First Full Range Test of Nissan LEAF Yields 116.1 Mile

[mwalsh]

Interesting:

Of course, that doesn't mean you can't drive fast. The instant we hit the highway, we throttled the Leaf up to its top speed, which is supposedly electronically limited to 90 mph. The digital speedometer read 95, which was cool until we noticed the range estimate dropping a mile every few seconds. That makes speeding a thrill for an entirely different reason (one for which GM has coined the term range anxiety). We did not have enough time, or unpatrolled highway, to verify the Leaf's range at top speed, but would guesstimate that it might go 20 miles, if you're lucky.

After we switched back to Eco mode, the range recovered some of its losses, and after two stints behind the wheel, we ended the day at 70 miles, with 12 miles of range remaining. Don't drive it like it's stolen, and with the air conditioning and heaters off, we have no doubt it could go 100 miles.

http://www.popularmechanics.com/cars/reviews/hybrid-electric/2011-nissan-leaf-test-drive?src=rss

 

[tps]

we could vary the speed of the car based on taking advantage of best case scenarios in converting gravity to motivational force which means NO REGEN going down hill. its basically a slingshot effect. and yes, it only works when there is no traffic.

Even with a "slingshot" effect the energy is not free, it comes fro somewhere. A famous gravity assist slingshot was used by the Voyager 1 spacecraft in its Jupiter flyby. The slingshot did give the spacecraft some extra energy, but this energy came by slowing Jupiter's rotation imperceptably. However, I doubt that cars going up and down hills are gaining significant energy from the earth's rotation.

 

[Coffee_Slurry]

If I can get 80 miles of raucous driving, I'll be thrilled.

 

[DaveinOlyWA]

wow... ok. lets look at it this way.

we have 2 one mile stretches. one flat. another a half mile downhill, half mile uphill.

on the flat course, we maintain a steady speed using power at say 250 watts per mile. total power used over that mile 250 watts.

on the hilly course. first on the downhill part, we apply a very negligible energy which will allow it to gain speed as gravity pushes us down the hill. when we start the ascent going somewhere above the target speed. we apply power at the rate of 250 watts per mile. now this is not enough to maintain speed, so we will slow down due to the fact that we are climbing the hill. now if we crest the hill at somewhat under the target speed the results are

first half of course power used; depends on the hill. if its steep enough, gravity will provide all we need as long as we put enough to the wheels to prevent regen. so we say zero.

2nd half of course; 125 watts for the half mile.

traveling the same distance while potentially using half the amount of power since we never exceeded the 250 watts/mile rate. because our downhill speed was greater than our target speed that would equalize our less than target speed as we crested the hill. making average speed near the same as the car on the flat course

now since we live in the real world; using only half the amount of power is not possible, but once again; if you look at my original statement i ONLY contended that rolling hills can potentially increase your range. there are conditions that must be met.

1) the willingness drive faster than your target speed.
2) a wide open road

but, i stand by my statement.

 

[Coffee_Slurry]

I appreciate you sticking with this, since it's certainly more fun to discuss examples than "I say so."

Now, just so we're clearly disagreeing. , I'm going to go on record here as stating that rolling hills can never, not at all in the slightest, potentially increase your range. (on a pure EV car) Moreover, it must always consume MORE energy than the same distance covered by flat road. They are not equal -- hills are worse for range to destination.

Even if you have perfect regen, and perfectly flat motor efficiency, any real-world vehicle has some rolling resistance (axle friction, rolling resistance of the tires, and drag).
In a scenario where you go through a big 'dip', you have covered more miles -- it's a longer route. That has to manifest as more rolling resistance to be overcome by powerplant energy.

One other thing someone will point out is that what you described as "power used" is measured here in kWh, a unit for energy. It has a time component. Instantaneous power is Watts. It has no time component. Watts is just a single measurement of how much power you're drawing right at this moment. So, there is no accurate interpretation of "250 watts per mile". It's a common misunderstanding, and doesn't really impact your explanation. A constant draw of 250 Watts over one hour would be 250 Watt-Hours. Anyway...

Everything that gravity "gives" in terms of kinetic energy, you have to pay back to climb out of the hole. Really, we're talking about potential energy -- mass at some height, chemicals in a battery, compressed springs, attracted magnets. They're all just storage of energy, not sources of energy.

If you take a marble and a perfect steel bowl, it will roll down the side, pick up speed, and roll up the other side of the bowl. Almost! Not quite to the edge of the bowl. It will fall short, just like your car. It gathered some kinetic energy as it coverted its elevated position at the rim, into motion at the bottom of the bowl. (Potential energy (battery) converting to kinetic energy (speed)) Now it has to climb the same slope at the other side of the bowl. If there was no friction, no drag, no energy loss at all, it would reach the same point on the rim. But there is always friction, drag, and loss. It won't make it to the lip.

And now the point: If your car is almost, but not quite to the lip of the bowl, you will have to step on the gas to make it there. In this last bit of climb, where it's all battery power to get out of the bowl, you will have used up MORE energy (kWh) than if you had just driven over a flat bridge in the first place.

 

[tps]

on the flat course, we maintain a steady speed using power at say 250 watts per mile. total power used over that mile 250 watts.

on the hilly course. first on the downhill part, we apply a very negligible energy which will allow it to gain speed as gravity pushes us down the hill. when we start the ascent going somewhere above the target speed. we apply power at the rate of 250 watts per mile. now this is not enough to maintain speed, so we will slow down due to the fact that we are climbing the hill. now if we crest the hill at somewhat under the target speed the results are.

The key to finding the best speed is to consider that the power needed to overcome the drag (wind resistance) increases by the cube of the velocity, therefore it quickly becomes the major component of power loss. This is why the reveiwers who drove 95 MPH found their estimated range dropping very quickly.

If one was to compare the least energy scenarios for driving on a flat road and driving on hills, I bet driving on a flat road would win. Nissan's 100 mile range (under average conditions) might drop to 60 miles at freeway speed, but climb to a rather high value if the driver was willing to make his entire trip in "limp" mode.

 

[Nubo]

For anyone who believes that hills can increase mileage efficiency over flat roads, I advise you to try this on a bicycle and the truth will quickly become apparent.

 

[sjfotos]

For anyone who believes that hills can increase mileage efficiency over flat roads, I advise you to try this on a bicycle and the truth will quickly become apparent.

No lie!

Of course, the only thing worse is wind!

 

[planet4ever]

I hereby withdraw my support for Dave's original assertion. It's clear now that he really did mean hills could be more efficient than flat land.

The key to the flaw is, as others have suggested, focusing on why the LEAF uses 250Wh to travel a mile at a constant speed on flat land. At highway speeds the energy is mostly used to fight air resistance. If you go down Dave's hill and back up the other side to the same elevation, your potential energy relative to the gravity pit is unchanged. But if you are only compensating for air resistance half the time then you will be going much slower by the time you get to the top of the hill. In fact you will be going even slower than you would be on flat land if you held speed for half a mile then coasted the second half mile (because air resistance increased as you sped up going downhill).

Since I suspect you would stop before you coasted half a mile on flat land, it follows that your velocity will be even less than zero before you get to the top of Dave's hill. i.e. you won't make it to the top at all.

 

[smkettner]

Of course, the only thing worse is wind!

And a headwind hurts more than a tailwind helps. (at same windspeed and vehicle speed)

 

[smkettner]

I kinda wonder about the efficiency of the electric motor at constant speed. Is it possible the electric is more efficient when under higher load such as accelerating or climbing a hill? Just thinking moderate acceleration for 30 seconds then coast (no regen) 30 seconds would that be better or worse? In moderation of course not full throttle.

My thought is running a 100hp motor at 15hp as you cruise may not be the most efficient. Anyone have an efficiency curve of a traction motor?

 

[LEAFer]

These two links make a great start to exploring efficiency:

http://www.teslamotors.com/goelectric/efficiency
http://www.teslamotors.com/blog/roadster-efficiency-and-range

Although the focus is on overall vehicle efficiency, some breakout of the components can be gleaned, including "drivetrain", which is more than motor, but should be comparable to LEAF.

 

[smkettner]

What I read is down to about 25% load the efficiency curve is very flat. This tells me climbing a hill may not cause the inefficiency that might be assumed. Where cruising at steady rate may actually drop the efficiency of the motor due to the light but constant load. This should be factored into the hilly terrain calculation as compared to the flat and level.

Using 40% power for for two minutes then coasting and using no power for two minutes might be better than running the motor at 15 to 20 percent power continuous. Not huge but if you could gain 10 percent it may well make up for some other losses.

 

[tps]

Looking at the Tesla curves, it looks as if the sweet spot is between 10 and 30 MPH, where ~150 wh is consumed per mile. Maybe the effect of lower motor efficiency is what causes the energy consumption to shoot up below 10 MPH. I'm almost sure that increasing drag is why the curve shoots up past 30 MPH. My thought after looking at this is that if you keep it between 10 MPH and 30 MPH on level ground, you'll get the most range. Probably, because there may be continuous loads, which would use more energry per mile at low speeds, it probably works best to keep the speed steady near the top of the sweet spot. I can't see how going faster than 30 MPH, even when coasting downhill, would help, becasue drag is drag, you have to add the energy to make up for somewhere.

 

[evnow]

Looking at the Tesla curves, it looks as if the sweet spot is between 10 and 30 MPH, where ~150 wh is consumed per mile.

For Leaf it is 38 mph - when Nissan says we will get 138 miles.

 

[Carlos]

Looking at the Tesla curves, it looks as if the sweet spot is between 10 and 30 MPH, where ~150 wh is consumed per mile.

For Leaf it is 38 mph - when Nissan says we will get 138 miles.

evnow,

How can the Range-AC at say @55mph be higher than at 50mph as the graph shows?
Where would you plot Range-AC at 40mph?
My commute in Phoenix is all on City streets posted at 40 mph.
I just need to know if I should pack a cooler of ice for the middle of the summer day commute home rather than use the AC unit for the 15 minute drive. jk
I can't wait for the forum title "Hypermiling the LEAF"
Carlos

 

[evnow]

How can the Range-AC at say @55mph be higher than at 50mph as the graph shows?

These were plotted using Nissan's disclosed ranges (as reported by media). The conditions are somewhat different ... if you search you may find a thread with a lot of discussion on this very question.

 

[Nubo]

How can the Range-AC at say @55mph be higher than at 50mph as the graph shows?

AC is a heavy consumer, and consumption is dependent on time, not speed. So if you go slower, the AC is consuming more power per mile. So at some points on the curve, the aerodynamic penalty is offset by fewer AC watt-hours per mile.

 

[DaveEV]

For Leaf it is 38 mph - when Nissan says we will get 138 miles.

It's likely a lot lower than that as DeaneG's calculations suggest (~20mph).

His estimate on "vampire draw" of 300W appears to be pretty good guess - the guys as CleanMPG noted that the car seemed to consume around 250W just sitting there.

CleanMPG previews the 2011 Nissan LEAF.

Wayne Gerdes used 144 Wh/mile on a 9.9mi test drive (1.43 kWh). If he can keep that up for a full charge he'd get 165 mi on a full charge.

 

[evnow]

For Leaf it is 38 mph - when Nissan says we will get 138 miles.

It's likely a lot lower than that as DeaneG's calculations suggest (~20mph).

Link ? I've not seen them.

I doubt anyone other than Nissan can actually calculate that at this point ...