Which Regen Mode is Most Efficient?

[DucRider]

The only scenario that regen increases efficiency (& range) is when it replaces the use of friction brakes.
The max level - low or high - modulated by the throttle pedal is irrelevant as long as using the lower setting does not require adding friction brakes to the equation

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[Ottoman]

You can’t turn it off.

I meant the brakes assisting the regen. Not turning the Regen off.

I prefer to decouple the two pedals and decide when I want to use the brake pedal myself.

Otherwise, I love one pedal driving and would never go back

One of my favorite aspects of owning an EV is the fact that I no longer convert kinetic energy into heat like an ICE car. The concept of being able to scavenge even part of it, scratches that efficiency itch in my brain

 

[racekarl]

It’s really boils down to basic electrical concepts. There are zero motors that are 100% efficient. Any regen at all will have losses converting potential energy to electricity. Coasting will always be more efficient than any form of regenerative braking.

You know what’s even more efficient than coasting? Not driving. A discussion of which regen level is more efficient presumes that you’re, you know, using regen

 

[Count Orlok]

My instant reaction would be that HIGH regen would yield more efficiency as it's more powerful(?, not sure if that's the best way to put it).

I once had a yahoo arguing that hi regen is worst for efficiency because it means you need more energy to get back to speed.

 

[HaveBlue]

Efficiency is a function of distance traveled. Theoretically coasting to a stop covers the most distance and high Regen covers the least. Although Regen is more efficient than friction brakes in recovering some energy used to get to speed, it is not 100% efficient. It also loses some energy to heat. The amount regained would not be enough to travel the same distance as coasting at the same average speed (time). Speed (wind resistance) affects this calculation. Otherwise you could cheat the calculation by regenerating to a slow speed and traveling the rest of the coast distance when wind resistance is low.

The problem with coasting is needing to touch the brakes to avoid obstacles and then the energy would be wasted.

How much this all plays out in the real world with a less than 100% efficient device with poor wind resistance, would be determined with practical tests most easily. I tried low Regen on the freeway for a while but haven't come to any conclusion yet.

 

[WhidbeyIsland]

As I get more used my R1T (12k miles, DM), I am slowly settling on... using Medium or High Reg on highways/freeways where I am traveling at a relatively high rate of speed. And using Low Reg on city streets to reduce the back and forth sensation of heavy breaking & acceleration.. it reduces my wife's motion sickness, and is a bit calmer way to drive.

 

[corb00]

apparently regen is one of the major factors in tire degradation, compared to ICE, who do not apply regen. The negative forces on the tire contribute to quicker degradation- so.. should that cost be factored in as well somewhere..? just saying..


It's not just the added bulk; regenerative braking, a feature common in electric vehicles, has a role in shortening the tire replacement cycle. These combined factors contribute to an accelerated rate of tire wear in an EV fleet.



https://www.frotcom.com/blog/2023/12/are-electric-vehicles-increasing-tire-wear#:~:text=It's%20not%20just%20the%20added,wear%20in%20an%20EV%20fleet.

 

[HyperionMark]

apparently regen is one of the major factors in tire degradation, compared to ICE, who do not apply regen. The negative forces on the tire contribute to quicker degradation- so.. should that cost be factored in as well somewhere..? just saying..


It's not just the added bulk; regenerative braking, a feature common in electric vehicles, has a role in shortening the tire replacement cycle. These combined factors contribute to an accelerated rate of tire wear in an EV fleet.



https://www.frotcom.com/blog/2023/12/are-electric-vehicles-increasing-tire-wear#:~:text=It's%20not%20just%20the%20added,wear%20in%20an%20EV%20fleet.

Nope. Added weight and instant torque at all speeds are the reason for increased tire wear. If anything regen should lower tire wear (for most drivers). It generally increases the time and distance someone is slowing down. The lower deceleration would have less force and therefore less tire wear.

 

[SSteveEV]

Why would you be coasting on the highway? Usually you coast to a stop which is what electruck is talking about.

https://www.rivianforums.com/forum/...gen-brakes-make-me-car-sick.22910/post-461232

We really need clear terms for "coasting"=no input, just air resistance etc.

Coasting to a stop over X feet will always be more efficient than power+regen over the same distance.
Same deal on a highway if you want to drift down a few MPH on flat land as you approach someone.

 

[JerseyGreens]

https://www.rivianforums.com/forum/...gen-brakes-make-me-car-sick.22910/post-461232

We really need clear terms for "coasting"=no input, just air resistance etc.

Coasting to a stop over X feet will always be more efficient than power+regen over the same distance.
Same deal on a highway if you want to drift down a few MPH on flat land as you approach someone.

You are spot on.

I think this is why I'm getting better efficiency in low Regen on the highway.

I also got tints all around the vehicle and maybe I'm driving "less aggressive".

Time will tell.

 

[corb00]

Nope. Added weight and instant torque at all speeds are the reason for increased tire wear. If anything regen should lower tire wear (for most drivers). It generally increases the time and distance someone is slowing down. The lower deceleration would have less force and therefore less tire wear.

not my assessment- automotive engineers pointed out that regen has an additional tire wear effect- one thing I noticed that when regen is set to strong and the asphalt gets even slightly slippery, the tires can slide, you can hear them screeching- that's gonna cost some rubber, even during normal regen circumstances- again not my assessment, but an automotive engineers.

 

[HyperionMark]

not my assessment- automotive engineers pointed out that regen has an additional tire wear effect- one thing I noticed that when regen is set to strong and the asphalt gets even slightly slippery, the tires can slide, you can hear them screeching- that's gonna cost some rubber, even during normal regen circumstances- again not my assessment, but an automotive engineers.

Source? (More than just a random blog that doesn't have any bona fides)

Have been in the EV world for over a decade now and have never heard someone give that reason for more tire wear.

 

[Tango001]

Another data point on regen for highway driving. I finished a 1,600 mile road trip a few weeks ago, finished with efficiency of 2.2 mi/kwh. Trip was mostly interstate driving with some county highway and city driving mixed in, 2023 dual performance max pack R1S with 21” road wheels. I exclusively used high regen. I’m currently 500-600 miles into another road trip but this time I’m using low regen and I turned off regenerative brake assist as well, and I’m at 2.55 mi/kwh. I know not exactly apples to apples because the difference of the regenerative brake assist but I don’t think that would make a huge difference because I’ve spent very little time above 85% SOC. Both trips have been very similar as far as types of roads, driving style, elevation change. The only other difference is that it was 10-15 degrees warmer for the first trip so the AC had to work a bit harder but I was also using a sunroof shade for that trip and am not for this one. Overall I figure there has to be at least a legitimate 10% if not 15% improvement in range for me using these different settings.

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