Why regenerative braking belongs on the brake pedal

[Electric700]

Regen does not belong on the brake pedal, it adds unneeded complexity and poor brake feel. Tesla got it right.

Agreed, great points too.

To keep the brakes in good condition since they probably won't be used frequently, I saw a post where Tesla recommends pressing them fully at least 1-2 times per week.

 

[JeffK]

Agreed, great points too.

To keep the brakes in good condition since they probably won't be used frequently, I saw a post where Tesla recommends pressing them fully at least 1-2 times per week.

I drive like a crazy person so for me engaging the brakes once in a while will be a non-issue.

 

[Lunarx]

Tesla will get it right, after......
they give people a choice.

They are 1/2 way there with Single Pedal Regen choices.
Now they need to offer Break Pedal Regen choices.

When I try Throttle Pedal Regen, on my Volt, I can only stand it for about 30s.
I could deal with it, but glad to have the choice, not to.

Are Flinstone Brakes the best Tesla can offer?
Blended brakes seem better to me (and many others).

 

[GHammer]

Tesla will get it right, after......
they give people a choice.

They are 1/2 way there with Single Pedal Regen choices.
Now they need to offer a Brake Pedal Regen choice.

When I try Throttle Pedal Regen, on my Volt, I can only stand it for about 30s.
I could deal with it, but glad to have the choice, not to.

Are Flinstone Brakes the best Tesla can offer?
Blended brakes seem better to me (and many others).

And another non-Tesla owner weighs in.

 

[jgs]

And another non-Tesla owner weighs in.

Indeed. I remember participating in this thread (or rather its clone, it repeats periodically, someone should just cut-and-paste it to save everyone the time) a little over a year ago, before I took delivery. All the arguments made sense, until I spent a little while behind the wheel (I was going to say "a few hours" but really, it didn't take that long).

 

[ThosEM]

I've driven both and I am in total disagreement with this thesis. Moreover, I judge it to be a matter of taste and not "correctness". If you want a car with weak accelerator regen, turn it down if you can, or buy a different car if you can't.

Now, as for my reasons for preferring strong regen on the accelerator pedal:
* regen is a function only of the motor-generator which should be controlled by a single pedal, the *accelerator* pedal.
* braking is a function only of the friction braking which should be controlled by a single pedal, the *brake* pedal.
* when the two are mixed on a single pedal, the inevitable result is mushy, unpredictable, and generally unpleasant to manage. These characteristics are not conducive to safe driving.
* also I like to know when I'm regenerating and when I'm burning energy, so I can avoid the latter. Having them on separate pedals is the best way to be informed.
* the limits of regenerative braking should never be a steering issue on wet or dry roads, but may be a factor on icy or snow covered roads when only front or rear regen is available, in which case it may be preferable to dial it back and use only friction braking. Regen is not a steering issue on slippery roads when four wheel regen is available.

 

[ModelNforNerd]

Indeed. I remember participating in this thread (or rather its clone, it repeats periodically, someone should just cut-and-paste it to save everyone the time) a little over a year ago, before I took delivery. All the arguments made sense, until I spent a little while behind the wheel (I was going to say "a few hours" but really, it didn't take that long).

I literally only have 45 minutes of driving time in ANY EV (Model S P90D-L test drive)...and I figured out the one pedal driving in the first few blocks from the Gallery to the highway. I only used the brake when I was at a complete stop in line at stoplights (creep was enabled).

If you've ever spent any time "feathering the gas" in an automatic transmission ICE in traffic, it will be second nature in short order.

 

[Az_Rael]

I wonder how many owners keep their cars on regen "low" mode. That would be interesting data, that only Tesla has unfortunately.

They added regen Low for a reason, so I assume some people prefer it.

 

[ThosEM]

Good to hear. Coasting is the most efficient. Regen should only be used when slowing down is actually needed, since it has efficiency losses.

This is a fallacy. Regen is also important when it is necessary to avoid acceleration, as in coasting down long slopes. Speeding up increases aerodynamic drag and wastes energy that would be recaptured by regen if it is used to limit speed.

The proper comparison is between regen and friction braking. If you can avoid any deceleration, coasting is of course best, but it's perfectly possible to coast when regen is active by keeping the accelerator in the neutral position (using cruise if necessary). Whenever any deceleration, including avoidance of acceleration, is needed, regen is far more efficient than the brake pedal alternative.

When you let your car accelerate downhill, you are throwing away some of the energy you used to climb that hill, which you could be harvesting for the next hill.

If it weren't for regen, hybrids would not be worth the extra equipment involved. If hybrids were done right (with strong regen on the accelerator), they would do considerably better than they do now, though not nearly as well as pure EVs.

 

[Az_Rael]

And another non-Tesla owner weighs in.

Eh, you are in the Model 3 forums. You guys are just going to have to humor us during this process.

 

[CarlitoDoc]

Tesla got it wrong when they put heavy regen on the throttle. It's one of several things they got wrong, but probably the most serious one

Sounds like you need to cancel your reservation. I'm sure you'll be happier on a Prius! ByeBye!!

 

[GHammer]

Eh, you are in the Model 3 forums. You guys are just going to have to humor us during this process.

Fair enough, since the OP's thesis is based on the Model S I forgot this was in the M3 forum. It is good however that you hear from the people who actually drive the cars on a daily basis.

 

[Topher]

When you let your car accelerate downhill, you are throwing away some of the energy you used to climb that hill, which you could be harvesting for the next hill.

Let's see your math for that. Harvesting via regen has losses, if no speed increase is involved in coasting, clearly coasting is better since conversion from gravitational potential energy to kinetic energy is near lossless. At what speeds have you calculated that regen losses are less than increased speed drag losses.

Thank you kindly.

 

[SageBrush]

At what speeds have you calculated that regen losses are less than increased speed drag losses.

Exactly.

Based on a presumed CdA of 0.4662 for the Model3, a speed increase from 115 to 125 kph will increase Aero drag by ~ 3 kW, or about 2.6 kW more when increasing speed from 105 to 115 kph. I want to see regen conversion losses anywhere near that low.

 

[JeffK]

I'm pretty sure he's saying when going down a hill your speed will increase due to gravity, therefore if you use regen to capture that energy it's more efficient than allowing it off bleed of via friction brakes trying to maintain constant speed. You cannot coast down a hill without changing speed without brakes or regen you'd have to pick one.

Think: going downhill on a mountain for example where the speed increase might lead to a dangerous situation.

Obviously if you're going down a small hill it's unwise to regen or brake if you'll just go up another hill the second you get down from this one.

 

[FlatSix911]

We should all be embarrassed by this type of attitude toward non-owners and welcome viewpoints from other EV drivers.

And another non-Tesla owner weighs in.

Indeed. I remember participating in this thread (or rather its clone, it repeats periodically, someone should just cut-and-paste it to save everyone the time) a little over a year ago, before I took delivery. All the arguments made sense, until I spent a little while behind the wheel (I was going to say "a few hours" but really, it didn't take that long).

Sounds like you need to cancel your reservation. I'm sure you'll be happier on a Prius! ByeBye!!

 

[SageBrush]

Obviously if you're going down a small hill it's unwise to regen or brake if you'll just go up another hill the second you get down from this one.

You do not have to go up a hill to make Topher's statement true.

 

[JeffK]

You do not have to go up a hill to make Topher's statement true.

if no speed increase is involved in coasting,

The assumption that no speed increase is incurred while coasting is physically impossible down a hill (without bleeding the potential energy somehow instead of turning it into kinetic energy or bleeding the kinetic energy generated). So his statement by definition of his original assumption is false.

 

[jgs]

We should all be embarrassed by this type of attitude toward non-owners and welcome viewpoints from other EV drivers.

I'm not quite sure what you're asking me to be embarrassed for. Sharing personal experience? Of the three things you quoted, only one of them was what I'd call combative.

 

[SageBrush]

The assumption that no speed increase is incurred while coasting is physically impossible down a hill (without bleeding the potential energy somehow). So his statement by definition of his original assumption is false.

Downhills still have road and aero forces to contend with.

But that is besides his point. Within a fairly wide range you save energy on downhills by increasing speed rather than using regen. Some situations of course do not allow that behaviour.