Cruise Control under 45mph drain on battery?

[surfingslovak]

I doubt many folks could beat the cruise control on level terrain, but certainly with hills, there should be "fixed power" mode instead of fixed speed. No, I don't think Nissan will come out with this, but it has been done in airplanes (and I've commented on it previously).

Isn't that how the accelerator pedal works in ECO mode? Perhaps Nissan should simply apply that to cruise control in ECO mode as well or make it a selectable user setting. Constant power would certainly help with range management. It's funny you should mention airplanes, last time I had to deal with this concept in practice was competitive cycling. It's important to pace yourself on hill climbs to avoid bonking and the accompanying loss of time. It's easy to misjudge the power output on climbs, you cannot rely on the observed speed. Anyway, I'm sure this approach would help EV drivers too.

I just wanted to direct your attention to this cool chart someone has plotted a while ago. It shows the projected range and by extension efficiency over a range of speeds. It's not super accurate, likely because it was put together before there were many LEAFs in the wild, but it gives you a good idea of what to expect. The average speed of several test protocols is marked as well for better comparison. While the typical owner might not want to drive this slow on a regular basis, knowing when peak efficiency occurs can be important. I remember relying on this a while ago, when I managed get 21 miles after the low battery before hitting turtle.

I would also hazard a guess that LEAFfan used this type of know-how to achieve his world record of 151 miles driven on a single charge. Here is one of the older threads he referred to.


Click to open

 

[Caracalover]

+1 I was able to obtain 9.1 m/kW h for 15 miles at 15mph. Someone else did even better driving below this speed.

One hour to go 15 miles? Really? If that is fun for you go for it, but measure the wall to wheels energy use next time.

Really! And no, it wasn't fun. Evidently, you didn't read about the experiments some of us did to find the optimum speed. Mine was done on a continuous loop.

Actually I did read that thread, and I believe I made this same comment then about Nissan saying 35 was the "best" speed.

I saw no reason to argue with you about it then, nor do I now. But I know what I read, and to state I am wrong is wrong. If a Nissan rep wants to chime in and tell me what they believe the optimal speed is, I will stand corrected (If it differs from 35). Short of that you and Tony are just stating your opinion on the knowledge you believe you have acquired. That does not alter what Nissan says, nor does it make either of you Nissan reps.

I still do not believe you measured wall to wheels, did you?

How much power does a Leaf use when powered on with the headlights on in one hour?

I am not trying to be difficult here. You and Tony think I am wrong to state what I read. I am not wrong about it, unless you two can show me what Nissan says to the contrary. I see no need to find my source at this time. If Nissan wants to sue me over it, I guess I will dig to find it, short of that, it ain't happening.

I do appreciate the work you and Tony have done to figure this stuff out. I am not saying you are wrong, I am saying that for a practical speed, 35 (Instead of 45 from the OP) may work better since I recall Nissan saying that was the speed to aim for.

Optimal speed is going to vary with the wind, surface density, temperature, and many other factors. To get back to the OP:

I use CC on steep upgrades to keep my speed at 25, the lowest CC setting. This keeps my speed high enough to get me there, and avoids spikes above 20KW. I also would like a fixed setting on the power use.

Nice graphic, but again it doesn't account for the constant drain of being powered on. Going nowhere for 7 hours with your lights on will kill how much of your battery? At some point the speed has to account for that loss, and I do not believe this graphic reflects that reality.

 

[surfingslovak]

Nice graphic, but again it doesn't account for the constant drain of being powered on. Going nowhere for 7 hours with your lights on will kill how much of your battery? At some point the speed has to account for that loss, and I do not believe this graphic reflects that reality.

Phil measured this, and the LEAF pulls somewhere between 300 to 500 Watts in ready mode. I believe you can see it on the energy information screen. Although auxiliaries are not measured, and their power draw is simulated, this screen gives you a good idea of their contribution to the total load.

If you assumed 500 Watts draw with all auxiliaries on, including the headlights, that seven hour trip you mentioned will consume 3.5 kWh in auxiliary power. Assuming 6 m/kWh energy economy, a fairly high number far outside the fleet average, this would be approximately 20 miles range reduction. If you contrast that with a one-hour trip at 70 mph, where only about 0.5 kWh are used to power everything aside from the drivetrain, the loss of range would be about 1.5 to 2 miles with a projected energy economy of 3.3 m/kWh.

So, yes, while there is an appreciable difference, auxiliaries won't put the chart upside down. Not even close. It's also fair to quote Nissan representatives. And when you do that, I would recommend that you started with the following video when debating the veracity and accuracy of some of their claims.

Please realize that Nissan is a large corporation, not everyone is technical, and sometimes even the members of the LEAF program can get something wrong. It wouldn't be the first or last time, and hopefully it will improve as the LEAF moves towards the mainstream.



Click to open (segment starts at 1:33)

Source: EPA

This particular test is commonly referred to as the LA4 test cycle and it is designed to simulate a drive in the city of about 7 1/2 miles taking almost 23 minutes. Top speed is 56.7 mph and average speed is 19.59 mph. Ambient temperature can vary from 68 – 86 degrees so no air conditioning or heating is used. In this EPA test cycle, the LEAF achieved 100 miles of range.

 

[Caracalover]

Intersting video, watched the first few seconds and I got your point.

My original owner's manual stated that number. (Yes I read it.) Not defending it as right, just saying that is what it said at that time, and I have found it to be a reasonable number to aim at. Again, without an official Nissan statement that says something else, you have no way to prove me wrong so get over it.

You guys really need to chill out and let other people state what they know, rather than just keep saying that others are wrong, especially when we are not.

It is distracting and adds nothing to the conversation. You are welcome to state a differing point of view, but to state others are wrong without proof is annoying.

Thank you for understanding the loss I speak of. Add bathroom stops to that 7 hours of driving and you can make that 3.5 a full 4, or 1/5 of your battery assuming a 20KWH usable battery.

Now let me see where you got your graph from, it might have been from here, which supports my number quite well:

http://livingleaf.info/2011/06/so-really-whats-the-real-world-range-of-the-nissan-leaf/" onclick="window.open(this.href);return false;

"In this simulation, the driver enters the car, starts it, and drives at a steady 38 miles per hour and doesn’t stop until the car stops moving. No climate control is used with ambient temperature of 68 degrees. Also, the drive is on a flat road. We suppose that you could actually replicate this in the real world in certain states but it would be difficult to achieve in most. Edmunds.com actually did a simulation of this test using four test drivers and a several mile long flat oval test track. The only real difference was in starting and stopping the car three times for driver changes, and they used a speed of 35 miles per hour. Edmunds achieved a total range of 132 miles – pretty much verifying the accuracy of Nissan’s computer simulation (within the variables cited)

 

[Caracalover]

Phil measured this, and the LEAF pulls somewhere between 300 to 500 Watts in ready mode. I believe you can see it on the energy information screen. Although auxiliaries are not measured, and their power draw is simulated, this screen gives you a good idea of their contribution to the total load.

If you assumed 500 Watts draw with all auxiliaries on, including the headlights, that seven hour trip you mentioned will consume 3.5 kWh in auxiliary power. Assuming 6 m/kWh energy economy, a fairly high number far outside the fleet average, this would be approximately 20 miles range reduction. If you contrast that with a one-hour trip at 70 mph, where only about 0.5 kWh are used to power everything aside from the drivetrain, the loss of range would be about 1.5 to 2 miles with a projected energy economy of 3.3 m/kWh.

So, yes, while there is an appreciable difference...

Oh, and your numbers are a touch off here. You opt to use 6m/kwh to say only 20 miles will be lost. Yet you have another person stating they achieved a 9m/kwh when driving at 15 mph (Which is 5 mph faster than our 7 hour scenario). That would alter the lost range by a bit more, wouldn't it? (More like 32- 35?) At 35 Mph you can likely get 6/mkwh on flat ground. I cross a mountain, have an average speed of 38 and almost a 4.5/mkwh average over thousands of miles (Dash).

Also note that the graph you posted shows 18 stops and starts with that 19MPH average speed. It is only a short test, and it also will not account for the energy draw that the car will have simply for being turned on.

 

[Caracalover]

Nissan says the optimal speed is 37...

No, they don't.

Practically, it's between 10-15mph.

Even the very heavy (4600 pounds) Tesla Model S is about 22mph.

Tony; is this comment necessary? since when is "10 to 15 mph" practical?

you want to circle the lot with Broder? leave us out of it...

+1

 

[Caracalover]

I recall reading in either my original owners manual or on line somewhere from Nissan that 37 (Actual speed 35 I assume since the speedo is off by 2.) was the optimal speed (Wind tunnel?). In practice it does seem correct.

Nissan did not say that 37 mph was the most optimal speed, it just used it as an example. For sure if they had used a speed between 10-37 mph it would have been more efficient than 37 mph.

Not sure why you're being so stubborn on this, many people have proven that 37 mph is far from the most efficient speed.

An efficient speed is relative. If you have 3 minutes to get to the hospital, the efficient speed is much higher than if you are heading to the ex wife's step son's 15th birthday party.

I am not being stubborn, I am defending my assertion that Nissan made that statement, and I have found it useful.

When I am going down a steep grade my efficient speed is not one that forces me to use the brake. It is often far in excess of 37 mph.

As for what Nissan said, it was not an example, it was computer generated or real world derived model to achieve over 132 miles of range. You are free to use another speed if you wish, derived from whatever source you desire. I will start with Nissan's number, and then adjust it to my needs. It has worked very well for me over almost two years and 27,000 miles.

How many miles have you got on yours? As a moderator you would think you might fill out that information...

 

[surfingslovak]

You guys really need to chill out and let other people state what they know, rather than just keep saying that others are wrong, especially when we are not.

Perhaps you should heed your own advice? This is not a contest. While it's perhaps not what you wanted to hear, and nobody wants to be ever wrong, especially publicly and on record, I found similar threads beneficial. I learned a lot more about EVs in general, and the LEAF in particular, than I would have otherwise. Just something to consider, have a good night.

 

[TonyWilliams]

Not defending it as right, just saying that is what it said at that time, and I have found it to be a reasonable number to aim at.

Again, without an official Nissan statement that says something else, you have no way to prove me wrong so get over it.

You guys really need to chill out and let other people state what they know, rather than just keep saying that others are wrong, especially when we are not.

It is distracting and adds nothing to the conversation. You are welcome to state a differing point of view, but to state others are wrong without proof is annoying.

Now let me see where you got your graph from...

You're all over the place here. Nissan doesn't claim in the linked graph that 38mph is the longest range; it's just the longest range depicted on their pretty graphic. Some "official word" from Nissan will never arrive on this subject, nor would that make it accurate (nor is it needed, except for you).

You seem to want to have the last word, so knock yourself out; the best range speed of the LEAF is between 10 and 15 mph and "you are wrong". The data to "prove" this has been posted on this forum multiple times. It's not a political two sided opinion piece; just fact.

Best wishes to you in your beliefs.

 

[surfingslovak]

Oh, and your numbers are a touch off here. You opt to use 6m/kwh to say only 20 miles will be lost. Yet you have another person stating they achieved a 9m/kwh when driving at 15 mph (Which is 5 mph faster than our 7 hour scenario). That would alter the lost range by a bit more, wouldn't it? (More like 32- 35?) At 35 Mph you can likely get 6/mkwh on flat ground. I cross a mountain, have an average speed of 38 and almost a 4.5/mkwh average over thousands of miles (Dash).

I selected two representative examples: one with 6 m/kWh energy economy and about 120 miles of projected range and another one with 3.3 m/kWh and 70 miles of projected range. This was done to highlight the differences in two scenarios, one for someone who hypermiles, and another one for someone who doesn't. It's also worth noting, that I picked a fairly aggressive auxiliary run rate at 500 Watts. I looked up an older post from Phil, and he seems to have measured about 200 Watts. If you add 50 Watts for headlights and some A/C or heat (from the traction pack), you could be looking at more than that, but 200 Watts seems to be the minimum.

Also note that the graph you posted shows 18 stops and starts with that 19MPH average speed. It is only a short test, and it also will not account for the energy draw that the car will have simply for being turned on.

I'm not sure where you are going with this. I referenced the LA4 cycle parameters to highlight that the Nissan rep addressing a valid question from one of the prospects was not able to give the correct answer. As I said before, I don't see any malicious intent, but communications is a tricky thing, and we cannot expect to always get reliable information, along with the right context.

This is similar to battery life estimates. When Nissan sources said 80% in 5 years, no additional qualifiers were provided. Was that a median value, what mileage was used to model this outcome, etc. Similarly with the 38 mph claim. I'm sure that someone in a lab at Nissan modeled a blend of driving behaviors, they took very hot and very cold environments into account, regenerative braking efficiency, etc. We don't really know the details. Out comes a number, 38 mph, and the rest is history.

I still believe that you cannot apply this recommendation blindly without taking your operating environment and other factors into consideration.

 

[RegGuheert]

I doubt many folks could beat the cruise control on level terrain, but certainly with hills, there should be "fixed power" mode instead of fixed speed. No, I don't think Nissan will come out with this, but it has been done in airplanes (and I've commented on it previously).

Isn't that how the accelerator pedal works in ECO mode? Perhaps Nissan should simply apply that to cruise control in ECO mode as well or make it a selectable user setting. Constant power would certainly help with range management.

Agreed that constant power helps improve range and that ECO mode makes driving with constant power very easy to do in the LEAF. That said, I don't think I would want a constant-power mode in the car because it wouldn't be very compatible with other cars around that often drive at a constant speed. When I do this myself I monitor the draffic around me, particularly in the rear view mirror so that I can accelerate to try to avoid disrupting others on the road.

 

[bruce27513]

What difference does it make what the best MPGe speed is. We as Leaf drivers do not want to be perceived as "Hypermilers". Be smart. Drive the speed limit, try to accelerate on flat or downgrades.
I have over 10,000 miles after 8 months. Have driven 150 miles in a single day (Change every chance you get). I use cruise control all the time. Avoid the highways since it seems doesn't make that much difference in time and you will get better MPGe with non highway.
Here is the best tip I can give. Even if you have to walk a few blocks to your destination. Think about is, you are not poluting the air and you are getting excersize.

 

[EVDRIVER]

What difference does it make what the best MPGe speed is. We as Leaf drivers do not want to be perceived as "Hypermilers". Be smart. Drive the speed limit, try to accelerate on flat or downgrades.
I have over 10,000 miles after 8 months. Have driven 150 miles in a single day (Change every chance you get). I use cruise control all the time. Avoid the highways since it seems doesn't make that much difference in time and you will get better MPGe with non highway.
Here is the best tip I can give. Even if you have to walk a few blocks to your destination. Think about is, you are not poluting the air and you are getting excersize.

But make sure to turn off your dome light and put it in neutral while coasting to a light and slowing all traffic. :lol:

 

[dgpcolorado]

My recollection from when speed and efficiency were discussed before was that 35 mph was the approximate speed at which drag overwhelmed other factors, such as tires, drive train losses, motor efficiency profile, and the like. Above that speed efficiency can be modeled by drag increasing at (approximately) the square of velocity. Below that speed the other factors start to become more noticeable.

Nevertheless, drag at 35 mph is fairly significant (stick you had out of the window at that speed sometime) so it is hardly surprising that the most efficient (miles/kWh) speeds are quite a bit lower than that. [Again: drag is not linear, it is exponential, which is why higher speeds kill range so dramatically.]

Back on cruise control: I agree with Tony that using CC on level ground would be hard to beat in efficiency. On rolling terrain cruise control in D seems likely to be a bit more efficient than Eco since it loses less to regen when going downhill. But a good hypermiler ought to be able to beat CC on rolling terrain without difficulty. I wouldn't think the difference would be large enough to be worth bothering with though. My favorite use of CC is to keep my speed under control so that I don't have to worry about tickets. It is so easy to get going too fast in the smooth quiet LEAF!

 

[TonyWilliams]

My recollection from when speed and efficiency were discussed before was that 35 mph was the approximate speed at which drag overwhelmed other factors, such as tires, drive train losses, motor efficiency profile, and the like. Above that speed efficiency can be modeled by drag increasing at (approximately) the square of velocity. Below that speed the other factors start to become more noticeable.

Nevertheless, drag at 35 mph is fairly significant...

Yes, that drag at 35mph is quite significant compared to any speed below it. What I find absolutely amazing is how many times this has been written about here, and yet we are debating this like it's a startling new revelation. I have personally used 10-15mph more times than I care to repeat in order to stretch the range of my two LEAFs over 36,000 miles of total driving. Now, with my Rav4, I never have to do that.

Through testing (not guessing or hypothesizing), 10-15mph is that speed intersection between rolling resistance / aero drag and the static energy loads on the Nissan LEAF. I suspect that the 2013 LEAF might be approaching one whole mph lower with its lower static loads.

Petrol cars obviously have much higher intersections of those two curves (actually, i think many gas cars are in the 35mph area).

...a good hypermiler ought to be able to beat CC on rolling terrain without difficulty. I wouldn't think the difference would be large enough to be worth bothering with though. My favorite use of CC is to keep my speed under control so that I don't have to worry about tickets. It is so easy to get going too fast in the smooth quiet LEAF!

I was terrible at controlling speed when I first got the LEAF almost two years ago; I did get a ticket for 84mph. I disagree with you on whether you could measure the difference over hills, but obviously the larger the hills, the high the potential for gain without cruise control.

 

[surfingslovak]

This is an old thread, but for the sake of the somewhat heated discussion of the days past it's worth noting that a new record for distance traveled on a single charge has been established. A Japanese team has managed to drive their converted Suziki Every van over 1,300 km (808 miles) on a 25 km long test track in the Akita Prefecture. The speed the team has selected for their feat? Approximately 30 kph (18.6 mph).

 

[DougWantsALeaf]

I would certainly second a constant power mode for freeway driving. The hills on cc are brutal to your range (now you may ask, what hills in Chicagoland), especially when you need 90+ miles on your charge. Can be done at 50-52/mph with a nearly new battery.

 

[surfingslovak]

The hills on cc are brutal to your range (now you may ask, what hills in Chicagoland), especially when you need 90+ miles on your charge. Can be done at 50-52/mph with a nearly new battery.

Doug, I have done 107 miles on one charge, and about 100 miles from that total were at 50 mph on cruise control on the freeway.

 

[Stoaty]

What difference does it make what the best MPGe speed is. We as Leaf drivers do not want to be perceived as "Hypermilers".

Speak for yourself. I am happy to be perceived as a "hypermiler"--and using some of those techniques I have beaten co-workers on a 4 mile stretch of surface streets that is a common approach to our workplace. They pass me thinking I am driving too slow, then are amazed when I sometimes arrive before they do.

 

[DougWantsALeaf]

Surfingslovak very nice. I am sure Tonywilliams knows the exact efficiency difference, but the range difference between 52 and 62 mph feels significant. Now just waiting for warmth to return to Chicago.