recommended approach for efficiency on-highway?

Are there any subtleties to appreciate about how to improve efficiency in driving at 70 mph?

- Should I use the cruise control? Does the energy-adviseability of this depend on whether it is hilly?
- Recommended settings for climate control? (When driving at lower speeds, depending on outdoor temps, I like to crack a window for ventilation and not bother with the climate control, though I suppose the reduction in aero could be hurting mpkWh more than the improvement in climate control energy use might help it. However, at 70 mph, this option seems to be moot as the cabin buffeting caused by opening a window is nasty). I think if there's a way to be sure I am turning on just ventilation, and not heating or cooling, then that would be one thing. Then of course we have recommendations to pre-cool or pre-heat the cabin before unplugging, ok. Lastly, if I do decide to operate A/C or heat when driving at highway speeds, maybe I can set the temperature or fan to moderate the energy use?
- Any other tips?

[Regarding speed: I've driven the I-5 and other routes in California, and know that some folks recommend going slower as one possible approach with the Leaf, but on the particular stretch that I drive, in Arizona, the limit is 75 and I am not sure but I don't think trucks in the right lane are as legally limited in top speed as trucks in California. So the net effect is that driving a Leaf at 55 mph in the right lane where I drive would be less safe (in my view) than it might be in California, and so slowing down is less of an option. .... maybe to 65, but that's about it.... basically I try to drive a safe speed for conditions and taking into account the speed of other traffic.]

Stay off the highway then so you can slow down.. or live with the high battery drain

70 MPH on a level road with no wind and no climate control is going to get you about 3.3 miles per kWh (courtesy Tony's range chart) and there is not much you can do to alter that. Doesn't matter, ECO or D. Getting rid of excess weight and increasing tire pressure will help some.

Range Chart: http://www.mynissanleaf.com/viewtopic.php?p=101293

Using heat or defrost is a killer. Cooling is quite efficient - at least here where the temps are moderate. I believe that even in AZ, I would use some cooling in preference to a cracked open window at 70 MPH.

No help to you, but in the WA metro areas the freeway speed limit is 60 MPH, and although many exceed that, driving at 60 is not at all uncommon. I usually travel just a tad over 60, just enough to keep the trucks off my rear bumper.

Guess you get the idea, but there's just no way to be efficient @70 mph; too much wind resistance. I keep it under 60 mph on the highway and routinely get efficiencies in the high 4's m/kWh.

jlsoaz said:

Are there any subtleties to appreciate about how to improve efficiency in driving at 70 mph?

Click to expand...

1. Don't drive 70 mph - slow down.
2. Follow a truck or pack of vehicles going the desired speed while maintaining a safe distance. You will get a reduction in drag without having to follow at an unsafe distance.

Slowing down is a control issue. When going faster you are in control to avoid the others. When going slower they are in control to avoid you. Same issues just the same only you perspective changes.

Find some slower people and hang with them for best economy and range. Leave 10 minutes early and arrive 9 minutes early.

scared of trucks? stay off the hiway. there is no way to be efficient at 75mph. it is physics.

While no one can deny that going slow is the best tip, I am in the same boat as you.
For part of my commute the speed limit is 70 and the trucks are all but running me over in the right lane. I have done allot of reading on Hypermilling techniques, and while they work really well on my hybrid...not so much on my Leaf. Pulse and Glide, leaf likes it better in cruise control from my experience. Coasting...leaf likes to glide...I use this quite a bit, cycling the Leaf in and out of neutral on down hills. Lastly I try to anticipate the hills...I cost most of the way on the down hill...then at the bottom I accelerate my speed with little power to assist with the climb on the other side. This usually involves speeding and I don't recommend it but it does work, sorry State Patrol I try to keep it under ten over when I do this. Don't worry I slow down really quick on the up hill.
The biggest thing I do is that I look at every trip on the highway as a challenge and try different techniques every time. I have yet to find one favorite over another yet, but I accept the challenge every day.

I did this summer a trip from Everett to Kent following a big rig doing 65-70. I got 6.2kw/m by drafting. Called the driver up on the CB let him know I was there. Used to do it all the time in my old VW diesel Rabbit.
I took local roads on the way back.

mrradon said:

I did this summer a trip from Everett to Kent following a big rig doing 65-70. I got 6.2kw/m by drafting. Called the driver up on the CB let him know I was there. Used to do it all the time in my old VW diesel Rabbit.
I took local roads on the way back.

Click to expand...

Thanks, some of the comments seem like they might prove useful. I'll keep this and another comment about drafting in mind. I'll have to see if it seems necessary to follow too closely to get benefit from this or if I can follow at my usual distance (for the speed and local conditions) and still get some benefit. I can see how it would have helped a bit for you to let the driver know you were there (i.e.: maybe allow for following a bit closer than usual).

On the comments about slowing down, I'd quick-estimate that at 70 I seem to be driving around the average (median) speed, with as many cars and semi-trucks passing me as my passing others, but I'll take another look at this and also I'll take it down to 65 mph and recheck my assumptions and see if that seems generally safe. My comments on trucks were made to acknowledge that in some areas there is a dual speed limit (one for cars, the other for semis), and so it might be possible to leverage that duality for some Leaf drivers in those areas, but around here as far as I know, there is no such duality, and it therefore might be a less viable plan.

I have already started to adjust to driving a bit more on city streets, but there are times or cases where that is prohibitively time-consuming.

HairyCairy said:

While no one can deny that going slow is the best tip, I am in the same boat as you.
For part of my commute the speed limit is 70 and the trucks are all but running me over in the right lane. I have done allot of reading on Hypermilling techniques, and while they work really well on my hybrid...not so much on my Leaf.

Click to expand...

Thanks Hairy. This is also very hilly area and I think a lot of folks who aren't using cruise control end up slowing down quite a bit from near the limit by the time they get to the tops of highway hills. Will keep your efforts in mind.

HairyCairy said:

Pulse and Glide, leaf likes it better in cruise control from my experience. Coasting...leaf likes to glide...I use this quite a bit, cycling the Leaf in and out of neutral on down hills. Lastly I try to anticipate the hills...I cost most of the way on the down hill...then at the bottom I accelerate my speed with little power to assist with the climb on the other side. This usually involves speeding and I don't recommend it but it does work, sorry State Patrol I try to keep it under ten over when I do this. Don't worry I slow down really quick on the up hill.
The biggest thing I do is that I look at every trip on the highway as a challenge and try different techniques every time. I have yet to find one favorite over another yet, but I accept the challenge every day.

Click to expand...

Since owning a Leaf for almost 2 years I've learned a lot of interesting alternate routes to avoid the highways. Many of the routes are back-roads with speed limits of 40 to 55 mph. What's interesting is when comparing actual travel time, there isn't that much difference. Primarily because the highway is often not the most direct route to where you want to go. So even though the back-roads are slower, I actually end up arriving in roughly the same amount of time, only with a lot more power left in my battery. Also the back roads tend to have less traffic and are less stressful.

There are also some highways in my area that have good access roads that run the entire length of the highway, but have almost no traffic on them since there are no businesses along these stretches. In many cases I'll just stay on the access road the whole way doing about 45 mph. There are occasional stop-signs to deal with, but no big deal.

Now, if I'm in a hurry and the range is not a problem I will most definitely jump onto a highway and do 80 mph or more. But most of the time I'm not in a hurry.

adric22 said:

Since owning a Leaf for almost 2 years I've learned a lot of interesting alternate routes to avoid the highways. Many of the routes are back-roads with speed limits of 40 to 55 mph. What's interesting is when comparing actual travel time, there isn't that much difference. Primarily because the highway is often not the most direct route to where you want to go. So even though the back-roads are slower, I actually end up arriving in roughly the same amount of time, only with a lot more power left in my battery. Also the back roads tend to have less traffic and are less stressful.

There are also some highways in my area that have good access roads that run the entire length of the highway, but have almost no traffic on them since there are no businesses along these stretches. In many cases I'll just stay on the access road the whole way doing about 45 mph. There are occasional stop-signs to deal with, but no big deal.

Now, if I'm in a hurry and the range is not a problem I will most definitely jump onto a highway and do 80 mph or more. But most of the time I'm not in a hurry.

Click to expand...

Thanks, I have found myself staring at google maps and then driving, learning about the roads you're talking about, both frontage roads and back roads. The point about the drive time not being substantially lengthened doesn't seem to hold so far in this area (a lot of the destination points are just off the interstate) but for some purposes it may, and in any event, it's a "we'll see" sort of thing. I just have to work out solutions suitable to this particular area, and taking into account that I probably will not see any public networked EVSE in the county for some years.

I haven't gone to the two red bars yet, and only a couple of times to three or four, so treating that as a proxy for 20%, I've stuck to that, but it seems unlikely I can stick to always-80%. Going slower on back roads will help, if-where I can find time to do that.

jlsoaz said:

I haven't gone to the two red bars yet, and only a couple of times to three or four, so treating that as a proxy for 20%, I've stuck to that, but it seems unlikely I can stick to always-80%. Going slower on back roads will help, if-where I can find time to do that.

Click to expand...

From Tony's range chart, when you are down to the last two bars you still have 31% of the battery left (44 miles at 35mph), when all the bars are gone you still have 17% left

Herm said:

jlsoaz said:

I haven't gone to the two red bars yet, and only a couple of times to three or four, so treating that as a proxy for 20%, I've stuck to that, but it seems unlikely I can stick to always-80%. Going slower on back roads will help, if-where I can find time to do that.

Click to expand...

From Tony's range chart, when you are down to the last two bars you still have 31% of the battery left (44 miles at 35mph), when all the bars are gone you still have 17% left

Click to expand...

Thanks, I guess I misunderstood what these two red bars signified, glad you went over this. I can't seem to confirm this by looking at the manual at page 2-10, but assuming I can find some confirmation somewhere in this forum, I will use the two red bars if need be, here and there, but keeping in mind I better be darned close to home by then.

jlsoaz said:

Herm said:

From Tony's range chart, when you are down to the last two bars you still have 31% of the battery left (44 miles at 35mph), when all the bars are gone you still have 17% left

Click to expand...

Thanks, I guess I misunderstood what these two red bars signified, glad you went over this. I can't seem to confirm this by looking at the manual at page 2-10, but assuming I can find some confirmation somewhere in this forum, I will use the two red bars if need be, here and there, but keeping in mind I better be darned close to home by then.

Click to expand...

The amount of battery left with two bars changed with the firmware update early this year. There are definitely a few more miles after you lose all your bars than there were before.

Pre-upgrade, I went turtle less than 5mi after I lost all bars. Post upgrade (I don't wish to do it again due to the psychological damage), this summer I have traveled 7miles on level terrain at 30-40mph with no bars (without reaching turtle). As always, your (no-bar) mileage may vary.

Herm said:

Stay off the highway then so you can slow down.. or live with the high battery drain

Click to expand...

+1

Here in Tucson it is the I-10. I never use it. The frontage roads are always empty, (everyone wants to do 70 on I-10). So I have them all to myself and cruise at about 42 and it is relaxing and efficient.

I have a couple of things that might be of intrest.

Use cruise control, but watch the energy use screen and when the energy use goes over the amount of energy you want to use, reduce your speed by 1 mph. If you know you have a thirty minute drive ahead, and you are using 25Kw, you will be using 12.5KWH or over half your battery. I figure on 18 KWH usable to give me plenty of buffer, and adjust my speed to get where I am going. If I need to drive for an hour, I keep my energy use under the 20KWH mark, which allows me to go over 60 most of the time. You will learn a lot from watching that energy use screen. If you are using 40 or more KW to keep your speed up, you will see the bars drop pretty quickly. At the full 80KW power use, you only have 15 minutes of driving, so while it is fun, remember that.

With the Leaf you will notice the wind drag far more than an ICE based car. With gasoline powered vehicles, the main product of the engine is heat. 75-90% of your fuel is used for heat production, not to get you down the road. The savings in MPG you can get by slowing down is only in that other 10-25%. With an electric car, the energy you have is used for what you want to use it for, almost entirely. If you want heat, 25% of your battery can be used for that on an hour long drive. A/C once the cabin is cooled uses very little, so keep the windows up and stay cool. It will use perhaps 1% of your battery. Wind drag with the windows down will always be less efficient at speeds over 50mph. If the temperature is lower than 60 outside the heater will come on, and that is something many of us hope they change with later models. On long trips you need to watch for that, as it can use up more energy than you want.

The great advantage the Leaf has over ICE vehicles is that you can gain energy while driving. You can not do that at 70MPH except on very steep declines, but using the regen when traffic allows can increase your range and still let you flow with traffic. This involves watching the rear view mirror and speeding up as traffic catches up to you, and slowing again as the packs of cars find there way around you safely. The most efficient use of energy is to keep the energy use graph on the 0 line. I use the N mode when I can. When you gain energy through the regen, you lose kinetic energy, which if you have to gain speed back you will lose more than you gain - this is why ECO mode may be less efficient in some situations. I prefer D in higher speed traffic, and of course timing traffic so I keep my speed up while not engaging the regen. When you have to slow down of course, ECO and a light foot on the brake will get you to the max regen - which at 30KW is like a fast charge! If you brake too hard you will engage the actual brakes, and lose the energy you might have been able to recapture. The ECO mode is also a bit more frugal with the energy the climate control uses I have heard, so if you want heat NOW! stay in D.

Seems the best mode for climate control is defrost and feet, 60 degree temp setting, A/C off. The heat can come on any time the system is on, so if the outside air is cold and you don't want to use energy for climate control, the cracked window may be the most efficient option. Sadly this is usually when it is raining, so the range is impacted. Happily almost everyone in these situations drives slower, so you can still stay with traffic and get home with clear windows.

Caracalover said:

Use cruise control, but watch the energy use screen and when the energy use goes over the amount of energy you want to use, reduce your speed by 1 mph.

Click to expand...

Good advice, and I do that most of the time myself on the freeway. But jlsoaz said the freeways in his area are very hilly. I think it's more efficient on a hilly freeway to try for a more steady pressure on the accelerator and let your speed adjust up and down except when you have a car behind you.

Ray

jlsoaz said:

Thanks, I guess I misunderstood what these two red bars signified, glad you went over this. I can't seem to confirm this by looking at the manual at page 2-10, but assuming I can find some confirmation somewhere in this forum, I will use the two red bars if need be, here and there, but keeping in mind I better be darned close to home by then.

Click to expand...

I think you may still misunderstand this. The two red bars are on the separate gauge of skinny bars at the far right edge of the dash. This shows your battery capacity, not level of charge, and you may have assumed (as I originally did) that it was just a scale for the charge bars. If your battery were ever to get down to those red capacity bars you would only be able to travel a few miles on a full charge, and I suspect you might be seeing a reduction in the maximum power it could deliver at all.

There is a graphic somewhere (I've forgotten where) that links the red bars to the blue and while charge bars, but that was created before Nissan remapped the meaning of the charge bars. The behavior now is that sometime after you drop to one bar (not three!) you will get a Low Battery warning. At that point you will have about 17% of your usable charge left. (Herm said 17% when the last bar disappears, but that is a bit optimistic.) That warning means it is time to start thinking about conserving energy or looking for a place to charge. I have driven 18 miles after getting that warning, but I did it by getting off the freeway and taking the "old highway" for half the distance, indeed slowing to 40 mph just to be safe. I'm pretty sure I could have gone several miles farther before getting the turtle, since I was only about three miles past the second (Very Low Battery) warning.

If you are going to worry about using the last two bars, then you'd better really worry about charging to 100% because using the top 15% of the capacity is probably as hard on the battery as using the bottom 15%. As for getting stranded, it just won't happen. You control how far you can go after you get the Low Battery warning; all you have to do is slow down. It's not even going to cost you that much time. 15 miles at 60mph takes 15 minutes. At 30 mph it takes 30 minutes. Any tow truck response is going to take way more than 15 minutes. The only logical behavior is to slow down and make it home.

Ray

P.S. Just for the heck of it I checked my records. I've been below LBW about 85 times and I've always made it home. The only time I got to turtle was when I did it intentionally, driving around the block. My battery has undoubtedly lost a little capacity in the past year and a half, but not enough to bother me.