Regen Braking for Beginners.... I have questions

[Gshenderson]

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.

Usually set autopilot at 79mph and enjoy the scenery. You don’t notice any sluggishness at all - quite the opposite, plenty of power to spare. But it does eat up a lot of juice from the battery.

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[Yoliber]

Do we know if Rivian is blended the brakes or are they only doing off throttle regen?

 

[electruck]

Do we know if Rivian is blended the brakes or are they only doing off throttle regen?

I don't believe it is possible to get by without ever using the brakes (such as for emergency stopping, fully charged battery, battery too cold, etc) so a blended application is a given. Are you asking about scrubbing the last few mph when coming to a stop? In that specific context, the braking appears to be blended. We don't yet know how much configurability they will allow but is seems they are aiming for minimal application of the mechanical brakes. It was reported in late 2018 that they may go so far as to apply motor torque (or reverse torque as necessary) for the purpose of hill holding.

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.

 

[Yoliber]

I don't believe it is possible to get by without ever using the brakes (such as for emergency stopping, fully charged battery, battery too cold, etc) so a blended application is a given. Are you asking about scrubbing the last few mph when coming to a stop? In that specific context, the braking appears to be blended. We don't yet know how much configurability they will allow but is seems they are aiming for minimal application of the mechanical brakes. It was reported in late 2018 that they may go so far as to apply motor torque (or reverse torque as necessary) for the purpose of hill holding.

Blended brake as in, when you press the brake pedal, it'll regen first, then use friction if needed.

An example of brakes that aren't blended are Teslas. If you touch the brake pedal on a Tesla, it'll use friction brakes no matter what. In other words, the regen is independent of the brake pedal which is solely used for friction brakes.

I want to be able to have a system like the VW where we can coast but get full regen via the brake pedal.

 

[electruck]

Blended brake as in, when you press the brake pedal, it'll regen first, then use friction if needed.

An example of brakes that aren't blended are Teslas. If you touch the brake pedal on a Tesla, it'll use friction brakes no matter what. In other words, the regen is independent of the brake pedal which is solely used for friction brakes.

I want to be able to have a system like the VW where we can coast but get full regen via the brake pedal.

The article I quoted above is, to my knowledge, the best information we have on this subject so far. Unless it is user configurable (which is entirely possible and I think likely), the behavior described in the article is for full-stop one-pedal regen and would not appear to support coasting. Unfortunately we just don't know if this will be the only available braking behavior or simply one of several options.

 

[Yoliber]

Ah... I didn't read carefully, but in that article it states that it is blended.

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.

 

[DucRider]

Blended brake as in, when you press the brake pedal, it'll regen first, then use friction if needed.

An example of brakes that aren't blended are Teslas. If you touch the brake pedal on a Tesla, it'll use friction brakes no matter what. In other words, the regen is independent of the brake pedal which is solely used for friction brakes.

I want to be able to have a system like the VW where we can coast but get full regen via the brake pedal.

Nothing has been released that can definitively answer your question. It sound like you want a system similar to Audi system as described below, but Rivian will not have paddles to adjust "on the fly".

Audi enabled "coast" mode to make it feel like an ICE vehicle. I don't think Rivian has the slightest aspiration to feel like an ICE vehicle. "Coasting" in EVs with regen tied to the throttle is achieved by modulating the pedal as appropriate. The BMW i3 has a "detent" in throttle position that is the "coast" mode. Some users have trouble feeling/finding it, for others it is obvious.

It is extremely likely (but not 100% confirmed) that Rivian will have adjustable regen settings. Adjustable or default settings that have less "off throttle" regen would be inefficient and negatively impact the EPA (and real world) range if using the brake pedal did not add some regen.

I doubt very much that Rivian will go the route Tesla did and separate the two systems entirely. The linked article above was from the reveal in 2018. Much has changed since then and while almost certainly blended braking has been retained, we haven't seen anything to confirm that.

Coasting is an issue slightly separate from blended brakes. Blended brakes are required for a "Coast" regen setting, but having blended brakes does not mean such a setting is available.

 

[electruck]

Ah... I didn't read carefully, but in that article it states that it is blended.

Blended... yes. As in the action of the brake pedal is blended. However, if you lift throttle, you won't coast but will get immediate regen unless they provide an option for the driver to disable regen.

What it boils down to is that we really just don't know how the finished product will behave.

 

[cwoodcox]

Prius has been doing blended brakes for a decade. Isn’t it configurable in Teslas as well? It seems crazy to me that they’d entirely separate the two systems. Prius (and other hybrid/EVs) have an enormous advantage when it comes to braking, the brakes on the Prius are undersized because it doesn’t need to rely on only them for braking force.

 

[DucRider]

Prius has been doing blended brakes for a decade. Isn’t it configurable in Teslas as well? It seems crazy to me that they’d entirely separate the two systems.

Tesla used to have two regen settings, but now only max regen is available. They have never utilized blended brakes. Throttle pedal controls regen, brake pedal controls friction brakes. Simple, but not to everyone's taste. The majority of EV drivers like "one pedal" driving, but some find it jerky and unpleasant (particularly when they are passengers).
The Prius has comparatively little regen potential (small motor) and is not capable of implementing one pedal driving.

 

[thrill]

... The BMW i3 has a "detent" in throttle position that is the "coast" mode. Some users have trouble feeling/finding it, for others it is obvious. ...

I never even noticed the detent you mention so I guess it's a very natural feel. I quite like the i3 regen but I have no experience in other EVs.

 

[cwoodcox]

Simple, but not to everyone's taste. The majority of EV drivers like "one pedal" driving, but some find it jerky and unpleasant (particularly when they are passengers).

Yup. I tried to convince my wife to go for a model 3 but she drove our friends’ and she hated the jerky regen. I tried to tell her “it’s configurable” and it is to a point, but I dunno that she could ever get used to it. It turned her off Tesla forever, prolly.

Maybe that just means I’ll have to put in for whatever hot hatch Rivian comes up with ?

 

[Trandall]

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.

Ouch, so round trip of 64 miles uses 87 miles of range at 79mph. wouldn't that be 36% less than Tesla's stated range. This is something I'm going to need to get used to.

 

[TessP100D]

Ouch, so round trip of 64 miles uses 87 miles of range at 79mph. wouldn't that be 36% less than Tesla's stated range. This is something I'm going to need to get used to.

My experience is that you will loose a lot of range when traveling Against the wind or up any grade even a small One. Traveling of a flat road you will get close to the rated range, but is disappears magically otherwise.

coming down from a 5,000 feet elevation, I just coast down the mountain and the regen keeps the Car at a constant safe speed and I gain about 12-20 miles of total range by the time I get to the bottom. That depends on the SOC when I start my trip down.

it should be noted that when you charge your car to 100% SOC for a long trip, your regen will turn off completely on its own until the battery range drops to allow for the regen to charge back up. That is a strange feeling the first couple of times it’s happens until you get used to it.

My Tesla allows me to either use Standard regen mode or a lessor regen Mode. I drive with the standard mode around town and let the car slow itself down until I have to apply the brakes for a coasting style full stop or in the case of having to stop more quickly I just use the brakes. However I have found that on the freeway, I change the regen setting to the lower mode, because I have found it slows to quickly and could cause the car behind me to hit me from behind, and if using AP, when fantom braking occurs, the car slows down way to fast for normal driving tendencies.

Finally, I use Creep Mode is for safety and I recommend it. Driving a Tesla is mostly one for driving but you do need two pedals. The real safety reason for using creep mode is, brake safety At slow slow speeds. electric cars have a lot of low end power, and it is very easy to go faster than you want at a low speed such as coming into a parking lot space, and just lightly touching the accelerator pedal could cause a crash. Instead using creep mode, just like an automatic trans car, I allow the car to creep forward and using the brake pedal to slowly control the car to a complete stop. I learned To drive on a stick shift car, and still have and drive them. It’s the same thing really, you let the clutch out slightly -in and out - to allow the engine to pull or push you into the parking stall, then just as you will want to stop, you push in the clutch all the way, and apply the brakes to come to a complete stop. This is the same features as creep mode prvoides

 

[kylealden]

Once you've gotten used to one-pedal driving, strong regen instead of coast, and no creep, it's hard to go back. I was skeptical (and grew up driving manual), but Tesla's approach won me over -

1. Braking is totally unambiguous - it actuates a physical brake and there's no mystical blending action. If you want maximum regen, don't use the brakes. If you need to stop fast, use the brakes. I very often will wrap up my entire commute without ever touching the brakes except to put the car in gear. (I really like that this encourages healthy following distances and helps smooth out stop and go, too.)
2. Achieving maximum regen is simple: avoid unnecessary speed fluctuations, give yourself room to brake primarily via regen, only use the physical brake if you need to.
3. While it's a little bit "lurchy" before you get used to it, with a little practice it's far easier to do "limo-style" smooth stops and incredibly graceful deceleration with one-pedal driving. The trick is to never lift off of the gas suddenly (unless you really need to) - the rapid swing from "acceleration" to "deceleration" happens way faster than it ever can in a two-pedal setup and is super uncomfortable for passengers.

One pedal combined with an excellent hill hold is also amazing in a place like Seattle - you can inch your way up the steepest hills with total precision with almost no effort. It's terrific.

Tl;dr, regen is great and any coasting or friction braking feels like such a waste of potential energy once you're used to regen. I really, really hope Rivian takes a similar approach (or at least makes it configurable - my wife hates everything I've described above.)

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