Why Does The Model 3 Not Use Regen When Using the Brakes.

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fsKotte

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#1
I just learned that my M3 (as I believe all Teslas) does not use any regen when I apply the brake pedal.

This surprised me, as I've had previous EV's that do use some regen when you hit the brake pedal, and I found it to be pretty efficient in utilizing the battery (coast and use no/less energy when you could, and then always use regen when you needed to scrub some speed, via "brake" pedal).

Anybody know why Tesla has chosen to not use any additional regen when you hit the brake pedal? This is interesting to me because I always thought the most efficient way to drive an EV would be to have the ability to coast when you can, and then regain some energy via regen when you need to slow down. I get that "One Pedal" driving can be fun, but I don't get how it's more efficient, when the regen is always on, and so you're never coasting, always applying energy/electricity to keep the car moving . . . .

I'm sure I'm missing something here, so appreciate any enlightenment. . . .
 
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fsKotte

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#3
It's simpler. The brake pedal just operates the hydraulic brakes.
Sure, and simplicity is nice. The plethora of other EV's that have blended/regen braking upon depressing the brake pedal makes one wonder why Tesla chose not to. It's actually common, among EV's. So is it really just because it's simpler?
 

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#4
I just learned that my M3 (as I believe all Teslas) does not use any regen when I apply the brake pedal.

This surprised me, as I've had previous EV's that do use some regen when you hit the brake pedal, and I found it to be pretty efficient in utilizing the battery (coast and use no/less energy when you could, and then always use regen when you needed to scrub some speed, via "brake" pedal).

Anybody know why Tesla has chosen to not use any additional regen when you hit the brake pedal? This is interesting to me because I always thought the most efficient way to drive an EV would be to have the ability to coast when you can, and then regain some energy via regen when you need to slow down. I get that "One Pedal" driving can be fun, but I don't get how it's more efficient, when the regen is always on, and so you're never coasting, always applying energy/electricity to keep the car moving . . . .

I'm sure I'm missing something here, so appreciate any enlightenment. . . .
Technically if you let your foot off the accelerator even a bit the car is already entering regen mode, so it is already capturing that energy.
I don't think Tesla needs to add extra regen to the brake pedal as just lifting off the accelerator fully will slow the vehicle down by a LOT.

If you manage the pedal in the right conditions, the car does sort of "coast" aka the energy bar is neither black nor green, which I take to mean the car is not using any energy, but also not gaining back energy
 

He Chen

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#5
You can just release the accelerator pedal and you get regen. You use the brake pedal to use the brakes. And the accelerator pedal to accelerate. And regen when neither is being used.
 

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#6
I agree with Maevra.
In order to press the brake you need to (well, should) take your foot off the accelerator. Assuming that you have Regen set to "Standard", the car will now be slowing as much as it can with regen. There isn't any more regen that it can apply when you start pressing on the brake.
 

garsh

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#7
Sure, and simplicity is nice. The plethora of other EV's that have blended/regen braking upon depressing the brake pedal makes one wonder why Tesla chose not to.
I drive a blended-brake Leaf every day.
I can't say that I find a blended brake to be "better" in any appreciable way.

It's more complicated. I'd rather just have stronger off-accelerator regen.
 

fsKotte

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#8
"
I drive a blended-brake Leaf every day.
I can't say that I find a blended brake to be "better" in any appreciable way.

It's more complicated. I'd rather just have stronger off-accelerator regen."
--------------------------------

I had a Fiat 500e for three years, and then a Leaf for about four months (long story there) up until I got the 3. So I too have mostly experienced regen using the brake pedal.

What I liked about it was that I got to choose when I coasted and when the regen happened. If I took my foot off the accelerator pedal, I mostly coasted, which is a great way to conserve energy sometimes, especially at highway speeds or similar situations. Then, when I needed to slow down, I hit the brake pedal, and then - and only then - did regen happen. Also I controlled the amount of regen because the harder I pressed on the brake pedal, the more regen occurred.

I'm not sure you really ever coast when regen is on "standard" in a M3 . . . . .
 

garsh

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#9
What I liked about it was that I got to choose when I coasted and when the regen happened. If I took my foot off the accelerator pedal, I mostly coasted
fsKotte, you are really misinterpeting what your Leaf is doing.

When you take your foot off the accelerator, you are regenning (unless your battery is as bad as mine, then you might be coasting). If you want to coast, you leave your foot on the accelerator part way so that there is only one central white bubble on the power graph.

Then, when I needed to slow down, I hit the brake pedal, and then - and only then - did regen happen. Also I controlled the amount of regen because the harder I pressed on the brake pedal, the more regen occurred.
Sure. But the problem is, when you hit the brake pedal, you're not only getting regen, but you're also getting frictional braking at the same time. So you're wasting a portion of that energy as heat in the brake pads. And when you press the brake pedal more, you do get a little more regen, but you get a LOT more frictional braking. It's inefficient.

With a Tesla, when you want more braking, you just let off of the accelerator more. Tesla provides a LOT more regen than Nissan does. And if that's not enough to slow you down, then (and only then) do you hit the brakes and waste energy as heat in the brake pads.
 

fsKotte

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#10
Technically if you let your foot off the accelerator even a bit the car is already entering regen mode, so it is already capturing that energy. (Right, I know. That's not really my issue here.)
I don't think Tesla needs to add extra regen to the brake pedal as just lifting off the accelerator fully will slow the vehicle down by a LOT. (Right. I get that too. Again, that's not really my issue here, that I'm asking about)

If you manage the pedal in the right conditions, the car does sort of "coast" aka the energy bar is neither black nor green, which I take to mean the car is not using any energy, but also not gaining back energy
Okay, now that last sentence, about coasting, that get's closer to what I'm asking about. So, you said it "sort of" coasts. Well, I wonder is it literally coasting, when you're on Standard regen mode, and you've feathered that pedal to get the regen guage right in between, so there's no regen green line and no "using battery" black line? If so, then perhaps problem solved, or question answered, at least in part. At least at that equilibrium you're not using any energy, it seems.

Because it seems to me what's really happening in "standard" (higher) regen mode, is that you're actually having to put energy into the rotor/motor, which is set for more resistance in standard mode, so that you have to overcome that regen resistance in order to get the car to move. In a sense, you're using battery energy to turn the rotor, which is harder to turn because you've set the regen higher, but you're actually simultaneously returning energy to the battery because, well because you're regenerating at the same time. The car doesn't move forward until you've put more energy into turning the rotor than the regen resistance.

Another way to cut through all this, is to say, simply, this: I like the feeling of coasting in my car. It's fun to me. I also like recapturing energy, and boosting range (or at least minimizing range loss). So I'd like to coast when I let off the accelerator, and I'd like to regen when I brake.

I can't do that in this car. It's either all regen all the time, or it's Coast and mostly use your brake pads.

I'm also not ever giving up the car because I love it more than any car I've ever owned (or leased). And it's because I love it that I wonder about stuff like the above. Just wondering why Tesla didn't go with an option where you could coast when you wanted to coast (or at least mostly coast) and regen when you wanted to (like when you needed to slow down). That's all.
 

fsKotte

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#11
fsKotte, you are really misinterpeting what your Leaf is doing.

When you take your foot off the accelerator, you are regenning (unless your battery is as bad as mine, then you might be coasting). If you want to coast, you leave your foot on the accelerator part way so that there is only one central bubble on the power graph.

Sure. But the problem is, when you hit the brake pedal, you're not only getting regen, but you're also getting frictional braking at the same time. So you're wasting a portion of that energy as heat in the brake pads. And when you press the brake pedal more, you do get a little more regen, but you get a LOT more frictional braking. It's inefficient.

With a Tesla, when you want more braking, you just let off of the accelerator more. Tesla provides a LOT more regen than Nissan does. And if that's not enough to slow you down, then (and only then) do you hit the brakes and waste energy as heat in the brake pads.
The Fiat 500e, at least as I understood it, as it's been advertised and reported on, did not use any pads when braking until around 8 mph. Above that your braking was 100% regen (except if you slammed 'em in an emergency stop). So that's different than your Leaf (and I guess, the Leaf I owned for four months, though it sounds like we had similar batteries :) ).

As I said, I like to coast sometimes, without having to keep pressure on the pedal, and then when I need to slow down, I'd like for it to be regenerating *fully* and not using pads, like my other EV, unless I'm slamming on the brakes in an emergency.

And the whole point of my OP is that I'm must wondering why it is that in Low regen mode (that regen being only the regen that occurs when you release pressure on the accelerator pedal) your braking doesn't also activate the regen, at all.
 

garsh

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#12
And the whole point of my OP is that I'm must wondering why it is that in Low regen mode (that regen being only the regen that occurs when you release pressure on the accelerator pedal) your braking doesn't also activate the regen, at all.
I think the answer is two-fold:
  • It's simpler. Brake pedal only controls hydraulic brakes.
  • And it's not worse than blended braking in any way. Some like it better - others like blended better.
Peoples' personal preferences can differ, but I don't think anybody can provide an argument that one way is demonstrably better than the other. So in that case, Tesla chooses to stick with their simpler system.
 
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Kbm3

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#13
I just learned that my M3 (as I believe all Teslas) does not use any regen when I apply the brake pedal.

This surprised me, as I've had previous EV's that do use some regen when you hit the brake pedal, and I found it to be pretty efficient in utilizing the battery (coast and use no/less energy when you could, and then always use regen when you needed to scrub some speed, via "brake" pedal).

Anybody know why Tesla has chosen to not use any additional regen when you hit the brake pedal? This is interesting to me because I always thought the most efficient way to drive an EV would be to have the ability to coast when you can, and then regain some energy via regen when you need to slow down. I get that "One Pedal" driving can be fun, but I don't get how it's more efficient, when the regen is always on, and so you're never coasting, always applying energy/electricity to keep the car moving . . . .

I'm sure I'm missing something here, so appreciate any enlightenment. . . .
It's simpler. The brake pedal just operates the hydraulic brakes.
In performance terms, having the brake pedal blended provides worse brake “feel” according to the car magazines. I guess the deceleration is not quite as linear?

You are correct that a coasting mode would provide the optimal efficiency. Iirc there is one EV that has a detent on the accelerator where you can use feel to hit the coasting point.
 

fsKotte

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#14
I think the answer is two-fold:
  • It's simpler. Brake pedal only controls hydraulic brakes.
  • And it's not worse than blended braking in any way. Some like it better - other's like blended better.
Peoples' personal preferences can differ, but I don't think anybody can provide an argument that one way is demonstrably better than the other. So in that case, Tesla chooses to stick with their simpler system.
Right, ok. But it doesn't have to be blended braking. It wasn't in my 500e, it was 100% regen until 8mph. I felt that was a good system (using brakes only at 8 mph or under really minimizes wear on them).

I'm also not convinced that brakes also controlling regen would be so complicated that it's undesirable. I'd be interested to know Tesla's thoughts on why they chose to go that way. We can speculate that it was because it was simpler, and that may well literally be why they did it the way they did. Or they could have other reasons that would be interesting to know, which other reasons I'd love to know.

I also think that actually there are arguments being made both for and against "high" regen settings (one pedal driving) versus a coast / regen braking when it comes to which is more efficient. And I find that question interesting. After all, with a Tesla, one component of why it's such a great vehicle is its efficiency. So a debate about what is the most efficient way to drive the car is right up Tesla and its owners' alley(s).

In terms of that particular argument/debate, perusing the forums reveals that it seems there is a consensus that your range is increased via the one-pedal / high-regen setting, versus the low setting (and if range is increased, clearly you're being more efficient). At first, I thought that this conclusion was wrong, but now that I understand there is no regeneration activated by depressing the brake pedal, I think that's probably correct,. But if you had the option to mostly coast when you let off the accelerator, and then regen a lot when you depressed the brake, well then that I think would be a closer call.
 

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#15
In performance terms, having the brake pedal blended provides worse brake “feel” according to the car magazines. I guess the deceleration is not quite as linear?
Correct, it's not very linear. The worse part with the leaf, is that if you're holding down the brake and slowing, at some point when the speed gets low enough, the regen stops. It feels like the brakes have suddenly stopped working to some degree. At that point, you have to push the brake pedal a little harder.

It's not horrible, but it is a little annoying. And definitely non-linear.

The worst is when you're braking down a steep road to just maintain speed, and you hit a pothole or other bump. The ABS kicks on for a second. When that happens, the car turns off regen altogether. It wouldn't be so bad, except the regen stays off until you take your foot off the brake pedal. So the end result is that whenever you hit a bump on a steep downhill, the car begins to accelerate. NOT AT ALL the type of behavior you want in that situation.
 

fsKotte

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#16
In performance terms, having the brake pedal blended provides worse brake “feel” according to the car magazines. I guess the deceleration is not quite as linear?

You are correct that a coasting mode would provide the optimal efficiency. Iirc there is one EV that has a detent on the accelerator where you can use feel to hit the coasting point.
Yes, to me that is the most convincing reason not to include regen in braking, though it seems to me this is an engineering problem that might be solvable. Still, as it stands today, even my Fiat 500e, which had 100% regen until very low speed, definitely had grabby brakes and could have stood to have a smoother "braking curve."

I find the Volt Gen 2 solution to maybe be a good middle ground - on that car, you can set it to low regen mode, but there is a paddle on the wheel that adds additional regen when pressed. The driver can then choose to add additional regen resistance when appropriate, and it also relieves the engineers from having to incorporate it into the braking mechanism (the brake stays being mostly, if not completely, an old-fashioned hydraulic one).

This sort of thing, if available in some form on the M3, seems to me to be a great solution.
 

fsKotte

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#17
Correct, it's not very linear. The worse part with the leaf, is that if you're holding down the brake and slowing, at some point when the speed gets low enough, the regen stops. It feels like the brakes have suddenly stopped working to some degree. At that point, you have to push the brake pedal a little harder.

It's not horrible, but it is a little annoying. And definitely non-linear.

The worst is when you're braking down a steep road to just maintain speed, and you hit a pothole or other bump. The ABS kicks on for a second. When that happens, the car turns off regen altogether. It wouldn't be so bad, except the regen stays off until you take your foot off the brake pedal. So the end result is that whenever you hit a bump on a steep downhill, the car begins to accelerate. NOT AT ALL the type of behavior you want in that situation.
Yes, I agree, and my 500e also had an uneven "braking" curve, and was pretty grabby - too grabby.

I also responded to Garsh about the Volt Gen 2 model. I think it offers a solution that would meet both of our concerns/positions. That Gen 2 Volt (and I believe it was first introduced on the Cadillac version of the Volt, the ELR) has a paddle on the wheel where you can press it to increase regen resistance, separate and apart from the brake. That would solve/alleviate my concerns, actually, almost completely. It would keep the brake system simple - could be all hydraulic - but it would enable one in "low" regen mode to increase regen when needed without having to completely switch over to the "one pedal" regen mode.

And maybe, since regen mode is a "software" controlled switch on Tesla, you could have a Volt Paddle-like feature enabled via OTA, setting one of the steering button directions to have that same effect (love the OTA stuff!).
 
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msjulie

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#18
The Fiat 500e, at least as I understood it, as it's been advertised and reported on, did not use any pads when braking until around 8 mph
I had one, I'll support that statement except when/if there's need for a panic stop - then you'll feel the car 'realize' that you want all the braking right now and the hydraulic brakes come right on.

I agree with some that being able to totally shut off regen could be a useful option for some, our A3 e-tron hybrid defaults to that behavior and uses some form of blended braking otherwise. That car is also 'clever' - on a long grade, if you apply the brakes to slow for some magic amount of time, the car will then continue to add regen to try and maintain that speed so you don't have to keep your foot on the pedal. Also manual downshifting of the auto tranny engages some amount of regen as well.

Personally I like the fact that the 3 gives full regen (or to it's configured setting anyway) when you take your foot off the throttle. It's a more straightforward implementation of the braking system to just apply hydraulic brakes based on pedal input vs blending in available regen. When I first got the Tesla, being used to the Fiat, I had a different opinion but I find this method to be much more predictable after getting used to it pretty quick
 

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#19
I'm also not convinced that brakes also controlling regen would be so complicated that it's undesirable.
I personally don't desire it. It is undesirable to me. I've lived with it for 6 years. i've gotten used to blended braking, but I don't like it.

Like I said - it's personal preference.
In terms of that particular argument/debate, perusing the forums reveals that it seems there is a consensus that your range is increased via the one-pedal / high-regen setting
The only situation where it should make a difference is when you need to slow down quickly. In that case, a low-regen setting means you have to use the friction brakes, thereby wasting some energy instead of recovering some of it. Other than that, it shouldn't make a difference.

For efficient driving, it's always best to avoid accelerating and decelerating quickly.
 

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#20
I also responded to Garsh about the Volt Gen 2 model. I think it offers a solution that would meet both of our concerns/positions. That Volt (and I believe it was first introduced on the Cadillac version of the Volt, the ELR) has a paddle on the wheel where you can increase regen resistance, separate and apart from the brake. That would solve/alleviate my concerns, actually, almost completely.
I've never driven the Volt, but I agree that Chevy's "paddle" solution does offer some advantages as far as controlling the regen compared to a Tesla.