Stupid modes again. If the accelerator and break peddles are in the home position the system should use enough regen breaking to keep the car at the current speed, not let it speed up coasting down hill or slow it down. When the break peddle is pressed the first part of the travel should be regen. If the break peddle is pressed hard, the system should apply the hydraulic breaks. When the accelerator peddle is pressed and regen is on, regen should be released slowly and then power applied to the electric motor. If the accelerator peddle is pressed hard, the system should accelerate as much as possible, regardless of any idiotic mode setting. So simple, but the manufactures seem blind to the simple solutions.
Honda Reinvents Regenerative Braking for Fit EV
As we discussed in October, the secret sauce of a good electric car is not how it accelerates, but how it brakes. Yesterday, I had two short rides in the Honda Fit EV at the company’s Twin Ring Motegi complex north of Tokyo—prior to my visit to the 2011 Tokyo Motor Show today. My driving impressions from behind the wheel are embargoed until Dec. 5—but I’m free to report on my discussion with Kunimichi Hatano, the engineer who created Honda’s new regenerative braking system.
Honda’s strategy rests somewhere between what Ford will do with the Focus Electric—make it feel like any conventional car without special modes or gears—and BMW’s strategy. Electric Bimmers will brake in an aggressive and distinct way, according to Aaron Singer, BMW product strategy manager. The Fit EV's braking is perhaps most similar to the one found in the Nissan LEAF, with a couple of key exceptions. Honda’s Mr. Hatano explained that the goal is to make the brake feel comfortable and familiar—yet the Fit EV will have a “B” gear, providing the driver the choice to engage an aggressive motor-only regen setting, as well as an “Econ” mode that removes regenerative braking in a coasting-type function. The current LEAF lacks such driver-managed controls.
Honda brake engineer Kunimichi Hatano. (Photos by Brad Berman.)
Again, I can’t speak yet about the relative level of performance achieved when toggling between Normal, Sport and Econ modes. But what’s important here is the role that Honda’s new electro-servo brake system—the first of its kind—in yielding about 75 miles of real-world range, and123 miles of range (in the forgiving LA4 cycle). The Fit combines a 94 kW motor and 20 kWh battery pack. (Honda is not yet sharing details about the weight of the Fit EV, but it's bound to be lighter than the LEAF.)
So far, the Fit EV is the only Honda car that has been (ahem) fitted with the new system, but it is also slated to go into Honda’s upcoming Accord-sized plug-in hybrid—which I also was able to drive yesterday.
Here’s an excerpt from my conversation with Mr. Hatano.
Many EV drivers like very aggressive regenerative braking. Why not give a unique aggressive feel to regen braking in your electric vehicles?
Honda does not intend to reduce the amount of regenerative braking to achieve satisfactory brake feeling. Obviously, we want to recuperate as much energy as possible. But if you try to recuperate too much energy, you might destabilize the vehicle. The question is how much energy can we recuperate without going over the threshold of losing stability. You have to bear in mind that vehicles are driven under bad weather, in snow, and rain, and when the road surface might not be good. You have to make sure the regenerative braking doesn’t go beyond what is reasonable.
But it can feel different and still be safe, right?
Sure, some prefer a different feeling. Whatever kind of brake feel you want—whether it’s like normal gasoline-powered cars or different—that’s one subject. And the limit of regenerative braking is another subject. The limit is more about preserving stability. Because this is an electric braking system, you can fine-tune the taste in many different ways.
How is the electro-servo braking system different than its predecessors?
In our system, you have two different main parts. In the first part, you create the brake feel. This is quite common with other carmakers. The way our brakes feel might be different, but the system is not very different. However, what is different is the part that actuates the brakes. Traditional hydraulic brakes use a vacuum to activate the brake system, and then pump oil to press the pads against the rotor. A hybrid system may use solenoids. Our new system is different because the medium to apply the brakes is using an electric motor to directly drive the pump that serves the brake fluid.
Honda slide showing benefits of new electric servo braking.
What’s the advantage?
This system has very high accuracy. This means more efficiency. It’s more faithful to the brake input from the driver. [Honda estimates that the servo-based system increasing efficiency by at least 5 percent.]
When you take your foot off the accelerator, you immediately have a little bit of regenerative braking. Then, you put your foot on the brake—and if you look at the curve on the hydraulic system, it goes up very sharply. But if you look at the yellow zone in the graph, [in the old system] the regeneration doesn’t go up as sharply and it’s delayed. The idea of the new system is to bring the regenerative yellow zone closer to the hydraulic response.
The first part of the slope is very similar to the hydraulic. Then, as you start reaching the regeneration limit, the slope gradually slows down a little and reaches the limit after what the hydraulic system can do. After that, you can keep regeneration system at the highest level longer than the current system. And just before you stop, the drop is even sharper than the old regeneration system.
All of this is possible because of the servo system? Could you have done this just with calibration?
No, you need the accuracy to achieve it.
Does the increased regenerative braking mean slowing down faster?
The braking distance itself is not shortened by this alone. The braking distance is determined by the weight of the vehicle, the speed, and the amount of energy you take out either by regenerative braking or traditional braking, and the tire grip. This system doesn’t mean that you’ll shorten the braking distance. That depends on the caliper or other brake operations.
How does the “B” gear mode affect regenerative braking?
B is for higher regeneration only when the throttle is off. If you are in B mode, it's only regenerating energy through negative torque at the motor level. [There’s no use of the brakes.]
And what’s the effect of Econ mode?
In the econ mode, on the contrary, it reduces the engine brake effect so the car can coast. The idea is to reduce the up and down demands on the engine—by having less engine braking, which means you don’t lose as much as speed.
The B mode is made to suit certain driving situations, like when you’re going down a slope and you see a red light at the end. You put it in B to recuperate energy, so you slow down, which is fine. And if you see the light changes to green, you just put it back into D. It’s a question of responding to all possible driving situations.
Postscript
I can guess that many PluginCars.com readers will like the sound of Honda’s approach—but the nagging question remains: Why is the company only producing 1,100 Fit EVs over the next three years, and not allowing customers who might fall in love with the car the ability to keep it beyond the lease period? Company officials here repeated the same “one step at a time” message—that they want to learn as much as possible from the first customers in order to refine the car into the best possible EV.
I spoke with multiple high-ranking executives to encourage them to reconsider—especially if it looks like the Fit EV is a winner. It’s too early to know, but I have a glimmer of hope that Honda could reconsider its lease-only approach and/or increase production. If indeed the Fit EV represents an improvement in electric car braking, along with controls for higher regen and coasting, it will only be a matter of time before competitors offer similar features in their battery-powered cars. Honda's apparent technology and feature advantage could evaporate in three years, just as the company is collecting and processing feedback from the 1,100 Fit EV leaseholders who have the distinction of driving the car. That would be a shame.
About the author
Bradley Berman is the editor of PluginCars.com. Brad writes about alternative energy cars for The New York Times, Detroit Free Press, Reuters and other publications. He is quoted in national media outlets, such as CBS News, ABC News, CNBC, CBC, and MarketWatch. Mr. Berman is a tireless researcher of the green car market. He is the transportation editor at Home Power magazine.
Comments
· Charles (not verified) · 24 weeks ago
· regman · 24 weeks ago
Brad
Great article. So according to Hatano-san, coasting is more efficient since they implement no/minimal lift A-pedal braking in Honda's econ mode. Interestingly, this is the opposite approach of BMW which puts its heaviest regen braking in their Econ Pro mode implying that heavier lift pedal braking is more efficient. Everyone that knows me will know what side of the fence I am on but maybe we could get Hatano-san to elaborate on this point and tell us why Honda thinks BMW is incorrect (or the other way around).
· Chris T. (not verified) · 24 weeks ago
The Karma has three regen braking modes: "normal", "hill 1", and "hill 2" (represented on the dash display by D, 1, and 2 respectively). The idea is that in D, taking your foot off the accelerator does nothing, while in 1 and 2 it slows the car down with regen-braking in "mild" or "aggressive", much like engine braking with a manual or auto-transmission car in a lower gear. What's a little bit backwards here is that "1" is like having your auto-transmission car in "2" and "2" is like having your auto-transmission car in "1", in terms of braking-ness.
Unlike the Tesla, the brake lights never light when using this regenerative braking. Also, although I only drove the Karma around the parking lot (so far—I get a second test drive on "real" roads and freeways before I put down the $5k...), it only seems to kick in the braking if you take your foot completely off the accelerator. I think the Tesla Roadster's method is superior. Still, it's not terrible, and I'm likely to drive around in "1" most of the time.
Note that actually using the brake pedal in the Karma also kicks up the regen. I could not tell by feel when it went from regen-only to regen-and-friction-brake (it might be easier to tell at higher speeds, or maybe not).
Given that in an electric car, much of the controls are (or should be) in software, it should be possible to update them. It would be nice if we could tweak the settings to "user preferences". Some people like sharp brake feel and some people like mushy brakes....
· alt-e · 24 weeks ago
Labeling something "econ" is just labeling something. You have to look at the physics of each situation in order to tell what is the most efficient for that case.
If your EV is in motion and you wish for it to continue in motion then regen can only take that energy away. Remember that every time that energy is converted from one form to another, energy is lost. So if something goes into regen and recharges the battery, the next time you accelerate you won't get it all back. So coasting is the most efficient thing to do if you want to keep your speed.
On the other hand, you don't get anything back from friction breaking. So having as strong of regen as is possible is what you want for stopping or otherwise slowing. Or if you are going down hill at a rate that causes you to go faster then you are wanting to go.
However the control system is set up, the best regen is one that allows the driver to coast when the driver wants to coast and regen up to a very strong level whenever the driver wants to do that. The controls should be easy to use and obvious to anyone who gets in the car and drives around for a few minutes.
I think the exact way to do this is really a preference issue. What I have always favored is coasting when you are touching nothing and a break pedal that has two springs: a soft spring under which it is all regen and, eventually, as you press the pedal further, a stiff spring where friction braking begins. This way the driver knows what is going on and can choose to ease off the pedal in order to stay in the regen range if appropriate.
But the controls could be any number of other things, such as shifting, buttons or nobs. I just like keeping it as simple and obvious as possible.
· darelldd · 24 weeks ago
Great article, Brad. So refreshing to hear an interview where both the asker and answerer (??) know some stuff! Really the only thing missing is the part about modulation of regen on the A pedal. I understand the selection of amount of regen... but is it on/off, or modulatable? OK, I'll stop making up words now.
@ Regman - it really isn't any mystery why the different companies are calling the opposite regen situations "econo." It all comes down to what you expect to achieve when you lift your foot from the A pedal.
BMW seems to assume that you'll want to slow down when you lift your foot. And the most efficient way to slow down is to recapture as much of the kinetic energy as possible. If you don't wish to slow down, you don't lift your foot all the way off the A pedal. If you wish to slow, you modulate the A pedal further to choose as much regen as needed to slow you down - without friction brakes. BMW combines the most efficient way to cruise (ability to coast) with the the most efficient way to slow.
Honda (and others) seems to assume that you'll want to maintain momentum as long as possible, and in general that means taking as little energy out of the system as possible. If you need to slow down faster than coasting allows, you'll have to move over to the B pedal, and combine some friction with some regen. Honda has arguably the easiest way to be efficient for coasting, and less efficient way for slowing more rapidly.
Neither one is incorrect. It is all about expectations. BMW is "econo" because it slows the the car in the most efficient way. Honda is "econo" because it coasts down in the most efficient way. The secret is that BMW can achieve exactly what Honda does by controlling the A pedal (this aspect is usually missed by the "let's keep doing it the old way" crowd), but the Honda won't be able to do what the BMW does (This assumes the Honda's A pedal regen won't be as stiff as BMW's as implied in the article... and that Honda's won't be as modulatable.) That's not a new made-up word. I made it up earlier already. Doesn't count.
And while banging this out, I see Alt-e said very much the same thing I was going after. It all depends on what you are trying to be most efficient at.
· regman · 24 weeks ago
Darell,
"If you need to slow down faster than coasting allows, you'll have to move over to the B pedal, and combine some friction with some regen."
This statement is totally incorrect. Both systems will achieve the same level of regen prior to applying friction brakes. The difference is that the request for regen in the BMW may come only from the A-pedal and the request in the Honda (and Ford and Toyota and GM and Nissan and any other vehicle with brake-by-wire system) may come from both the A and B Pedal. In both cases, friction brakes are not applied until the motor/battery regen limits are reached (see the upper left green corner of the last chart). For a given level of deceleration, the only difference is driver preference, controllability (easily modulatable-no I didn't make up this word, you did), recovery from vehicle instability and perceived efficiency.
Based on the chart, it appears that the old Honda system was not capable of completely holding off friction brakes but the new one can. Toyota, Ford, GM, and Nissan's systems already had this capability and therefore, this appears to be a "reinvention" of Honda's brake system and not a "reinvention" of regen brake systems in general.
Hatano-san also mentions several points that I have brought up in previous posts that give the advantage to coasting. The biggest one is the tendency to over-brake with heavy A-Pedal systems "The idea is to reduce the up and down demands on the engine [motor]". This is the main reason why I (and any hypermiler) insist that coasting is more efficient. And yes, there are exceptions to all rules, the main one is going down a hill where you don't want to coast to a terminal velocity (or >10 MPH over the speed limit).
· regman · 24 weeks ago
Brad,
Hatano-san talked about B Mode and Econ Mode but in your intro to the interview you mention "Normal, Sport and Econ modes". I assume normal provides ICE like A and B-Pedal, Sport is the B-Mode and Econ is Econ. i.e. there are 3 selectable modes.
· NeilBlanchard · 24 weeks ago
It sounds like Honda has it about right. Coasting uses the kinetic energy in the best way -- to carry the car forward, which is the whole point. Coasting downhill is "road candy" (great term coined by someone else) and is the most efficient way to drive. Several of the most efficient EV's that I know of have easy coasting: Dave Cloud's 'Dolphin' (200+ miles on a lead acid pack with DC drive and no regen at all), Illuminati Motor Works '7' (210+ miles on ~33kWh lithium pack with AC drive), Edison2 'VLCe' (90+ miles on a 10kWh lithium pack with DC drive), and FVT eVaro (125 miles on ~21kWh lithium and AC drive). The FVT eVaro has a 20kW serial hybrid "range extender" as well.
On the Honda Fit EV, will you be able to tell us more about the battery pack, etc. on December 5th? They certainly should sell this car in quantity to meet demand. The Fit is an excellent chassis and they have apparently improved the aero, and I think it is the best EV from an OEM, so far.
Neil
· regman · 24 weeks ago
Neil,
95% agree. Can't give you 100% (although I agree with your statement that Honda has it right) because there is one situation of coasting down a hill that is not as efficient: coasting at terminal velocity (where the gravity forces match the aero forces). In this case, it is more efficient to slow down with regen until you get close to the bottom of the hill where you want to go back to coasting and achieve the maximum velocity when you hit the bottom. This was the only scenario that I found regenerating to be better than coasting. Therefore, as long as the vehicle is speeding up while going down a hill, you want to coast. If the vehicle stops speeding up, apply some regen. With this said, you don't want to apply more regen than what the battery can absorb and this is where A-Pedal regen has the advantage because with B-Pedal, it may not be easy to tell when friction brakes have come on.
· regman · 24 weeks ago
I should note that Darell pointed this scenario out in a previous post so I want to give credit where credit is due however all other scenarios that I have looked at, coasting was the same or better.
· darelldd · 24 weeks ago
Aw shucks. Thanks. ;)
As we all know, coasting is typically better (with an exception or two), if maintaining momentum is the primary goal. Nobody questions that. And none of us has challenged that (though that keeps being implied for some reason). The question that I've tried to deal with (and I fully admit that I get pulled off subject often!) is the braking aspect. That part of driving that we all have to do at some point. If we could always coast up to a stop, or coast down to the correct speed when we need it, then we wouldn't have this vibrant discussion. But we don't always have that luxury. In congested areas, we rarely do. Coasting can always be maximized (I certainly do it!) but can't always be achieved out on the road. So really, it would be great to just stipulate that coasting is typically good when you can do it - so we can move on to the braking aspect. That's where the action is. That's where we still have some discussion. Efficiency, convenience, safety. The goal is to optimize all three. And we all know where I stand on that!
More responses to the above comments when I have more time!
· darelldd · 24 weeks ago
> Coasting uses the kinetic energy in the best way -- to carry the car forward, which is the whole point.
Correct, of course. Except for the part about this being the "whole point." This article references a previous one that Brad wrote, and correctly claims that we already know how to move the car forward the most efficient way. We can put that to bed. In general, coasting is good of you wish to keep rolling at an ever-decreasing speed on level road. There. Done.
No... the point of this article and the previous one is BRAKING. Regenerative BRAKING. This has very little to do with coasting (unless you have miles to come to a stop every time). It has to do with the most efficient, convenient and safe way to slow a car when it needs slowing... while driving on the road. NOT how to be most efficient when you want to keep it rolling.
Should I say that again? Coasting is good when you ant to keep going. It is the BRAKING aspect that we (and the car makers!) are trying to sort out. Coasting and braking can both be done with A-pedal and B-pedal systems (another huge point that seems to get lost for some reason. It keeps being implied that A-pedal proponents don't think that coasting is efficient). The only question is: Which is the most convenient, the most efficient and the safest way to get a car from point A to point B. Heck, we might as well add in most fun just so we don't get all boring.
Can we all get on that same page?
· darelldd · 24 weeks ago
> This statement is totally incorrect. Both systems will achieve the same level of regen prior to applying friction brakes
Outstanding! I hate being accused of going "part way." Go big or go home, I always say! I'm not just incorrect. I'm *totally* incorrect. Sweet!
So... this all hinges on the interpretation of that tiny chart up there. I admit that I don't see that detail the same way you do, and I'll get to that later. If you are correct that the new Honda system is 100% regen until the max has been reached, then I stand *totally* corrected, and am truly thrilled. This is how it *should* be. Up until this point, it was NOT like that, of course. And my statement would have been *totally* correct - if we were talking about any other car on the road! Man, so close!
The new Honda system will be the first time I've heard of it operating this way - and for good reason. Up to this point, the only way to make the transition from regen to friction seamless, was to have the friction pads doing their thing - at least a little bit - every time the B-pedal is used. If this new actuator technology can achieve what you read that chart as saying, then I'm thrilled to be totally wrong. This means that B-pedal braking can finally be as efficient as A-pedal regen. Outstanding! If true, we only have two remaining items to debate on this subject: Safety and convenience. Let's add fun - because three things is always better than two.
However... I'll still need to be convinced that the dark green line sitting on top of the yellow "regen box" is not the hydraulic friction brakes. What gives it away for me is the little green corner of "hydr" before the regen limit is increased. This tells me that the friction system is being employed the whole time the B-pedal is pressed, and fills in at that junction until the regen catches up. Here's the quote that makes me thing I'm not totally incorrect: "The idea of the new system is to bring the regenerative yellow zone closer to the hydraulic response."
Can we get a jury in here!? My total correctness lies in the balance! I don't want anybody telling me that I'm partially correct. Either free me or hang me!
· regman · 24 weeks ago
" The new Honda system will be the first time I've heard of it operating this way".
Well now everything makes sense. It appears that your understanding of xEV brakes systems was not complete. This explains you stance on B-Pedal braking.
Let me assure you. The Toyota, Ford, GM, Nissan, and I believe Hyundai ALL have systems that do not apply any friction brakes until there is no more regen to be had. Honda is just now catching up (Note that prior to this, Honda has only dabbled in vehicles that had high regen capability. Most of their vehicles were mild hybrids). If this is the first time you have heard of it you have not read enough.
· regman · 24 weeks ago
Wow, we have come a long way. It sounds like we are almost in partial agreement.
Where we will continue to have differences of opinion will be our interpretation of what is efficient (or not inefficient), convenient and safe.
Ill start with the most controversial one first (the one that I believe can never be resolved): convenient.
What is "convenient" is purely a matter of opinion. If costing is better (and it is if your driving behavior is non-aggressive) then a gear that gives you no regen with A-pedal is more convenient. If you are generally an aggressive drive (or your vehicle does not have a BBW brake system) then A-pedal braking is more convenient. Note that this argument is convenience of driving efficient so there is some overlap on these points. If the discussion is pure convenience (what you like), everyone is different and the solution is to provide driving modes which I believe few disagree with. We will never agree on something that is a preference.
Efficiency. If your driving behavior is not aggressive (anticipate stops, slow steady braking when possible, don't over speed) then coasting is more efficient. Once braking is required, obviously regen is better however with BBW systems, it doesn't require the braking to come from the A-pedal. The down hill scenario is an exception as stated earlier but in this case, if the vehicle is equipped with a mode/gear that provides heavier A-Pedal braking, just shift into this gear when going down a hill. Therefore I would argue that providing easy way to coast along with a mode that provides A-Pedal braking is the best solution (this is what Honda seams to be doing).
· NeilBlanchard · 24 weeks ago
Regman & Darell, point taken on the terminal velocity issue. All cars and especially EV's should be made more aerodynamic, so this will not likely be the issue at safe highway speeds. I'd like to point out the inverse of this: with a very low aero drag car, coasting gets even more efficient, because the aero losses are such a large part of energy consumed.
I am in total agreement that when you need to slow down more quickly than coasting, then regen is the best thing to reclaim as much energy as you can. Aero and all other drag still happen even when you are slowing down, and regen has an additional loss.
If you have to slow down quickly (in a non-emergency situation) -- then you have accelerated too much. With a car that can coast easily, and that has low drag, you learn to use less acceleration when you come into a stopping point "too hot". So, once you drive a car that coasts by default, you will find that you accelerate less (investing less energy in the kinetic energy of the moving car), and you lose less energy to the losses inherent in regen.
Neil
· darelldd · 24 weeks ago
> you learn to use less acceleration when you come into a stopping point "too hot". So, once you drive a car that coasts by default, you will find that you accelerate less (investing less energy in the kinetic energy of the moving car), and you lose less energy to the losses inherent in regen.
You are certainly preaching to the choir, at last in my case. Please note that I have been driving EVs as our main vehicle for over ten years. And every one of them has had the option of coasting as default. I am able to squeeze more range out of a given EV than most other EV drivers. I don't say this to brag, but to let you know that I have many years and miles of experience in efficient driving. And as I've said many times before, I agree with most of what you say. The only time I've take exception is when you've implied that coasting is an efficient way to get somewhere. To be accurate, I need that to change to: Coasting is an efficient way to slow down. I do like the term "Road Candy!"
· darelldd · 24 weeks ago
> Let me assure you. The Toyota, Ford, GM, Nissan, and I believe Hyundai ALL have systems that do not apply any friction brakes until there is no more regen to be had.
Well, the good news is that we've managed to uncover something that is not universally understood, and is an important part of the braking efficiency discussion. While you are assuring me that you are right, I can't help but tell you this: I have owned some of the regenerating cars from the makers that you are talking about here. And I have driven all of them. I work on my own cars. I have intimate, direct, first (dirty) hand knowledge of at least some of the brake systems. I have instruments that show me hydraulic pressure of the brake systems in real time. And I can assure YOU that you are wrong. I can't put it more simple than that. The only wiggle room here is *which* cars from these makers? My experience comes from the EVs built in the 90's through 2000's
And until we can resolve this, there's not much sense in arguing efficiency. For the previous generation of EVs (do I have that right, or am I off base?), the brake pads hit the front rotors (how the rears are handled is different - especially the EV1) from the B pedal is applied. It isn't aggressive friction braking (at least at first) but there is ALWAYS a friction component during braking in every car you've listed. The amount of friction differs in each design, but in every case, the pads are touching the rotors at all times during braking. Please understand that I drive one of these cars every day. I can run along side the car and watch and hear the pads hit the rotors during braking. This action can be seen. It can be felt. It can be heard. It can be proven with instruments that monitor the hydraulic pressure. It happens at every speed, and at every pedal pressure.
On top of all that - what of the green "hydr" line that runs along the top of the yellow regen box in the graph above? You're still convinced that the Honda has zero friction braking during regen? Of that I am still NOT sure. I *am* sure of the operation of the earlier EVs, and most of the modern hybrids. I can't say I know how all the newest cars work. I can only repeat what I first said: This would be the first I've heard of it. And I do tend to keep my ears open.
· regman · 24 weeks ago
Darell,
Not to belittle your experience because from a miles driven basis, you are one of the most experienced. The areas ,though, that I believe you may be lacking in (correct me if I'm wrong) is that all of the vehicles you owned did not have brake-by-wire systems and you live in a "hilly", warm climate area. I have just the opposite problem. Most of my experience is on vehicles with BBW systems and I am a flatlander in a 2 climate region (winter and almost winter). These experiences tend to bias us. You may have learned how to optimize an EV with a non-BBW system but once you have one with BBW, a significant number of the techniques used to drive efficient become moot or actually reduce efficiency under some conditions.
· darelldd · 24 weeks ago
regman - That's the beauty of experience. Nobody gets to belittle it. :)
For the record, I live in North/Central CA. Not many hills in my local area, but I can (and do!) get to them easily (Tahoe, Mt. Shasta, Sierra Nevada, etc). Most of my EV-driving experience is on level highway. The EV1 was partially brake by wire with fully electric rear brakes. My direct experience is in driving every production (and several non-production) EV that's been in the US to date... and a 2006 Prius, which is our secondary vehicle for the long trips. I don't have experience with most of the other modern hybrids running around.
I really should sit down and list the EVs I've driven. That would be a fun exercise.
· regman · 24 weeks ago
"Let me assure you. The Toyota, Ford, GM, Nissan, and I believe Hyundai ALL have systems that do not apply any friction brakes until there is no more regen to be had."
Sorry, I didn't know I needed to be specific. The Toyota, Ford, GM, Nissan, and I believe Hyundai IN PRODUCTION TODAY all have systems that do not apply any friction brakes until there is no more regen to be had. Prior to the 2004 vehicles, there were few true BBW systems prior to this. So your Ranger and RAV4 did not have BBW systems. The Pre-2004 Prius had a system that has similar hydraulic behavior to the old Honda. Everything that Ford has after 2004 is BBW. All full xEVs from GM after the Tahoe are BBW.
· EVNow · 24 weeks ago
@regman · "Sorry, I didn't know I needed to be specific. The Toyota, Ford, GM, Nissan, and I believe Hyundai IN PRODUCTION TODAY all have systems that do not apply any friction brakes until there is no more regen to be had."
Not entirely correct in the case of Leaf, atleast. Leaf blends friction & regen to make it as seamless as possible. It also behaves defferently in D & Eco - with Eco mostly in Regen for a significantly longer time than D.
· KeiJidosha · 24 weeks ago
The Fit gets more interesting. What could be better than a rolling experiment with BMW / Nissan / Toyota regen options at the push of a button. 1100 cars with data loggers will answer the question of preference. Better yet, make everyone happy and leave the choice.
· regman · 24 weeks ago
EVNow,
"Not entirely correct in the case of Leaf, atleast. Leaf blends friction & regen to make it as seamless as possible. It also behaves defferently in D & Eco - with Eco mostly in Regen for a significantly longer time than D."
Actually it is correct with the Leaf. You have to be careful when you read thing like " blends friction & regen to make it as seamless as possible". They are usually referring to the ability to transition from pure regen to partial or all friction brakes at low speeds or when regen power limits are reached. The ability to hold off on friction brakes until all regen is used up is part of this system as well as all other systems mentioned above. Here is a link to Nissans brake system http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/edib.html. Note the chart where friction brakes are held off at the beginning of the brake apply. The curved part of the chart is where the battery/motor power limit is exceed. This characteristic is there on all systems (see the small green corner of the bottom chart on this article) but the size of this "corner" is dependent on the motor/battery capability as well as the speed that is applied. These are torque charts and torque is roughly power/speed, hence this curved torque profile.
· dgpcolorado · 24 weeks ago
In addition to the hill plus terminal velocity scenario, I'd like to point out that some of us live on roads that curve. Coasting down a hill into a hairpin with a 14% grade will lead to "launching" and I've seen several cars do just that when the road is icy. Braking may be inefficient but it is sometimes necessary. Just to get down a hill safely.
I'd like to highlight something that Hanato said that is sometimes overlooked in all the back-and-forth discussion about aggressive versus mile regenerative braking:
"The question is how much energy can we recuperate without going over the threshold of losing stability. You have to bear in mind that vehicles are driven under bad weather, in snow, and rain, and when the road surface might not be good. You have to make sure the regenerative braking doesn’t go beyond what is reasonable."
For those who don't drive slick road conditions, I'd like to point out that the safest way to drive through a slick patch of ice or snow is to not accelerate or decelerate (keep constant velocity). That is because tires will lose their grip if one accelerates or brakes in such marginal traction conditions. With my ICE cars I step on the clutch or shift into neutral until I am through it. Braking can cause a skid. (This is also a reason one shouldn't use cruise control in wet or icy conditions: the controller can spin the tires at exactly the wrong moment.)
Why does any of this matter to the regenerative braking discussion? Because if one has aggressive regen on the A pedal and lifts off, the braking can cause loss of control. I think this is why the car manufacturers are being circumspect about how they implement regen braking. I realize that this may be of no concern to mild climate EV drivers but it is a big deal for those of us who drive on snow and ice. So, don't bash the auto engineers for being careful about how they implement regen. It isn't the case that more is always better.
Add to that, some LEAFers are finding out that a cold battery can't accept charge quickly enough to have high levels of regen in cool weather. How about when it is really cold, say 0ºF? This stuff isn't quite as simple as some fair weather folks make it out to be.
· darelldd · 24 weeks ago
> Sorry, I didn't know I needed to be specific. The Toyota, Ford, GM, Nissan, and I believe Hyundai IN PRODUCTION TODAY all have systems that do not apply any friction brakes until there is no more regen to be had
I'm sorry as well. I shouldn't get all uppity until I'm sure what we're talking about! I truly thought you were speaking of the production BEVs of yesteryear.
OK, so now I can stop harping on my ancient car experience at least!
· darelldd · 24 weeks ago
> The ability to hold off on friction brakes until all regen is used up is part of this system as well as all other systems mentioned above. Here is a link to Nissans brake system http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/edib.html.
As with the chart included with this article, the chart included in the link you posted here still doesn't tell me that regen is first maxed out before friction takes over. I see it blended in both cases - except for the very brief, steep regen-only situation of the Nissan chart right at the start. As the car continues to slow, more regen is shoveled on - demonstrating to me that it was NOT first maxed out. Is there some relevant documentation that shows otherwise? Either I'm not reading these graphs correctly (I'm not discounting that in the least!) or they're telling us something different than "all regen at first, then friction blend."
What am I missing here that you are seeing? As I've asked before: Does the dark green line on the chart in this article NOT represent friction braking? Does it not follow - or go above - the regen portion for the whole braking time? I'm not trying to be snarky! I want to understand why I can't interpret the chart as you see it. Truly, I assume that I'm just not reading them correctly.
· regman · 24 weeks ago
Darell
"I really should sit down and list the EVs I've driven. That would be a fun exercise."
.For the record. I have had seat time in every production full HEV (can't think of one I haven't driven) and all "Production/public lease fleet" BEVs except the Roadster, MINI-E, and EV1. Even a few FCEVs. Obviously the best/most refined BEV is the Leaf (can't wait to drive the Focus). Least favorite was the City (couldn't get out of it's own way). My favorite Full HEV I think is the Fusion.
· darelldd · 24 weeks ago
regman -
We need to find a way to get you into a Roadster!
· Ken Fry · 24 weeks ago
I hate throttle-controlled regen!
I want braking to be fully-controlled by the driver, in a way that is as similar to ICE braking as possible... because there is nothing at all wrong with the way it works in an ICE car (other than regen not coming into play, of course). Frankly, I don't want the lawsuit issues of front wheel skidding when an inexperienced driver suddenly lifts off the throttle in icy conditions. The natural reaction in a "quick-reaction-but-sub-panic" situation on ice is to lift off, move instantly to hover over the brake pedal, evaluate, and then apply brakes as necessary. The accelerator controlled system gives you too much braking too soon. Using the throttle to brake requires learning. Why impose that upon customers and upon people who borrow the car, valet parking people, etc?
(In many auto trans cars, lifting off quickly forces an upshift, and no retardation at all in the first several tenths of a second.)
Here's the future newspaper article: "New York, NY: Valet Parking Attendant Cripples Pedestrian when Electric Car Skids Unpredictably.
Joe Valeto said "I don't know what the heck happened. I pulled out of the restaurant's valet lane and onto Park Avenue, backed off the throttle on that little downhill from the lot... just like I did with 45 other cars today, and the front wheels just started to skid. I went wide on the turn and ran into Mr Legless, who had stopped walking across Park to let me go by. It was almost like downshifting or something... almost like I hit the brakes... but I swear, I didn't hit the brakes. I wouldn't do that on an icy day like today. I'm not that stupid."
As you apply the brakes, then regen should come smoothly into play, and the amount applied should be under full control of the driver: press harder, more regen, until regen alone can't slow enough, and the friction brakes come into play. There is no need for the friction brakes to come into play until regen is full on.
The Zing! works that way, and if feels like driving a car instead of some fork lift truck or golf car. The Prius also works that way, albeit with the friction braking point cranked in a little too early.
· EVNow · 24 weeks ago
@regman · "You have to be careful when you read thing like " blends friction & regen to make it as seamless as possible". They are usually referring to the ability to transition from pure regen to partial or all friction brakes at low speeds or when regen power limits are reached."
I'm going with my own experience (and the collective experience of MNL). Yes, it blends friction & regen.
There is even some actual CAN message "proof" (don't go by that thread's title).
· darelldd · 24 weeks ago
@ dgpcolorado -
All good points, for sure. I'm aware that not everybody has the luxury of living in a habitable environment. ;)
And while this is true:
> Because if one has aggressive regen on the A pedal and lifts off, the braking can cause loss of control...
It is equally true to say that if one has no regen on the A pedal and presses the brake, that the braking can cause loss of control. I do get your point of course. And it is valid. Car makers are tasked with the impossible: make a car that's safe and enjoyable for every type of driver in every condition. Tough job!
But I bring this point up just to once again point out (what I know you already know...) that even when regen is available at the A-pedal, that it is fully controllable by the driver. From zero to 100% regen. Just having it there, doesn't mean it will be used. I agree that there should be a simple way of switching it off (to stretch your leg on a long drive (though you can do that with cruise control!) or drive on ice, or any other exciting thing that would be better with no regen on the A-pedal). Every car I've owned has more power than I've ever needed. I've used it to see what it is like, but in daily driving, I only use what I need. Same with braking.
· darelldd · 24 weeks ago
> I hate throttle-controlled regen!
I want braking to be fully-controlled by the driver, in a way that is as similar to ICE braking as possible..... because there is nothing at all wrong with the way it works in an ICE car <
I hate automobiles. I want my transportation to eat grain, poop in the road, and have all the braking tied to the reins.... because there is nothing at all wrong with the way it works on my horse. Just imagine the lawsuits when an unsuspecting horse rider jumps into a car, gives it a kick and is suddenly going 100 mph! Then pulls on the wheel, and the damn thing won't slow down! Carnage!
Should we just stagnate here to avoid introducing people to something that *may* be better? Or just fear it because it is different? Never mind. The answer is all around us.
Are we not going to use our great anti-skid/anti-lock/traction control technologies on our new cars? They work better on EVs than on gas cars... so why not?
> I don't want the lawsuit issues of front wheel skidding when an inexperienced driver suddenly lifts off the throttle in icy conditions. The natural reaction in a "quick-reaction-but-sub-panic" situation on ice is to lift off <
How does that work out in a manual trans car? Do we all want to drive cars that are designed for inexperienced drivers? It really is sad how low we've stooped to accommodate bad drivers. Remember when driving used to be a privilege, and not a right?
· dgpcolorado · 24 weeks ago
@darelldd, I think Ken Fry has it exactly right:
"The natural reaction in a "quick-reaction-but-sub-panic" situation on ice is to lift off, move instantly to hover over the brake pedal, evaluate, and then apply brakes as necessary. The accelerator controlled system gives you too much braking too soon. Using the throttle to brake requires learning."
That is what I do when I hit ice. In theory I could learn to feather the A pedal so as to not apply regen. But my reflexive action is always to back off the "gas" and work on controlling the skid. If I have to think about it, I'm already in the ditch.
Ideally this would be user selectable and in potentially slick conditions I would select to have regen on the B pedal. The LEAF offers this, and I hope that all A pedal regen cars do as well.
Yes, I don't live "in a habitable environment" by your standards. But I would hate the intense heat of the Sacto/Davis area. I'm an old guy and I've never lived in a place that required AC: Kailua, Tiburon, Pacific Palisades, La Jolla, Mira Mesa, Boulder, far western Colorado. And I hope to keep it that way! When I was a kid growing up in Hawai'i (fifth generation Hawaiian born) snow was a picture in a book. Now, decades later, I still love snow. It's pretty, especially here in scenic Ouray County!
· darelldd · 24 weeks ago
@ dgp -
yeah, I agree that is the natural scenario. I've been there myself plenty of times. And I ask again: What happens to the untrained masses if they're driving a manual trans car (as I have been driving in this situation)? When they yank their foot off the A-pedal, they're going to get some uncontrolled compression braking, are they not? Why don't we see all the manual trans cars stuffed into the snow banks? We don't see it, because they've learned out to drive their cars. But we're talking about inexperienced drivers. What happens to them? Should we not allow manual trans cars in deference to people who can't drive well? I still hold a shred of hope that humanity can learn some new tricks.
Trust me when I say that I also hate the intense heat of the Sac Valley. Ug. Not my favorite thing. But the other 10 months are pretty great! And having a 12-month cycling season is not to be dismissed! Brrr. It got down to 45 here last night!
· Ken Fry · 24 weeks ago
Hi Darrelldd
Nowadays we could switch the functions of the brake pedal and the throttle pedal in software, (both can be drive by wire, with linear motor/hydraulic hybrid braking) so that you can set it the way you want it: brake on the right, throttle on the left.
Manufacturers used to be able to change shift patterns: PRNDL to PNRDL or one-down-four-up to one-up-four-down in motorcycles.
But we don't screw around with this stuff anymore because there are very long standing norms (and regulations), and accident records that have pointed the way to standardization.
>> Do we all want to drive cars that are designed for inexperienced drivers?
Yes, that's what we do now. There are already enough deaths and injuries from ICE cars. Why strive to make electric cars even more dangerous?
· dgpcolorado · 24 weeks ago
@darelldd, "How does that work out in a manual trans car?" My instant reaction is to step on the clutch to take the car out of gear. But 90+% of my driving experience is with manual transmissions, so I don't know what an inexperienced driver would do. Or what those driving automatic transmission cars would do.
It is possible to bicycle commute in winter, I did it every workday in Boulder for 14 years. And I did the bicycle commute to town here yesterday. Not as far as you ride but more vertical gain (300' outbound and 1000' homebound, nearly all of it in one two mile stretch).
· darelldd · 24 weeks ago
>> Yes, that's what we do now. There are already enough deaths and injuries from ICE cars. Why strive to make electric cars even more dangerous? <<
Ooh. You pressed a button there! Rant alert!
If your concern is truly one of safety, then you should be lobbying for real, on-going driver education. NO amount of hand-holding by the car will be as safe as an alert, skilled driver. Dumbing everything down, and inviting unskilled drivers to come and play on the freeway is NOT the path to safety. The proof? What you just said: "There are already enough deaths and injuries from ICE cars." Aren't almost all of these cars designed for bad drivers? Have any of these deaths and injuries been a result of A-pedal regen, or any sort of non-standard control implementation? In contrast, what percentage of these "accidents" can be attributed to unskilled driving or poor choices by the driver (including sleep, DUI, distraction, poorly-maintained vehicle, lack of education)?
Decreasing brake reaction time with A-pedal regen is not "striving to make EVs more dangerous." Accommodating and accepting poor driving skills is.
· EVNow · 24 weeks ago
@darelldd · "Accommodating and accepting poor driving skills is."
Such is life. Afterall, we can't boil the ocean ...
@Ken Fry "Frankly, I don't want the lawsuit issues of front wheel skidding when an inexperienced driver suddenly lifts off the throttle in icy conditions."
Good point. I think the best would be to have "ICE" driving as the as the std option. Any pure coasting/high regen (on A pedal) would be other options/modes that driver has to select.
· ex-EV1 driver · 24 weeks ago
There appear to be 2 kinds of people here: Those who hate the idea of aggressive A-pedal braking and those who have actually tried it.
· regman · 24 weeks ago
Boy, I go away for a few hours and this happens.
· regman · 24 weeks ago
EVNow
"There is even some actual CAN message proof"
From this data traces, there are several places where regen is being applied with no friction brakes. This data looks more like it proves my point that the system is capable of holding off on friction brakes and delivering all braking with regen.
· Charles (not verified) · 24 weeks ago
So this is almost a re-post. If the B pedal is at home position and the A pedal goes there, do not engage regen except to keep the car from accelerating. This would work for slick conditions. It works for dry conditions. It also lets there be smart regen for down hills.
Please keep in mind that a lot of ICE cars have engine breaking, even those with automatic transmissions.
· regman · 23 weeks ago
Darell, Sorry to go back to an older post but let me try to explain what you are missing in the charts.
"What am I missing here that you are seeing? ... I want to understand why I can't interpret the chart as you see it. Truly, I assume that I'm just not reading them correctly."
.
As I stated, the curved part represents the power limit of the propulsion system. These charts are torque curves. Torque = power/speed (note: there are losses but this is a general high level description). All electric powertrains have this type of torque curve (here is Tesla's torque curve http://webarchive.teslamotors.com/performance/acceleration_and_torque.php. Note that this is an acceleration curve which accelerates from left to right. A regen curve is similar and decelerates from right to left). When you step on the brake, regen is done up to the power limit. At high speeds, this may not be much torque/deceleration. For example, the Leaf is rated at 80 kW (although I think regen power is less). At 60 mph (about 90 radians/second wheel rotation) the torque is 80,000/90 or about 850 Nm. This is about 0.2 g deceleration assuming a 1500 kg vehicle with 0.3 m tire radius. Therefore, any braking above 0.2g at 60 mph will require friction braking because the regen power has achieved the limit of 80 kW. This is what is shown on the left side of these charts. The brake is applied, regen is used up to the limit (say 80 kW), and friction brakes are applied above this. As the vehicle slows down, the 80 kW can produce more torque. At 30 mph, the torque that 80 kW can produce is about 1700 Nm or 0.4g. At 15 kw, the torque doubles again and will continue to increase asymptotically as the speed decreases to 0 but because the transmission components (and tire adhesion) has limits, the torque is usually limited to some level so the torque curve will go flat. You may think that this is inefficient because you see friction braking in this chart but this chart represents braking above and beyond the power capability of the motor/battery and friction brakes are required to meet the braking request from the driver. These charts have no numbers on them so I don't know how much deceleration the or how fast the initial brake event is on these curves.
· regman · 23 weeks ago
Note to Brad: If you want reader comments, just mention regenerative brakes.
Oh wait, Tom already said this the last time Brad did a regen story
· Chris T. (not verified) · 23 weeks ago
@ex-EV1 driver: "Those who hate the idea of aggressive A-pedal braking and those who have actually tried it." Indeed. :-) This is why I almost (but don't quite) like Fisker's "hill mode" switch. If it just had one more position—"aggressive A-pedal braking"—that would do the trick (of course they would also need to light the brake lights when using the A-pedal to brake hard).
(For people who argue that "agressive A-pedal braking" will "startle the valet" or whatever and lead to incidents like the one quoted above, note that Fisker's "hill mode" starts out turned off by default. So all you have to do is stop the car—in the Model S, this means "unbuckle the seat belt", although in the Fisker it means push the start/stop button—and the mode is off.)
· ex-EV1 driver · 23 weeks ago
What I really wish we could find out would be the efficiency of the regenerative braking. As this efficiency approaches 100%, the vehicle efficiency in city driving will increase significantly.
· regman · 23 weeks ago
"What I really wish we could find out would be the efficiency of the regenerative braking."
Are you talking about the wheel to battery to wheel efficiency or the % of braking that is done with regen (i.e. not friction braking)
Wheel to battery to wheel efficiency is somewhere between 55% and 75% depending on the type of transmission, the speed and torque levels. In some hybrids where the motor is on a front end belt, it can be even lower.
The % of braking done with regen can be as high as 95%. From Brad's last regen story, "According to Marakby, this system captures 94 percent of the brake energy from the brake system in a city cycle".
· Brad Berman · 23 weeks ago
@Regman - Yep, gotta love regen braking. I agree that it's the thing that separates one EV (and one EV maker) from another. Thanks for reminding me to keep my eyes open for access to EV braking engineers. Will do.
· Ken Fry · 23 weeks ago
>> "According to Marakby, this system captures 94 percent of the brake energy from the brake system in a city cycle". <<
Hi Regman,
I doubt that this is really true as stated. Your interpretation is closer. The system does not capture 94% of the braking (deceleration) energy. 94% of the braking in the city cycle can be handled entirely by regen, but as you point out, regen is not 100% efficient. Round trip (wheel-battery-wheel) is perhaps not fair to regen engineers, (and hard to quantify... because who knows how that energy is re-applied to the wheels?), but regen efficiency varies with motor speed and torque, and motor efficiencies alone can be very low in regions far from the efficiency peak: 50%, 30%, even 10%.
In the Zing! I can drive in such a way that the friction brakes are stone cold after a trip around town. All of the braking is handled by regen, and the friction brakes are used only to hold position against rolling forward or back at stops. The Zing! motor is permanent magnet, and is a bit more efficient than many AC motors at part load. (I have the dyno data from an AC induction traction motor, and there are many regimes in which efficiency is far below 50%... and of course right at start-of-motion efficiency is 0%).
In intense stop-and-go routines, the controller, the motor and the battery cells all increase in temperature (all waste heat). I'd guess that 50% efficiency from wheel kinetic energy to energy in the battery is about typical, in cars in which you can avoid the friction brakes entirely for the standard EPA city cycle. (This does not apply to hard stops, panic stops, etc. of course.) And any estimate can only apply to a particular, well-specified city cycle: there is only one braking torque and motor speed at which peak efficiency is attained, everywhere else, the efficiency varies quite a lot.
[Further complicating the issue: There are decelerations in the city cycle that can be handled mainly by aeodynamic and rolling resistance alone (no pedal braking of any type required) depending upon how bad these drag figures are. A Jeep Wrangler uses far less braking than a EV1 would, because the Wrangler resistances are so high that it's like driving with the brakes on all the time. Per pound of vehicle weight, the Jeep tires generate almost twice the drag of the EV1 low rr tires, and the product of Cd and area is actually more than twice as high.]
· Ken Fry · 23 weeks ago
>> What I really wish we could find out would be the efficiency of the regenerative braking. <<
Hi Ex EV1,
The figure can only be pinned down by running a simulation on a particualar car through a particular driving routine. What we are apt to call 90% efficient motors are only 90% efficient at peak, and some motors are far less efficient off peak. So at each braking instant, efficiency varies. In a given cycle, different cars require different levels of braking. (See response to regman.)
But as a rule of thumb, with today's motors, controllers and batteries, regen is about 50% efficient in getting the change in kinetic energy caused by applying the "brakes" into the battery. The rule of thumb that converters have used is that regen can extend the range of an EV by about 10%, at best. (Obviously, in long highway drives, it doesn't help at all.)
· Ken Fry · 23 weeks ago
>> It also lets there be smart regen for down hills. <<
Hi Charles,
The smartest regen for down hills is a human driver and a regen brake pedal.
On my drive home there is a long hill with a light at the bottom. Sometimes I must turn at the bottom, sometimes I must go straight. Sometimes I think I can "make the light", other times I think I cannot. So sometimes I want to coast to maybe 10 over the speed limit, to make it up the next hill. Other times, I want to stop at the bottom.
A brake pedal and a real brain lets me do the most efficient thing, in a way that "smart" regen is not likely to accomplish.
· darelldd · 23 weeks ago
Indeed (I mean except for regen only on the brake pedal)! It is much like the Prius trying to charge my battery on the way UP a big hill, so I start the descent with a full HV battery pack for the regen event all the way down. :sigh:
· Ken Fry · 23 weeks ago
Hi Darell,
You ask "Have any of these deaths and injuries been a result of A-pedal regen, or any sort of non-standard control implementation? "
Yes, of course there are many instances of non-standardized controls causing accidents. That is why PRNDL is now standard, but there used to be PNRDL cars. It's why the prop controls are a different color than the mixture control in airplanes, and why the gear lever knob looks like a little wheel. Even highly-trained, sober pilots demonstrate time and time again that they can function as idiots, killing themselves and others in the process.
** Rant Start
I never spun my Corvair, but many people did, believing them to respond as a typical car would. I had an Explorer and never flipped it, but others have. I once owned a Blazer of the type that would burst into flames, but my good driving, you seem to say, prevented mine from doing so. I have even survived driving a Pinto, although I never owned such an abysmal POS. Was I unusually good at looking at the rear view mirrors and avoiding getting rear ended?
You ask: "In contrast, what percentage of these "accidents" can be attributed to unskilled driving or poor choices by the driver (including sleep, DUI, distraction, poorly-maintained vehicle, lack of education)?
Bad drivers and drivers unable to deal with the unexpected behavior of their vehicles generally take innocents with them. About 40% of all accidents involve more than one vehicle. Are you saying that it is the fault of the teacher who gets hit by a drunk – she should have known, somehow, not to be there? In 2009, an average of four children ages 14 and under were killed every day in auto accidents. I don't think we can blame the kids.
I am an advocate for: modern emission controls, better driver certification, stricter regs against drunk drivers, seat belts, airbags, crush zones, collapsible steering columns, four wheel brakes, hydraulic brakes instead of cable operated brakes, ABS, traction control, stability control, rollover control, decent headlights, etc. But I have driven vehicles without any of the safety features in this list and survived. Would I give my daughter a model T? No.
I am a member of SAE, and value the engineering advances that have been made over the years and all the studies they have done (and regulations they have promoted) to standardize controls. For any car that needs more than a 120V extension cord, their standard is pretty good I think. Sure, if we are all electrical engineers then we can evaluate the risks and use rubber gloves and wire nuts to hook up our cars -- hookups like this happen in India all the time (but without the gloves). If you're good, you don't even need the wire nuts... the sparks alone can make a good temporary weld.
Regarding safety issues, I am not laissez faire.
** Rant over.
· regman · 23 weeks ago
@Ken Fry
"The system does not capture 94% of the braking (deceleration) energy. 94% of the braking in the city cycle can be handled entirely by regen, but as you point out, regen is not 100% efficient". Yes. My assumption is that 94% braking energy required is done with regen but it not all of it makes it to the battery. Another way of saying it is only 6% of the braking energy is done by friction brakes. This is what Ford says on ford.com "It [Focus BEV] captures more than 90 percent of the energy normally lost as heat during braking, and recycles it to recharge the battery".
I think your efficiency assumption from wheel to battery to wheel are a little low. Yes, it can be lower than 60% at times (primarily low speeds) but most of the energy absorption is done when wheel to battery efficiencies are > 70% so on average, the overall efficiencies W-B-W should be in the 65-75%. Also, every regen torque curve that I have seen from the manufactures do not do regen at low speeds (below 3-5 mph) and start to ramp out regen at 8-15 mph. The above curves from Honda are a great example. This may seem inefficient but there is little energy at these low speeds and efficiencies can actually go negative (i.e. it cost energy to brake) below around 2 mph because the losses exceed the energy absorption. I would guess that this low speed friction brakes is where Ford's 6% comes in.
· darelldd · 23 weeks ago
@ Ken Fry -
Thanks for the reply, Ken. I'll try to answer your questions and clear up some places where I was not specific enough.
>> Yes, of course there are many instances of non-standardized controls causing accidents. That is why PRNDL is now standard <<
Dang. My fault for being lazy and asking if there were *ANY* cases of "accidents" caused by non-standard controls. And of course there are always going to be *some* cases. It is like asking, "does anybody think smoking is good for you?" My point was lost, apparently, but my poor use of the too-precise word "any." What I meant, and what I should have written was, "HOW many?" or "what percentage compared to poor driving skills?" Of course there will be instances when non-standard controls cause a problem. We definitely need standards where they make sense. And they need to evolve with technology. If they don't evolve (as with my earlier point) - braking will be done with reins on your horse. Is changing a standard our biggest cause of automobile "accidents?" Is this where we should concentrate our resources if safety is the goal? My point is that we do almost nothing to fix the poor driving skills part of the equation. And until we do that, the rest is just noise. The rest is just trying to survive being clobbered by a car.
The bulk of your message seems to support my point, though it is obvious that I confused you with my post. Cars bursting into flames or flipping over due to faulty or under-inflated tires is again a small percentage here that doesn't need to be part of the discussion. Do you contend that poor driving skills has an insignificant bearing on driving safety? You seem like such a reasonable guy. I can't figure out why you're so happy with so many people killing themselves and others - even when they're driving cars that have 100% standard controls, and that aren't prone to flipping or bursting into flames.
>> Bad drivers and drivers unable to deal with the unexpected behavior of their vehicles generally take innocents with them <<
Pow. That's a big part of my point. Want to keep people safe? Educate drivers.
>> Are you saying that it is the fault of the teacher who gets hit by a drunk – she should have known, somehow, not to be there? <<
Cringe. My point again, but tangled up with a confusing assumption. Of course that isn't what I'm saying. What I'm saying is that it is the fault of the unskilled drunk! By my definition, skilled drivers don't drive while impaired. The point is we need ALL drivers to be skilled. Not just you and I. You and I (and the teacher) aren't really safe unless OTHERS are skilled. I don't know how else to put this. If you run a skilled and non-skilled driver at each other, somebody might get hurt (like in your case when the teacher is hit). If you run two unskilled drivers at each other, somebody is bound to get hurt. If you run to skilled drivers at each other, there's a high probability that nobody gets hurt. The more skilled drivers we have on the road, the safer we all are.
And as I put it before, I'm using "skilled" as short hand for educated, alert (not sleepy or drunk or high) and trained.
I am not discounting that we need safety equipment in cars. However, I think we all agree that most (not all! I won't fall into that trap again) of these items only help us after a collision is in progress. It is the same reason many people buy huge cars - thinking that they'll be safe *IN A COLLISION." Training drivers (and better brakes and lights and some of the other stuff), on the other hand, helps *prevent* the collision before it happens. Should we be putting all our money and effort into helping us survive a crash, or in preventing the crash in the first place? We need to work on both, for sure. I just hate seeing collision prevention being swept under the rug while we put so much effort into collision survival. You can put all the latest safety equipment into a car that you want - and still the driver's skill is a huge part of the safety equation.
You are obviously deeply involved in safety issues, and deal with them regularly. Why is it that you're so comfortable being out on the road with unskilled drivers? Is it because we're now more likely to survive the idiots with our crumple zones and air bags - to the point where we shouldn't care that there's effectively zero driver training in this country? If you're that driving teacher being clobbered by the drunk, are you thinking that the best way to keep this from happening again is to make bigger crumple zones and air bags?
Wow. And this all started from A-pedal regen. Fascinating how these things work.
· Tom Moloughney · 23 weeks ago
"Note to Brad: If you want reader comments, just mention regenerative brakes. - Oh wait, Tom already said this the last time Brad did a regen story"
My head is still hurting from the last discussion :)
Whatever the effective efficiencies, I know one thing: I've driven both left and right pedal regen cars extensively and I personally like the driving experience of strong right pedal regen 100% more. I feel so much more in control of the car, it's just not that easy to explain. Again, if anyone in my area wants to drive my MINI-E for a while to see how it drives just email me and we'll do it. Time is running out though, I give the car back on December 16th when I pick up my BMW ActiveE (Not too sure I'll be loaning that one out for test drives just yet!)
· Mike I (not verified) · 23 weeks ago
Wow, this is quite a discussion. I will just make two quick points.
In both the Honda and Nissan charts, my interpretation is that the colored areas should be considered to be stacked, not overlapped. That means that the torque contribution of the hydraulic brakes is only the height between the yellow and green lines at a given slice of the chart.
Any discussion that asserts that A pedal regen is unsafe in low traction situations assumes that the vehicle's engineers are negligent in their duties to establish proper traction and stability control programs in a modern EV. I particularly enjoyed the Tesla blog on this subject from 2008 here: http://www.teslamotors.com/blog/spin-stops-here
Here's my idea - control the A pedal regen on the shifter:
...P
...R
...N
B D C
where B is heavy A pedal regen, D is ICE-like regen, and C is full coasting on A pedal release. The dots above just provide the alignment to show that P through D is a straight line and B and C are on either side of the D. Personally, I don't understand why the Prius shifter doesn't have a P position and has a separate button instead. This is the most intuitive implementation that gives the driver an easily accessible way to select they behavior they want. Some that like the BMW/Mini heavy regen may always drive in B, many will just drive in D, and some may go back and forth between B, C, and D frequently depending on the situation.
· Ken Fry · 23 weeks ago
Hi Darrell,
Active vs passive safety is not an either/or situation. As I implied, sure, there are loads of idiotic drivers, loads who are mildly incompetent, and many who become incompetent under emergency conditions, but appear competent at other times.
(Motorcyclists demonstrate this last point. To do an evasive maneuver, you have to counter steer -- you can't just will a motorcycle to quickly bank. Almost every state teaches "push right, go right" (developed by the motorcycle safety council) as part of the licensing process, but still, people who can easily pass the test and do fine in ordinary driving, do exactly the wrong thing when going too wide in a turn, putting them straight into the grill of the truck they were trying to avoid. The problem is that the motorcycle is not a safe machine, from a human factors perspective. People cannot be expected to "not panic." We accept that the death rate is 38 times higher than it is for cars. Motorcycles are fun, and the driver is less likely to take an innocent along on that last ride.)
The fact remains that aircraft still crash even with pilots who are more than 10 times as well-trained and well-tested (I'm being conservative: car drivers get no retraining at all, and pilots do 40 hours retraining and retesting every 6 months). But still we find things to do to improve the airplane as a machine, especially in terms of human factors.
I've been quite lucky in avoiding accidents, and (perhaps by virtue of racing experience) avoided at least one completely where everyone else in the car thought we we were all going to die. But I also had an accident in which I was driving a Ford F150 with anti-lock on the rear axle, but not the front. I was driving conservatively and hit a patch of oily wet road, at what would have been a safe speed were it not for the oil. The truck went perfectly straight from that point on, as I experimented with braking heavily, locking the fronts, or pumping (defeating the rear anti lock but allowing the fronts to make a stab at steering. The driver should not have to make those decisions: the truck should have had anti-lock on all four wheels, or none. The truck was totaled; I was fine.
You wrote: "Why is it that you're so comfortable being out on the road with unskilled drivers?" I have written nothing to indicate that I am comfortable with the idiots on the road: I see examples of bad driving every day. (Even the Zing! which people rarely fail to notice, has been hit from behind.) I am saying that we need engineered-in passive safety, engineered-in active safety, good human factors design, and far better drivers.
The last should go without saying, but so should acceptance and knowledge of science, understanding of statistics, understanding of the the actions causing global warming, general math literacy, understanding that one should not molest kids, that presidential hopefuls should have a clue, etc.
If only.
I enjoy your posts, by the way, and think of this as friendly debate, not bickering.
(BTW, I can't tell you how many patently dangerous things I've done: motorcycle road racing, car racing, aerobatics, hang gliding, getting married, having kids, etc. But then there is this other side, the dark side: I've done a lot of OSHA-related work and training, developed training about Volvo's safety features, produced a videotape on human factors for airline pilots, etc.)
The image of a head flying through the air in front of our car repair shop when I was at Penn State [I used to work on Franco Harris's car, and Joe Paterno was the coach then] still comes up. The accident was not the fault of the woman who left three orphans. In a modern car, she would have lived: she had no seatbelt, and the windshield frame of the convertible restrained only part of her body.
· darelldd · 23 weeks ago
@ Ken Fry -
>> I enjoy your posts, by the way, and think of this as friendly debate, not bickering. <<
All good, and I really appreciate your posts as well. Anybody who knows what the hell they're talking about is OK in my book - even if they don't agree with all of my brilliant opinions!
In general, we agree more than we disagree on the big-picture stuff. I think we all learn something when we disagree on the details. I know I do! I can tell that you and I have had some similar life experiences. I've never built a crazy-cool car though. When can I buy one (with my PIC discount)?
· ex-EV1 driver · 23 weeks ago
@Mike I,
I actually like the way the Volt maintains the currently expected gear shift pattern yet offers more and less A pedal regen. I just think they should go a bit futher:
If an EV simply offers P R N D L2 L1, it will act just like an automatic ICE and you'll get a lot of engine braking on the A pedal in L2 and even more in L1. Its just that you won't tear up the transmission if you shift into one of these lower gears all the time.
· Charles (not verified) · 23 weeks ago
@Ken Fry, the nice thing about my method is that if you want to coast just leave you foot on the A pedal until you reach the speed you want. Take your foot off the A pedal the car will slow due to external forces, not regen unless the hill is steep enough to accelerate the car. If you want regen, step on the B pedal. The harder you press the more regen you get. With a break coach (Focus EV?) you can keep the friction breaks off and maximize regen.
· Mike I (not verified) · 23 weeks ago
@ex-EV1 driver,
I think the problem with L1/L2 is that people have a pre-conceived idea about what those mean. By using different letters, you make it clear that the function is different. Also, I made them lateral instead of sequential so that the normal driver will just pull it straight to D. Also, B and C, if placed sequentially after D, would not add regen progressively like your L1 & L2. Maybe a coast button on the shifter like an existing O/D button could be used with (simply renamed) B1 & B2.
· darelldd · 23 weeks ago
For the record, the Rav4EV calls it's two regen positions:
EB (for engine brake - tries to mimic the feel of a gas car)
B (for Brake - more aggresive regen)
Of course these are both just on/off. No way to modulate them, so they're a bit clunky!
· alt-e · 23 weeks ago
My perspective is that of an EV designer more than an EV driver. Although I have certainly spent a lot of time behind the wheels of EVs, most of my concentration has gone into how they should be designed. And this means that I try not to pay attention to what I might want, but what would work out best for most people. And most people don't have the time or attention to get extremely precise with controlling the balance between acceleration, coasting and regen off of one pedal. And most people don't really even try to hypermile. So they don't try to optimize where they are on that balance between the three states. The LCD screen will typically tell them, if they look at the screen. But most people, most of the time, are just attentitve enough to pay attention to what is happening visually out on the road.
This is why I prefer a system where the acceleration pedal provides acceleration, touching nothing is coasting, pushing against the brake pedal half way (working against a soft spring) is different levels of regen and pushing the break further (working against a stiff spring) is friction braking. It is really easy for the driver to pick up on this kind of a system. And this system encourages the driver to automatically do the most efficient thing in just about any situation, without even thinking about it.
My concern is not how efficient I drive my own car. Or how efficiently hypermilers drive. Because hypermilers are a small percentage of the population. What I am concerned with is how to save the most amount of energy overall. And this is best accomplished with a system where everyone is driving efficiently whether or not they are trying to.
To do this you have to encourage coasting the most and then regen before friction. And also encrouage people not to accelerate when they don't need to. I think the method of no-contact = coast and the two level spring brake pedal does that.
I do not dispute that a good hypermiler would do just as good with an A pedal system. Or that some people might like an A pedal system better. But it takes skill, generally paying attention and quite frankly giving a damn to know where that coast point is and to always be there when you should be.
We can be mad at people who don't care or who don't have the skill. But will us being mad at them really change their behavior?
Because the regen round trip efficiency is not all that great. Better than friction, but nothing like coasting.
· EVNow · 23 weeks ago
@regman "From this data traces, there are several places where regen is being applied with no friction brakes. This data looks more like it proves my point that the system is capable of holding off on friction brakes and delivering all braking with regen."
That was not what I was responding to. I was responding to
"Sorry, I didn't know I needed to be specific. The Toyota, Ford, GM, Nissan, and I believe Hyundai IN PRODUCTION TODAY all have systems that do not apply any friction brakes until there is no more regen to be had."
Long before "there is no more regen to be had" - Leaf starts blending some friction brake.
· darelldd · 23 weeks ago
> We can be mad at people who don't care or who don't have the skill. But will us being mad at them really change their behavior? <
Nope. It won't change their behavior. which is why we need on-going, mandatory training and testing in order to keep driving.
For the record, I'm not mad at bad drivers. I'm mad *about* bad drivers. But really, that whole bit was a tangent.
The people who have not driven a car with aggressive A-pedal regen typically assume that it is hard to "learn" and not intuitive. Even that it is less efficient because of the holy grail of coasting. The people who HAVE driven with this system typically have the opposite view. Really, it is as simple as that as several of us have said.
Your points are all well-taken. And they generally make sense. Except for the one where you assume that proper A-pedal driving takes some sort of extra attention or even skill. In fact, it quickly becomes so "second nature" that you do NOT need to think about it. It's as natural as can be - push the pedal for more go, release the pedal for less go. And in the real world, the difference in efficiency between coasting and supplying some tiny bit of power or regen is insignificant. Folks with no A-pedal driving experience seem to assume that aggressive regen braking will be used in every slowing instance, and that acceleration to get back up to speed will subsequently be needed. No, in fact the A-pedal driving allows you to choose the exact speed for every situation in the most convenient, safe and efficient way. And all this comes from a HUGE proponent of coasting when possible, mind you! Until I drove my first A-pedal car, I argued the same side of the equation that you're on.
If you design a car for poor drivers... if you give them an easy coasting option- that coasting function still won't be used! In my experience, poor drivers aren't comfortable with coasting. They want to be in control, and that means power or brake in just about every situation. I've known far too many drivers that can't handle being off both pedals. They MUST be on one or the other or they don't know what to do with themselves. The foot oscillates, and it's just luck of the draw which one they decide to use.
Let's not be mad at poor drivers. Let's also not design cars for poor drivers. Let's build GREAT cars, and create skilled drivers so we can all get where we want to go safely, efficiently and enjoyably.
And that's all I'll say about that. For now. :) Man! I am so far behind on the stuff I need to get done, I can't even see the end from here.
· JRP3 · 23 weeks ago
Damn, a regen thread and I missed out! As I've stated before A pedal regen does not mean you cant find a coasting position, so assuming you can't coast with A pedal regen is false. I doubt what Honda is doing will provide any noticeable difference in range extension compared to other vehicles, braking is a small portion of driving, even in stop and go, and if most schemes already recoup most of the regen available then any system that might recoup the rest of it will only add a very small amount. I expect that Honda can get good range from a smaller pack because the Scib batteries they are using can be more deeply discharged and fully charged and therefore have more usable capacity.
As to skidding from regen, since when the tire skids the motor stops turning, regen would stop, then the motor starts turning again regen starts, if it then skids regen should stop, etc., similar to ABS braking. No? Has anyone tried hard regen on a slippery surface? If that does not happen inherently I'd think it could be programmed to do so, like ABS.
· Ken Fry · 23 weeks ago
Hi Darell,
I failed to answer your critical question:
"When can I buy one (with my PIC discount)?"
Now. There are four launch customer slots, one of which is filled. You can even have the regen on the A pedal!
We'll build the launch customer cars in 2012, and on the last 2 expect to make money.
· Ken Fry · 23 weeks ago
Hi JRP3
>> As to skidding from regen, since when the tire skids the motor stops turning, regen would stop, then the motor starts turning again regen starts, if it then skids regen should stop, etc., similar to ABS braking. No? Has anyone tried hard regen on a slippery surface? If that does not happen inherently I'd think it could be programmed to do so, like ABS<<
One problem is that the motor is driving both front wheels. If one wheel is on ice braking on both would be reduced to restore the skidding wheel to rolling. In real ABS, the wheel with good grip continues to brake at full force.
Another problem is that on a slippery surface, the wheel does not need to stop fully to cause a skid. Reducing the wheel speed from 50 mph to 30 mph means that the wheels are skidding and steering is compromised.
I think the Honda guy is correct that too much regen can be destabilizing on slippery roads.
(In the Zing, I've been able to screach the tire from regen even on a dry road... but there are some extenuating circumstances there.)
· darelldd · 23 weeks ago
>> I think the Honda guy is correct that too much regen can be destabilizing on slippery roads. <<
Oh yeah. Too much of anything is bad... by definition. ;)
Traction control coupled with regen braking certainly does work! We can predictably, confidently and safely slow RWD cars at a peak of ~0.6g using only regen without any perceptible wheel slip. (I can hear regman's pencil scratching already! And I'm prepared to be wrong)
· darelldd · 23 weeks ago
> We'll build the launch customer cars in 2012, and on the last 2 expect to make money. <
Wow, Ken. I had no idea you were so close. How cool is that?
· regman · 23 weeks ago
Darell,
"We can predictably, confidently and safely slow RWD cars at a peak of ~0.6g using only regen without any perceptible wheel slip. (I can hear regman's pencil scratching already! And I'm prepared to be wrong)"
Is this a challenge.
The short answer is (and excuse me for being blunt) you are wrong. I say short answer because there isn't enough space in this post to explain it without lots of charts and graphs and pictures with circles and arrows and a paragraph on the back of each one explaining what each one was.
With that said, let me give it a shot. What it comes down to is brake balance, ideal brake balance curves, PFC (Peak friction coefficient) lines, CG height, etc. An understanding of brake balance dynamics isn't an easy thing, even for those who work in the area of vehicle dynamics.
To get to 0.6 g with pure regen on the rear axle, you need a vehicle that is at least 60% rear weight distribution (most RWD vehicles are 25-40% rear bias), a CG height of 0, and tires/surface that can get you to 1.0g with under ideal braking distribution. Now before you totally start to dismiss my analysis, I do understand that the Tesla Roadster is a potential exception that may come close to potentially being able to pull 0.6g. This is because it has 65% rear weight distribution and tires that can exceed the 1.0g capability. The spec that I couldn't find (and therefore could not calculate the theoretical rear wheel capability) is the CG height which will lower the rear braking capability at higher decelerations. But even this is the exception to the rule, most xEVs (even with the batteries in the back) do not get over 50% rear bias and don’t have the performance tires that the Tesla has. The thing that xEVs have in their favor is usually a lower CG height which helps the weight shift at higher decelerations. But even with a CG height of 0, you still need a 60% rear weight to get to 0.6g on a typical, non-performance car. Most xEV vehicles that I have analyzed top out at about 0.3-0.35 g pure rear regen capability, and that is under ideal surface conditions. From a brake controls standpoint, you do not want to operate right at the edge of the capability because you will be constantly dropping out regen with every little bump in the road.
· darelldd · 23 weeks ago
@ regman -
Excellent! I love being called wrong, and then having everything described to make me right. :)
Yes, you need enough tire. Yes you need low cg. And yes you need significant rear weight bias. And no, I'm not talking about the (relatively) un-high performance Roadster. Heck, the Roadster has doors! I wasn't speaking in terms of "rules" or "exceptions to the rule." And I'm certainly not talking about family cars. I'm only talking about what can be done. And in that I am not wrong. You've already done the pencil work, so I think we can agree on that.
I'm only saying that it can be done because it HAS been done. I didn't bother working out any of the equations, because I've experienced the reality. You can call that wrong because it won't translate to the family sedan. But I'm just saying that it is possible. It exists. To translate it into the family sedan, everything needs to be toned down. But we need to know what is possible to determine what is realistic.
Just for grins, I'm digging up the data that I'm sure you'll like to see. I couldn't put my finger on it easily, or I would have posted it here.
· regman · 23 weeks ago
Darell,
Your original statement was "We can predictably, confidently and safely slow RWD cars at a peak of ~0.6g using only regen without any perceptible wheel slip."
The fact that you used the word "cars" lead me to believe that you were talking generalization. My answer was based on the normal range of xEV specs. The Roadster is an extreme example of all production vehicles (maybe the most extreme) when it comes to weight distribution, tire adhesion capability, and low CG. With this said, even this vehicle is, at best, on the edge of rear slip if driving 0.6g braking only on the rear. Even this vehicle could not "predictably, confidently, and safely" decelerate at this level repeatably under all normal driving conditions based on the specifications that I am aware of.
Does anyone know the CG height of the roadster as well as the published stopping distance?
· darelldd · 23 weeks ago
@ Regman
Agggh! Yeah, I raced back here to try and head off y our post. After being a bit surprised at your initial response, I finally went back and read the quote you included. Too late I realized that it was my poor word choice that sent the message off in the wrong direction. My whole comment hinged off of the word "cars," it seems. Making it sound like a generalization - something we'd expect from the family sedan. Something we can do for everybody.
If I'd taken the time to wordsmith that a bit better, I would have ended up with something like:
"We can build a RWD car that will confidently and safely slow at a peak of ~0.6g using only regen..."
I do think that you missed the "peak" part that I did include - but either way I had no intention of making it sound like your average Honda Civic will be capable of this.
Toss all that. My entire point (and in trying to keep better to the topic on this thread) is that we can slow cars with stiff regen when it is coupled with appropriate traction control. I was merely trying to provide some evidence of the extreme - by using RWD which is obviously a much tougher braking/traction situation. If we can do it with RWD, we can surely do it with FWD.
So please... the take-home message here:
"we can slow cars with stiff regen when it is coupled with appropriate traction control."
My apologies for the confusion.
· darelldd · 23 weeks ago
Some data as promised:
68% rear weight
CG ~9" off the pavement
Consistent, repeatable 0.4g of rear-wheel braking with traction control. Peak of 0.6.
OK... moving on...
· alt-e · 23 weeks ago
Four motors, one per wheel, each independantly controled for both traction and regen is a wonderful thing.
· regman · 23 weeks ago
Darell,
"68% rear weight" – This is close to what I read of 65%. May be the difference between curb weight or GVW.
"CG ~9" off the pavemen"t - I don't believe this number. This is 3 inches below the center of the axle and only 4 inches above the ground clearance. 9" seems a little low to me but I could be wrong.
"Consistent, repeatable 0.4g of rear-wheel braking with traction control. Peak of 0.6". – These numbers are believable but you have to remember that a peak braking capability is not sustainable so this number does not mean anything to me. I am more interested in the maximum sustainable number (0.4g) which is reasonable.
· Ken Fry · 23 weeks ago
Hi Darell,
You wrote: " Wow, Ken. I had no idea you were so close. How cool is that? "
Thanks. Yes, it is pretty kewl. My first customer has a 120-mile round-trip commute, and has been paying over $5000 for gas. He will charge at work, so will do 80 miles a day on electricity (20,000 miles per year @ $.01 per mile = $200. 10,000 miles at 100 mpg = 100 gallons @ $350 Total $550.) He should be much happier in a Zing!
· darelldd · 23 weeks ago
Regman -
Ahhhh. I Like "believable" and "reasonable" way more then "wrong."
Please note that these numbers have nothing to do with the Tesla Roadster as you seem to have assumed. I don't have the Roadster numbers and my only experience with Roadsters is having the pleasure of driving a few. Something I recommend to anybody who starts to think that EVs aren't "all that."
You can believe or not believe any of the numbers. I'm only telling you what they are for the vehicle in my example above - the one car that I called "cars." A car that is not formulas and calculations... but a street-legal vehicle. It was likely a mistake to even come back and post the numbers, but I said that I would. I apologize if they don't meet your standards. Please note that from the beginning, I did say "peak." I messed up the word cars, and you might have missed the word peak. Let's call it even! I assume there's nothing more to debate here.
· darelldd · 23 weeks ago
> He should be much happier in a Zing! <
@ Ken -
How come your Zing! Site is so hard to find?! At least put it in your profile so folks can visit. Sorry for OT... I have to ask - will you offer a full EV version with better battery range than the hybrid?
· Ken Fry · 23 weeks ago
Hello again Darrell;
You wrote: "Traction control coupled with regen braking certainly does work! We can predictably, confidently and safely slow RWD cars at a peak of ~0.6g using only regen without any perceptible wheel slip."
Others have corrected your wild, borderline psychotic notions. ; )
The issue re the Honda and Leaf is that the front wheels are not independent in terms of regen. If a wheel slows too much, you can only reduce regen to the whole axle. (You may remember the "slippery road" switch on Solectrias. It disabled regen.)
Wheel motors help here, but add a large burden in unsprung weight. Someone is using wheel motors inboard on a concept car -- which, while complex, removes the weight problem, and permits independent control.
Years ago, my brothers and I drove around in an industrial electric cart (a Victor Electicar) and to slow down, we used plug braking. The friction brakes were not intended for use on hills nor for the high speeds we liked to try to attain. We'd switch it into reverse, push the speed lever down, and voila! Frequently, we'd snap the axle keys and have a wild ride.
· darelldd · 23 weeks ago
@ Ken -
Ah, sounds like my misspent youth!
Re. the FWD EVs and regen - couldn't that issue be mitigated with proper thought and design? I get that it's like that now, but it *could* be different if we wanted it different, yes? Using traction control and ABS, I would assume we could do better than, "oh well, this is how it is!"
Inboard wheel motors. Now there's a concept I hadn't heard of. A bit of an oxymoron, but one with merit!
A friend just installed a dyno hub on his bicycle He loves it, but I want to make it more functional. I've offered to wire up an automotive high beam that he can switch on for a drag brake when descending. Of course that would probably ball the thing up into a smoldering heap of lava, but with a red lens, that would be a heck of a brake light out the back!
· alt-e · 23 weeks ago
There have been quite a few experimental EVs built with 4 motors that are on the car side of the suspension system, not the wheel side. It is by far the best EV configuration in my view. You can do all kinds of interesting control things.
One advantage of electric motors over ICE is that motors are scalable. In fact small motors are easier and cheaper and can be aircooled more readily.
Great in accleration, great in regen. Very efficient. Very high performance in every way.
And electric motors, when made in high volume, can be cheap. And the electronics can be cheap. So it is not as much more expensive as it may sound (compared to one big motor). And if you are clever, these motors can be small enough to fit into the volume of space where the suspension system is. So they don't have to take up a lot of space either. Often this strategy is space saving as the axle does not penetrate into the car body region.
· regman · 23 weeks ago
Derall,
"and you might have missed the word peak."
No I didn't but your statement "predictably, confidently and safely slow RWD cars at a peak of ~0.6g using only regen" implies that this peak is sustainable by tacking the words "predictably, confidently and safely" to it. I do (and did) concede that 0.6g "peak" decel is possible in a vehicle that has a 60%+ rear bias, low CG and good tire but it is not possible to sustain peak coefficient braking for several reasons and in fact you don't want to brake anywhere near peak coefficient braking because once wheel lockup starts, you have to dump braking well below the peak braking capability to get it back. Not to mention the fact that lateral force capability does not ever peak and can drop in half by the time a wheel starts to slip causing oversteer and understeer conditions. So mentioning peak capability in braking does not mean you can actually brake at this level.
· JRP3 · 23 weeks ago
Check out Mate Rimac's Concept One for an awesome application of independently controlled inboard motors for each wheel:
http://www.rimac-automobili.com/concept_one/propulsion-system-8
· alt-e · 23 weeks ago
@JRP3 - that would be the super car version. A lot of the one off exotic EV race cars have gone that way since the performance is so good. But to do the same thing in a regular car only requires small pancake motors. So they can be packaged in a small space. Little high torque permanent magnet motors.
· JRP3 · 23 weeks ago
You can size the motors as you like using the same concept. I like his version because he still uses gear reduction to allow the motors to spin faster than wheel speed, which is usually too slow for efficient motors and loads them unnecessarily.
· darelldd · 23 weeks ago
@regman - UNCLE! Now we're getting too word-picky even for me. White flag. You win. I'm done. I am learning lots though - about sentence structure if nothing else.
@JRP3 - Whoa. Neat what you can do if there's no budget! The whole idea of independent power and braking of all four corners really is boggling.
· alt-e · 23 weeks ago
Sure. You can gear them if you use traditional motors. Or you can go direct drive if you use an advanced high magnet to electromagnet area motor. You can do a lot of things.
I think this is the future of EVs. And there are a lot of variations to it. But it really takes advantage of the things that electric motors can do that ICE can't. And it makes it even easier to have a powered platform that you can set different vehicle bodies on in the auto factory. So there are real production benefits to this concept.
· JRP3 · 23 weeks ago
Yeah, I always like the skateboard concept:
http://www.gizmag.com/trexa-electric-vehicle-pricing/14119/
· darelldd · 23 weeks ago
@ alt-e
You and I are on the same page in this regard! I just keep wondering why this remains a "concept" after all these years. Why is nobody really doing it? Expense? Lots of one-offs. Nothing on the radar for production.
· alt-e · 23 weeks ago
JRP3 - A handmade skateboard for $16k. That is pretty amazing. Just one motor per axle though. But still impressive.
· JRP3 · 23 weeks ago
Unfortunately the updated design is less impressive:
http://www.green.autoblog.com/2011/04/12/skateboard-concept-trexa-enertube/
· darelldd · 23 weeks ago
Boy, I don't know. The new tubular one may have me MORE impressed.
· alt-e · 23 weeks ago
@ darelldd - I have no idea. It is what I have been advocating for many years now. The closest I have seen the major car companies of agreeing to it is the GM Autonomy concept vehicle. Which was around 2001 or so. It was a skateboard with 4 motors.
There are just so many advantages to this. Including benefits to the auto industry by having more common parts and assemblies between many models of cars. No more debating what kinds of cars to put out. Just build them all with a limited number of power platforms.
I can tell you that if you do a cost study it trades cheaper in mass production at high volume levels. And is more energy efficient. And is higher performing. Because it is so much easier to make a small motor than a big one. I am sure we will get there eventually.
The only thing I can figure is that it may appear easier and faster to develop a one motor car over a 4 motor car. The car designers could have been itimidated by their short design schedule. The electronics of a one motor system are certainly easier to design.
· JRP3 · 23 weeks ago
Yes I think it has a lot to do with complexity and cost, one motor is just cheaper and easier, and works fine for most applications.
Darrel the new tube shape has only one motor, and doesn't provide the nice skateboard platform which can hold more batteries in a thinner platform and allow different bodies to be easily bolted on.
· darelldd · 23 weeks ago
@ Alt-e - My best guess that it is the same old story: The emphasis is on how to make a profit next quarter. Not next year or next decade. Building one common platform will take more time, but would have benefits over the long haul. So it would sacrifice the short term profits for the long term profits. And the auto industry has not historically embraced what is good for it in the long term!
I recall the GM Autonomy. I remember two versions, in fact. It was billed as the reason to go with fuel cell if I recall correctly! As if it wouldn't work with a battery car. One version had the crazy "airplane" yoke steering "wheel." Ahh... Takes me back to when GM hated all battery cars, and pounded into us that if we insisted on battery cars that we'd never see the fuel cell cars that were *almost* ready!
· darelldd · 23 weeks ago
@ JRP3 -
Oops. Missed some of the important details I guess. I'm easily distracted by bright shiny objects.
· darelldd · 23 weeks ago
@ alt-e - can I get you to turn on your "contact" feature in your profile? It is an anonymous way for other members to get in touch with each other. Thanks!
Your account -> Edit Profile Settings -> Contact checkbox at the bottom of the edit field.
· alt-e · 23 weeks ago
Done.
· ex-EV1 driver · 23 weeks ago
Don't worry folks, you'll see that skateboard concept coming out soon. Its the Tesla Model S. The first will be a sedan but an SUV will follow shortly after. They will both have the same chassis except, of course, that they will be developing a powered front-end option for the SUV as well.
GM clearly chose to support their corporate structure with the Volt, rather than sticking with the logical approach of the skateboard concept.
· Ken Fry · 23 weeks ago
Hi Darrell,
You asked: "How come your Zing! Site is so hard to find?! "
Actually, I haven't looked at my profile in ages. Thanks for the heads up. I fixed it.
· Ken Fry · 23 weeks ago
In general re the skateboard:
Auto manufacturers already use this concept, too much. (A RAV4 is really a Camry, etc.) But when you go from a sedan to an SUV, then the suspension arms all have to change with the change in ground clearance: just lifting the thing up, and letting the arms droop to a different angle is inadequate for a production car. Gear ratios must change with changes in gross weight rating, as must tires, etc.
This tendency to use the skateboard concept is what leads to criticism for "parts bin" cars. A fully optimized car will have unique components. The trend has been toward fully optimizing each design (Honda were the masters at this) using "right sized" engines, chassis components, brakes, wheels, tires etc etc. The trend (in the more successful manufacturers) has been away from things like the original Mustang, which was severely compromised (and still is) by using standard components. All the Civic variations (sedan, coupe, old Del Sol, CRX,) etc are very similar, but each is optimized for a particular mission. Very few components are shared with the Accord, because the Accord is bigger and more luxurious, and any Accord component on the Civic is too big and heavy, and therefore degrades performance.
GM has always built skateboards and sold the same basic cars as, for example, the Chevy Citation, the Pontiac 6000, the Buick Century. But even the station wagon models of these had many different components based on mission, GVWR, etc.
Ya can't make a silk purse out of a sow's ear... but the manufacturers keep trying: thus the Cavalier and the Cimmaron -- the latter being roundly criticized for being a gussied up Cavalier.
I consulted with Ford many years ago when they were bringing out a Worldwide Engineering Release System to help standardize components across models around the world. There are obvious benefits in doing so. But using the same chassis for a Focus and a Fusion is not possible, without compromising the fuel efficiency of the Focus. Ford would love nothing more than being able to sell Expeditions universally: the whole truck world is very modular, and severely compromised in every aspect of performance. The Expedition is an absolutely idiotic people carrier, but fully embodies the skateboard concept: just pop off the pickup body, drop on the SUV body.
The Prius is the best example of a fully optimized design, with virtually nothing shared with any other model. As a result, it gets twice the mpg of an Accord (of one generation ago) , which serves the same mission.
· darelldd · 23 weeks ago
You make a compelling case against it, Ken. (and thanks for the updated profile!)
· alt-e · 23 weeks ago
@ Ken Fry - I agree and disagree with your skateboard comments.
On the agree side: it is true that if you go up or down a size class such as from the Focus to the Fusion those should be different designs. But I would say different skateboards.
On the disagree side: there are so many designs of vehicle in a given size class. There are different numbers of seats. There are different numbers and types of doors. There are different cargo capacities. There are different cosmetic features which radically change who the vehicle appeals to. There are just so many things that can be done to make the vehicles work for a broader population by making each type more what someone is looking for. Without having to re-engineer the power train or the suspension.
· Ken Fry · 23 weeks ago
Hi alt-e
The things you disagree with are mainly things that require major changes to the body, and therfore to the whole structure. Only in trucks and truck based SUVs can you get away with separate frame and body construction -- because in that market, fuel efficiency is not a strong motivator, and nobody expects responsive handling -- they very low levels of torsional rigidity to weight. All other cars are monocoques, and changing door size and type requires a complete redesign. If there were no European and Japanese competition, we'd still have frames under our cars, and we could have more of a skateboard concept there, as we do in trucks. But trucks and SUVs demonstrate the compromises. High profit for the manufacturer, sub optimal to poor performance.
There is a tremendous advantage to using the roof and even the glass structurally. A monocoque can be many times stiffer than a body frame combo for a given weight. A thin structure, like the GM skateboard, is inefficient from a stiffness standpoint. Other things being equal, the bending stiffness of a beam goes up as a cube of its thickness. A similar principal applies to torsional rigidity.
Modern cars always beat the heavy old frame based cars in crash tests, because they are more efficient structures.
Engines and drive trains have always been and remain quite modular. Thus 4 cylinder and 6 cylinder versions of most cars, and use of a given engine transmission package across many model.
· alt-e · 23 weeks ago
@ Ken - take a look at the BMW i3. That is not exactly what I am talking about, but it illustrates a modern design that is an aluminum frame with a carbon epoxy body.
Now imagine designing a bit more generic version of the aluminum part and a variety of different carbon epoxy tops. With different features but the same foot print.
All of them designed with computer structural analysis to get the carbon epoxy top to play an appropriate role in the structure.
The neat thing about having new materials and new computer analysis techniques is that you can do more of a variety of things and get each of them to work out. It isn't as expensive as it used to be because you can do crash test and structural performance simulations in the computer and get it right there before you build one.
· Ken Fry · 22 weeks ago
Hi alt-e,
Ironically (because I have been advocating for a fully-integrated monocoque structure), the Zing! production version has an aluminum frame and polycarbonate body.
The POC, on the other hand, is a full monocoque, and is much lighter. The entire body (not including steel tube front and rear subframes) is about 60 lb. Most of it is just plain wood, with only the central portion technically a composite with wood core and fiberglass skins in epoxy. Wood (plywood especially) is a a remarkable material. (About a year ago I built a kayak for a customer who was interested in a very light boat, and it came out to 19 lbs, less than half the weight of a production kayak of the same size. Every surface was skinned in fiberglass cloth in epoxy.)
The original Beetle was a lot like the BMW (other than in material choices), or like a more sophisticated and workable version of the Trexa). Although VW did not use that platform for anything other than the Beetle, it was used as the basis for numerous kit cars.
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