Video of LEAF traveling at 98 MPH (157 KPH)

[gudy]

based on 70 miles at 55mph (with AC on), 95mph would give you about 24 miles of range.

Thank you, Carnac the Magnificent.

Seriously, how can you with 1 speed / range determine what the range will be at another? Given that range is (speed * 24kWh / Power) and power required to overcome drag is proportional to the cube of the speed, all we can say for sure is there is some quadratic equation (with a reciprocal term, 1/v) that would determine the reciprocal range under those conditions. Solving for such an equation would require 4 distinct speed points with all other variables being equal. 70 mi at 55mph would only give you 1 of those. One could just as easily guess that the equation is v * 24kWh / ((v - 55mph)**2)kW + 18.8 kW, which is 70.2 mi at 55mph and about 1.4 miles at 95mph.

TimeHorse : I used a shortcut approximation that range goes by the square root of speed, but I can obviously be completely wrong.
Here's the reasoning :
IF you exclude other drag / friction / losses :
Power required to overcome drag : P = some constant * speed ^ 3
Distance D = t (time) * speed
Time to empty t = C (battery capacity) / P

from these : D = C * speed / P
D = C * speed / ( some constant * speed^3)
D = C / (some constant * speed ^2)

If you increase speed by 95/55 = 1.72 , you'll reduce range by 2.98, hence going from 70 miles to 23.46 miles ...

Of course, drag does not account for 100% of the power you need, and there are also a lot of other factors which go both way (you're discharging the battery faster, therefore reducing its actual capacity, and you have high currents, increasing losses in power transmission).

Sadly, I don't feel like driving at 95 mph in a brand new leaf in the US, so I won't be the one doing the experiment ;p

 

[TimeHorse]

TimeHorse : I used a shortcut approximation that range goes by the square root of speed, but I can obviously be completely wrong.
Here's the reasoning :
IF you exclude other drag / friction / losses :
Power required to overcome drag : P = some constant * speed ^ 3
Distance D = t (time) * speed
Time to empty t = C (battery capacity) / P

from these : D = C * speed / P
D = C * speed / ( some constant * speed^3)
D = C / (some constant * speed ^2)

If you increase speed by 95/55 = 1.72 , you'll reduce range by 2.98, hence going from 70 miles to 23.46 miles ...

Of course, drag does not account for 100% of the power you need, and there are also a lot of other factors which go both way (you're discharging the battery faster, therefore reducing its actual capacity, and you have high currents, increasing losses in power transmission).

Sadly, I don't feel like driving at 95 mph in a brand new leaf in the US, so I won't be the one doing the experiment ;p

A++ for showing your work! Though to nit, it goes as the reciprocal of the square, not the square root -- but your math shows you know what you were talking about, just had a typo. Yes, I agree with your calculation. It's impossible for us to know the true power function (see the thread a few down started by me), and clearly there's going to be some constant term even, like running the head lamps and such, as well as linear, like rolling resistance and going up or down hill though theoretically no acceleration, which is basically your square term. But at speed, clearly the cube term, drag, dominates, so again, A++!

Now, if I was getting my LEAF in Montana, I might try pushing 95 once, but not in the Class-6 Misdemeanor Commonwealth. :roll:

 

[indyflick]

Wouldn't the range at 98mph actually be 29.4 miles? At 98mph the 80kw motor would be pegged. So an 80kW motor would deplete a 24kkWh battery in .3 of an hour. Therefore, 98mph * .3 = 29.4 miles.

 

[walterbays]

I doubt i will ever exceed 65 miles per hour, but still nice to see that quick smooth and quiet acceleration

http://www.thenorthernecho.co.uk/business/8394472.Echo___s_test_drive_proves_Leaf_is_no_lightweight/

“Nissan claims the Leaf can reach a top speed of 90mph, but on the track it hovered just under the 100mph mark, cornered smoothly and negotiated steep hills with ease.”

 

[danwat1234]

Wouldn't the range at 98mph actually be 29.4 miles? At 98mph the 80kw motor would be pegged. So an 80kW motor would deplete a 24kkWh battery in .3 of an hour. Therefore, 98mph * .3 = 29.4 miles.

No, because the 80KW motor isn't pegged (at least with ideal conditions on a highway) . It is an electronic speed limit (governor if you will).

 

[turbo2ltr]

Most of the time when a car is electronically governed, it has nothing to do with the drivetrain and everything to do with the speed rating of the tires that it comes with.

With the Leaf it's probably more of a function of the base speed of the motor. With the hybrid systems we design, we typically start limiting motor current at a certain RPM (depends on base speed of the motor) as supplying more current to the motor does little to increase torque so it is just wasted energy.

Thanks OP for posting the vid.

 

[tps]

With the Leaf it's probably more of a function of the base speed of the motor. With the hybrid systems we design, we typically start limiting motor current at a certain RPM (depends on base speed of the motor) as supplying more current to the motor does little to increase torque so it is just wasted energy.

Since the LEAF has a synchronous AC motor, wouldn't the speed be controlled mainly by the frequency the inverter is putting out at any given moment? To limit current, wouldn't one design it to first decrease the frequency, but actually do a hard output current limit mainly as a fault protection feature?

 

[garygid]

Most likely there is an upper mechanical "safety" RPM value for the electric motor. The inverter probably has an upper limit to the AC drive frequency that it can produce. Then, there are current limits for the inverter and motor windings, which are usually more the issue at low speeds. The voltage limits on the motor's windings and on what the inverter can produce will usually be a limiting factor for high-speed operation.

At least, I think so.

 

[DaveEV]

With the Leaf it's probably more of a function of the base speed of the motor. With the hybrid systems we design, we typically start limiting motor current at a certain RPM (depends on base speed of the motor) as supplying more current to the motor does little to increase torque so it is just wasted energy.

Since the LEAF has a synchronous AC motor, wouldn't the speed be controlled mainly by the frequency the inverter is putting out at any given moment? To limit current, wouldn't one design it to first decrease the frequency, but actually do a hard output current limit mainly as a fault protection feature?

It's probably a combination of frequency and voltage...

 

[TomT]

I can say affirmative on that one. With that kind of torque, I should be able to take a vette off the line easily. I heard it will feel like a V6, but with instant torque. ICEs don't have instant torque.

Ummm... I don't think so. First of all, front wheel drive cars are at a real disadvantage during acceleration due to weight transfer. Second, the Vette has so much torque at idle rpm anyway and revs so quickly that it can light up the tires to well over 40. Its problem off the line is usually that it has TOO much torque. I've owned one - I know.

Also, I have not seen it mentioned anywhere here but I would believe the 98 mph speed much more readily if it was off a GPS. We have no idea how accurate the Leaf speedometer is at that speed and thus an indicated 98 might actually be 90, 91 or who knows...

Tom

 

[LEAFguy]

If you're interested, I addressed this topic awhile back on my blog.

The short of it is this - the electric motor can run at 10,390 RPM max (according to Nissan(click LEAF Technical data under Documents)). Based on that, reduction gear ratio, and tire diameter, the LEAF is capable of roughly 94 MPH. If going downhill when a speed run is attempted, I suppose it might be possible for the tires to drive the motor, vs. the other way around, thus exceeding the aforementioned max speed. Plus, as previously mentioned, we don't know the error of the LEAF speedometer.

 

[LEAFfan]

I can say affirmative on that one. With that kind of torque, I should be able to take a vette off the line easily. I heard it will feel like a V6, but with instant torque. ICEs don't have instant torque.

Ummm... I don't think so. First of all, front wheel drive cars are at a real disadvantage during acceleration due to weight transfer. Second, the Vette has so much torque at idle rpm anyway and revs so quickly that it can light up the tires to well over 40. Its problem off the line is usually that it has TOO much torque. I've owned one - I know.

Also, I have not seen it mentioned anywhere here but I would believe the 98 mph speed much more readily if it was off a GPS. We have no idea how accurate the Leaf speedometer is at that speed and thus an indicated 98 might actually be 90, 91 or who knows...

Tom

I highly doubt that the speedo will be off by 7 or 8 mph. I've NEVER seen one off that much. I could believe anywhere from +4-+1, but the only speedo I've ever had that was calibrated perfectly was a VDO gauge on my VW Rabbits. My Civic GX is off by 1 at 75 and that's only because I put different tires on it.

 

[garygid]

Production speedometers in cars are required by law to read high, usually at least 1.5% to 2% high depending upon the country.

As I recall, the EU is higher than the USA.

The CAN bus "Speed" usually has the "correct" speed.

I think that odometers are required to be "correct", right?

 

[TimeHorse]

If you're interested, I addressed this topic awhile back on my blog.

The short of it is this - the electric motor can run at 10,390 RPM max (according to Nissan(click LEAF Technical data under Documents)). Based on that, reduction gear ratio, and tire diameter, the LEAF is capable of roughly 94 MPH. If going downhill when a speed run is attempted, I suppose it might be possible for the tires to drive the motor, vs. the other way around, thus exceeding the aforementioned max speed. Plus, as previously mentioned, we don't know the error of the LEAF speedometer.

The amount of acceleration a car can obtain through downhill slope is less than it's free-fall terminal velocity.

 

[garygid]

Apparently Governmental rules/laws require car speedometers to display higher than your actual speed, something like "at least" a percent or two.

In the EU I think it is "at least 2% high". My Prius reads 2 mph high (about 3%) when going around 65 and 70.

So, reading 2 to 4 mph high at 90 should be expected.

 

[leafme]

Here's an interesting video of a LEAF accelerating to 98 MPH (157 KPH) on a highway somewhere in the EU.

Cool post. Thanks. One subtle point most Americans will not notice in this video is that drivers move to the right to allow the faster cars to pass. In America everyone seems to think they are the only one on the road and stay in the left lane even with others right on their tail.

 

[LEAFfan]

Production speedometers in cars are required by law to read high, usually at least 1.5% to 2% high depending upon the country.

As I recall, the EU is higher than the USA.

The CAN bus "Speed" usually has the "correct" speed.

I think that odometers are required to be "correct", right?

I can tell you...if the speedo is off, so is the odo. My Scangauge II proved that.

 

[garygid]

How did SGII prove that odo and displayed speed errors are correlated?

On my Prius, at 69 indicated, the SG says 67.

So, the indicated odo could be correct, right?

 

[TomT]

Many also do not realize that, as tires wear, the speedometer error also increases due to a smaller tire circumference which makes the indicated speed higher. Tire pressure will also play a small role.

 

[markuss64]

Hallo everyone, I drive very often at 160km/h here in Italy. The speed is self limited by Nissan, in downhill can't go faster and the power indicator is at 3 or 4 dots. Going that fast significantly reduces the range by half... abt 80km. Not much sound from engine, just wind & tires. Ciao!