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Regen misconceptions......

4569 Views 112 Replies 38 Participants Last post by gasbandit, 11 d ago

Fjpod

Discussion Starter · 18 d ago

did I get your attention?

In various threads, and even on YouTube videos, I see many people saying wrong things about regenerative braking.

Let's make a list of all the ones we've heard. I'll start it off with 3.

1. "The more regen you score on your car's computer, the more you saved.". ...Generally wrong. If you are using regenerative braking to excess, that means you are accelerating more than you should be. As a general rule, regen only earns back about one third of the energy it took to get up that speed in the first place. Using less acceleration would be a better way to save battery.

2. "A paddle on the steering wheel saves more battery than using the brake pedal." Generally wrong. The brake pedal and the paddle use the same regenerative system. If you apply the brake judiciously it is the same as using the paddle. Certainly when you have to come to a complete stop in a hurry, the friction brakes kick in.

3. "One pedal driving will automatically save battery." Not likely... especially on the highway. Every time you ease off the pedal, maybe from fatigue, maybe due to distraction, you are slowing down and will just have to accelerate again to get back to cruising speed. Certainly, some decelerations are necessary for traffic, safety, etc.

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ARob

· #2 · 18 d ago

Ongoing debate on every EV forum...

It depends... on a lot of factors.

In general, I have seen a lot of passionate debate about coasting vs regen. I suspect the jury is 50/50 on which method is most efficient.

That said, it is undeniable that in certain situations, regen is a great benefit. For my typical driving, I use One-Pedal mode almost exclusively, not so much for efficiency, but to reduce the use of friction brakes. I also like to make a game out of stop and go traffic on the Interstate, can I arrive at my destination without touching the brake pedal... in 99% of the cases, yes I can!

On many of my trips in CO, there are stretches of 10-40 miles of downhill driving where OPM pays off in spades, sure, you have to use energy to reach 11,000 ft elevation, but coming back down the mountain recapturing some of the energy is a great benefit.

Nobody will ever "win" the debate on which method is most efficient, but they will surely get excited and worked up about their perceived "superior" opinion.

Welcome to the forum, a little searching in this section will yield a number of similar threads debating this topic, with no real conclusion and a lot of hurt feelings. Sorry, just pointing out reality.

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PhilipD

· #3 · 18 d ago

Fjpod said:
If you are using regenerative braking to excess, that means you are accelerating more than you should be.

Thanks for posting your insights on regenerative braking. But, I don't quite follow you on this one. How can you use regen excessively? I believe everyone accelerates in a manner they deem appropriate. I like the torque of the car and I am not afraid to use it. Others may think it is excessive, but to me, it is juuuust right.

Reactions: 5

GJETSON

· #4 · 18 d ago

If you feel the need to hypermile, you bought too big/inefficient a vehicle.

Reactions: 5

Sheldon

· #5 · 18 d ago

PhilipD said:
Thanks for posting your insights on regenerative braking. But, I don't quite follow you on this one. How can you use regen excessively? I believe everyone accelerates in a manner they deem appropriate. I like the torque of the car and I am not afraid to use it. Others may think it is excessive, but to me, it is juuuust right.

Think gas automobile efficiency where coasting is better than breaking and then accelerating. I think maybe the Prius is an exception in that the Prius hypermiling techniques explicitly charger the better by using the brakes. But that Prius hypermiling technique doesn't help Bolt efficiency.

So back to the coasting is better, for the Bolt it means efficiency is optimized by using the brakes as lightly as possible. For the Bolt, braking regneration efficiency is the same whether you use the brake peddle or one-peddle or the paddle. That might not be true on other EV's (Teslas do not use blended braking. The pedal is 100% friction) that use the friction brakes unless you drive in one peddle mode. But the Bolt minimizes the friction brake usage even when you use the brake peddle.

Reactions: 2

PhilipD

· #6 · 18 d ago

Sheldon said:
Think gas automobile efficiency where coasting is better than breaking and then accelerating. I think maybe the Prius is an exception in that the Prius hypermiling techniques explicitly charger the better by using the brakes. But that Prius hypermiling technique doesn't help Bolt efficiency.

So back to the coasting is better, for the Bolt it means efficiency is optimized by using the brakes as lightly as possible. For the Bolt, braking regneration efficiency is the same whether you use the brake peddle or one-peddle or the paddle. That might not be true on other EV's (Teslas do not use blended braking. The pedal is 100% friction) that use the friction brakes unless you drive in one peddle mode. But the Bolt minimizes the friction brake usage even when you use the brake peddle.

I'm not interested in efficiency. Everyone drives the way they see fit (mostly within legal limits) so there is no such thing as excessive regen. Just what you determine to be best for you.

Reactions: 4

Fjpod

Discussion Starter · #7 · 18 d ago

PhilipD said:
Thanks for posting your insights on regenerative braking. But, I don't quite follow you on this one. How can you use regen excessively? I believe everyone accelerates in a manner they deem appropriate. I like the torque of the car and I am not afraid to use it. Others may think it is excessive, but to me, it is juuuust right.

Well, certainly if you have to slow down, getting the benefit of regen is absolutely worth it... but you only get back about a third of what you put into it in the first place. Also, using the deceleration pedal lightly upon initial slowing is no different than using OPD or the paddle. Harder braking, of course, engages the friction brake.

Voldar

· #8 · 18 d ago

This subject is such a beaten dead horse...
Since 2014, when I first got my Volt, I realized that using D or L, you get the same efficiency at the end of the day, if you play it right.
Using regen is a lot better when you come down a long hill than not using the regen at all, only gliding. Why ? Because you can add a lot of kWh back in the battery through regen, while gliding, being limited to a certain speed, you lose the benefit of covering more distance than the one gave you back by the regened kWh.

All in all, I only try to say that your three "big truths" aren't what you think. The right answer is : IT DEPENDS.

Reactions: 5

Packard V8

· #9 · 18 d ago

Fjpod said:
did I get your attention?

In various threads, and even on YouTube videos, I see many people saying wrong things about regenerative braking.

Let's make a list of all the ones we've heard. I'll start it off with 3.

1. "The more regen you score on your car's computer, the more you saved.". ...Generally wrong. If you are using regenerative braking to excess, that means you are accelerating more than you should be. As a general rule, regen only earns back about one third of the energy it took to get up that speed in the first place. Using less acceleration would be a better way to save battery.

2. "A paddle on the steering wheel saves more battery than using the brake pedal." Generally wrong. The brake pedal and the paddle use the same regenerative system. If you apply the brake judiciously it is the same as using the paddle. Certainly when you have to come to a complete stop in a hurry, the friction brakes kick in.

3. "One pedal driving will automatically save battery." Not likely... especially on the highway. Every time you ease off the pedal, maybe from fatigue, maybe due to distraction, you are slowing down and will just have to accelerate again to get back to cruising speed. Certainly, some decelerations are necessary for traffic, safety, etc.

Talking/listening to the wrong people about EVs is like listening to the wrong network to get your news. The above generalizations are only true because some EV owners don't know how to drive an EV.

Hypermiling is a last century ICE concept which has little-to-no application with the Bolt and most other EVs.

As with tire mileage life, some can get twice as many miles from the same tire. Some obsess about tenths of a percent in efficiency; some above have mentioned they have fun with their Bolt and minor differences in efficiency are moot.

jack vines

Reactions: 5

gasbandit

· #10 · 18 d ago

Even when I drove an ICE, I made a game of driving in which using the brakes meant I "lost" the game. IE, I was timing the lights, paying attention on the highway to way down the road, etc, so that I was only ever coasting to slow down. It made for very efficient driving.

I've found the same to be true in my EV. The most efficient use of power is to drive in such a manner that you don't need to use ANY sort of brake - be it regen OR friction. Once you've taken electricity out of the battery and turned it into momentum, your choices are to (1) keep it in momentum, (2) waste half of it regen-braking, or (3) waste ALL of it friction braking.

So yes, by all means if you're having fun dumping 150kw into your motor to go from 0 to 60 in 6 seconds, then do so! I'm all for people enjoying their cars in the way they see fit (as long as they don't smash into somebody else).

But if you're looking to squeeze every last mile out of your battery that you can on long distance, my advice is to keep it out of OPD mode and drive smoothly and with as little Delta-V as possible. And never cruise above 60, because unlike every other form of travel resistance which are linear as a function of speed, wind resistance is exponential. You experience twice as much (100% more) wind resistance at 70 as you do at 50 even though you are only going 40% faster. Of course, the tradeoff there is it will take you 40% more time to reach your destination.

Of course, going around in town in stop-and-go traffic, it can't be helped. And there, OPD/Paddle-based Regen braking will at least make sure you get some of the energy back that otherwise would have just been frictioned off into waste heat in another car.

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Reactions: 5

Packard V8

· #11 · 18 d ago

gasbandit said:
So yes, by all means if you're having fun dumping 150kw into your motor to go from 0 to 60 in 6 seconds, then do so! I'm all for people enjoying their cars in the way they see fit (as long as they don't smash into somebody else).

Thanks for your permission to have fun. Acceleration to a given speed consumes a given energy, regardless of the rate. Those us who enjoy an occasional hustle up to cruising speed are not costing ourselves any range.

jack vines

Reactions: 3

H8cloz

· #12 · 18 d ago

"coasting is better than breaking and then accelerating" If you're breaking your Bolt, you're doing it wrong. Some Bolts were breaking while braking in L mode, so I don't use it anymore. Don't need it to break when I brake.

Reactions: 5

gasbandit

· #13 · 18 d ago

Packard V8 said:
Thanks for your permission to have fun. Acceleration to a given speed consumes a given energy, regardless of the rate. Those us who enjoy an occasional hustle up to cruising speed are not costing ourselves any range.

jack vines

You are if it requires any kind of braking - regen OR friction.
You also are, to a lesser degree, because more time at high speed means more time with additional wind resistance. It's not MUCH more, but it is noticeable in my experience.

But definitely if you're stomping on the accelerator only to then immediately pull the regen paddle, you are, in fact, hampering your range.

I do like that I worded my post as unconfrontational as possible and someone still managed to find a way to take it offensively.

Reactions: 4

Factoryhack

· #14 · 18 d ago

Fjpod said:
did I get your attention?

In various threads, and even on YouTube videos, I see many people saying wrong things about regenerative braking.

Let's make a list of all the ones we've heard. I'll start it off with 3.

1. "The more regen you score on your car's computer, the more you saved.". ...Generally wrong. If you are using regenerative braking to excess, that means you are accelerating more than you should be. As a general rule, regen only earns back about one third of the energy it took to get up that speed in the first place. Using less acceleration would be a better way to save battery.

2. "A paddle on the steering wheel saves more battery than using the brake pedal." Generally wrong. The brake pedal and the paddle use the same regenerative system. If you apply the brake judiciously it is the same as using the paddle. Certainly when you have to come to a complete stop in a hurry, the friction brakes kick in.

3. "One pedal driving will automatically save battery." Not likely... especially on the highway. Every time you ease off the pedal, maybe from fatigue, maybe due to distraction, you are slowing down and will just have to accelerate again to get back to cruising speed. Certainly, some decelerations are necessary for traffic, safety, etc.

Fjpod said:
did I get your attention?

In various threads, and even on YouTube videos, I see many people saying wrong things about regenerative braking.

Let's make a list of all the ones we've heard. I'll start it off with 3.

1. "The more regen you score on your car's computer, the more you saved.". ...Generally wrong. If you are using regenerative braking to excess, that means you are accelerating more than you should be. As a general rule, regen only earns back about one third of the energy it took to get up that speed in the first place. Using less acceleration would be a better way to save battery.

2. "A paddle on the steering wheel saves more battery than using the brake pedal." Generally wrong. The brake pedal and the paddle use the same regenerative system. If you apply the brake judiciously it is the same as using the paddle. Certainly when you have to come to a complete stop in a hurry, the friction brakes kick in.

3. "One pedal driving will automatically save battery." Not likely... especially on the highway. Every time you ease off the pedal, maybe from fatigue, maybe due to distraction, you are slowing down and will just have to accelerate again to get back to cruising speed. Certainly, some decelerations are necessary for traffic, safety, etc.

I believe you’re mostly right, although I’d argue your point #2 seems a bit off.

If you’re using the brake pedal vs. pure regen, in stop and go traffic, I’d think any energy that’s converted into heat via brake friction would be wasted vs. more of that energy being put back into charging the battery when using pure regen to make the same stop.

jefro

· #15 · 18 d ago

You forgot that regen is only about 25% recovery. Seems people like to believe in perfect perpetual motion machines.

Reactions: 4

Fjpod

Discussion Starter · #16 · 18 d ago

Packard V8 said:
Talking/listening to the wrong people about EVs is like listening to the wrong network to get your news. The above generalizations are only true because some EV owners don't know how to drive an EV.

Hypermiling is a last century ICE concept which has little-to-no application with the Bolt and most other EVs.

As with tire mileage life, some can get twice as many miles from the same tire. Some obsess about tenths of a percent in efficiency; some above have mentioned they have fun with their Bolt and minor differences in efficiency are moot.

jack vines

I can see I've struck a nerve with this thread. As they say, "... your mileage may vary..."

Reactions: 2

Fjpod

Discussion Starter · #17 · 18 d ago

Factoryhack said:
I believe you’re mostly right, although I’d argue your point #2 seems a bit off.

If you’re using the brake pedal vs. pure regen, in stop and go traffic, I’d think any energy that’s converted into heat via brake friction would be wasted vs. more of that energy being put back into charging the battery when using pure regen to make the same stop.

Yes, at a full stop, friction braking kicks in if you use the foot pedal. But at the same time, if you are stopping with OPD or the paddle on the wheel, and you need to slow a little faster, you have to engage friction.

Admittedly, the driving situation and safety often dictates how we do it. And sometimes we may choose OPD for convenience.

Reactions: 1

Packard V8

· #18 · 18 d ago

gasbandit said:
You are if it requires any kind of braking - regen OR friction.
You also are, to a lesser degree, because more time at high speed means more time with additional wind resistance. It's not MUCH more, but it is noticeable in my experience.

But definitely if you're stomping on the accelerator only to then immediately pull the regen paddle, you are, in fact, hampering your range.

I do like that I worded my post as unconfrontational as possible and someone still managed to find a way to take it offensively.

Unconfrontational does not equal factual. You'll note I specifically stated "to cruising speed." The reply added in braking negatives which were specifically excluded.

If one can notice the energy difference in a few more seconds at 60 MPH in an extended cruise, he's welcome to the savings, but most of us can't.

jack vines

Reactions: 2

Fjpod

Discussion Starter · #19 · 18 d ago

...I've found the same to be true in my EV. The most efficient use of power is to drive in such a manner that you don't need to use ANY sort of brake - be it regen OR friction. Once you've taken electricity out of the battery and turned it into momentum, your choices are to (1) keep it in momentum, (2) waste half of it regen-braking, or (3) waste ALL of it friction braking....

[/QUOTE]
Exactly! Of course, normal traffic and driving situations like turning, require us to use some sort of braking. Certainly regen is better than friction.

Reactions: 1

Factoryhack

· #20 · 18 d ago

Being very new to EV driving, I can’t get over how nice regen is in traffic. I wasn’t expecting it to be so easy to adapt to. Unfortunately, it makes my ICE cars seem kinda old school.

Reactions: 5

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