Regen Braking for Beginners.... I have questions

sheydon

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What a fabulous wealth of information collectively assembled on this forum. I'm new to EV vehicles. I've read a lot here, learned a lot. One thing I don't totally understand is regen braking. Sure I get the high-level - regen device slows the vehicle while also charging the batteries (do have even that basic concept correct?). But many other things I've seen referenced (paddles, one-peddle operation rusting brakes) I don't fully understand. Don't get me wrong, this won't affect my purchase decision - I'm in. But for a newbie it would be good to know. So here goes:

- How does the vehicle know when to apply regen braking - what if I just want to coast (no brake, no acceleration)?
- How much does the regen braking slow the vehicle? Is that adjustable? If adjustable - through settings or something more dynamic (like paddles??)?
- How much re-charging actually happens?
- I've seen mention of "crawl mode" (in Tesla's I presume) - what the heck is that? Will Rivian have that?
- Is the regen braking system separate from the regular brake mechanism?
- Any maintenance over time of the regen system?
- What exactly is "one peddle" driving? Is this something Rivian will sort-of enable? How?
- How much do we know about how this will all work within the Rivian platform (R1T / R1S)?

Thanks in advance to all the knowledgeable and better-informed responders out there.

sheydon
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DucRider

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  • The vehicle knows to apply regen when a request to slow the vehicle is received - using the electric motors is the "first line" of slowing with friction brakes as the secondary source.
  • How much it slows varies by vehicle, and adjustability does as well. It appears that Rivian will not have paddles to adjust "on the fly", but it is very likely that the amount can be set thru the center screen (and maybe Alexa?).
  • Not sure how to quantify "how much re-charging". Regen is deemed to be 50-70% efficient at recapturing energy that otherwise would have been converted to heat thru the friction brakes.
  • "Creep" or "Crawl" modes mimic an ICE with an automatic transmission - if you release the brakes, the vehicle will start to move slowly under power. On some vehicles it is selectable (or mode dependant), on others the manufacturers select one or the other and that is what you get. I believe Rivian is likely to make it selectable. As kind of a side note - creep mode is a PITA in parades as you are constantly on the brake pedal (and most auto follow cruise control systems aren't real smooth at walking speeds)
  • The regen system uses the motors instead of friction brakes to slow the vehicle. On most it is integrated where pressing the brake pedal will first engage regen, then transition to (or add) friction brakes as needed. Tesla separates the systems entirely - lifting the throttle engages regen (no longer adjustable as to amount), pressing the brake pedal engages the brake pads. Rivian s likely to embrace the "blended braking" model.
  • Maintenance over time means not changing brake pads ;)
  • One pedal driving is when the vehicle has strong enough regen to slow the vehicle to (or very nearly to) a stop by taking your foot off the throttle.
  • Rivian has not released much detail on this yet. More will come when the Guides are talking and/or when test drives are made available
 

jcook01

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We have two EVs a 2017 Volt and a 2021 Mach-E. The Volt regen can be engaged via a flappy padel on the steering column or via the brake pedal. Depressing the brake pedal initially engages regen braking only but if you press harder you can engage metallic braking as well.

Putting the Volts transmission into Low will make it drive more like one pedal driving, release the gas while in Low and the regen will slow the car until it slows down to the point when not enough EMF is generated ~5mph then you'll need to depress the brake pedal to come to a full stop. I like how seamless the Volt braking system is, the transition from Regen to metallic braking occurs without you knowing or feeling it...it just plain works well many cudos for Chevy for getting that right. When in Drive and you lift off the gas it'll coast until you press the brakes of or the regen paddle.

Our Mach-E has three driving modes, engaged, whisper and and unbridled. Whisper drives just like the Volt does above, regen comes on initially until you press hard on the brake pedal then metallic braking assists the regen braking.

When in engaged and unbridled you'll get regen brake lag as soon as you lift off the accelerator...we both prefer to coast so it stays in Whisper mode. There's also one pedal when you turn it on it'll bring you to a complete stop once you life off of the accelerator...but as I said we prefer the managed regen feel brining the car to an almost complete stop then metallic brakes brings it to a stop.

Most EVs give plenty of options for everyone's tastes.
 

Gshenderson

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The best simulation for regen is put your ICE vehicle in low gear and start driving. Get the speed/RPM’s up there where it feels like you are pushing the motor. Let off on the gas - either gradually or all at once - and notice how it slows the car. Regen, in essence, works very similarly. It’s using the motor to create resistance which slows the car.
 

ATL_Canes

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  • The vehicle knows to apply regen when a request to slow the vehicle is received - using the electric motors is the "first line" of slowing with friction brakes as the secondary source.
  • How much it slows varies by vehicle, and adjustability does as well. It appears that Rivian will not have paddles to adjust "on the fly", but it is very likely that the amount can be set thru the center screen (and maybe Alexa?).
  • Not sure how to quantify "how much re-charging". Regen is deemed to be 50-70% efficient at recapturing energy that otherwise would have been converted to heat thru the friction brakes.
  • "Creep" or "Crawl" modes mimic an ICE with an automatic transmission - if you release the brakes, the vehicle will start to move slowly under power. On some vehicles it is selectable (or mode dependant), on others the manufacturers select one or the other and that is what you get. I believe Rivian is likely to make it selectable. As kind of a side note - creep mode is a PITA in parades as you are constantly on the brake pedal (and most auto follow cruise control systems aren't real smooth at walking speeds)
  • The regen system uses the motors instead of friction brakes to slow the vehicle. On most it is integrated where pressing the brake pedal will first engage regen, then transition to (or add) friction brakes as needed. Tesla separates the systems entirely - lifting the throttle engages regen (no longer adjustable as to amount), pressing the brake pedal engages the brake pads. Rivian s likely to embrace the "blended braking" model.
  • Maintenance over time means not changing brake pads ;)
  • One pedal driving is when the vehicle has strong enough regen to slow the vehicle to (or very nearly to) a stop by taking your foot off the throttle.
  • Rivian has not released much detail on this yet. More will come when the Guides are talking and/or when test drives are made available
This is a pretty good summary. I'll just throw in some real world experience from driving a Tesla for a while, knowing that this can vary among manufacturers:

Regen braking to me was the equivalent of engine braking if you ever drove a manual (which is a dying art). As you release pressure on the accelerator, regen starts to kick in and you can feel the car slowing itself. If you gradually release pressure on the accelerator, the car gradually slows down. If you remove all pressure, it slows quicker. But it is not the equivalent of hitting the brakes, so any sudden stops need the brake pedal to be applied.

Tesla's regen cutoff at about 5 MPH, and then you had to use the brake pedal to slow to a complete stop. So Tesla doesn't truly have one pedal driving since you can't bring the vehicle to a complete stop using just regen. Curious what Rivian does here.

Tesla had three options (at least on the S) - off, low, and standard. I guess it's not for everyone, so the option exists to turn it off. I sold my MS last month, so maybe that option doesn't exist anymore based on DucRider's post.

In just day-to-day driving, it takes a few days to get used to slowing down this way but it becomes second nature. In my experience, it doesn't put a lot of charge back into the battery but the lack of wear and tear on the brake pads is a nice perk. There were times driving back down the North Georgia mountains where my battery would go from 80% to maybe 84% state of charge by the time I got to the bottom - it's nice, but not enough to add any real distance.

Hope that helps!
 

KenJ

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Good explanation from DucRider.
I’ll add to your question about rusting brakes. Some of the hardware on my Model S seized up from rust / road salt here in northeast. Used as traditional brakes the small motions of the pistons/pads would “wipe” surface rust, but since there’s so much less movement the rust built up until they froze and some minor hardware had to be replaced. Didn’t harm actual brake use, but I think Tesla even recommends some “inspection” and light maintenance even though you won’t need new pads/rotors. To me it’s still maintenance at a similar interval and labor is the cost, maybe not the parts.
 
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sheydon

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Thank you all for the great information! :idea:
 

azbill

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GM uses true "one pedal", I can drive my Bolt all day and never use the brakes, only need them for emergencies. It even holds the vehicle at a stop on slopes. That mode can be turned off, then you get more gentle regen and have to use the brakes to completely stop. They also have paddles on the steering wheel, those can be used with or without one pedal and they increase the regen and stop the car faster. If one pedal mode is off, then pushing the paddle will also bring the car to a complete stop, as long as you push on the paddle.
 

Kickaha

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What a fabulous wealth of information collectively assembled on this forum. I'm new to EV vehicles. I've read a lot here, learned a lot. One thing I don't totally understand is regen braking. Sure I get the high-level - regen device slows the vehicle while also charging the batteries (do have even that basic concept correct?). But many other things I've seen referenced (paddles, one-peddle operation rusting brakes) I don't fully understand. Don't get me wrong, this won't affect my purchase decision - I'm in. But for a newbie it would be good to know. So here goes:

- How does the vehicle know when to apply regen braking - what if I just want to coast (no brake, no acceleration)?
- How much does the regen braking slow the vehicle? Is that adjustable? If adjustable - through settings or something more dynamic (like paddles??)?
- How much re-charging actually happens?
- I've seen mention of "crawl mode" (in Tesla's I presume) - what the heck is that? Will Rivian have that?
- Is the regen braking system separate from the regular brake mechanism?
- Any maintenance over time of the regen system?
- What exactly is "one peddle" driving? Is this something Rivian will sort-of enable? How?
- How much do we know about how this will all work within the Rivian platform (R1T / R1S)?

Thanks in advance to all the knowledgeable and better-informed responders out there.

sheydon
Launch R1S - Limestone / white
Duc gave a great summary but I will add some of my experience. I have a 2016 Tesla Model X which is my first (and only, so far) EV. I have not driven any others but from what I have read, driving a Rivian will be pretty similar to a Tesla.

- How does the vehicle know when to apply regen braking - what if I just want to coast (no brake, no acceleration)? On a Tesla, if you have regen braking turned on, when you let off the accelerator, regen braking engages. The strength of the brake will depend on the setting. From what I can tell, most EVs have 3 settings - off, low, normal. I use normal.

- How much does the regen braking slow the vehicle? Is that adjustable? If adjustable - through settings or something more dynamic (like paddles??)? On my Tesla with normal regen braking, its a decent amount of slowing but it is NOT meant to avoid crashing into someone - you will still need to actively brake. But if you are coming up to a stop 150 feet away, you can let off the brake and it feels like a light amount of braking. You will get used to it.

- How much re-charging actually happens? Honestly, not much. But, over the course of 200 miles, could be a bit - I have never measured. Its more a matter of "something is better than nothing". What else are you going to do with your built up momentum other than wear and tear on brakes?

- I've seen mention of "crawl mode" (in Tesla's I presume) - what the heck is that? Will Rivian have that? Duc covered this - its just like in an ICE car and you let off the brake and you slowly move forward. Its nothing mysterious.

- Is the regen braking system separate from the regular brake mechanism? yes, separate but not equal or substitutable. Dont assume regen braking will keep you from rear-ending someone in an emergency situation. Regenerative Braking is not really a system but more of how the motor works when not actively propelling the wheels. Its not separate equipment from the motors whereas the manual brakes are a complete seperate system.

- Any maintenance over time of the regen system? No. As Duc mentioned, you save on brake maintenance. In over 5 years, I have never had any brake pad or regenerative braking maintenance done. But, the Tesla Model X brakes are VERY over-engineered - I can stop that puppy on a dime.

- What exactly is "one peddle" driving? Is this something Rivian will sort-of enable? How? This is basically you learning how far in advance of a stop or slow down in traffic you should let off the accelerator and slow down through regen braking by not engaging the manual brakes until you have to. You are trying to minimize the amount of activating the manual brakes by "coasting" as much as possible. The only difference here is that when you "coast", your EV will use the momentum of your vehicle to gather electricity from the resistance in your motor to charge your battery. This is one of those things thats kind of hard to describe but you will understand it in about 10 seconds once you do it.

- How much do we know about how this will all work within the Rivian platform (R1T / R1S)? Very little. We all make a lot of assumptions (mine is that it will be like my Tesla) but we really dont "know".
 

DuckTruck

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What a fabulous wealth of information collectively assembled on this forum. I'm new to EV vehicles. I've read a lot here, learned a lot. One thing I don't totally understand is regen braking. Sure I get the high-level - regen device slows the vehicle while also charging the batteries (do have even that basic concept correct?). But many other things I've seen referenced (paddles, one-peddle operation rusting brakes) I don't fully understand. Don't get me wrong, this won't affect my purchase decision - I'm in. But for a newbie it would be good to know. So here goes:

- How does the vehicle know when to apply regen braking - what if I just want to coast (no brake, no acceleration)?
- How much does the regen braking slow the vehicle? Is that adjustable? If adjustable - through settings or something more dynamic (like paddles??)?
- How much re-charging actually happens?
- I've seen mention of "crawl mode" (in Tesla's I presume) - what the heck is that? Will Rivian have that?
- Is the regen braking system separate from the regular brake mechanism?
- Any maintenance over time of the regen system?
- What exactly is "one peddle" driving? Is this something Rivian will sort-of enable? How?
- How much do we know about how this will all work within the Rivian platform (R1T / R1S)?

Thanks in advance to all the knowledgeable and better-informed responders out there.

sheydon
Launch R1S - Limestone / white
sheydon,

jcook01's Chevy Volt incorporates the identical regen braking as my Cadillac ELR. When engaging the regen paddle to slow the vehicle, the amount of braking is measured at 0.2 g's. It is not linear as it's all (0.2 g's) or nothing. At that level, it's subtle, but slows the vehicle quite nicely. As jcook01 and others have mentioned, when driving in "Low", lifting the accelerator pedal initiates a similar braking feel as using the paddle. Again, it's not dramatic, but it will slow you fairly quickly. Either method will bring the car almost to a complete stop on a flat roadway. To come to a complete stop, the mechanical brakes will be needed. No matter which method you use, any regen braking you initiate, either through the paddles, or by lifting your right foot while in "Low", will activate the brake lights.

Although I don't know the amount of braking g-force developed when using the paddles while also in Low, the paddles do boost the regen above and beyond the slowing created simply by lifting the pedal. Again, it won't stop the car completely, but it comes very close. Only the slowest of pedestrians are at risk in the crosswalk. 😉

For me (in part, because of where I live), rust on the discs has not been a problem. Because I'm in a somewhat urban area, I'm coming to a complete stop quite often. As such, the mechanical brakes are utilized on every trip, even if minimally. Therefore, the pads are scraping the discs at least a few times every drive.

This system is probably different in some way from all others, but it is nice that this group has that wealth of experience mentioned often here.

Safe braking to all!
 

Gshenderson

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How much re-charging actually happens?
I frequently drive from Park City to Salt Lake City. That drive involves a 10 mile stretch down through Parley’s Canyon that has 2,000’ of elevation drop. I typically gain 2-3 miles of range on that stretch. I’m in various levels of regen pretty much the whole time.

It takes ~22 miles of range to drive the 32 miles from my place in Park City to SLC airport. It takes about ~65 miles of range going the other way.
 

NashvilleR1S

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Do the brake lights automatically come on when you take your foot off the gas if youre in a high regen mode?
 

SANZC02

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Do the brake lights automatically come on when you take your foot off the gas if youre in a high regen mode?
Technically the accelerator, but yes. In the Tesla it gives you feedback on the dash when the break lights are on. They come on as you start slowing down Like they would if you were putting your foot on the break.
 

Gshenderson

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Yes, depending on the amount of regen activated. So if you barely feather your foot off, you may have some regen, but not enough to trigger the brake light. If you completely take your foot off the accelerator,then brake light comes on. The biggest adjustment is learning to feather your foot off the accelerator vs. taking it completely off and moving it to the brake pedal. But you’ll get used to it really quickly. And then never want to go back!
 

UT Rivian

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I frequently drive from Park City to Salt Lake City. That drive involves a 10 mile stretch down through Parley’s Canyon that has 2,000’ of elevation drop. I typically gain 2-3 miles of range on that stretch. I’m in various levels of regen pretty much the whole time.

It takes ~22 miles of range to drive the 32 miles from my place in Park City to SLC airport. It takes about ~65 miles of range going the other way.
Curious as to how fast you drive up Parley’s on the way home. That would seem like a tough stretch for an EV, from a mileage standpoint.
 

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