The Secret to a Great Electric Car? How It Brakes

By · October 19, 2011

What's the secret sauce of electric cars? In a speed-obsessed society, you’d expect it to be acceleration—which most EVs have in spades. But actually the thing that distinguishes one electric car from one another is not how quickly it gets going, but the way it stops. In recent weeks, I’ve reached out to engineers from BMW, Ford, Toyota, Honda and Tesla to learn about each company’s approach to regenerative braking—the system that provides the feel or flavor of their electric cars.

I say it’s secret, because not everybody is talking. Toyota isn’t saying much, which is ironic because this investigation was inspired by my drive, last April, of the “phase zero” version of the new RAV4 EV—a co-production of Toyota and Tesla. That vehicle had the most aggressive regen of any EV I’ve driven—bringing the car to a rapid halt when you let off the accelerator pedal. The Tesla Roadster-esque acceleration and deceleration made it a blast to drive, but I expect it will get dialed way back in the production model, based on the single line that Toyota was willing to offer for this mini-survey of electric car braking. “What exactly is it going to look like when it comes to market? I can’t tell you that,” Jana Hartline, Toyota’s environmental communications manager, told me. “Toyota always strives for the best drivability and smoothest ride for the customer.”

Toyota RAV4 EV

An early prototype of the new Toyota RAV4 EV. (Photo: Brad Berman.)

I thought Tesla could shed light on the subject, both in terms of the RAV4 EV and the upcoming Model S—but after multiple emails over several weeks, I’m still waiting for a response.

Like Toyota, Honda only offered a banal comment about regen braking, and only as it relates to its IMA hybrid system—declining to say anything about plug-in hybrids or EVs. The message from the central office in Japan: “Honda's IMA System is designed to be a very familiar system to the driver, so that drivers who are used to the internal combustion system can use our hybrids without awkwardness or sacrifice.” I can only assume that the same would hold true for the company’s electric cars.

Ford: Seamless Driving and Maximum Regen

On the other hand, Sherif Marakby was happy to talk. The Ford executive is in charge of engineering and business regarding the Ford Focus Electric and the Ford C-Max Energi plug-in hybrid, as well as the company’s hybrids.

Marakby believes that Ford’s series regen brake-by-wire offers the best of all possible worlds: maximum regen under all conditions and a brake feel that is seamless to the driver. On PluginCars.com, there’s been a lot of discussion about where to place the regen functionality: on the accelerator (go) pedal or on the brakes? “We blend it,” said Markby. “This is trying to simulate what a gas vehicle does. When you let off, you start the regen process, and as you apply the brake pedal, it continues.”

Ford C-Max Energi Plug-in Hybrid

Ford C-Max Energi Plug-in Hybrid

According to Marakby, this system captures 94 percent of the brake energy from the brake system in a city cycle—allowing almost all of the braking to be regenerative, with almost no friction braking. The system can throw as much as 15 kW to 20 kW into the battery pack.

Ford utilizes the same brake-by-wire system on all its electric-drive vehicles, from hybrids to pure EVs. The company is on the third-generation of that system. “What we learned from the first couple of systems is that if the brake system is any different from what the customer would expect as normal operation, we get complaints,” said Marakby. “And when you give them more regen, we actually don’t see a big benefit. If you get more aggressive, you’re not going to put any more energy into the battery pack.”

This means no special eco, performance, or coasting modes for Ford’s EVs—to increase and dampen acceleration or deceleration. “This is one of the things we debated internally,” explained Marakby. “But braking is purely a pedal map. You can do the same thing [as special modes do] by yourself [by how you apply the pedals]. If you’re cruising on the highway, it doesn’t make any difference. It’s just a matter of how deep you are into the pedal. You’re really not saving anything.” Marakby reiterated his confidence that Ford’s EVs and PHEVs would require no special modes or actions from drivers accustomed to gas-powered vehicles, and still absolutely maximize the efficiency and range of the electric-drive vehicles.

BMW: The Ultimate Braking Machine

BMW is taking a much different approach—trying to create a new category of driving and braking experience that is unique to electric vehicles. Aaron Singer, BMW product planning and strategy manager for electric vehicles, graciously answered my questions by email. It’s so different than the competition and such as departure from the current path of other EVs coming to market that I wanted to share his answers in detail.

PluginCars.com: What's your overall strategy for regenerative braking in your electric cars?

Aaron Singer: Feedback from the MINI E field trial clearly indicated our driver’s preference for aggressive regenerative braking coupled with the ability for “one pedal driving.” This provides immediate feedback that they are driving something special, and is a unique feature of eMobility. The BMW strategy, as demonstrated in the upcoming ActiveE (all electric 1-Series coupe), is to maintain this aggressive regenerative brake feel as a unique eMobility selling point.

BMW ActiveE

The driving feel of the upcoming BMW ActiveE will reveal the company's progress on its EV-specific approach to braking.

How do you strike the balance between maximizing regenerative energy, and providing a braking "feel" that mainstream drivers are accustomed to?

For pure electric drive, emphasis will be placed on the regenerative aspects of the braking system. However, for increased driver acceptance, a “sailing mode” has been implemented, allowing the driver to coast at highway speeds – similar to a gasoline vehicle.

Will you provide the ability for drivers to control how much regen is happening via buttons/modes? Why or why not? Other driver-selected controls?

Yes. The ActiveE will be equipped with an “Eco Pro” mode. Once selected, this mode will slightly reduce HVAC and throttle response, and provide additional regenerative braking response. This mode allows the user to place a higher priority on range, extending the driving distance of the car by slightly reducing the creature comforts.

What's your strategy for balancing the benefits of coasting (periods when no regen occurs) versus strong regen (for example, when traveling downhill)?

Allow customer to choose. Due to the one pedal driving, the user can select whether the car is sailing or generating power.

How do you plan on displaying regen, state-of-charge, and range on the dashboard?

The dashboard will have a small display, allowing the customer to quickly assess their remaining battery state of charge. Additionally, a digital display shows the battery percentage, remaining range, and histogram of past performance. There is an analog gauge displaying the motor performance; communicating whether the motor is using or generating power.

Comments

· · 6 years ago

Interesting. I'm a fan of one-pedal operation, but I'd like a button/mode switch where I could disable regen for "sailing" as well. I live in rolling hills. This leads to a LOT of places where regen would be best to prevent overspeed when going down. However, it also leads to a lot of glide strips - places where it's downhill, but not so much that you gain a lot of speed. Some of these are 1/2 a mile long or more!

My issue with putting regen on the brake pedal is that there is a large portion of the population that has had it drilled into their heads "never ride the brakes going down a hill!" In a hybrid, riding the brakes is what you WANT to do, so that regen is there nice and strong.

No matter what system/method is used, or what brand of vehicle is purchased, EDUCATION is the key in getting the most out of it. They give you a manual for a reason!

· · 6 years ago

Having regen when you take your foot off the accelerator seems like a waste to me. No matter how efficient the regen is, it's not gonna be 100%. I spent energy getting the car up to speed so I want as much of that energy to go into pushing the air out of my way as possible, so I'd want to coast freely. If I want to slow down I'll use the brake pedal, so THAT should give me as much regen as possible, proportional to how hard I'm hitting the pedal, so as little energy goes to heating the rotors as possible.

I do have to agree with NevynPA about the hill thing to a point... but people will learn in time, just like they had to learn to NOT pump the brakes on icy roads when antilock brakes became popular.

· Montreal EV fan (not verified) · 6 years ago

Very interesting and informative article.

A question that keeps coming up in my mind, and which I think is not discussed enough, is the nature of brake light operation with strong regenerative braking. With a conventional brake light system, the light is only activated when the brake pedal is depressed. With strong regeneration, significant braking will occur with a lifting of the accelerator alone, so, with a conventional layout, the brake light will not turn on.

Perhaps, in addition to the brake pedal switch, the brake light could be activated by sensing regenerative current. Alternatively the brake light could be activated through an accelerometer (sensing deceleration), or through signals from the brake-by-wire system. Does anyone know if there are systems of this type used already in EVs, or planned for future models?

The whole question of brake light operation with strong regen might be a good question to ask Aaron Singer at BMW.

· · 6 years ago

Having had my Leaf for over a month now. I have to say the re-gen isn't strong enough for me. Eco mode slightly improves the re-gen, but it kills the accelerator responsiveness.

I think the best solution is to have a "sport mode" combining both aggressive re-gen from letting go of the gas and max acceleration. In sport mode, I want it to feel like the equivalent of downshifting 1-2 gears when I let go of the gas completely. In a BMW, sport mode should naturally be the default, and it sounds like it is.

One concern with aggressive re-gen on the gas pedal is that if it slows you down significantly, should the brake lights come on? I would say this, how about brake lights that are a small circle surrounded by a larger circle surrounded by a larger circle. Under aggressive re-gen, the inner circle comes on, under light braking the middle circle also comes on, under heavy braking the outer circle also comes on. This gives the driver behind you feedback as to how fast you're slowing down.

· · 6 years ago

There are definitely times when coasting is preferred to aggressive re-gen though, so it should also be possible to get out of sport mode and send the re-gen back to the brake pedal.

· · 6 years ago

In both the MINI-E and ActiveE, the brake lights come on when there is strong regen. Personally in the MINI-E I think it comes on with just the right amount of regen. You don't want the brake lights coming on with very mild regen, because the car is barely slowing down. I wasn't able to test exactly when the brake lights come on when I drove the ActiveE last week, but if BMW does the same programming as they did for the ActiveE then I'll be happy with it.

· · 6 years ago

What they should do is allow it to be adjustable. It's all digital now anyway. From the car's UI have an Advanced Options screen that allows you to set the % regen for each setting.

For the Leaf:
Drive - Lift A and regen at 30% (max strength)
Eco - Lift A and regen at 75% (max strength)

Me? I'd go Drive - 0%. Eco - 100%.

I too live in a hilly area but what I end up doing is setting it to N for downhill

· TjKinMT (not verified) · 6 years ago

It would be fairly easy to use a low cost accelerometer to sense the deceleration and turn on the brake lights at the appropriate level regardless of the breaking mode.

· · 6 years ago

I am a proponent of easy free-wheel coasting, because it is the most efficient. Not only because it covers more ground on the energy you have already used to accelerate and uses the kinetic energy of the car to carry you farther with the only losses coming from aerodynamic drag and rolling resistance -- but also because this invites you to drive with just enough acceleration to get you where you are going.

You can always use regenerative braking to slow the car when you need to slow down. But having regen on the accelerator makes it harder to coast.

Having three modes of driving: acceleration, coasting, and braking is much more efficient than having just two: acceleration and braking. Because regen is less than 100% efficient and you always have aero and rolling resistance losses anyway.

So, if you accelerate less, then coast, then brake with regen, it will use less energy from the battery in the first place, and use less overall.

This will also make it much better for longer trips -- you can lift your right foot and stretch your muscles without losing as much speed. And when you have to concentrate and fine tune the pressure of your right foot on the accelerator to hold it precisely in the "sweet spot" in order to coast, your right leg muscles get a lot more tense, and this is tiring because of the concentration.

It should be easy and repeatable and as efficient as possible.

Neil

· · 6 years ago

I was thinking about the brake light issue, but forgot to mention it when I posted - good thought!

As far as the learning thing, good point. It goes with what I said - learn the car, learn how to drive it properly. It's all in education.

The Leaf maxes out at 15 kW of regen, right? Does anyone know what the Mini-E max regen level was/is?

· · 6 years ago

Neil - Agreed about the three mode/two mode setup. I'd like to be able to choose between the two, however. Similar to shifting from Drive to Neutral, I'd like to have the ability to shift the car from "regen on gas pedal mode" to "coasting" mode.

· · 6 years ago

Another way of describing an accelerator pedal with strong regeneration (such as BMW's) is that it is a velocity control. If you push the pedal half way down and top speed is 100 mph, then the car tries to get to 50 mph regardless of whether that means speeding up or slowing down as fast as it can.

So we should not call that an accelerator pedal but rather call it a velocity pedal. It is a completely different driving experience from an "accelerator" and much more pleasant when you only move your foot up and down, not sideways. Ford and Toyota are nuts to try to maintain the "familiar" way a gas car works. But the Model T which looked like a horse drawn carriage changed over time. Glad BMW gets it right away.

I am not sure but I would guess the Mini E had nearly 60 kw of regen depending on speed. At least the early release did. They kept reducing it as the "upgrades" came along. Taking your foot completely off the pedal at 90 mph was amazing with the early programming. You bet the brakes lights came on!

· JeffN (not verified) · 6 years ago

The Chevy Volt separates the concept of heavier regen from the concept of a 'Normal' versus a more reactive 'Sport' accelerator pedal mapping. Sport mode is determined by a button on the center console whereas regeneration is determined by the transmission shifter position.

In 'D' or Drive position the regeneration is mild and is almost the same as coasting by shifting into neutral. In 'L' or Low position the regeneration is much stronger and simulates engine compression braking when driving downhill. I don't have the personal experience to compare the level of regeneration versus a Tesla Roadster or a Mini E but it is useful for single pedal driving. The 'L' position also enhances the regenerative response of the brake pedal.

I usually use 'L' in city driving or stop and go traffic on the freeway. I drive in 'D' on the freeway and longer expressway or rural road stretches that have fewer stops. Driving in 'D' while in cruise control allows a little more drift in speed whereas 'L' maintains a tight adherance to the speed that has been set. I understand that the EV-1 had stronger regenerative braking as in the Volt's 'L' position but also had an override coasting switch on the shifter. That seems like a desirable combination but I've never tried it.

The maximum braking regeneration in the Volt is about 60 kW although I suspect that requires active use of the brake pedal and may not be sustainable for more than a few seconds (may switch to friction braking eventually).

· Michael Thwaite (not verified) · 6 years ago

Just a note for those that like coasting. I've played with putting the Tesla into neutral to save power. On the Tesla and MINI E you can switch between drive/neutral whilst on the move. I've also tried to simply move the accelerator back enough to find the dead space between drive and regen.

The result: Just the same power consumption over the same 20 mile circuit that I drive once a week for the last couple of months, within a few hundred watts either way.

I believe that you can have the benefits of both on the same setup with the added benefit that, with heavy type A regen (on the accelerator) you're milliseconds away from heavy braking at any moment. Regen did actually save the front of my car once!

Lastly, Tesla have said that they didn't offer adjustable regen on the Roadster as it complicates the stability control calculations.

· · 6 years ago

> but also because this invites you to drive with just enough acceleration to get you where you are going.

Brilliant point, Neil. One that I've been trying to formulate for years, but never could. That's a huge point that is lost in all the fumbling around with "what is most efficient." It isn't all about the mechanicals of the car - we must think of how it affects the driver response as well. Do we want to install everything in incites us to drive faster? Because we can?

I'm glad to see this article finally in print, Brad! Thanks for the work on it. The BMW approach just makes me giddy.

Anyway... lots more to write, but I have to go ride my bike. Tough life but somebody's gotta do it.

· · 6 years ago

> Having three modes of driving: acceleration, coasting, and braking is much more efficient than having just two: acceleration and braking.

Neil, I agree it is more efficient, but it's not always better or safer. As Michael pointed out, if you need to slow down fast, you'll be able to slow down faster if heavy re-gen already started by the time you let go of the gas.

Generally, coasting can be useful in light-traffic freeway and rural driving. However, in the city, suburbs, and stop and go freeway driving, heavy re-gen is preferable. For mountain driving, it depends on the slope, and other factors.

So there should be a way of switching type-A (accelerator) re-gen on and off without affecting accelerator responsiveness like an "eco" mode would. Sounds like BMW is taking this approach with "sailing" mode and the Volt already has this by switching between "D" and "L".

I'm afraid of calling it "L" because it makes me think of low gear which is not what it is, you might still want to drive fast in that mode.

· Kei Jidosha (not verified) · 6 years ago

On straight, open highway, “coasting” may offer small incremental benefit. But in any situation requiring response to traffic or road conditions, right pedal regen is superior. Control is simpler in that the accelerator controls the motor and the brake pedal controls the mechanical brakes. Efficiency is simpler in that touching the mechanical brakes wastes energy. The argument against strong, right pedal, regen is a lack of first hand experience, i.e. ignorance. Live with it, and in short order, you will love it.

· · 6 years ago

Another point that I hoped to make, but ran out of time; is this: only the EV1 is an EV that takes advantage of the better aero that is possible (with greatly reduced cooling requirements), and the rear wheel track is narrowed to lower the drag, as well. The taper in the rear must comply with the laws of nature, and the trailing shape is absolutely key to achieving a low drag car.

A smooth floor pan is also more possible on an EV since there is no exhaust system. Air flow through the engine bay accounts for about 10% of the overall drag, and having a smooth nose can greatly reduce the overall drag.

Smooth wheels and wheel skirts also are important. The wheels and the wheel openings account for 20-30% of the overall drag.

When the car *allows* you to coast much farther (by being very low drag), and/or to take full advantage of lower slopes than a higher drag car, then coasting becomes even more important. And when you have low drag, the consumption at highway speeds especially, but all speeds are helped, you can improve range by 100% or more. The Leaf is rated at 340Wh/mile, while the Illuminati 7 can do the same with just 155Wh/mile. They weigh about the same, and they seat about the same number of people, but the Leaf has a Cd of 0.29 while the 7 is ~0.23 if I recall correctly.

I'm hoping that CarBEN EV5 will have a Cd of <0.15 and I'm aiming at 100Wh/mile. CarBEN EV5 will seat 5 people.

Neil

· vfx (not verified) · 6 years ago

Really love what BMW is doing. It's paying attention to drivers, not worried about scaring off old ICE owners. That you can single foot drive if you want or turn it off if that's not your thing. The "velocity peda"l is good. "Torque pedal" also works.

Tesla's S is said to have adjustable regen. I just want it on the steering wheel to change at will.

I have also suggest just the third center taillight turn AMBER on regen slowing.
Having all the brake lights go on when you have not even touched the brake makes freeway traffic behind you slow down unnecessarily.

· · 6 years ago

@Kei Jidosha

I'm not sure I understand your argument in favor of right-pedal regen. coasting freely is exactly the same as driving at the same speed with foot on the accelerator. At the very worst it's the same as driving on cruise control, but realistically you're not likely to be coasting far enough to warrant taking your foot away from the accelerator or brake.

You mention "road conditions" - I wonder if the heavy right-pedal regen would be intelligent enough to know when heavy regen braking forces cause loss of traction on icy roads? Hit some black ice, let up on the throttle and end up in a ditch! I currently drive a car with a manual transmission, which is a decent analog to right-pedal regen, and I can tell you it does not lend itself to better control in all situations (esp. in lower gears).

@vfx - Good call on the amber lights. Public transit buses around here blink yellow lights when they're coasting. The light makes people pay attention but doesn't trigger the "red = stop" instinct. Others have suggested a UV-Meter style brake light but that's too confusing IMHO.

· · 6 years ago

Ahem... "VU-Meter"

· · 6 years ago

Niel, +1 on all things you have written.

@Kei "The argument against strong, right pedal, regen is a lack of first hand experience, i.e. ignorance. Live with it, and in short order, you will love it."

I've been hearing this nonsense for a long time. I think with more than 7 months of Leaf ownership I can safely say I've "lived" with it for long enough. I don't like regen (strong or light) on A pedal most of the time.

BMW seems to be offering what I really want. Smooth "sailing" and strong regen when I want. I want strong regen in both modes when applying the brake.

Back to the article - looks like Ford is going to do what Leaf has done. "D"rive is like a gas car with slight regen. But they won't have an Eco mode.

· VoltSkeptic (not verified) · 6 years ago

The Prius has used single pedal regen for years, its very subtle. To coast I just lightly press on the pedal, for some regen I take my foot off the accelerator, and for stronger regen I use B (effectively the same as L when you take your foot off the gas, but it allows normal acceleration). I'm fine with it.

The brake light suggestions for when regen is active makes me think people have never driven a stick shift. If I drive with a standard transmission and take my foot off the accelerator the car slows down, a lot, depending on the gear sometimes more than my LEAF regen mode. I never considered this dangerous. A driver shouldn't depend on brake lights to avoid hitting the car in front, one should constantly evaluate the distance between their car and the car in front. Sometimes it requires brakes, sometimes it doesn't. Brake lights are an important warning, but it's an elevated indication/alarm that the car in front is slowly quickly, certainly not the only indicator.

@smidge204 - I always use a lower gear as an alternative to brakes when roads are icey, and I downshift to slow down to make sure I maintain control of the car on turns. Not sure how using the engine to slow down the car would result in loss of control unless I was doing something insane which would result in loss of control anyway.

· Mike I (not verified) · 6 years ago

Mapping an accelerator pedal to target velocity is nonsense. The best approximation of proper pedal mapping for an EV's accelerator position is motor torque. Heavy regen is simply a larger negative torque when you foot is off the pedal. Drive by wire braking should be the same - braking torque should be proportional to pedal force, with just enough pedal travel to mimic hydraulic brakes. So, blending friction braking force with regen should be straight forward, but a little tricky in practice. I see the logic of Ford's configuration, but I think I would like one pedal driving better.

· · 6 years ago

> You mention "road conditions" - I wonder if the heavy right-pedal regen would be intelligent enough to know when heavy regen braking forces cause loss of traction on icy roads? Hit some black ice, let up on the throttle and end up in a ditch! I currently drive a car with a manual transmission, which is a decent analog to right-pedal regen, and I can tell you it does not lend itself to better control in all situations (esp. in lower gear)

There is no rocket science needed for traction control on regen braking. All modern cars that offer regen braking also include traction control - analogous to ABS brakes. MUCH safer than full manual transmission slowing that absolutely can be dangerous.

· · 6 years ago

> I've been hearing this nonsense for a long time. I think with more than 7 months of Leaf ownership I can safely say I've "lived" with it for long enough. I don't like regen (strong or light) on A pedal most of the time.

Owning a Leaf is not the same has having experience with real right pedal regen. I'm not saying that you'll ever like it (which seems unlikely given that you determined that you wouldn't like it even before you tried it). I'm just saying that you still haven't experienced it if the Leaf is the extent of your EV experience.

· · 6 years ago

@darelldd · "Owning a Leaf is not the same has having experience with real right pedal regen."

Do you mean by "real" some arbitrarily strong amount of regen that you have determined to be the "real" thing ? Because in eco mode Leaf has quit a bit of regen.

· · 6 years ago

> Do you mean by "real" some arbitrarily strong amount of regen that you have determined to be the "real" thing ?

Yup! Pretty much the same as the arbitrary measurement of "quite a bit." But I definitely shot wide of the mark since you did say you don't like either "strong or light" regen - which pretty much covers the spectrum. I'm easily willing to stipulate that you don't want regen in the right pedal - strong or light - with or without experience of same. ;-)

I admit that I'm spoiled. I've driven an EV with right-pedal regen that is capable of 0-100-0 mph in about 11 seconds. And the braking part of that equation is done completely with the right pedal (until the last few mph to bring it to a complete stop).

· · 6 years ago

I like the LEAF's A-pedal regen in ECO mode, and wouldn't mind if it were stronger. Using the brake pedal, there is always a good chance the car will blend friction braking with the regen, which can be wasteful and less smooth. With strong A-pedal regen, one is less likely to engage the friction brakes.

· · 6 years ago

@abasile, Do you find any grades on your mountain descent that exceed the "Eco" mode regen? It has been so many years since I drove your mountain roads I can't recall how steep and curvy they are. I suspect that I have to deal with steeper grades (up to 14%) and more hairpin turns here than you have there. Given the reported "mild" LEAF regen — as opposed to Tom's mini E regen — am afraid that I will have to use friction braking to get down my hill safely, which is a waste.

I'll find out soon enough I guess.

· · 6 years ago

For the most part, eco mode regen is enough to control speed on our mountain descents. However, there are some steeper, secondary roads where the brake pedal is really needed. On those roads, I try to minimize friction brake application by holding down the brake pedal gently and continuously. This requires braking early, in anticipation of the steeper sections.

Also, I try not to start long descents with an SOC above 60 - 65%. On my big 5000' descent, it's not hard to pick up 15% SOC in regen, almost akin to a bit of DC fast charging.

· · 6 years ago

Don't forget folks: The Brake pedal also uses regenerative braking on the Leaf so you aren't necessarily wasting energy if you have to push on that other pedal. It's just more convenient to only need one pedal.

The biggest problem I have with descending is that I live up on the side of the mountain. If I do a 100% charge, there's no place to put the regenerated electrons. I always try to do an 80% charge but, with the Leaf's pathetic range, there are times when I need 100% for the day and have to burn brakes.

· · 6 years ago

ex-EV1: You need to be able to charge to 90% or 95%. Alas, the only available settings are 80% or 100% on the current LEAF. Perhaps another aftermarket hack will take care of this eventually. Oh well; brakes are comparatively cheap.

· · 6 years ago

Also, when pressing the brakes, the LEAF's eco/tree gauge in the upper left gives an idea of how much friction braking is being blended in at any given time. Generally the higher the indicated efficiency, the greater the percentage of braking being done by regen.

· · 6 years ago

@ex-EV1: Is there a % SOC where above that, your Roadster stops doing A-Pedal regen? Does it give you full regen up to 100% or does it start to decrease at a lower %. I assume you have figured out that 80% gives you the cushion to get full regen capability all the way down the mountain from you home.
The Leaf should not be any different. You just need to figure out what to charge it to so that you get close to 100% when you get down the mountain. This is one of the problems with BEVs, it is better to live on the bottom of a hill than the top although it is not a problem that can't be managed.

· · 6 years ago

@VoltSkeptic
"I always use a lower gear as an alternative to brakes when roads are icey"
Not a good idea. There are reasons for and against this depending on the type of vehicle you are driving (i.e. an ICE or xEV) but in the case of an electric vehicle, it is not a good idea.
Low gear in xEV vehicles, with the exception of some HEVs with true transmissions like the Sonata, do not have physical gears to change. i.e. there is no change in gear ratio or torque multiplication. When a BEV is put into low gear (or some eco gears), the control system will map more braking torque to the A-Pedal. When a patch of ice is hit, this braking torque will lock up the wheels and you will loose steering on a front axle or spin out on a rear axle. To counter this, the vehicle may detect the wheel lock up and remove the braking torque. I don't know how all BEVs control under this situation but some may remove the torque completely (resulting in loss of deceleration, e.g. Toyota recall), some may not remove any braking mapped to the A-Pedal (resulting in loss of control). If you minimize the A-Pedal braking during ice and snow conditions and use the brake pedal to decelerate; 1) you are not giving up efficiency since all production BEVs (except the Roadster, and MINI-E) use brake systems that optimize regen first using the B-Pedal and 2) and reduction in braking required when ice is hit can be modulated properly and evenly with the ABS system. Regen can't be modulated during ABS efficiently for many reasons that I won't go into because this explanation is already too long. Bottom line is, Low gear may be OK on a gas vehicle but not a good idea on a xEV.

· · 6 years ago

@abasile,
Unfortunately, the Tesla Roadster only give the options of "Standard" or "Range" charging and I believe the "Standard" gives you about 90%. This is about the same headroom as the LEAF's 80% charging option since the Roadster has about twice as much battery as the LEAF.
It would be nice if they offered the option of setting the actual SoC level at full in the future. The Roadster also has a 'storage mode' where the SoC is kept at about 50%.
I, personally, hope that neither car permits hacking at this level as hackers can kill people if they get into safety-critical computers such as those that control automobiles. The last thing we need is some hacker tying up a major control bus, thus preventing the brakes from working or allowing the batteries to overcharge and catch fire or destroy themselves.
I also agree that some sort of definite indication as to when friction braking kicks in would be nice.

· · 6 years ago

@Regman,
It seems like the Roadster stops allowing much regen when the SoC is a bit above 90% but it is hard to tell for sure. My steep descent is only 700 ft vertical in ~1.5 miles, during which time, I regenerate ~250 Watt-hours. I always do it at either 90% or 100% SoC and get pretty good regen at 90% and essentially none at 100%. I haven't tried to manually stop charging at 95% or other intermediate points. My impression from when I've driven with 100% SoC over hilly terrain and the SoC decreases is that there is a maximum amount of regen current allowed for the SoC. In other words, as the SoC decreases from driving, it seems like the amount of regen slowly increases too.
The ultimate EV, of course, will have a separate motor driving each wheel and essentially all braking will be regenerative. They could even put in a big heater on the outside, like train locomotives do (called "dynamic brakes") to bleed off the regenerated energy when the batteries are too full to accept it.

· · 6 years ago

@regman, Thanks for posting that. I'm not surprised that "low" (regen) gear for EVs is a problem in slick conditions. I've had to learn not to use cruise control on wet or icy roads for similar reasons.

@ex-EV1 driver, Whether one uses regen on the A pedal or B pedal, if the regen is too weak and the hill too steep or curvy (requiring low speeds for safety) it means the potential energy is going to be wasted. I'd like Tom's "parachute" MINI-E regen mode to be an option on the LEAF. For dry roads, at least.

I have a similar problem to what you describe: I live on a hill and with 100% charging I can't recover the energy of descent. But, for routine trips to town 80% is fine and for 100% trips to the "big city" I can take a back road with a gentle slope that doesn't involve regen. (But it does include 10 miles of dirt road, which is often rough, muddy or dusty. That's life in a county where 90% of the roads are unpaved.)

It is possible to charge a LEAF to 80% and then for an additional time to get it to 90% or whatever. But that is a nuisance and it would be helpful if Nissan allowed the charge level to be user defined. However, I understand that they are trying to make a mass market car and keep the complexity level within reasonable limits!

· Joe Foerster (not verified) · 6 years ago

I'm very happy with the way my Volt does it. I keep it in Drive most of the time as it's the most natural feeling as compared to cars I've driven all my life. And like said cars, when I'm in traffic or hilly terrain, I can quickly slap the gear shifter into Low for greater speed control. Nothing to learn, nothing to scare a die-hard ICE cr driver off with. Just a very natural feeling car to drive. The right amount of regen happens for the conditions and I don't have to think about it. I'm just looking to get to work, not have the ultimate driving experience orgasm.

· · 6 years ago

@ex-EV1 driver: Regarding a future LEAF "hack" to stop charging at a user-configurable SOC, I agree it would be much better if Nissan just updated our firmware to allow this, as well as to display an SOC percentage.

· · 6 years ago

After re-reading this article I feel a little disconcerted. On one hand, you have Ford that says there customers complain "if the brake system is any different from what the customer would expect as normal operation". On the other hand, BMW says its customers want heavy A-Pedal braking. Then you have 3-4 other OEMs with no comment. This hardly settles anything and I can see why Brad took so long to write it (Brad, I'm not complaining, I am sympathizing with you).

Now here comes my op-ed (as everyone knows from my all my previous posts regarding my concern for heavy a-pedal braking). I personally think Ford has the correct approach. They claim they can get 94% energy recovery on the city drive cycle without compromising driving experience (i.e. make it feel "normal"). BMW says its customers want the heavy A-Pedal braking but BMW has significantly fewer customers (< 1000) than Ford (Ford has been building regen systems since 2005 and probably has more than 200,000 customers) and BMW's customers are somewhat hand picked as a test fleet. Ford has years of real world customer experience and I believe that if they say some customers complain, I believe them. With all that said, the correct approach may be to provide a selectable A-pedal braking, something that Ford has ignored and BMW is attempting to give with this "Sailing" mode although I have not seen a good, complete explanation on how this mode works.

· · 6 years ago

> BMW says its customers want the heavy A-Pedal braking but BMW has significantly fewer customers (< 1000) than Ford (Ford has been building regen systems since 2005 and probably has more than 200,000 customers) and BMW's customers are somewhat hand picked as a test fleet

Missing in this - again - is the simple fact that while Ford does have far more customers driving with regeneration systems, it is BMW who has infinitely more "heavy" A-Pedal regen customers. Ford has none. BMW has hundreds. So if Ford polls their customers (they don't of course, but let's pretend) how they want regen to work - will they respond that they'd like something they have never tried and in most cases never heard of? Something that sounds odd an maybe even a bit scary? Or would they pretty much like it the way it is - as it has been for over 100 years and works just fine, thankyouverymuch.?

Shocking! Ford says their customers want everything just they way they're building it. And - what's this? - BMW says the same thing about their system! Experience and the status quote are about to butt heads.

· · 6 years ago

Ford has been building regen systems since 2005 and probably has more than 200,000 customers
I'm not sure where the 200,000 customers you refer to are. With an HEV with a small battery and motor, there's a limit to how much regeneration one can actually achieve because the battery can't accept very much current.
I would say that, other than the RangerEV from the 1990's, Ford has close to zero experience with heavy regenerative braking.
I agree that the <1000 BMW mini-E and ~2500 Tesla drivers aren't a huge sample but you really can't discount the percentage of these drivers who really like the heavy A-pedal regen. I'll grant that there could be some selection among the sample space that may be biased towards people who appreciate driving enough to pay a lot for their car, not people who really don't want to be or are fundamentally uncomfortable with driving, but not enough to totally discount the statistics.

· · 6 years ago

@darelldd, " BMW who has infinitely more "heavy" A-Pedal regen customers", actually Ford has more customers with heavy A-Pedal with their Electric Ranger which offered an economy gear with heavy A-Pedal braking. You should know this since you owned one. I don't know if it was as heavy as the MINI E but it was apparently heavy enough for them to decide that their customers didn't accept it.

@ ex-EV1 driver, "With an HEV with a small battery and motor, there's a limit to how much regeneration one can actually achieve because the battery can't accept very much current." This statement isn't exactly true. The small battery only limits continuously capturing regen over a long period such as going down a hill. There is more than enough reserve energy to capture regen for several braking events due to HEV's battery power management. The main limit is the battery/motor power which is around 30-35 kW for most full HEVs in the market from Ford and Toyota (compared to >70 for the BEVs). This is more than enough power to get over 0.12-0.15g of deceleration for speeds below 30 mph which is 90% of most peoples driving. If Ford's claim is correct at 94% energy recovery, this can't be achieved unless the system is capable of >0.15g since that is what is required on the city drive cycle. Ford's hybrid system is capable of doing heavy A-Pedal braking, they just choose to "blend it,” as Mr. Markby says.

· · 6 years ago

@regman,
I agree that there's enough energy capacity potentially in a discharged FEF or FFH battery but I don't know how much power it is capable of absorbing. Generally, the power a battery can absorb or discharge is a function of C, the power for a 1 hour charge or discharge. The more battery capacity, the more power in can charge or discharge.
I don't know and Ford certainly doesn't want to confuse us dumb customers by actually giving us much real data on their products.

· · 6 years ago

As part of the MINI-E program, we were required to take the cars in at 3,000 miles and then subsequently every 5,000 miles for service which consisted of data downloads and quite often a software "tweak".

The service took less than an hour and you could usually wait for the car unless there happened to me a few MINI-E's there at the same time for this service. BMW would tweak different things to see how we liked or didn't like it, but what I found to be most often tweaked was the regen. They would make it less aggressive, more aggressive, grab more initially, grab less initially and then progressively more, etc. This has gone on for over two years now and the MINI-E fleet has recently surpassed 8 million miles driven, in seven different countries and with over 1,000 different drivers (some cars were leased by multiple people). The two things I find most notable about the data they have revealed (other than the fact that an overwhelming number of lessees now want to buy an EV after the MINI-E experience) is that as far as I am told, there have been no instance where a MINI-E was involved in a vehicle to pedestrian accident, so these quiet cars evidently will not leave a wake of dead people in their paths due to their quietness. And secondly, an extraordinarily high number of drivers urged BMW to keep the regenerative braking as strong as possible, and complained whenever the service visit tweaking resulted in less aggressive regen.

Also, as far as us being hand picked, I suppose that is true to an extent, but BMW had no idea who I was or whether I would even like the car (Hell I didn't know if I would like the car) before they accepted me into the program. I wasn't an EV advocate back then, I just thought it would be cool to drive an electric car for a year, I really didn't even know about regenerative braking. I had driven priuses, and knew they had some kind of energy recapture in the braking, but didn't really think much about it because it was difficult to notice. Now that I've driven many volts and 3 different LEAF's I can say unequivocally that I like the strong regen on the A-pedal much better than the other set-ups. That's not to say someone else would prefer it otherwise, but virtually everyone I know that has extensive experience driving vehicles both ways tends to agree with me, Darrell & ex-EV1. There aren't many of us, so I guess the jury is still out and we'll be arguing this here for years to come : )

· · 6 years ago

Tom, I hope I didn't offend you by using the term "Hand Picked". The point I was trying to make is that BMW need customers that were at least partially interested in EVs from a technology standpoint, are willing to take the time to log info, go to the dealers for data dumps, and quite frankly, be willing to pay a significant lease rate for a vehicle that has limitations. The customers that Ford and Toyota have been dealing with are more everyday customers and not all of these types of customers will be willing to accept heavy A-Pedal braking. BMW may have found that a large number of drivers urged them to keep the heavy A-Pedal braking but I am sure there were customers that didn't like it. Unfortunately, large production vehicles have to be designed for the person that is going to complain the most and as a result, features that some think are great may not be implemented because a few people will complain.

· · 6 years ago

Tom, I hope I didn't offend you by using the term "Hand Picked":

No, not at all! Honestly, the most important criteria BMW used was where you lived in relation to a participating MINI dealership, as they didn't want the service visits to be inconvenient, also if they needed to frequently tow the cars there, it would cost less. Your financial condition was also considered as the initial year was quite ($850/month with subsequent years $600/month) expensive and you needed to be approved. I've read on various sites how the MINI-E drivers were celebrities and people with connections in BMW, and nothing could be further from the truth. We really were a cross section of people: doctors, lawyers, engineers, IT techs, mechanics, restaurateurs(hello) and I even know one guy that was on unemployment the whole time he had the car(I wondered how he got approved). Most of us never sat in an EV before the MINI-E. There were however a decent amount of experienced EV drivers in California that leased one, but the East Coast drivers were basically all virgins.

Back to the topic though. The point I was trying to make is that when BMW reduced the regen to make the car feel more like an ICE, there was an overwhelming response to restore it to maximum strength. I am not privy to the official data that BMW collected, but the MINI-E drivers would communicate amongst ourselves through social media sites and I honestly don't ever remember anyone saying they liked it milder. Now I know there had to be someone out there that did, but they didn't offer that opinion to the group, perhaps because they knew they were in the minority and didn't want to go against what everyone else was saying.

· · 6 years ago

regman: I don't know where you live, but if you live near me in NY/NJ you are welcome to drive my car for a day.

I let lots of people drive it. I feel it's part of the program to allow others to experience electric drive. If anyone here wants to drive my MINI-E, you can send me an email and we can set it up. My email address is my name at gmail.com, no space between first and last name.

I'd like someone that is skeptical of strong a-pedal regen to drive it for a while, just to see how they like or dislike it.

· · 6 years ago

> The customers that Ford and Toyota have been dealing with are more everyday customers and not all of these types of customers will be willing to accept heavy A-Pedal braking.

If you're looking for a technology that ALL will like, then you have a long, long time to wait. There is no such thing. The "everyday" driver has never been exposed to this technology, so how can we even determine what *most* of them will accept (or want?) much less *all* of them?

· · 6 years ago

> actually Ford has more customers with heavy A-Pedal with their Electric Ranger which offered an economy gear with heavy A-Pedal braking. You should know this since you owned one. I don't know if it was as heavy as the MINI E but it was apparently heavy enough for them to decide that their customers didn't accept it.

There seems to be some significant confusion as to what "heavy A-pedal braking" is. Yes, I owned a Ford Ranger. And no, it had NOTHING that could be considered "heavy" regen in the pedal. And certainly nothing that was controllable at the pedal. No, it was NOT heavy enough for them to decide that their customers didn't accept it. If this "fact" is what you are basing your assumptions on, then you've got a bit more research to do. Or more accurately, you have a LOT more research to do. But no research can replace experience - as I've said so many times that I'm sure I'm being annoying with it.

The fact of the matter is that consumers are not being asked what they like. I have driven more EVs than 99.999% of the world's population. My name and website are somewhat public at this point. How many times do you suppose my experience has been polled to determine what might be best for future EVs? I'll give you a hint. The answer starts with N. Or Z.

· · 6 years ago

Tom, Thanks for the invite. Unfortunately I don't live in the area but I had already planned on contacting you if I was ever in the NY/NJ area. I have had an opportunity to drive almost every HEV, BEV, and even a few Fuel Cell vehicles. The only 3 BEVs that I have not had a chance to drive is the EV1, MINI-E and the Roadster and I would love the chance to drive the MINI-E or ActiveE.

Darelldd, I understand the Ranger EV did not have as heavy A-Pedal braking as the MINI-E or Roadster but it was heavier in econ gear than anything at its time toping out at close to 0.1g, over 2 times more than a gas vehicle D-gear. Personally, I didn't think it was too heavy but don't know if I would want it any heavier. I also didn't like the fact that the A-Pedal braking was not available for the first 5 miles of driving after charging. Since these late 90s EVs, every xEV with a brake-by-wire system has had "conventional" A-Pedal braking (Toyota, Ford, GM, and Honda) with some offering heavier (but not as heavy as you would like) in special modes. I find it difficult to believe that these 4 companies do not know what their customers like or don't like.

· · 6 years ago

regman:

"I find it difficult to believe that these 4 companies do not know what their customers like or don't like"

Really? I don't! :)

· · 6 years ago

> Since these late 90s EVs, every xEV with a brake-by-wire system has had "conventional" A-Pedal braking (Toyota, Ford, GM, and Honda) with some offering heavier (but not as heavy as you would like) in special modes.

I'm having difficulty trying to figure out if we're even talking about the same thing. It would appear that I have driven all the cars you have PLUS I've driven the ones you list that you have not driven. And the ONLY cars that you've mentioned that have A-pedal regen are the Roadster and the Mini-E. The EV1 didn't. The Rav4EV doesn't. The Ranger doesn't. Nothing from Toyota, Ford, GM or Honda did.

So how do these car makers know what customers want if their customers have never experienced A-pedal regen? How do YOU know what you want if you've never experienced it?

Before we can have a relevant discussion, we really need to define A-pedal regen. And for me that is driver-modulated regen on the right pedal. Drive-modulated, and enough braking to not need the friction brakes in normal driving except to come to a complete stop. This isn't a matter of "not heavy enough" in the Ford Ranger. Or the Rav4EV. Or the EV1. Or the Honda EV+. The regen on those cars could not be modulated. The car makers you mention have no experience with real A-pedal regen, so neither do their customers.

So can we first agree on what we're talking about? And only THEN talk about what system is better?

· · 6 years ago

Darell, Yes, I believe we are talking about the same thing but there are different levels of A-Pedal braking that have been implemented, and I have driven them all. Typical gas vehicle A-Pedal braking will top out at about 0.04g but will not hold this for the entire speed range. Several production xEVs provide more aggressive braking but not as aggressive as the Roadster. The example that I gave is the Electric Ranger which provided about 0.1g down to around 10 mph in Econ Gear. The S10 and RAV4 were similar and yes I have driven all 3 of these. This level will not give you enough braking for most stops but will cover about 60-70% of your braking needs. The Roadster and MINI-E exceed this and give you >0.15g of deceleration which covers about 95% of braking. Although I have not driven these, I have driven several test fleet vehicles from several OEMs that provide braking up to these levels. No, I didn't drive them for a long period of time and yes, I could probably get use to it and maybe even learn to like this feel but in general I felt it was difficult to drive, especially as the speed decreased and this heavy A-pedal braking went away as you came to a stop. My company leased an Electric Ranger so this vehicle I probably had the most experience with (I probably drove for >2000 miles total). I did not particularly care for the 0.1 g deceleration in the E Ranger Econ Gear primarily because of the variation in deceleration under different driving conditions, and this level isn't even close to the heavy level you are talking about.

Tom, "Really? I don't! [find it difficult to believe that these 4 companies do not know what their customers like or don't like]"
I would not find it difficult that any one company could (and does) make design blunders based on what they think their customer like. There are numerous examples of this throughout history. But when multiple companies come up with a similar answer, I do find it hard to believe they don't know what they are doing.
What will be interesting is to see if Toyota design influences the Tesla in the Model S or will the Rav4 inherit some of the Tesla characteristics. This collaboration is a great experiment on many levels.

· · 6 years ago

regman: The reason why I believe that is because I have had first hand discussions with various industry insiders from an assortment of OEM's. Being one of the high profile MINI-E participants, I have been approached at many events by people that work in the EV programs for a variety of car manufacturers. I've talked at great length about regen, range, charge rate, thermal management and what visual displays are desired and I can tell you unequivocally that in every company there are battles going on about what do customers want, re: Should the EV mimic an ICE, or do the customers want a different experience? Even inside BMW(and I really can't elaborate as much as I'd like to) there are camps that have differing opinions on this, luckily I think the progressive, out of the box thinking people are getting their way.
I honestly think that most of the OEM's really don't know how to treat the EV customer. This is new to them and outside their comfort zone. Auto manufacturers are notoriously slow to adjust to new concepts and are very concerned that they will out pace the public's ability to adapt to changes so they err on the side of caution more often than not.

· · 6 years ago

Tom, 100% agree and understand everything you are saying. All OEM understand the pros and cons of this issue (and other unique xEV issues) and struggle with it. What most people don't realize is that in the automotive business, customer satisfaction is huge. You may be aware of this but for those that aren't, there are quality metrics called TGWs and TGRs (Things Gone Wrong and Things Gone Right). In addition to failures (anything that fails to do what it is supposed to do), TGWs include anything that may be functioning as designed but people just don't like. TGRs are generally things that a customer likes that they weren't expecting (surprise and delights). A-Pedal braking falls under both of these categories. For some people, heavy A-Pedal braking is going to be a huge TGW. For others, it is a TGR. Unfortunately, they don't cancel each other out and TGWs always win. TGWs have a direct impact on vehicle quality ratings and avoiding any TGWs at the expense of TGRs occur all the time. It takes vary few TGWs at the volumes for these vehicles to significantly lower quality. This is why they will " err on the side of caution" as you say.

· · 6 years ago

@regman,
Your TGW -vs- TGR philosophy comes in all large, political organizations. It is also often referred to as CYA (Cover Your A**), where job performance and promotion are more based on not making mistakes instead of doing good things.
Sadly, it generally leads to stagnation since, if you do something long enough, something is going to go wrong so the best way to keep that from happening is to do as little as you can get away with.
Yes, it appears that the major auto OEMs suffer from this terribly. Perhaps that's why they are doing so poorly. If every product is basically just as bland as the next, the only way to differentiate is by reducing price. This isn't exactly good for business or labor and it stifles innovation.
We either need to do something to break them of this (history doesn't offer a lot of examples) or give up on them and support newcomers who are saddled with as much baggage.
In the computer industry, it took an Apple, Intel, and Microsoft to break the rest of the industry from its stagnation. Maybe Tesla will break the auto industry from it.
Otherwise, I guess we're just destined for dullness from the company who pays its workers the lowest salaries.

· · 6 years ago

> Otherwise, I guess we're just destined for dullness from the company who pays its workers the lowest salaries.

Nicely (sadly) said, ex-EV1.

· · 6 years ago

Ex-EV1, I couldn't disagree with you more. To say there is stagnation in technology among the major auto makers is a ridiculous statement. Year over year advancements in fuel economy, safety, emissions and performance have never increased faster while simultaneously continuing the trends of improved quality and customer satisfaction for all major manufacturers. To say otherwise is just spewing anti-corporation propaganda that only fuels the fire of hate towards the companies that have the best resources to bring these technologies to market.
What you claim would be correct if OEMs refused to develop technology that would only result in improvements that are unquestionably wanted by everyone. This is an absurd assumption with many examples of highly complicated and advanced systems like park assist, various active safety features, smart air bags, telematics, various engine efficiency technologies, electrified powertrains, battery technology, by-wire technology, and I could go on. For any OEM to stay stagnant in this market is to fall woefully behind. But some things like regen braking feel are so subjectively polarizing that displeasing any customers will be devastating to that products competitiveness due to the low quality and customer sat numbers from organizations like JD Powers. This means that any controversial technology that may result in any customer complaints (not from poor execution but rather from customer preferences) will probably not be implemented, even if there is a population that is screaming for it. BTW, I don't consider heavy A-Pedal braking complicated or advanced technology. It is strictly a preference on how you map your pedal. Anyone can do it but the fact is that there is a significant number of customers that will absolutely hate it. You may think peppermint ice cream is the best and that if everyone would just eat it every day they will learn to prefer it over vanilla.
And to say that history doesn't offer a lot of examples is also absurd. Toyota, Ford and GM have taken huge financial losses for years on their electrification programs where they could have spent this money on more lucrative products. It's possible that, with the exception of the Prius that has a high enough volume, there are few electrified vehicles out there that are profitable today. Historically, Ford and GM started BEV programs in the early 90s, way before any legislative mandates were in place. They have tried out of the box thinking like gas turbine engines, rotary engines, CVTs, dual clutch transmissions, roll stability control, high tech materials, etc. Some of these panned out and some didn't but anyone that says that the auto companies are just treading water probably thinks they are all colluding to hide that allusive 100 mpg carburetor.
I am tired now and wish to stop.

· · 6 years ago

I think Tesla already broke the automakers out of their stagnation. It is debatable whether the Leaf and Volt would be around today if it weren't for Tesla. That is the power of competition. Automakers typically refresh their models every 5 years, and it does look like we'll have plenty more plug-in choices in the next 5 years. Autos are a highly regulated industry, hence the slower product life cycles, when compared to computers.

A small company like Tesla has the ability to innovate faster with less overhead, and fewer preconceived notions, and can force larger companies to do the same. On the flip side, the small company may have a harder time scaling up production numbers.

Back to re-gen, BMW has the right approach of making heavy a-pedal re-gen a mode you can switch on an off. Clearly some people love it, some people hate it, and some people, like me, want it in certain conditions.

· · 6 years ago

Jose: Just to clarify, you cannot switch off the regen on BMW EV's, and you won't be able to in the future either. There is an intermediate position on the accelerator pedal that is in between acceleration and regeneration, in this position, the car coasts without until you either press the accelerator to speed up or back of the pedal a bit and the regenerative brakes engage.

I spoke to BMW about the possibility of a switch to turn off the regen on long highway drives and they immediately canceled out that idea. They are concerned people might forget they switched off the regen and then back off the accelerator expecting the car to slow down with regen and end up rear ending the car in front of them. It makes sense to me. Sometimes when I'm driving my ICE car I momentarily forget there is no regen because I primarily drive the MINI-E and have become so accustomed to it.

· · 6 years ago

Tom, you just pointed out one of my biggest issues with heavy A-Pedal braking and why A-Pedal braking needs to be substantially similar to a conventional vehicle. Anyone with a second, conventional vehicle will inevitably forget and either expect the braking when they don't have it or don't expect it when they do. If my second car only had heavy A-Pedal braking, I wouldn't let my teenager drive it for this reason as he is not experienced enough to adjust to the different feel. This is not unlike the increase in accidents when ABS was introduced because it resulted in an unusual brake pedal feel that people weren't use to and would often take their foot off the brake when they felt the ABS pulse.

· · 6 years ago

regman: I drive about 30,000 miles per year in the MINI-E and 2,000 in my Toyota Tacoma pick-up and it's never been an issue where I almost hit someone. I do think that the ability to turn off the regen would be problematic though.
Again, I know you don't like the argument "We'll I've experienced this and you haven't" but I'll have to pull that out on you here. It's not a problem. I've been doing this for about 2 1/2 years now and on a couple occasions I had a fraction of a second delay before I hit the brakes. Admittedly I don't tailgate(unless I'm drafting!) so that isn't a problem. Plus, if I ever needed to stop quickly, the instinct to hit the friction brakes still is sharp, because that is what I would do with the MINI-E anyway. When you are using the regen to slow down the car it's in instances where you don't need to stop so quickly that you'll hit someone if you don't react quickly enough so if I'm driving a car without regen and lift off the a-pedal expecting to slow down and don't, it's not a problem, because I'm not in need to stop rapidly or risk hitting someone. That's the best way I can explain it. It really isn't a problem at all.

· · 6 years ago

@ Regman -

If a driver can't figure THIS out, that driver should not be on the road. As Tom again points out - and as I have tried to make clear a few times - you have NOT experienced this if you have not driven a Roadster or a Mini-e or one of several other low-production cars that feature significant A-pedal regen. No, the Ranger, nor the S10, nor the EV1, nor the Rav4EV, nor the Honda EV+ count.

Now, onto adaptation. You realize that there are people who own both an automatic and a manual-shift car, yes? I was one of them for many years. Is that dangerous? The EVs I've owned have basically toggle switch regen. If you leave it on and lift your foot, you get all of the regen available, right now. When you forget either way, there's no danger involved. If you need to slow down more - you do what you always do and jump on the brake. If you need to slow down less, you get back on the throttle. I suppose if you're a wanna-be racer dood who tailgates everybody, then your issue could have some merit. If we're designing cars for that demographic, we have bigger problems than this though! For the rest of us thinking adult drivers, I'm pretty sure we can manage switching between our Porsche and pickup. Between our motorcycle and bicycle (hey, look at that - the front brake is operated with the OTHER HAND). Between our automatic trans and manual trans cars. And certainly between A-pedal regen and any other sort of car.

If we're afraid of a system that is fundamentally better because it might scare off people who shouldn't be driving in the first place, I'll lose some faith in the human race.

If you don't think drivers can handle switching between cars with and without A-pedal regen, I would very much enjoy hearing how you reconcile human adaptation from manual and automatic transmissions. And from front brake lever placement on motorcycles and bicycles.

I've been in cars that'll haul themselves down from 100 miles per hour to 5 mph in a matter of a few seconds - all with A-pedal regen. I then drive home in my mundane Prius, and never even have a second thought to switching driving styles.... save for the fact that I then hated how the Prius responded to the right pedal (plus or minus direction!)

And my final wonderment of this post: Should we have abandoned ABS because it was too dangerous for people to figure out?

· Roh Vemula (not verified) · 6 years ago

I own Chevy Volt since May 2011. It is a great car in all respects. In any Plug-in electric car whatever technology they use it is very important to get attain the MILES per CHARGE which is crucial. And will be selling point to car manufactureres.

· · 6 years ago

Darell, all of your examples you provide are irrelevant. Everyone of these require different driver interface. A manual transmission requires the driver to control the vehicle with a clutch and gear shifter whereas a automatic only has the A and B pedal. In the case of an Automatic and a BEV, the driver interface it the same and certain drivers will expect the same driving characteristics.

Do I think people can adapt. Yes, most can. But some that can will complain. Some will not want to adapt, and it only takes a few incidents and an ambulance chasing lawyer to cost a company millions of $. When customers get in accidents, they will look for any reason to not take the blame.

I completely understand your argument and respect the opinion of anyone that has experience above and beyond everyone else but I feel your issue is that you feel everyone should and will (if given the chance) come to the same conclusion as you. Not everyone is you. This feature is extremely subjective and not everyone will like it.

"I've been in cars that'll haul themselves down from 100 miles per hour to 5 mph in a matter of a few seconds" This is physically impossible with regen only to do this in a "few seconds". It takes around 30 seconds to go from 100 to 5 at 0.15g which I believe is around the deceleration of a Roadster A-Pedal. Not to mention the fact that it would take over 100 kW of power to do this. I already corrected you on this claim on a previous post and you acknowledged this correction.

"If we're afraid of a system that is fundamentally better..." Your claim that it is fundamentally better is false. For any vehicle that has a high tech brake-by-wire system that is capable of providing regen only when the brake pedal is pressed, there is no efficiency difference. All major OEM xEVs (Toyota, Honda, Nissan, Ford, GM and Hyundai) have by-wire systems and all provide more conventional A-Pedal feel in normal driving modes and even moderate (by your standards) A-Pedal braking in special modes. Vehicles that have a low tech brake system (Roadster, MINI E, and other low production cars) DO require this heavy A-Pedal braking to achieve the efficiency and minimize use of friction brakes that will always come on when you step on the brakes. If your definition of better is that you like it more, than I can't argue with that but since there is no efficiency advantage (if you use a high tech brake system) and it is only driver preference based, I find this claim of being "better" to be unsubstantiated.

"Should we have abandoned ABS because it was too dangerous for people to figure out?" Absolutely not. There is a clear safety advantage to ABS (and stability control) systems. Other than preference of driving style, heavy A-Pedal braking does not have any clear advantages (and has some disadvantages).

· · 6 years ago

> Everyone of these require different driver interface.

I contend that the right pedal of all these cars is an identical user interface. As is the right hand lever of a motorcycle and bicycle.

> you feel everyone should and will (if given the chance) come to the same conclusion as you. Not everyone is you. This feature is extremely subjective and not everyone will like it.

While I do suspect that most will come to the same conclusion as I do (and the conclusion that all who have experienced - save for the rare exception). I don't expect everybody to be me. And I don't think *everyone* will like it. It is the same with EVs. Those who don't drive them tend to be the "non-likers." Some people don't like pickup trucks, even though they're great vehicles for their purpose. Some don't like 4-door sedans. Some don't like motorcycles. Some don't like bicycles. ALL great vehicle. All superior vehicles for their intended purposes. Yet some people don't like them. I get that. Believe me when I say that I don't want everybody to be like me. I only want folks to give a new tech a chance before dismissing it as "I won't like it because it seems different or dangerous" or... whatever.

> It takes around 30 seconds to go from 100 to 5 at 0.15g which I believe is around the deceleration of a Roadster A-Pedal.

It was not the Roadster in question. Which by comparison has very weak A-pedal regen. The vehicle in question goes 0-100-0 in 11 seconds total. Let's just say the car pulls WAY better than 0.15G in every direction.

> There is a clear safety advantage to ABS (and stability control) systems. Other than preference of driving style, heavy A-Pedal braking does not have any clear advantages (and has some disadvantages).

I'm confused again. According to your account, ABS caused all kinds of accidents, but we kept it because somebody determined that it was still clearly "better." I'm not sure where all the ambulance chasers were at that time. But we're worried about A-pedal regen not being better because some of us think it might be dangerous - though there is no evidence to support that while there IS clear evidence that a car can be slowed and brought to a stop significantly sooner with A-pedal regen.

What I find most amusing in all of this is that before I drove with the system, I was a firm non-believer myself. I wanted all future EVs to operate just like the EVs that I've owned before. Then I drove a few cars with real A-pedal regen. And now here I am getting all uppity about it. Really it is much the same way as EV acceptance went for me. Before driving one I was pretty luke-warm to the idea. And now... I get all uppity about them. Experience will do that for you sometimes.

· · 6 years ago

Darell, "The vehicle in question goes 0-100-0 in 11 seconds total." To achieve this feat would require an average of over 0.8 g acceleration and deceleration and over 500 kW at the upper speeds (assuming a 1500 kg vehicle). I called you on this claim before and you acknowledged that this performance included friction brakes.

As far as getting uppity, I urge you not to ever give up in the future regarding your passion on various subjects just because you get strong resistance. It is the passion of people like you that have helped pushed manufacturers and the government to get mobile electrification to the point it is today.

Besides, I enjoy riling you up.

· · 6 years ago

Note to Brad: If you want reader comments, just mention regenerative brakes and we'll be at each others throats for weeks. ; )

· · 6 years ago

I think Brad's title for this article speaks volumes. We've got the "go" part down pretty well. The stop part is still being ironed out.

· · 6 years ago

Darell,
Here is your post from the Robot Guy's Volt story a half year back or so.

"@regman -You, of course are correct in your correction of my braking story. Big shame on me. The 100-0 stopping was done with the binders in addition to the regen. I'd mixed up my number with the 0-60-0 runs where the friction brakes were not in use. Dang it. I hate it when that happens. And I appologize for the confusion (wish I could edit!)
So for the record, the 0-100-0 runs in 11 seconds were done WITH the friction brakes in addition to the regen. "

Just for curosity sake, what was the time 0-60-0 with no added brake pedal? You never gave this.

· · 6 years ago

That's where I think my confusion was running rampant. I believe that they were both around the 11 second mark - but I only have documentation for the 0-100-0. The fast one with the binders and the slow one without. In my advanced age, I can't remember stuff like I used to, obviously, so don't quote me (or hammer me) on the 0-60 one!

I'll try my best not to biff the 0-100-0 one again. But no promises. ;) It still boggles my mind that a street-legal vehicle can do 0-100-0 in 11 seconds. That's the length of a good yawn.

· · 6 years ago

It is clearly the case that coasting is efficient with a piston engine because of high frictional losses. But there is no basis in science or engineering to support the claim that coasting (decelerating) is more efficient than constant speed with an EV that has negligible fictional losses in the motor.

Not that I know of anyway. Is there something I missed in physics or dynamics?

I assert that the most efficient mode in an EV is constant pedal position which equals constant speed.

· · 6 years ago

Darell, 0-60-0 in 11 is plausible. I ran the numbers and this is an average of around 0.5g peaking out at over 200 kW. Definitely doable however that much deceleration can easily cause stability issues on wet pavement so I guarantee nobody is will ever give you this much deceleration on a production vehicle.

"I'll try my best not to biff the 0-100-0 one again." Don't worry, I will keep you honest.

Jamcl3, Actually there is an good, scientific reason for coasting and hyper-milers take advantage of this. The answer lies in motor efficiency. Motor efficiency maxes out at between 70 and 90% rated power and drops off significantly at low power levels. Hyper-milers will use a technique called Pulse and Glide where they will go to about 3/4 accelerator pedal (trying to hit the high efficiency point) and over shoot their speed target. Then they will glide, often literally shifting into N, and coast until they get below their target speed. Then repeat the process. The amount they overshoot and allow to slow down depends on how many irritated drivers are following him. The theory is that the average energy required to get an average speed will be approximately the same but the when this energy is being created by the motor, it is running at a higher efficiency point compared to running at a low power level during constant speed. I have personally tried this and it does work, even in a gas vehicle.
Also, there are those that say heavy A-Pedal braking will promote over braking which is inefficient due to the round trip energy storage and usage efficiency which can be <60%. (example: Trans efficiency = 95%, Motor braking efficiency = 90%, battery charge and discharge efficiency = 90%, motor propulsion efficiency = 90% and trans efficiency = 95% equal a round trip efficiency of around 65%).

· · 6 years ago

> I guarantee nobody is will ever give you this much deceleration on a production vehicle.

Ah, but they already do! They just offer it up in the brake pedal, of course. The stability issues are greatly attenuated in either case with ABS/traction control.

· · 6 years ago

Regarding "pulse and glide", there is a certain 'LEAFfan' on the MyNissanLeaf.com forum who uses this technique to achieve a "fuel efficiency" average above 6 miles/kWh. Given a usable battery capacity of approximately 21 kWh in the LEAF, that would translate to 120+ miles of range. He uses 'Neutral' quite a bit, since it is next to impossible to continuously hold the accelerator pedal at exactly "zero".

Personally, I will typically do closer to 5 miles/kWh, from the battery to the wheels. 100 miles of range is quite achievable in the LEAF once you learn the ropes.

· · 6 years ago

Regarding "pulse and glide", there is a certain 'LEAFfan' on the MyNissanLeaf.com forum who uses this technique to achieve a "fuel efficiency" average above 6 miles/kWh. Given a usable battery capacity of approximately 21 kWh in the LEAF, that would translate to 120+ miles of range. He uses 'Neutral' quite a bit, since it is next to impossible to continuously hold the accelerator pedal at exactly "zero".

Personally, I will typically do closer to 5 miles/kWh, from the battery to the wheels. 100 miles of range

· · 6 years ago

I couldn't help myself. All this talk about 0-60-0 and strong regen made me do a test with the MINI-E. It took me exactly 20.4 seconds to go 0-60-0 without using the friction brakes at all. BMW states the MINI-E goes 0-60 in 8.5 seconds and that looked just about right while I was doing the test, so the regenerative brakes will stop the car from 60 in 12 seconds flat. However I think it's notable that the car crept very slowly for the last 2 seconds until it stopped. I'd say at around the 18 second mark, I was rolling at a pace under 5mph, so it really just about stops from 60 mph in 10 seconds.
I'd love to see a similar test done on a roadster and a LEAF, just to compare. Any takers?

· · 6 years ago

Tom, that's great data!

· · 6 years ago

Wow, I just checked back on this thread and I had a lot of catching up to do! Here's my blog post on regenerative braking:

http://neilblanchard.blogspot.com/2010/11/on-regenerative-braking-and-co...

"If you have to use the brakes, then you have accelerated too much. Regenerative brakes should only be used to slow the car in unanticipated situations, and at the last moments to come to a stop."

Neil

· · 6 years ago

Tom, Yes, this is interesting numbers and it gives me a new perspective on how aggressive BMW MINI E is. If this time is correct, 60-5 in 10 seconds, this is 0.25g deceleration, about 0.1g more aggressive than I was assuming. It tops out at about 100 kW at 60 mph to decelerate a 1500 kg vehicle 0.25g which is well within the 150 kW rated power. Does the MINI E creep because you said that it did come to a stop without stepping on the B-Pedal although the last few mph were low deceleration (and no I don't want to start the creep debate again)? Also, was the deceleration the same for the whole speed range or was it lighter at the higher speeds?
I also would like to see the times for the Tesla and Leaf. I know the Leaf will be significantly slower but I also expect the Roadster to be slower since the rumor I heard was that Tesla had to dial back from 0.2g to something lower. This would put the 60-5 in the > 12 second range.

· · 6 years ago

Neil, Great blog. I am glad I am not the only one in the low A-Pedal braking camp. I was feeling like I was being ganged up on.
The only thing you have missing in this blog is the point about optimizing the efficiency point of the motor when you pulse vs operating at a lower motor efficiency point to maintain a constant speed. This is why Pulse and Glide is more efficient than constant speed (note: this works for gas engines also which also run at lower efficiencies at low loads during gliding).

· · 6 years ago

regman: No there is no creep. When you slow down to under 5 mph or so, the regen lightens up so the car does roll freely a bit, that's why I mentioned that.
The deceleration isn't perfectly linear. When you release the a-pedal, it gradually gets stronger and then as you slow down to under 20mph, it gradually becomes less aggressive until you stop. The 50mph down to 15mph area is very strong. This is what the reporters that drive it for the first time have called "deploying a parachute"

· · 6 years ago

"If you have to use the brakes, then you have accelerated too much. Regenerative brakes should only be used to slow the car in unanticipated situations, and at the last moments to come to a stop."

That's flatlander talk Neil! If you can coast down a 14% grade into a hairpin without "launching" you're a much better driver than I ever will be.

· · 6 years ago

> When you slow down to under 5 mph or so, the regen lightens up so the car does roll freely a bit,

In fact somewhere between 5 and 0 mph, the regen has to release completely. There is a lower threshold below which the kinetic energy just isn't enough to to use. So at some low speed the car truly is just coasting with your foot off the right pedal. Or at least that's how it has worked in all the cars that I'm more intimately familiar with. If you pay close attention in certain situations, you can feel where that very subtle transition is from super light regen to zero. It is a long way of saying that I agree that you should remove the last few mph from any regen braking equation, because after that you're just coasting down with nothing more than rolling resistance.

· · 6 years ago

@Niel -

Thanks for the pointer to your blog. In general, I understand the logic you are going for - wasting kinetic energy in the battery round-trip inefficiencies is bad. However, there are several places in your blog that are confusing - and with a bit of tuning up, your point would be more clear, if a bit weaker.

Here is my issue. You state:

>> Think about it: there are three possible modes of driving, right?

1) Accelerating
2) Coasting
3) Decelerating <<

And this is incorrect. #2 and #3 are identical. "Coasting" decelerates you. If you don't keep adding power to overcome various resistances, the car will slow. It usually happens more gradually than braking, but "coasting" still results in slowing the vehicle. Braking slows the vehicle with driver-controlled drag (friction brakes or regen) and coasting slows the car with drag that the driver cannot control drag (rolling resistance, mechanical linkage resistance and air resistance).

You say:

>> coasting is by far the most efficient way to roll <<

And I say that coasting is - technically, in some specific situations - the most efficient way to decelerate, not to "roll" or "cruise" or drive somewhere. We agree on that, yes? You cannot get any significant, relevant distance by "coasting." You must add power to get somewhere (we're ignoring down hill and down wind, of course). When you wish to slow down, you can coast to slow slowly, or you can brake to slow faster. Either way, you are not really "rolling" you are decelerating.

We can't use "coasting" as a way to drive somewhere. So every instance of coasting should be referred to as decelerating. In your list of three driving modes, #2 should be "cruising" - defined as maintaining constant speed. And that, of course, requires an input of power. It is NOT possible through coasting. The three modes are:

1. Increase speed (accelerate with power input)
2. Maintain speed (with power input)
3. Decrease speed (decelerate by coasting or braking)

Whew. OK, I'll stop there.

· · 6 years ago

And now a new thought: While coasting is technically the most efficient way to slow the vehicle in perfect situations - many of us rarely find ourselves in perfect driving situations. Especially those of us who regularly drive in congested areas. I'm a HUGE fan of coasting and do it all the time in both my EV (easy!) and in my Prius (takes a bit of practice to get the pedal position for a real "glide). I do it when I can. And there are far too many times when that just isn't possible. I am an experienced "eco driver" as you call us. I regularly beat EPA estimates handily, and get way more range out of my EVs than most other drivers can ever manage.

And finally, here's my point (I hope). When we drive in the real world, using regen to slow the car is often the most efficient way to decelerate. Something to consider is how much energy is thrown away to air resistance at high speed. If you're going 70, and you see the traffic way ahead is going 30, you can "coast" and watch the wind rob the car of energy until you are down to 30 mph where very little of your energy is lost to wind. You never get that energy back that was lost to wind. Or you can regen the car a bit quicker down to 30 mph. You don't get all of that kinetic energy back, but at the same time, you haven't lost all of that kinetic energy to wind. You stored some back in the battery. And now you're going 30mph sooner than you would have with coasting... but hey, look at that. The car is far more efficient at 30mph than it was at 70.

So in case the point is lost in my babbling - coasting does NOT give you something for free. It is far more complicated than that (mostly because of the HUGE wind resistance variation with speed. So in the end, the simplistic "It is always more efficient to coast" is not true. The fact of the matter is - it is *typically* (not always of course) more efficient to go slower. So in many situations, driving slower for longer by storing some of your kinetic energy back in the tank can be the more efficient process. And the times when braking to make the car slower is NOT more efficient, it is not the HUGE difference that many make it out to be. This I know from many, many miles of practical, direct experience.

At least think about it. And I look forward to the discussion.

· · 6 years ago

Darell, that is an excellent point. An example of real-world application would be exiting the freeway. Most drivers do not brake until they have no choice. However, particularly if there is no one right behind one's car, it makes sense to decelerate using regen right after leaving the freeway, then coast relatively slowly to the traffic signal at the end of the off-ramp. This technique enables more energy to be captured in the battery, and of course also works well in hybrid cars. You just have to be watchful so as not to be a pain to other drivers or get rear-ended!

As for a 0-60-0 test in a LEAF, there aren't any suitable, open, flat sections of road in my immediate vicinity, so perhaps someone else can try that...

· · 6 years ago

Many years ago, in a discussion with the fine folks at ACP, I mentioned how great it would be to coast for maximum efficiency. Oh boy, did I get an earful. One that gave me pause, and sent me back to research. The smart folks at ACP don't guess at things. They have studied inefficiencies of various systems in minute detail. It was their finding that while coasting can be the most efficient way of slowing in some (just about perfect) situations, that using some amount of regen to get you slower faster is more often the most efficient (and more convenient?) way to drive.

If there is one thing that I think we can all agree on - it is that slowing a vehicle *always* wastes kinetic energy. And to claim that coasting down is uber-efficient, or that it is significantly more efficient than using regen, definitely overstates the case.

· · 6 years ago

Darell, I don't believe Neil ever implied that coasting was maintaining speed as you assume. You have lumped coasting with decelerating because vehicle speed does decrease but if you read his blog closely, he explicatively states that coasting is under no power. If you want to further define the modes of driving to stress your point I would add a mode and make it

1) Accelerating (vehicle speed is increasing with power required to accelerate and counter road load power)
2) Maintaining speed (vehicle speed doesn't change with power required to counter road load power)
2) Coasting (speed decreases due to road load power)
3) Decelerating (speed decreases due to road load power and motor brake power along with friction power if applicable)

For those that don't know, road load power road load power = av + bv² + cv³ where a comes from static rolling resistance, b from dynamic rolling resistance and c primarily from aero drag.

As far as your 70 to 30 scenario, I don't know if your assumptions are completely correct. The thing that you are missing is that if you brake hard early to get regen, you will then have to maintain speed, requiring propulsion power for a period of time to achieve the same point A to point B in a similar distance and/or time. The propulsion power required will counter the power recovered, not to mention the round trip energy efficiency, may result in more net energy usage. I do have to admit that you got me thinking about the aero affects of getting to a lower speed faster so I have not fully decided what is better. I am in the process of building a model (yes I am an engineer) to test these 2 theories under different driving scenarios. I will let you know my results.

· · 6 years ago

> Darell, I don't believe Neil ever implied that coasting was maintaining speed as you assume.

I will let Neil tell me differently. He didn't really claim that it was maintaining speed NOR did he clearly point out that it was a deceleration situation. But in the end, it doesn't matter what that implication was. The fact is, we slow down when we coast and I think that point was at least mostly missing in the blog. Yes, he states that coasting is under no power (I think we all agree on that) but he skates all around the issue of coasting actually resulting it deceleration. He almost implies that very little energy is lost with coasting. He calls it the most efficient way to roll which is so vague that we have to guess at what he's implying. While I get your 4th point, I don't think it really matters much. Slowing is slowing. And energy is being taken out of the system. Lost to air resistance or lost to regeneration inefficiency. It is still lost. When road load slows us, we lose all of that kinetic energy and stay at higher, more energy-robbing speeds for longer. When we regenerate, we recover some of that energy (while wasting some as well) and more quickly get down to more efficient, slower speeds.

> As far as your 70 to 30 scenario, I don't know if your assumptions are completely correct. The thing that you are missing is that if you brake hard early to get regen, you will then have to maintain speed, requiring propulsion power for a period of time to achieve the same point A to point B in a similar distance and/or time

Please don't confuse my purposefully simplified 70-30 scenario with making incorrect assumptions. I simply left out some of the details that should be (and happily were for you) obvious. And that you're thinking about them now is an important point of me bringing this up. Yes you have to add traction power for a bit longer to maintain 30 mph. But you've also recaptured some of the kinetic energy that was lost in the coasting scenario. And 30 mph creates significantly less wind drag. So the big losses happen the longer you're at higher speeds, bleeding energy into the air. That's my big point about how there are going to be efficiency differences - and EVERY driving situation will require a different amount of coasting and regen for max efficiency - but in the end the differences are going to be negligible except at the extremes. (I hope that we can avoid bringing up extreme examples in an attempt to disprove the most common scenarios). And speaking of extremes - please don't jump the scenario I proposed, to "brake hard early to get regen." Nowhere did I mean imply hard braking. Just like with acceleration, a moderate amount of regen is typically going to be more efficient than a huge amount.

I'm thrilled that you'll try to model this. For well over ten years I've tested this at full scale out here in the real world. I'll happily share those results when it makes sense to do so - though they're pretty well summarized in my last couple of posts!

> so I have not fully decided what is better

I can make it work out so that one is better than the other - just by picking the assumptions that give me the result I want. As you are modeling this, just keep your eye on how big (or NOT big as the case may be) the difference is between "better" and not so better. I'm quite confident in what you'll find in that regard - no matter which side of the graph each scenario lands on. As I've mentioned - I've already spent quite some time doing this in full scale. I'm just glad that we finally arrived at a point where I could bring up this crazy idea that seems to fly in the face of "coasting is always more efficient."

· · 6 years ago

By coasting I do mean no power input or braking. The rolling drag and aero drag are always there, whether you are accelerating (or climbing a hill) and when you are coasting, and when you are decelerating, too.

I drive in congested traffic, too, and sure there are times when you *have* to slow down, and then it is great to have regenerative braking to be able to reclaim a percentage of the kinetic energy. Since you are always losing the aero drag and the rolling resistance, regen is losing more energy than coasting; by definition.

Ecodriving involves learn about the traffic, the hills, the places where you can take advantage of conditions, etc. Coasting down a hill (aptly called "road candy") should be as easy as lifting your right foot. If you then get moving too fast, then use the brake pedal to get just enough regen to keep you safe. And if you learn how your car works in various places, you can fine tune your "coasting points". You can do this in traffic, too. Anticipating what speed will get you just close enough to the car in front of you *just* as they get moving again will save you a *lot* of energy. Keeping rolling even just a bit, is a lot better than having to "reinvest" all the energy it takes getting your car rolling again.

When your car is low aero drag, you can coast a *lot* farther and faster. When you pump up your tires to the sidewall maximum, this helps, too. Take a look at Dave Cloud's Dolphin, with amazing aero and DC drive (so no regen):

http://ecomodder.com/forum/showthread.php/ultimate-aerodynamic-car-dave-...

He is using SIXTY lead acid batteries (used ones) and he has driven the Dolphin ~200 miles on a single charge.

Darell, you're right about maintaining speed -- this is a fourth mode for longer drives on the highway, on flat ground. Climbing hills is like accelerating. Coasting is for when you are going downhill, or when you are approaching a stop or a slow down. Regen should be reserved for slowing down faster than coasting, only when this is required.

Both the Illuminati Motor Works '7' and the FVT eVaro have free-wheel coasting; and have regen on the brake pedal. The 7 has gone 214 miles on a ~33kWh pack, and the eVaro goes ~125 miles on a 21kWh pack. The eVaro get all of it's active braking from regen only.

Neil

· · 6 years ago

@darelldd "If you're going 70, and you see the traffic way ahead is going 30, you can "coast" and watch the wind rob the car of energy until you are down to 30 mph where very little of your energy is lost to wind. You never get that energy back that was lost to wind. Or you can regen the car a bit quicker down to 30 mph."

Two possibilities
- You keep going at 70 and then use regen to slow down to 30 quickly
- Slow down to 30 quickly and then spend energy maintaining that 30 mph

In both cases you have to spend quite a bit more energy than if you were to coast down to 30. Whether that energy spent is the same, less or more than the energy captured through regen needs to be tested (or calculated if you have the formulas).

BTW, in the second case above, you end up potentially with a large gap between you & the car in front inviting others to fill the gap which could be dangerous.

BTW, according to an older Tesla blog - regen is about 64% efficient (80 in and 80 out).

· · 6 years ago

> Since you are always losing the aero drag and the rolling resistance, regen is losing more energy than coasting; by definition.

This, unfortunately, is where your assumptions are off target. I have personally proved it time after time. Not in a model. But in the real world in a real car on real roads. There is no ONE way to be more efficient. Every situation calls for a different amount of coasting and regen to be the most efficient. Allowing the car to coast is definitely NOT using the least amount of energy in *every* situation. And even when coasting does use less energy, it isn't a significant amount that would add even 1% to the range of the car - so in the end, this whole discussion is all but moot. I'm not guessing at this, or using cold hard logic. I'm simply speaking from experience.

Yes, you are always losing energy to aero. And you are losing much MORE energy to aero the longer you stay at high speed. And every bit you lose to aero can never be recovered. As I said before - you can throw ALL of your kinetic energy away to air drag, or you can recover a bit of it with regen and re-use that recovered energy to maintain the lower speed for longer, or to accelerate back up to speed when needed. The car is (almost) always more efficient at lower speed. So the more time you spend at lower speed, the more efficient you are. Coasting keeps you at higher, less efficient speeds longer. I'd say, "by definition" but that just seems silly.

This is not as simple as "we aren't losing the recharge losses when we coast, so coasting MUST be more efficient." When we coast to slow down, we don't recover any of the energy. So we can't keep thinking of coasting as some super-efficient way to slow the car. We haven't even touched on the convenience aspect of coasting vs slowing the amount you want WHEN you want. But I'm sure we all agree that is another discussion.

Eventually I'll share an un-challenged specific example or two of regen being more efficient than coasting. But I'm holding off so that the discussion doesn't shift to simply disproving my examples - which from experience becomes either frustrating or boring. Or both.

If I had a single, simple take-home message here, it is this: If and when coasting to slow down is more efficient than using any amount of regen for slowing, it is not significant enough to even bother worrying about.

· · 6 years ago

> Two possibilities
- You keep going at 70 and then use regen to slow down to 30 quickly
- Slow down to 30 quickly and then spend energy maintaining that 30 mph

Sometimes I seriously wonder if anybody reads my posts. You really think these are the only two possibilities? Even when I already clearly stated that "heavy regen" wasn't what I was ever considering? Here is a quote from my post of just two posts above yours: "Nowhere did I mean imply hard braking. Just like with acceleration, a moderate amount of regen is typically going to be more efficient than a huge amount."

How about this for a possibility you have not considered:

- Assume that coasting from 70 to 30 takes one mile. Instead of coasting down, we get down to 30 using mild regen over 1/2 mile. And spend the other 1/2 mile at a steady 30 mph.

> In both cases you have to spend quite a bit more energy than if you were to coast down to 30. Whether that energy spent is the same, less or more than the energy captured through regen needs to be tested (or calculated if you have the formulas).

In the case where you maintain high speed longer, you use "quite a bit" more energy than in the second case. They will be *significantly* different from each other. How the second case compares to coasting is not nearly as obvious as you think, and would likely surprise you. You seem to have already made up your mind about the result without testing or calculating. In my third scenario, you'd be hard pressed to measure the difference in energy used as compared to coasting.

>BTW, in the second case above, you end up potentially with a large gap between you & the car in front inviting others to fill the gap which could be dangerous.

Yeah, we don't need to go there in this discussion. We're purely talking about efficiency. If we want to talk about practical or safety aspects of coasting vs braking to slow down, I think the convenience of choosing your speed directly with braking (regen or otherwise) will most often win. Certainly in congestion! We often don't have the luxury of slowing down over the course of a mile, do we?

> BTW, according to an older Tesla blog - regen is about 64% efficient (80 in and 80 out).
It will be different for every car, but ~60% is a good ballpark figure. How does that compare to the 0% efficiency of slowing down with wind drag? (no, I'm not ignoring the fact that you'll then have to maintain a slower speed for longer - just as you aren't ignoring the fact that coasting leaves you at higher, wind-energy-robbing speed for longer than braking)

Man, I'm just itching to give one example of regen winning handily... but the discussion is going along so well!

· · 6 years ago

@darelldd, A "special case" example of what you are talking about would involve going down a long hill. You can descend the hill using some regen at, say, 30 mph (case A). Or you can descend the hill by coasting up to terminal velocity*, perhaps 70 mph (case B). At the bottom of the hill in case A, the car is going 30 mph with some extra energy in the battery. In case B one is going 70 mph at the bottom of the hill and has some extra momentum (MV) but has collected none of the potential energy of descending the hill in the battery because it was all lost to drag.

If the hill is long enough, case A will lead to more range than case B because the extra momentum at the bottom of the hill when going 70 versus 30 isn't nearly enough to compensate for the potential energy lost to drag while at terminal velocity.

The reason, of course, is that drag increases approximately as the square of velocity and the energy needed to overcome the drag increases as cube of velocity (in the case of going down a hill the energy comes from the acceleration of gravity). Since drag isn't linear with respect to speed, slow speeds can more than compensate for the reduced efficiency of regen in some scenarios.

*Terminal velocity is when the acceleration due to gravity equals the deceleration due to drag.

· · 6 years ago

dgpcolorado -

"slow speeds can more than compensate for the reduced efficiency of regen in some scenarios."

Hello! And thanks for swinging by. Yes indeed - high speed coasting *can* throw energy away faster than regen + powered low speed driving. I've attempted to say that about four different ways now, and I welcome your attempt!

Of course, now I'm going to have to ban you from playing this game. You are considering all of the variables involved instead of ONLY worrying about the efficiency losses of regen. What fun is that??

That said, you've just outed one of my "proof" scenarios. One that I've tested about 100 times over the past 11 years. Mine goes roughly (well, roundly, actually) like this:

Test a:
Crest the 2-mile down-hill at 50 mph and lift off the throttle (to coast). Car accelerates down the hill to 70 mph in about 0.25 miles. Maintains this terminal velocity for 1.75 miles, then coasts down to 50 mph on the flat. End test. Amount of energy consumed from crest of hill to the point it reaches 50 mph: zero kWh.

Test b:
Crest the 2-mile hill at 50 mph and maintain 50 mph with regen for 1.75 miles. Release regen and the car accelerates up to 70 mph in the final 0.25 miles of hill. Car then coasts down to down to 50 mph on the flat. End test. Amount of energy consumed for the same distance traveled: Negative 0.1 kWh.

Test b with regen braking gained some amount of energy over the same distance (the roll-out distance to 50 mph is identical since in both cases the car was at 70 mph at the bottom of the hill) that test b gained zero energy with coasting.

Should we put this one to bed now, or does anybody still want to play the "coasting is always (significantly?) more efficient because nothing is lost to regen inefficiencies" game?

· · 6 years ago

The question is how far can you drive for a given amount of energy. Coasting allows you to "recover" more energy than does regenerative braking because you cover more ground for less energy this way.

When you must slow down quickly, then yes, regenerative braking is a wonderful thing. But if you have to use regen to slow down all the time, you have accelerated too much.

Neil

· · 6 years ago

Neil: I'm not sure very many people would(or could) drive how do(or describe). It sounds like there are no other cars on the road and you can drive like a hypermiler does all the time. That's just not how most of the population can(or wants to) drive. Yes people accelerate unnecessarily fast and then need to slow down quickly and repeat this time and time again as they drive down the road. They aren't going to change. Having regenerative brakes will help them recapture some of the energy they already wasted, coasting does not.
Saying "if you have to use regen to slow down all the time, you have accelerated too much" just isn't reality, at least where I drive(NY/NJ). There are just so very few circumstances where I can gently accelerate and then gradually coast to a stop in my driving environment. There are too many other cars in front and behind me to drive like that.

· · 6 years ago

> Coasting allows you to "recover" more energy than does regenerative braking because you cover more ground for less energy this way.

Sometimes it does. Other times it does not. Your position that coasting is always more efficient is not reflected in reality. And as I've already said too many times - during those times when coasting IS more efficient, it rarely is any significant amount more efficient than using a bit of regen. There are always edge cases to prove it one way or the other - but in the end, it is "best" to drive the way that is most practical, the safest for the situation, and the least dramatic.

I love coasting. I do it all the time when it makes sense. I have the luxury of owning cars that allow easy coasting, and I have the luxury of sometimes driving in areas where I can make great use of it. Coasting forces you to look farther ahead, and I contend that it makes you a better/safer/more efficient driver as a result. Yet the fact of the matter is that coasting doesn't always make sense, and is not always the most efficient way to slow the car.

> The question is how far can you drive for a given amount of energy

Right! And the answer is to not always coast, as dgp and I have already described in excruciating detail. And the energy use difference between always coasting and sometimes using some regen is going to be very difficult to measure.

I'm not sure how many different ways I can say this same thing, but I guess I'll keep trying until somebody cries uncle.

· · 6 years ago

Hang in there darelldd! My next step was to pull out the drag equations and "plug-in" some actual numbers to show how "squares" and "cubes" drastically change energy consumption at different velocities. And I really don't want to do that because I'm lazy!

· · 6 years ago

dgp - you've never struck me as the lazy type, but I'll take your word for it. ;)

Yes, speed differences (and the resulting energy consumption (loss?) difference) is what makes this whole situation more complicated than, "it is always more efficient to coast". High-speed driving and low-speed driving are not the same animals. I keep waiting for somebody to point out that the hybrid hypermilers NEVER use regen to achieve their amazing efficiencies. But now I guess we've given up the response to that one as well... Show me somebody who hypermiles at high speed, and I'll show you somebody who doesn't hypermile.

· · 6 years ago

Darell, I finished my model and put a few driving scenarios in and I apologies for the long posts but here are my results.

Assumptions
Mass = 1500 kg
Coast Down F terms
F1 = 30 lbs
F2 = 0.4 lbs/mph
F2 = 0.03 lbs/mph^2 (note: this is high for most EVs but I wanted to make sure the aero affect is worse case)
Wheel to battery efficiency 65%

Driving Scenario #1 = 70-30 mph coast vs. 70-30 with 0.15g regen (I hope you don't consider this "hard" braking. I can re-run with a different braking level if you want) and maintain 30 mph (requires propulsion power to counter road load power) until distance is the same as coastdown.

Results:
70-30 coastdown
Time = 51.5 seconds
Distance traveled = 1066 m
Energy into the battery = 0
Energy out of the battery = 0
Net energy used = 0

70-30 regen with 0.15g regen to 30 mph then constant speed
Time to 30 = 9.5 seconds
Total time 74.1 seconds
Distance traveled = 1066 m (matched coasting
Energy into the battery during regen = -84.7 W-h (negative energy is charging)
Energy out of the battery during constant speed = 111.4 W-h
Net energy used = 26.7

Conclusion: There was a net energy usage when regenerating then maintaining speed vs coasting so coasting is more efficient.
If wheel to battery is 100% efficient, the net energy INTO the battery would be 58 W-h and it would be more efficient to regen first for reasons Darell gave (getting to a lower speed where aero drag is less) but the round trip energy losses more than make up for the aero losses. The break even efficiency point (for this driving scenario) is around 75% wheel to battery. Another issue is that it took over 45 kW of power to decelerate 0.15g at 70 mph. This is higher than most HEVs can achieve so efficiency would be worse if I assumed a 30-35 kW power limit. Also, coasting took less time to achieve 30 mph and the speed is always larger than decelerating first. Therefore, if at any time, the driver decides to accelerate back up, less energy is required when coasting first.

· · 6 years ago

Driving Scenario #2 = Driving at 60 mph and approaching a vehicle doing 30 mph 100 m ahead. The purpose of this test is to match speed, distance and time with 2 braking scenarios. 1) coast first and apply 0.15 g regen when required to match speed of the 30 mph vehicle ahead, 2) apply 0.15g regen first to a speed between 60 and 30, maintain speed until approach the 30 mph vehicle and apply 0.15 g regen when required to match speed of the 30 mph vehicle ahead .

Results:
60-30 coastdown then apply 0.15g regen to match speed and time of lead vehicle
Time = 11.6 seconds
Distance traveled = 255 m (note: the 30 mph vehicle ahead traveled 155 m during this time)
Energy into the battery = -49.3 (negative energy is charging)
Energy out of the battery = 0
Net energy used = -49.3

60-30 with 0.15g regen first, maintain speed, then apply 0.15g regen to match speed and time of lead vehicle
Time = 11.6 seconds
Distance traveled = 255 m (note: the 30 mph vehicle ahead traveled 155 m during this time)
Energy into the battery = -63.5 (negative energy is charging)
Energy out of the battery = 37.0
Net energy used = -26.5

Conclusion: Coasting first resulted in more net energy charge so was more efficient. Again, the reason is the wheel to battery efficiency. Without the break even point for this scenario was over 97%. This break even point is so high because this scenario is a point A to point B in the same time and distance.

I ran a few more scenarios but have yet to find one that is more efficient to regen first. I will be happy to run anything other scenarios that anyone wants.

· · 6 years ago

The problem with these scenarios is that they assume initial deceleration all the way down to 30 mph, thereby creating the need to expend energy in order to maintain 30 mph henceforth.

I believe the most efficient scenario would be to immediately use regen to slow from 70 mph to, say, 45 mph. Then coast down to 30 mph. That post-regen speed (45 mph is a guess) needs to be high enough to permit coasting until the driver is forced to slow or stop anyway. Thus, one maximizes regen while still avoiding the need to expend energy.

· · 6 years ago

I will try to add you hill crest test to my model. This will take some time to add grade affect.

· · 6 years ago

Thanks regman! I was beginning to get worried about you. ;) I appreciate you taking a stab at these.

I have several (OK, more than several) questions about your model assumptions. But before I even get into those (ah, abasile has already pointed out some of the complication with linear assumptions... not the way we normally drive), I want to ask how excited you are about a few tens of Watt hours either way from a vehicle that uses about a thousand Watt hours to drive just four miles. Would it keep you up at night?

Also, in a broad way, I wonder how much confidence you would have in your models if full-scale, real-world testing showed different results. If you can model something that shows my hill descent example using less energy when coasting... we have a problem. A direct conflict of model and reality.

I like that you showed where the break-even point was in regen efficiency for your model assumptions. That's quite interesting for me. Another interesting number to find would be that start speed that would get us to break-even with your regen model assumptions. In fact, I wonder if your assumptions will ever reach a break-even start speed. It may be that we can only search for the "sweet spot" or "least lossy" start speed.

Good stuff. I'm glad I got you scratching your head about it more!

I've gotta stop... time for a ride. And I'll tell you what - NOBODY tries to conserve momentum more than I do on a bicycle!

· · 6 years ago

Abasile, I agree, coasting will never beat regen then coast under the condition you described but you are comparing apples to oranges. The regen first then coast will achieve the final speed in both a quicker time and shorter distance. To get a fair comparison, you must match either the time, distance or both. Think of it this way. If you are traveling 30 mph and want to come to a stop at a stop sign that is a half mile ahead. You could coast the whole way to a stop (lets assume the half mile is what it takes too coast down from 30 without any brakes), or you could regen down to a speed then coast to a stop but it would take less distance and you would stop well before the stop sign. To travel the same distance, you either have to maintain speed (under power) until you get closer to the stop sign or regen to a lower speed then maintain that speed (under power) until you get close enough to coast the rest of the distance. Either way, there has to be a time period where you operate under power. You are not considering this power usage in your comparisons.

· · 6 years ago

@ regman -

I need to let Abasile answer for himself... but I don't think he is ignoring your "same distance" aspect of the models. He's just saying that it may be better to not brake at a constant rate from speed A to speed B. But instead to brake for a shorter period (maybe not as hard, or even linearly!) and then coast a bit after the vehicle has slowed to between speeds A and B. Think of it as a hybrid of your examples - with a bit of calculus thrown in for good measure. We don't brake or accelerate linearly very often or for very long. Yes... even when we coast.

What would be neat to see is a chart showing Velocity vs time of a car coasting from 100 mph to zero through still air. I already know how it would look, but it would be great to have that as a background, and then we could all draw on it with lines showing our different scenarios and assumptions.

For the record - for anybody who wants to give a shot at modeling - 30-35mph is considered the sweet spot for EV efficiency. Below that, rolling resistance starts to overtake the air resistance. About that, and air resistance rises exponentially. They're about balanced in that speed range, and I know from experience that an EV's range can be extended 50% or more by spending time in that zone vs, say, 65 mph. Traffic jams are your friend.

Wasn't I supposed to be out riding?

· · 6 years ago

Darell, "I want to ask how excited you are about a few tens of Watt hours either way from a vehicle that uses about a thousand Watt hours to drive just four miles. Would it keep you up at night?"

Actually, it would keep me up. A loss of 25 W-h every brake event is a loss of 10 miles range if you just have one brake event per mile. (25 w-h per mile x 100 miles = 2.5 kW-h out of 25 kW-h). and most drivers average over 5 brake events per mile. So 25 W-h is a lot and it will add up.

· · 6 years ago

Yes, I would have to agree with Darell. You brake (regen) early so as to convert some kinetic energy into battery battery instead of losing it to high-speed aerodynamic drag. Then you ease off the brakes while retaining enough momentum to cover the remainder of the distance by coasting. This of course takes more time, but it helps to extend your range.

On the other hand, if the distance to cover before stopping (or markedly slowing) is great, you're generally better off just coasting unless you're descending, or about to descend, a long hill.

I don't have time for the math right now, but yes, some charts could be helpful.

· · 6 years ago

> Actually, it would keep me up. A loss of 25 W-h every brake event is a loss of 10 miles range

Good to know. Also good to know that this isn't the case (that 25 w-h will happen with every - or even most - regen slowing events). A 10% range reduction is huge. It doesn't happen like that out here in the real world. We use braking in two of three driving modes. On flat or down hill. We rarely use it on up-hill. On the flat, it may cost us a little to use regen. On down hill we can recover a little bit instead of coasting at terminal velocity.

And that brings us to the second question: Model vs practical application. Which holds more weight for you?

· · 6 years ago

> On the other hand, if the distance to cover before stopping (or markedly slowing) is great, you're generally better off just coasting unless you're descending, or about to descend, a long hill.

Right! Generally, as you say... and depending also on the speeds involved, and traffic and other outside factors. In the end, we find that in real driving, using a bit of knowledge and skill to blend both types of braking to their maximum advantage - the difference of "better off" and not so better off isn't much either way. Nothing that would even keep regman up at night!

· · 6 years ago

@regman

Thanks for the calculations. Helps put some things into perspective.

With Leaf - I can do some interesting tests. When I charge to 80% I can do full regen, but when I charge to 100%, I can't do any regen for a while i.e. pure coasting. Near home where I've a few gently slopes and some flat portions, without touching the A pedal I can travel a couple of miles. This is where coasting really shines.

· Leaf Driver (not verified) · 6 years ago

This article seems hollow without commentary on the Leaf regen technology -- which I would characterize as similar to an ICE (light regen) in normal mode, and perhaps double the regen in ECO mode, but still pretty soft. Slowing from 30mpg with foot-off indicates -1 unit on the power gauge in the normal mode, and -2 in ECO mode.

Experience suggests that ECO mode is relatively useless - as far as I can tell, it remaps the pedal response curve and not much else. Upon engaging ECO, the range indicator jumps by 10-20%, but within a couple of miles, has dropped back to about the same endpoint.

Regardless of how much regen is on the A or B pedal, driving for range would seem to preference early long steady slowing, maximizing the opportunity for regen, rather than coasting until the last minute and slowing abruptly, which may exceed the power recovery of the motor and require frictional braking. By contrast, in an ICE driving for economy, long soft braking vs. short abrupt braking are both frictional losses, and deferring braking to retain speed as long as possible seems to maximize the potential economy. For example, in stop-and-go traffic, in an ICEV there is more premium on maintaining a steady average speed even at the cost of occasional sudden stops, while the EV can be fit the the stop and go traffic pattern with more efficiency.

· · 6 years ago

> while the EV can be fit the the stop and go traffic pattern with more efficiency.

This is for SURE the case. EVs do far better in stop and go than an ICE could ever hope for. It is amazing to me that our mail is still delivered by gas-burning vehicles. :sigh: There was a time there when the PO used some Ford EVs... but soon after that program started (with public money, btw!) Ford decided to offer the PO a deal on their gas vans that couldn't be refused. Neat for Ford - they got to sell 2x the number of vehicles for the same program!

· JeffN (not verified) · 6 years ago

I measured 60-5 MPH in 'L' shifter position in my Volt today on the drive to work. I had a long stretch of expressway and no cars behind me and a red light ahead. I took a video of the driver display with my iPhone and then measured the timing after I got into work.

It took 20 seconds to go from 60-10 and another 4 seconds to go from 10-5 so a total of 24 seconds for 60-5 MPH. The Volt does 0-60 in about 9 seconds in EV mode so I suppose a round-trip of 0-60-5 would be something close to 33 seconds.

That's slightly less than half the deceleration of Tom's 10 second result on the Mini-E but still usable for one-foot driving most of the time except for the last few MPH. If I also step on the brake pedal lightly it feels as if I'm increasing the regen further but it's really hard to know when the regen stops and the friction begins without having a fancy OBD-II scan tool. Supposedly GM has said that the Volt can regen up to 60 kW but I don't know if anyone has validated that yet with a scan tool.

· · 6 years ago

Darell, I was somewhat aware of the USPS program to buy EVs from Ford around 10 years ago but did not know what happened to this. Do you know of any ariticles that state the reasons for stoppoing the program. The only thing I could find was a USPS history pdf file (about.usps.com/who-we-are/postal-history/electric-vehicles.pdf) that stated
"In October 2002, Ford advised the Postal Service that it was cancelling its electric vehicle program and that the producer of the vehicles’ battery pack, East Penn Manufacturing Company, Inc., was planning to end production.... Other factors that influenced the Postal Service’s decision to exchange the vehicles were: the Ford EV’s limited range, water pump and wiring harness problems, the cost and uncertain success of long-term battery storage, and the uncertainty of successfully maintaining the vehicles after their warranty period."
According to this, they had a few performance and technical problems but the main problem was battery supplier issues.

· TjKinMT (not verified) · 6 years ago

I tried the 0-60-5 mph test in a LEAF this morning. It went from 0-60 in about 10 seconds each time I tried the test. I did it in ECO mode and then Drive mode. The 60-5 took about 60 seconds in ECO mode and 70 seconds in Drive mode. I did the test over the same stretch of flat road in each direction in case there was a slight change in elevation.

· · 6 years ago

Nice job TjKinMT. I'm surprised at how much less aggressive is than the volt. I knew it would be way less than the MINI-E, but not so much less than a volt. I've driven both and I thought the regen was a bit stronger on the volt, but comparable. I guess it's really not.

· TjKinMT (not verified) · 6 years ago

I was expecting more in the econo mode. If it is only a software upgrade it sure would be nice to be able to set it to my driving style.

· · 6 years ago

This is interesting. Based on the 60-5 times of the 3 vehicles, the MINI E has an average deceleration of 0.22g, the Volt 0.11g in L and the Leaf 0.04g in eco. I too am supprised that the Leaf is so much less aggressive. In fact, I believe this eco gear is about the same as a gas vehicle in L.

· · 6 years ago

I had an opportunity to briefly "test drive" a prototype RAV4 EV this morning! (It got charged at my house, which is in the PlugShare network, on its way to Big Bear Lake, CA at 6750' elevation.) Especially for an SUV carrying around a 36 kWh pack, I found the vehicle peppy and fun to drive. Driving around my little mountain town, the A-pedal regen didn't seem to be noticeably stronger than ECO mode in our LEAF.

· · 6 years ago

abaslie: It sounds like Toyota must have dialed back the regen a bit then. Brad observed that the RAV 4 EV he drove had the most aggressive regen he'd ever experienced, and he's driven just about every EV. Maybe the one he drove last spring was still being modified. I think you would have really noticed a difference if it was as strong as what Brad described.

· · 6 years ago

TjKinMT · @ "The 60-5 took about 60 seconds in ECO mode and 70 seconds in Drive mode."

Is this with no brake applied ? How many regen circles were lit ?

· TjKinMT (not verified) · 6 years ago

I just took my foot off the accelerator and let it "coast" to a stop. The brake pedal was not used. I do not recall the number of regen circles lit. I will try it again this weekend and try to monitor that also.

· · 6 years ago

@TjKinMT

Yes, the regen is strongest only when you brake lightly. If you can try that as well, would be an interesting stat.

· Anonymous (not verified) · 6 years ago

Whew... Read the whole discussion. Well i imagine that the best solution will be something like this:

On a steering wheel you have 4 buttons for different modes. The sequence of modes is doesn't matter, it's just example

1) "Coasting". In this mode you just coasting after taking foot off the A pedal. On B pedal Strong regen mixed with friction braking in most energy-efficient way.
2) "A-pedal regen" mode. Mode for single-pedal driving fans. Now you have strong regen on the A-pedal. Situation with B-pedal is the same as in "Сoasting mode"
3) "Maintaining velocity" It's not a mode actually, it's just a simplified cruise control. You achieve desired speed at any previous mode, then you push that button and this speed automatically maintained (within as possible wide limits) without necessary of holding foots on pedals, regardless of the slopes, until you tap the B or A pedal. Then you return to previous mode.
4) "R" - Just reverse. The A-pedal behaviour is the same as in 2nd mode.

So, every mode can be chosen in motion depends of driver's preferences (except "R" ofcourse).

Sorry for possible grammar mistakes. English is not my natural language.

· · 4 years ago

Dear members of PluginCars,

I am currently joining Climate-KIC, which is a summer school funded by European Union. The aim of the summer school is to develop an innovative business idea that can help to mitigate climate change.

My group's business idea is called "Blow Batt". The idea is to have Supercharging stations for electric cars on highways, in which the energy is generated using wind energy from existing wind farms near highways (So we are going to be partners with the wind farmers).

As you all might know already, it takes approximately 20 minutes for a Supercharger to deliver a half-charge. The reason why we are putting Supercharging stations on highways is so that electric car drivers who are in hurry to get somewhere can charge their cars instantly. The other reason is so that long-journey drivers who are low on battery can charge their cars at Blow Batt.

As I recognize that all of you are members of PluginCars, I am writing you this post to ask if it would be possible for you to help my project by filling in the questionnaire below:

https://docs.google.com/forms/d/1TPFa85GYd9-o4ot9rEXcjjnxldkkpJvajeTKAEF...

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Thank you

Priska Prasetya

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