Which Regen Mode is Most Efficient?

[electruck]

You lack basic understanding of reality

And you of science.

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[DucRider]

If you're decelerating, you're not "spending any energy" - as in not consuming from the battery. However, you are consuming the kinetic energy of the vehicle to overcome those friction forces and that is wasting a portion of the vehicle's total available energy. You're also not consuming any energy from the battery if you use regen to decelerate. The difference is, when coasting, you are wasting 100% of the vehicle's kinetic energy. With regen, you are wasting less than 100% of the vehicles kinetic energy.

Regen is additive to the forces slowing the truck when coasting.
Coasting down a hill and gaining speed that is later bled off as the slope flattens is more efficient than using regen to maintain a set speed downhill and then switching using battery power to maintain that speed.

 

[NeedSumCoffee]

And you of science.

Let me ask you this then Mr Science. Why do absolutely zero EV hypermiliers ever use regen if its more efficient?

You can’t convert 100% of the kinetic energy into electricity. You will have 20-30% energy losses converting it to electricity and another 20-30% converting it back into power. Coasting with no regen, you’ll have losses from air resistance and tire friction. But with regen you still have all those exact same losses PLUS losses from the regen inefficiencies.

the only time regen is better is if you use it as a replacement to braking and recapture wasted energy from the braking process.

 

[Ktran825]

I don’t have concrete data but I’ve used low regen with brake assist regen off and I feel like I get better miles per kWh than before. Especially in conserve mode. I could never get over 2.6 before, and I’ve been able to get 2.8 on similar drives. I hardly use the brakes even on low regen.

 

[NeedSumCoffee]

If you're decelerating, you're not "spending any energy" - as in not consuming from the battery. However, you are consuming the kinetic energy of the vehicle to overcome those friction forces and that is wasting a portion of the vehicle's total available energy. You're also not consuming any energy from the battery if you use regen to decelerate. The difference is, when coasting, you are wasting 100% of the vehicle's kinetic energy. With regen, you are wasting less than 100% of the vehicles kinetic energy.

You are not “wasting the kinetic energy”, it’s still being used to move the car forward.

I think the big concept you’re not grasping is that you still have to go an X distance. If you coast, you’re converting the kinetic energy into distance traveled. If you use regen, you convert a portion of the kinetic energy back into power, but you also traveled a much shorter distance. You now also have to use that energy to move the car to travel that remaining distance. You add significantly more losses with regen to travel the same distance.

 

[emoore]

I once Ascended sequoia, it was around 7,000ft.. It took 40% or so to get up the mountain.. and I only Regenned like 6% on the way down.. I was so disappointed I felt robbed..

I turned off regenerative assistance ever since.

You can’t turn it off.

 

[electruck]

Regen is additive to the forces slowing the truck when coasting.
Coasting down a hill and gaining speed that is later bled off as the slope flattens is more efficient than using regen to maintain a set speed downhill and then switching using battery power to maintain that speed.

Yes, this is where the specific driving scenario matters. You aren't simply comparing slowing to a stop via coasting to slowing down via regen here (as I was). In this particular scenario, you are comparing different tactics to maintain minimum speed most efficiently. In your scenario, you are leveraging gravity to accelerate the vehicle (increasing its kinetic energy) to maintain a minimum speed for a longer time vs using regen to maintain a constant speed thus requiring you to dip back into the battery as soon as the road levels out. And yes, in that scenario, I agree you can get from A to B more efficiently using gravity than regen. You're not wrong but neither are my previous statements. The problem here is most of the "debate" in this thread is the result of everyone comparing apples to oranges.

 

[electruck]

Let me ask you this then Mr Science. Why do absolutely zero EV hypermiliers ever use regen if its more efficient?

You can’t convert 100% of the kinetic energy into electricity. You will have 20-30% energy losses converting it to electricity and another 20-30% converting it back into power. Coasting with no regen, you’ll have losses from air resistance and tire friction. But with regen you still have all those exact same losses PLUS losses from the regen inefficiencies.

the only time regen is better is if you use it as a replacement to braking and recapture wasted energy from the braking process.

See my last response to DucRider. Apples and oranges. We need to stop speaking in generalities here because the details make a difference. DucRider describes a perfectly viable scenario where coasting is beneficial. That's also not the scenario I have been describing, which is slowing to a stop and what I think you were trying to allow for in your last sentence.

It's called regenerative braking for a reason. If you're wanting to decelerate the vehicle, regenerative braking is the most efficient way to do that. If your goal is not to decelerate the vehicle then, absolutely, regen is counterproductive.

 

[electruck]

You can’t turn it off.

Ottoman appears to have confused turning off regenerative assistance (supplemental friction braking) with turning off regenerative braking (which can't be fully disabled as you noted).

 

[NeedSumCoffee]

See my last response to DucRider. Apples and oranges. We need to stop speaking in generalities here because the details make a difference. DucRider describes a perfectly viable scenario where coasting is beneficial. That's also not the scenario I have been describing, which is slowing to a stop and what I think you were trying to allow for in your last sentence.

It's called regenerative braking for a reason. If you're wanting to decelerate the vehicle, regenerative braking is the most efficient way to do that. If your goal is not to decelerate the vehicle then, absolutely, regen is counterproductive.

You replied to multiple comments about coasting, not breaking. Clearly breaking to a stop is not what you meant when talking about highway driving and coasting. You said “Coasting is absolutely not more efficient than regenerative braking.” This is flat out wrong. Also you said “Look at it this way, if you coast to a stop, you waste 100% of the vehicle's kinetic energy (lost to the environment). “ This is also completely wrong.
I am glad you finally realized your comment were ridiculous.

 

[emoore]

You replied to multiple comments about coasting, not breaking. Clearly breaking to a stop is not what you meant when talking about highway driving and coasting. You said “Coasting is absolutely not more efficient than regenerative braking.” This is flat out wrong. Also you said “Look at it this way, if you coast to a stop, you waste 100% of the vehicle's kinetic energy (lost to the environment). “ This is also completely wrong.
I am glad you finally realized your comment were ridiculous.

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

 

[NeedSumCoffee]

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

Have you ever driven on a highway before?

 

[electruck]

You replied to multiple comments about coasting, not breaking. Clearly slowing to a stop is not what you meant when talking about highway driving and coasting. You said “Coasting is absolutely not more efficient than regenerative braking.” This is flat out wrong. Also you said “Look at it this way, if you coast to a stop, you waste 100% of the vehicle's kinetic energy (lost to the environment). “ This is also completely wrong.
I am glad you finally realized your comment were ridiculous.

Clearly you still don't know what I meant. Coasting just means you are not applying power/torque to the wheels and does not insinuate acceleration or deceleration as that is a function of the road grade (and other factors to a lesser degree), nor does it suggest anything about highway driving or coasting to a stop.

My comment about coasting to a stop is 100% correct and if you're going to call me out for being wrong, you need to back up your claim. Doesn't matter though, I'm tapping out as this pissing match isn't worth my time.

 

[Lrak1973]

CO93 to down around Colorado Mills.

That is a a much prettier commute, but definitely some good rolling hills and side wind!

 

[emoore]

Have you ever driven on a highway before?

Haha. Is that a serious question?

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