apply to every drive due to all the possible variables. Similarly, no ICE car returns identical MPG on every single drive.

 

[Joe c]

Sorry I'm not referring to the friction brakes (brake pad touching the disc). I'm referring to the fact that when you press the brake pedal, the mini will do regen braking first before getting into friction braking, as BMW says on their blog. This happens in many if not all EVs. It definitely happens in my PHEV (Pacifica hybrid). When I press the brake there's significant regen happening before friction brakes kick in.

 

[CuriousGeorge]

If you come from 3 pedal driving, low regen feels similar to engine braking

I think this is a key point. If you're accustomed to the "point-and-shoot" style of driving encouraged by an automatic transmission, then yeah, 1 pedal driving in an EV may feel weird at first, especially on high regen. However, it's not really any different than driving a car with a manual transmission (or the bumper cars at the fair).

 

[Puppethead]

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."

I'm not sure it's clear from that statement that the friction brakes employ regeneration. It sounds more like the regen is "always active" as the blog entry states, and one could imply you get regeneration by taking your foot off the accelerator to move to the brake pedal.

Since the SE uses the exact same friction braking components as the ICE model, I'd be surprised if there's anything special with them. On the other hand, I believe it is a "brake by wire" system (no physical cable between pedal and actual brakes) so it's conceivable there could be extra software. But I haven't seen anything that confirms such a thing, and the SE isn't exactly cutting edge when it comes to electronic features.

 

[tesrivmini]

Sorry I'm not referring to the friction brakes (brake pad touching the disc). I'm referring to the fact that when you press the brake pedal, the mini will do regen braking first before getting into friction braking, as BMW says on their blog. This happens in many if not all EVs. It definitely happens in my PHEV (Pacifica hybrid). When I press the brake there's significant regen happening before friction brakes kick in.

OK, gotcha.

Short answer:
In my personal experience, yes, you get better range by using high regen. Stopping with regen alone will generate more electrical energy than: regen + any amount of friction braking.

Long answer:
I am not an electrical or mechanical engineer, but I guess mathematically, simplistically it's a case of : electrical energy returned to the battery = amount of regen being applied x elapsed time (minus all the inefficiencies in the system). Also it takes a given amount of energy to bring a vehicle of a given mass, traveling at a given velocity to a stop.

If you don't use the friction brakes at all (or until almost stopped) in either case (high or low regen), then I could see how it could potentially be an interesting question as to which regen setting returns more electrical energy to the battery.

However, if, you also use the friction brakes at any point, then some of the energy needed to slow/stop the vehicle that could have been generated by regen alone has come from the brakes. Therefore, stopping with regen alone will generate more electrical energy than: regen + any amount of friction braking.

In the YouTube video, as I recall he was more coasting/slowing down on low regen with very long stopping distances available.

As I said in another thread, when I tested high Vs low regen in my Model 3, controlling the variance in all the variables as much as I could in the real world, I found the high setting resulted in about 20% less energy usage for the same journey than the low setting - this result was repeatable.

As a bonus, using higher regen and less brakes, definitely results in less brake wear, there's barely any wear on my Model 3's pads after 2.5 years.