ECO Mode + Cruise Control

It seems to me, if we understand ECO mode correctly, that ECO Mode + Cruise Control would be the best of both worlds. If the Cruise had a tolerances of say 5% or so, such that the cruise set would be a maximum speed which is allowed to dip to 5% of that before accelerating back to the maximum speed, where, once reaching the target speed, the LEAF coasts until it's decelerated to that 5% target and it all starts again. Seems to me this is ideal for highway driving: if you target 65, that's a minimum speed of a little under 62 mph, so your car would rev up to 65, then coast until it was at 62 then rev again, charging the battery during the coast because of ECO-mode.

The trick would be to set the right tolerance. A tolerance of only 1.5% would only be 1 mph difference between target and minimum and may end up revving too often for benefit. Also, a tolerance of exactly 5 mph would wreak havoc if cruising at slower speeds, like 35 mph, since those speed changes would be fairly sudden for the drivers around you. And theoretically, they could have a high tolerance, like 10%, but that represents 6 mph at 60 mph which might again be too big a jump at that speed.

Ideally, IMHO, Nissan would make the Cruise Tolerance configurable so that I could adjust it to traffic conditions. But Cruise + ECO would take some of the guessing out of how to handle an EV with ECO mode, letting the car figure out when best to speed up and when best to coast.

I don't know what you're driving now, but take it out and engage cruise control at 65. I would be astounded if it slowed to 62 mph on a straight and level road. CC today is very accurate (typically electronic vs. old-style vacuum). Variation will typically be within 1 mph at that speed on a straight and level road.

I hardly notice any variation in speed in my Soul with CC

Even on the gentle freeway grades, my 2010 Prius's cruise control (tried it at 3am this morning) did not allow the speed to vary by even 1 mph. However, the motor does indeed turn noticably faster and suck more gas on the inclines, and drop to the low-rev "no gas" mode (around 120 to 140 mpg) on the gentle downgrades.

Slick, and nice speed constancy, but not as energy efficient as losing some speed on the upgrade and gaining the speed again on the down-slope.

Also, accelerating the LEAF to 65 and having it Regen-coast down to 62, etc. would be a terrible way to try and conserve energy. True non-Regen coasting would be what is needed for this scheme to work well.

I think most cars are within about 2 kmph; certainly mine is usually hovering around there when I cruise as measured by my GPS. I think most cars want to be in the ±1 mph range since a) they can be that accurate and b) users would get annoyed if they weren't so configured.

My point is that the LEAF could do things differently because coasting is much more cost-efficient on it.

As for more efficiency with ECO-mode off, I would like to point something out, if I understand things correctly. My take is still:

Regular Regen: Regen on IFF Breaking
ECO Regen: Regen on IFF Not Accelerating

The Regen works, it's my understanding, by simply turning the motion of the tires into electrical energy. When breaking, this is done between the point where the break is first applied and when the tire stops rolling. For ECO mode, this would be any time the car was not being accelerated with the foot on the accelerator. Again, here the battery is charged by the motion of the tire, but the charge is slow and the inertial torque of the motor / generator on the tire is the only force felt on the car from the regeneration. In other words, it will take some potential to generate electricity in the generator in order to overcome the resistance of the metal magnets to turning and generating an electric field in the electro-magnetic coils. This torque (angular force) is what the tire will feel when charging. I posit that this is small with respect to the other forces acting on the car, especially drag. So while coasting you are loosing speed due to rolling resistance and drag but you can capture a small amount of energy from the momentum of the car. You can then continue this cycle of accelerating and coasting-charging along the highway for more distance on a given charge.

Now, that said, I do it worth a moment to consider the value of ECO mode. Clearly, the energy you put into to accelerating a car and maintaining its speed is always going to be greater than amount of energy you can get out by turning the forward motion of the car into electricity via the motor / generator. So if you simply speed to 65 and coast to 60, you'll get there in slightly longer time than if you had ECO mode on since the ECO mode is eating some small portion of the Kinetic Energy of the car. Either way, when you reach 60, you have to apply the same amount of energy to get back to 65. This shortening of the cruise distance should be proportional to the amount of energy received from ECO mode and since ECO mode is less efficient than acceleration, the increased frequency of accelerations would not gain you anything since the average energy usage over the entire trip will be higher for ECO mode due to the more frequent need for acceleration. And again, since it makes sense by the first law of thermodynamics that the energy gained in ECO mode cannot be more than this increased energy usage. In other words, you can't get something for nothing and I will concede that ECO mode must fall under that Rubric.

I still think, though, that this is an interesting idea and I'd be curious to see what the actual distance penalty was for ECO+Cruise. Would that we could only have our LEAFs today.

It is the current belief that (with cruise control off) there is always Regen with "foot-off" driving, just less (slight) in "Drive" and more (noticable, unknown how much) in "ECO" mode.

As far as we know, the only no-power, no-regen point might be with the "go-faster" pressed just a little. Again, the exact details still seem to be missing, I think.

While it is possible that the Cruise Control can keep the LEAF in a no-power, no-regen mode when the speed is "just right", it is not known that it does this.

There is no benefit from invoking regen unnecessarily. It never fully recaptures the energy that went into accelerating the car. Pulse and glide may benefit a hybrid because of the interaction of gasoline motor and batteries. But on a pure EV, I don't think so. I reckon the best economy will be to maintain a steady speed, within certain limitations of power draw (wind gusts, steep hills).

I agree. Let the car slow down a couple of mph on hills, if there's a way to determine and coordinate the pitch of the hill, but otherwise the most fuel efficient way to go is to maintain a steady speed.

Actually, for an ICE vehicle, the best fuel economy is obtained by maintaining constant engine speed at the engine's most efficient rpm, but that can result in excessive vehicle speed variations as terrain changes and so is not a safe thing to do. I don't know enough about electric motors to know if they have a single most efficient operating speed.

Nubo said:

There is no benefit from invoking regen unnecessarily. It never fully recaptures the energy that went into accelerating the car. ..... I reckon the best economy will be to maintain a steady speed, within certain limitations of power draw (wind gusts, steep hills).

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Nubo said:

Pulse and glide may benefit a hybrid because of the interaction of gasoline motor and batteries. But on a pure EV, I don't think so. I reckon the best economy will be to maintain a steady speed, within certain limitations of power draw (wind gusts, steep hills).

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My intuition says nubo is right, but I have no prior experience with EVs. Can some of you currently driving them weigh in on this?

I also suspect Gary is right when he says:

garygid said:

It is the current belief that (with cruise control off) there is always Regen with "foot-off" driving, just less (slight) in "Drive" and more (noticable, unknown how much) in "ECO" mode.

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That is certainly the way our Prius works. Slowing without braking in "D" shift builds little regen cars in the display. Doing the same in "B" shift builds them more rapidly, and slows the car much more dramatically.

I've heard of Prius owners Hypermiling to achieve +100mpg results utilizing coasting (Downhill & to traffic lights) in neutral vs regen.

Is there even a neutral gear that allows coasting in the Leaf? Or would this result in some negative results?

I'm sure there will be all sorts of new techniques to achieving the most mileage per charge.

My commute is mostly stop & go urban traffic so ECO mode sounds like my ticket overall.

I've been wondering about the ability to coast, also. According to everything I've read and seen, Nissan does not provide an automatic way to do this. When you take your foot off the accelerator, you automatically go into regen mode. However, seeing the layout of the shifter, I wonder if you could simply pop it into neutral when coasting as an option. For example, I suspect that I would achieve the best speed on some of the hills I commute over everyday by coasting. Without the ability to coast, I might be on and off the accelerator when going downhill to try to stay with the flow of traffic.

The only issue is how well the Leaf would handle popping yourself back into drive from neutral when you're going 55 to 60 mph. Works great for my converted electric vehicle because it coasts automatically. Even if it had regen, with the manual transmission and clutch, coasting would still be an option but this is not advised for an automatic transmission vehicle.

Has anybody seen any documentation on the Leaf that says this is NOT advised or might work?

With my naive understanding of the Leaf mechanical works, going into Neutral while rolling would be identical to holding the accelerator at just the right level to cancel the regen drag. So, no pull, no push.

There's nothing to disconnect or clutch in the transmission, so it's just a question of whether or not you are allowing the regen to slow the car.

In other words, you might as well leave it in drive, and just hold speed steady with your accelerator or cruise control. Identical to neutral.

(My best guess)

I asked about coast and did it during my test drive. My handler told me to push the shifter knob to the left and hold it for 2 seconds...the car shifted into neutral (with N on the dash) while rolling along. Then, normal over-and-back and the car went right back into Drive.

I have NO idea if Nissan will try to discourage it, but it is possible.

My drive to work is 30 miles, one way, with a fair number of rolling hills (San Diego). I plan on running at set speeds, using hypermiling techniques, and also using neutral-coast and see which produces the best range.

If the Leaf works like converted electric vehicles that I'm familiar with, the motor is already spinning (but supplying no power, nor generating any) when you are in "neutral." If that's the case, putting it back into drive while coasting with your foot off the accelerator shouldn't cause any problems at all. Of course, you wouldn't want to put it in drive with the accelerator depressed, and maybe not while braking. Which brings up another question. If you're going 60 mph in neutral and hit the brakes with no regen available (since you're in neutral) what will happen? Is the software smart enough to go right to the mechanical brakes or would it be confused by the fact you are going so fast and try to engage regen first? Can it apply regen if you're in neutral?

Perhaps those of you who will have test drives soon can ask and, maybe even, test these questions.

Since the cars are now being delivered, I hope we find the answer to the Cruise Control + ECO Mode soon!

TimeHorse said:

Since the cars are now being delivered, I hope we find the answer to the Cruise Control + ECO Mode soon!

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Just put the AC or heat on low and use cruise, ECO only increases regen which is likely not needed when using a cruise control and it also reduces the AC and heat levels which one can do on their own. Cruise control is a bit silly on a car with a sub 100 mile range, if you are driving on flat ground at slow speeds you likely won't be using cruise control and on the highway who needs cruise to drive 70 or so miles. In addition cruise usually wastes energy by keeping speed even on hills where one should back off the accel pedal to conserve. It seems like a feature that was added more for marketing because most cars now have this feature so they put it on. I can't see ever using it where I live but if one drives at 45 on a flat empty road for long distances often I could see it helping with an uncomfortable foot.

I will probably try cruise control initial, but will become more and more a hypermiler as I get a feel for the range issues. I like cruise because it's nice to just relax the pedal and also cruise let's me set the speed to the $#@%^-you-trooper speed and not exceed it.

Word of advice: Do not speed in the Commonwealth of Virginia! Class 6 Misdemeanor on your permanent record if convicted of going just +20 over the limit or 80 mph.

EVDRIVER said:

Just put the AC or heat on low and use cruise, ECO only increases regen which is likely not needed when using a cruise control and it also reduces the AC and heat levels which one can do on their own.

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What about on highway downgrades? The feature I hate most (*) about our Prius is that cruise control won't hold the desired speed going downhill, because there isn't enough regen unless you put it in "B", and as soon as you do that the cruise control is disabled.

(*) Well, OK, the feature I hate MOST is that it gets all its power from gasoline.

planet4ever said:

cruise control won't hold the desired speed going downhill

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I think that's a problem of all ICE / hybrids, unfortunately. If we can have Eco-mode Cruise, it might work, but it depends on how fast the initial speed is and how steep the grade.