First Full Range Test of Nissan LEAF Yields 116.1 Mile

[planet4ever]

great article on driving. now without details we can imply from his article

1)rolling hills could mean a lot of regen helping to boost his mileage.

1)Speaking of physics, you may want to brush up because this is 100% the opposite.

A few of you guys seem dedicated to the belief that regen is always bad. Scenario:

You're in rolling hills on a through road which is not a freeway. [Sound familiar?]

Added conditions: It's a two-lane road with significant traffic in both directions.

Now, I don't know what Dave might have been thinking, but he could well have been thinking of a case like that. So you crest a hill, and there is a slow truck in front of you. You can't pass because of oncoming traffic. The only way you are going to make it down that hill without hitting the truck is brakes or regen. Which one is going to result in better mileage? That's what I thought. Regen boosts mileage over not having regen. Nobody said it boosts mileage over driving on level ground. Nobody even said that it boosts mileage over [WHEEE!] coasting downhill in excess of the speed limit.

Prudent drivers keep their vehicle at a fairly constant speed except when traffic or road conditions force them to slow down. Hypermilers vary their speed up and down, up and down, and drive other people on the road nuts. If you are going to be a prudent driver, regen is your friend.

 

[tps]

great article on driving. now without details we can imply from his article

1)rolling hills could mean a lot of regen helping to boost his mileage.

1)Speaking of physics, you may want to brush up because this is 100% the opposite.

A few of you guys seem dedicated to the belief that regen is always bad.

No, EVDRIVER wasn't questioning regen. He was trying to point out that hills do not boost mileage, as opposed to driving on a level surface. The only way a hill can boost mileage is if you only drive down, but with a round trip, you have to return to the same altitude you left. The hill can be thought of a another battery, when you're on top, you've "charged" it. Coasting will allow you to capture some of the potential enegry stored in the "altitude battery" as kinetic enegry by charging the car's "momentum battery" (this is the energy stored in the mass of the car when it is in motion), however tire and bearing friction and wind losses mean that not all of the potential engery gets converted to kinetic energy. Regen adds an additional set of conversion losses in the motor, invertor and battery. In normal driving, where you don't often have the oportunity to coast all the time, regen is better than burning the energy heating up the brake pads.

 

[mitch672]

this doesn't prove pack size at all.

Maybe you can use %95 of the usable pack. It is believed that Nissan discharges down to %10 and charges to %90,
to the USABLE range is %80 of the total capacity, they are saying THAT the %80 is 24KW usable. this makes the pack 24KW + %20, or 28.8KW. Of course this doesn't help you, because you can't use the bottom %10 or the top %10, so the usable KW is really all that matters.

time will tell the full story, but 28-30KW seems reasonable for total pack size. with a usable amount set to 24KW.

 

[Norway]

this doesn't prove pack size at all.

Maybe you can use %95 of the usable pack. It is believed that Nissan discharges down to %10 and charges to %90,
to the USABLE range is %80 of the total capacity, they are saying THAT the %80 is 24KW usable. this makes the pack 24KW + %20, or 28.8KW. Of course this doesn't help you, because you can't use the bottom %10 or the top %10, so the usable KW is really all that matters.

time will tell the full story, but 28-30KW seems reasonable for total pack size. with a usable amount set to 24KW.

Hi Mitch,

Just a small point: 24 kWh is 80% of the total capacity, so the total capacity would be 24 / 0.8 = 30 kWh.
(80% of 30 kWh is 24 kWh, as a check.)

But I agree with you, it is of course the usuable range which matters.

 

[DaveinOlyWA]

umm, rolling hills has a HUGE potential to boost mileage.

there was a PC'er who sig states he lived in the "rolling hills of Central Texas" who was one of the first to get an 800 mile tank on his gen 2.

the objective is to increase your speed as much as you can going down the hill that is "charge neutral" (actually as we all know, that is not really possible so we call it very minimal charge) then as you hit the bottom of the hill and begin ascent you slowly bleed off power to provide very minimal charge with the goal of being within 5-10 mph of speed limit at the top the hill. (45+ mph in a 55)

the one guy in question had something like a 35 mile one way commute with 80% of the commute under the rolling hills condition and his speed limit was also 55 mph. so his commute ran typically from 45 to 75 mph and was averaging nearly 70 mpg. now if its a multiple lane hiway OR no traffic, you can do this.

using more regen to control speed down the hill is what common sense tells us. but that is a mistake. regen captures less than 10% (could be more in a Leaf) of power used. you are much better off to use as much of the gravity power you can "legally" get away with.

now this may seen like extreme measures to many and its up to all of us to determine what we will do on a personal comfort level, but i do this on I-5 and just as an FYI, ( i dont below 55 mph, speed limit is 60 around here) when i am at the upper limits of speed, i am frequently only going about 5 mph faster than the fastest people on the road.

 

[DaveinOlyWA]

Hi Mitch,

Just a small point: 24 kWh is 80% of the total capacity, so the total capacity would be 24 / 0.8 = 30 kWh.
(80% of 30 kWh is 24 kWh, as a check.)

But I agree with you, it is of course the usuable range which matters.

actually i use different math. if 95% of the the stated 24 kwh is useable=22.8 kwh

i think the charge range runs from 90 to 10% as well when we go to limp mode. so if 22.8 = 80% then total capacity would be 28.5 kwh

 

[Norway]

Hi Mitch,

Just a small point: 24 kWh is 80% of the total capacity, so the total capacity would be 24 / 0.8 = 30 kWh.
(80% of 30 kWh is 24 kWh, as a check.)

But I agree with you, it is of course the usuable range which matters.

actually i use different math. if 95% of the the stated 24 kwh is useable=22.8 kwh

i think the charge range runs from 90 to 10% as well when we go to limp mode. so if 22.8 = 80% then total capacity would be 28.5 kwh

The last 5% is also usable, albeit in "safe mode", I assume.

 

[tps]

umm, rolling hills has a HUGE potential to boost mileage.

Why would this be so with the LEAF? Nissan's example to obtain extended range from the LEAF is to drive at 38 MPH on a flat surface.

 

[Coffee_Slurry]

umm, rolling hills has a HUGE potential to boost mileage.

Even if that is true in a Prius (due to some optimal use of the engine/battery charge/discharge cycle), there is no possible way rolling hills will benefit a Leaf.

Just basic physics here. What goes down must climb back up.

Adding hills between two points on a map makes the rolling distance further as well.
A sine wave has something around 7 times the surface length of a straight line.

Think this through: Pick two points on a map, A and B. Consider two routes: one has a straight flat boring highway, and the other a long straight route through rolling hills.

We start at A.
You head for the hills while I head for the flats, and we both drive 45mph. Who gets to B first? Who has more battery charge remaining?

 

[evnow]

A sine wave has something around 7 times the surface length of a straight line.

I never imagined it would be so high. But it is - some 7.6 infact.

http://www.mathforum.org/library/drmath/view/52038.html

 

[Coffee_Slurry]

Amplitude is everything.

I'm not buying "7" either.. sitting here playing with a piece of string. I know it's the math-major answer, but it's not the number I'm looking for.

I'm thinking 2.4, but can't prove it.

 

[gudy]

.. If you drive slow for long distances and use climate control you will use much more power. There are exceptions.

Just for fun I made a spreadsheet to estimate range loss vs. vehicle mph for a given climate control energy load. I estimated vehicle energy consumption as a fixed component of about 0.3kW for basic operation, plus 0.07kW per mph linear drag (frictional losses), plus 0.0035 kW per mph squared (wind drag). The first constant is a WAG, but the second two give a range vs speed graph that looks reasonable based on what we've heard.

Anyway, adding a climate control energy load of 1kW reduces range in my model by about 20mi at 30mph, 7mi at 50mph, or 3mi at 70mph. Peak range (120mi) is found at about 20mph.

Adding a climate control energy load of 2kW reduces range in my model by about 64mi at 30mph, 13mi at 50mph, or 6mi at 70mph. Peak range (100mi) is found at about 25mph.

Of course, these are all guesses, but are probably reasonable.

DeaneG,

You should have motor efficiency in your model as well, as it is usually lower as lower speeds.

 

[jrhubott]

EVDriver,

Any chance you can make the spreadsheet public? If you want send it to me and I will make it a public google doc.

Thanks

 

[DeaneG]

DeaneG, you should have motor efficiency in your model as well, as it is usually lower as lower speeds.

Good idea. Any EV guys willing to make an informed guess as to the Leaf's motor efficiency vs. speed?

 

[DaveinOlyWA]

Amplitude is everything.

I'm not buying "7" either.. sitting here playing with a piece of string. I know it's the math-major answer, but it's not the number I'm looking for.

I'm thinking 2.4, but can't prove it.

a sine wave is a mathematical representation of a circle in relationship to potential charge. so

the formula is 2*pi*R or the circumference of a circle

so it not be "around 7" ... its more like around ~ 6.28 or 2*3.14159 etc...

and back to the coasting thing. ya'll can spout physics all ya want, but we have real life results here that say you are wrong, so we need to examine the physics closer.

sure, the objective is to drive a nice steady speed to maximize range. but on hills, we have too much variance in gravity, so when going down a hill, regen converts gravity into power to the battery... at about a 9 to 1 loss ratio.

so now we go up the hill maintaining the same speed, we lose again from the extra amount of power needed to maintain speed because its now speed + gravity.


or 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.

**edit** even MY math aint working. it would be pi, since the length is not equal to the radius but the diameter, so it would 3.14159.... times more

 

[evnow]

a sine wave is a mathematical representation of a circle in relationship to potential charge. so

the formula is 2*pi*R or the circumference of a circle
...
**edit** even MY math aint working. it would be pi, since the length is not equal to the radius but the diameter, so it would 3.14159.... times more

That is not correct. It is the x-axis that equals the arc length of a circle.

http://staff.jccc.edu/swilson/trig/sinewave.htm

Just search for "arc length sine wave" - you will see a number of sites describing that as a integral ...

 

[LEAFfan]

.. If you drive slow for long distances and use climate control you will use much more power. There are exceptions.

Just for fun I made a spreadsheet to estimate range loss vs. vehicle mph for a given climate control energy load. I estimated vehicle energy consumption as a fixed component of about 0.3kW for basic operation, plus 0.07kW per mph linear drag (frictional losses), plus 0.0035 kW per mph squared (wind drag). The first constant is a WAG, but the second two give a range vs speed graph that looks reasonable based on what we've heard.

Anyway, adding a climate control energy load of 1kW reduces range in my model by about 20mi at 30mph, 7mi at 50mph, or 3mi at 70mph. Peak range (120mi) is found at about 20mph.

Adding a climate control energy load of 2kW reduces range in my model by about 64mi at 30mph, 13mi at 50mph, or 6mi at 70mph. Peak range (100mi) is found at about 25mph.

Of course, these are all guesses, but are probably reasonable.

Peak range of 120? Someone has already obtained 138 miles on one charge, and if they got that, I can hit at least 140.

 

[planet4ever]

sure, the objective is to drive a nice steady speed to maximize range. but on hills, we have too much variance in gravity, so when going down a hill, regen converts gravity into power to the battery... at about a 9 to 1 loss ratio.

That's the second time you've said something like that, Dave, and I really find it nearly impossible to believe. (The first time you said regen was only 10% efficient.) Sure, there is loss in the generator, the battery, and the motor, but where is all the energy going? It must be going to heat. Are you saying that regen creates almost as much heat as brakes?

I thought I had read that regen could typically recover at least 50% of the energy, and that some recent vehicles did considerably better than that.

 

[Coffee_Slurry]

and back to the coasting thing. ya'll can spout physics all ya want, but we have real life results here that say you are wrong, so we need to examine the physics closer.

Gravity is not a source of energy, any more than a spring or a magnet is.

Let's imagine an unpowered car. Maybe a toy car.

You have two tracks.. one straight and level, one a straight row of rolling hills.
Same distance from start to end.

You give the car a push down the level track, and it rolls to the end, barely.
If you give the same push to the rolling hill track, would it get to the end? Would the odometer reading be higher?

Having a longer track with a bunch of elevation changes doesn't imbue the car with any bonus energy. (Assuming the start and end elevation are the same) That's nonsensical.

I just can't get past this point -- that you really believe hills will somehow extend range over flat roads. Explain more why you think so.

 

[DeaneG]

..Anyway, adding a climate control energy load of 1kW reduces range in my model by about 20mi at 30mph, 7mi at 50mph, or 3mi at 70mph. Peak range (120mi) is found at about 20mph.

Peak range of 120? Someone has already obtained 138 miles on one charge, and if they got that, I can hit at least 140.

My "120" was with 1kW of added climate-control load on the battery.