regenerative braking on the Model S

[SByer]

It bugs me that the damaged slush box style of driving is thought to be the desired default. It screws up traffic when brake lights flash even though cars aren't really slowing down, especially with the dumb chickens ahead in the HOV lane that always put their brakes on, too.

 

[dmckinstry]

+1. The regen could be stronger especially at low speeds.

I wouldn't mind strong regen. It'd be nice to have it so you'd hardly have to use the brakes. If you don't want to slow rapidly, then just lift your foot gently. I'd think that with practice you could learn to coast, or glide as with the Prius.

 

[Jaff]

It doesn't take long to master this in the Roadster...it is part of the pure joy of driving electric imho...

I wouldn't mind strong regen. It'd be nice to have it so you'd hardly have to use the brakes. If you don't want to slow rapidly, then just lift your foot gently. I'd think that with practice you could learn to coast, or glide as with the Prius.

 

[TEG]

The regen in the Leaf isn't nearly as strong as in the Roadster. I find myself frequently wishing I had more regen when driving the Leaf.

 

[vfx]

http://www.evfinder.com/testdrive_ebox.htm

TT

...The first thing that you notice when driving the eBox is the regen braking. Regen is controlled by a slider mounted vertically on the dash that runs from minimum at the top to maximum at the bottom. When I started driving the car the slider was set to about three quarters of the way to maximum so it gave you quite a lot of slowing when you took your foot off the accelerator. The regen has been strong enough to hold the car still when it was sitting in forward with no pressure on the accelerator.

... The regen on the eBox took some getting used to and as I came to stop signs I found myself slowing too quickly and having to give it a bit more juice. After a ten minute drive however I found that I was getting used to the different regen and I am sure that it would become second nature after a couple of weeks....

Driving West on Aviation we came to a fairly steep down hill. Taking the regen up to minimum put the car into coast and it began to pick up speed on the down slope. Towards the bottom of the hill I adjusted the slider back to maximum and the car started to slow as the regen whined loudly. The car came almost to

The EBox slider is actually kinda clumsy in it's placement on the dash vertically. The way it is a dynamic driving tool I would like it on the steering wheel like cruise control.

 

[mpt]

Awesome. I wonder what power level they will define as 100%.

Hope it's just before the rear tires lock up and not a smidge less :biggrin:

 

[Kipernicus]

I like the idea of a dedicated dial or slider on the dash. If you're going down a long hill you could accelerate by turning the regen to zero, and slow down by dialing in more regen.

Alternately, have it all controlled by the brake pedal - foot off = 0 regen, slight pressure = 5-25% regen (no brake lights), moderate pressure = 25 to 75% regen, with brake lights, and yet more pressure = 100% regen with friction brakes (maybe even flash the brake lights). I suppose I'd be ok if regen control was built into the accelerator pedal, so long as I could tell at which point the car was coasting (zero power from battery, zero regen). I don't want a sudden transition from power to high regen, that sounds like a jerky and unpleasant ride.

 

[Doug_G]

I like the idea of a dedicated dial or slider on the dash. If you're going down a long hill you could accelerate by turning the regen to zero, and slow down by dialing in more regen.

Alternately, have it all controlled by the brake pedal - foot off = 0 regen, slight pressure = 5-25% regen (no brake lights), moderate pressure = 25 to 75% regen, with brake lights, and yet more pressure = 100% regen with friction brakes (maybe even flash the brake lights). I suppose I'd be ok if regen control was built into the accelerator pedal, so long as I could tell at which point the car was coasting (zero power from battery, zero regen). I don't want a sudden transition from power to high regen, that sounds like a jerky and unpleasant ride.

Weird, people keep saying this stuff. I imagine you've never driven a Roadster, right? The Regen control on the gas pedal is smooooooth.

 

[Jaff]

Agree Doug...there are many unusual comments about regen braking, for the most part as comments to articles about TM / Roadster / Model S on other websites...it is fairly evident from reading these comments that most folks have not spent any appreciable amount of time either in or driving a roadster.

It also appears (to me anyway) that most Roadster owners want a heavy regen (akin to the Roadster) in the Model S...

Weird, people keep saying this stuff. I imagine you've never driven a Roadster, right? The Regen control on the gas pedal is smooooooth.

 

[Kevin Harney]

I only drove the roadster for a few minutes on a test drive. I loved the regen and I was totally accustomed to it by the end of the test. I can not see a big problem here at all.

 

[smorgasbord]

Weird, people keep saying this stuff.

Yeah, it's amazing what people get comfortable with and then want, even though it's not ideal.

It's not ideal to have a separate brake pedal. It takes time for your foot to move from the accelerator pedal to the brake pedal, and in emergency situations that is braking time lost. Regen on the accelerator pedal gives you braking while your foot is moving to the brake pedal, thus decreasing your overall stopping time and distance. For small speed adjustments, being able to feather the accelerator pedal alone is a big advantage and improves driveability.

Some people also think that coasting in an automatic saves energy. It doesn't. As a rule, manual transmissions get better gas mileage than automatics.

Combining regen and friction braking in a single control is complex in cars like the Prius, incorporating things like artificial resistance to give some feedback during mostly regen modes, speed sensors to detect how quickly you're pressing the pedal (to engage friction brakes sooner), etc. Many people don't like the brake pedal feel or control of the Prius.

The Chevy Volt has an "L" model that puts regen on the accelerator pedal. Despite it being described in the manual for downhill only situations, many drivers on the gm-volt.com forums report using "L" mode almost exclusively.

The truth is that regen on the accelerator pedal is one of the best things about driving the Roadster.

 

[Kipernicus]

I've taken a test "ride" in a roadster (and yes it was smooth) but never driven one myself, so I'll take you guys' word that regen on the accelerator is the way to go!

@smargasbord, yes I do drive a manual today and find that I can put it in neutral and lay off the gas well in advance of where I need to stop or slow down, and that's why I'm so focused on coasting in the model S. I find it rather wasteful the way people keep on the gas full tilt until they have to slam on the brakes right before a red light or off-ramp.

 

[Adm]

Actually it's better to keep it in (high) gear and keep your foot off the accelerator. This will cut the fuel stream to your engine, where as when you put it in neutral the engine will be idling (using gas). I just shift down when I need more stopping power and use the brake as a last resort or when I need to come to a full stop.
Now I am not this smart, but it's what the car's computer tells me.

 

[strider]

I like the idea of a dedicated dial or slider on the dash. If you're going down a long hill you could accelerate by turning the regen to zero, and slow down by dialing in more regen.

Alternately, have it all controlled by the brake pedal - foot off = 0 regen, slight pressure = 5-25% regen (no brake lights), moderate pressure = 25 to 75% regen, with brake lights, and yet more pressure = 100% regen with friction brakes (maybe even flash the brake lights). I suppose I'd be ok if regen control was built into the accelerator pedal, so long as I could tell at which point the car was coasting (zero power from battery, zero regen). I don't want a sudden transition from power to high regen, that sounds like a jerky and unpleasant ride.

Regen on the brake pedal is a horrible idea. I've driven a Prius a few times (been given them as rental cars) and they are hands down the worst driving cars on the planet. The problem is that they cannot make the transition from regen to mechanical brakes linear. If you were to plot a graph of braking force with steadily increasing applied pressure to the pedal, there it s huge spike when the mechanical brakes kick in. I'm no Schumacher but I have a pretty good sense of where my feet are and can apply force in a pretty linear fashion but I don't even think Schumacher could make that transition smoothly.

As others have said, the Tesla way is REALLY smooth - you can dial in as much or as little regen as you want. I'm not into hypermiling so I don't even look at the dial - I just adjust my foot based on how fast I want to go. Simple.

 

[mnx]

I loved the feel of the roadster based on the test drives I took it on. I agree with all the owners comments above. The only reason I can think of to have less (or no) regen is for the hypermiling crew since coasting is more efficient the using regen since regen isn't 100% efficient.

Personally I like the strong regen and would drive my car like that 99.9% of the time. It might be nice to turn regen off for a track day or for hypermiling if possible but if it's not user selectable no biggie (as long as the regen is strong).

 

[ckessel]

yes I do drive a manual today and find that I can put it in neutral and lay off the gas well in advance of where I need to stop or slow down, and that's why I'm so focused on coasting in the model S.

This is usually considered poor driving technique. You have less control over your car if you need to do something since it's not in gear and, as @Adm mentions, it's not likely saving you anything. I do it myself somewhat as I coast up to a stoplight, but that's an artifact of knowing I'm going to need to put it in neutral anyway as I stop rather than an attempt to be efficient.

 

[tennis_trs]

Regen on the brake pedal is a horrible idea. I've driven a Prius a few times (been given them as rental cars) and they are hands down the worst driving cars on the planet. The problem is that they cannot make the transition from regen to mechanical brakes linear. If you were to plot a graph of braking force with steadily increasing applied pressure to the pedal, there it s huge spike when the mechanical brakes kick in. I'm no Schumacher but I have a pretty good sense of where my feet are and can apply force in a pretty linear fashion but I don't even think Schumacher could make that transition smoothly.

...

Doesn't the Roadster have some "regen on the brake peddle"?
If I press the brake peddle during maximum, or very significant regen, the Wattmeter still appears to show regen for some seconds and it feels to me like there is probably still regen happening; although I'm not sure when the friction brakes kick in.

 

[Doug_G]

Doesn't the Roadster have some "regen on the brake peddle"?
If I press the brake peddle during maximum, or very significant regen, the Wattmeter still appears to show regen for some seconds and it feels to me like there is probably still regen happening; although I'm not sure when the friction brakes kick in.

No. The friction brakes kick in when you press the brake pedal, but the regen braking does NOT stop.

You can really notice this if you're braking and the car hits a hard bump. If one of the rear wheels leaves the road momentarily it trips the traction control and your regen disappears for about a second. This has the unnerving effect of halving your braking force for a moment. For this reason I sometimes turn off TC when on dry pavement.

 

[tennis_trs]

No. The friction brakes kick in when you press the brake pedal, but the regen braking does NOT stop.
...

So the Roadster can have regen when you are on the brake peddle.

 

[Doug_G]

So the Roadster can have regen when you are on the brake peddle.

Well, yes, if you're on the brake pedal then regen definitely is active. But it is active because you are not pressing the gas pedal. The brake pedal ONLY controls the friction brakes.