gudy
Posts: 306
Joined: Thu Aug 19, 2010 10:17 am
Delivery Date: 20 May 2011
Location: Mountain View, CA

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Thu Sep 09, 2010 10:15 am

TimeHorse wrote:
gudy wrote: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
1st Leaf Order (order made and confirmed on 08/31 10:40am)
Delivered on December 11th 2010
15000 miles so far

User avatar
TimeHorse
Posts: 999
Joined: Thu May 13, 2010 4:40 am
Delivery Date: 02 Nov 2011

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Thu Sep 09, 2010 10:42 am

gudy wrote: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:
RIP CO2 Fre, 27 months, 42,282 mi & 11 bars.
unAmerican Job & Nissan's Rapid Depreciation cost $20,000!
5 hours on the road daily w/o Charge at Work on 100%.

Long Live CO2 Fre, Maxed 2013 SL, 20,000 mi/yr lease.
http://aecn.timehorse.com/" onclick="window.open(this.href);return false;

indyflick
Posts: 505
Joined: Fri Jul 09, 2010 8:18 am

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Fri Sep 10, 2010 6:33 pm

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.

User avatar
walterbays
Posts: 1209
Joined: Wed Sep 01, 2010 2:41 pm
Delivery Date: 26 Jun 2015
Location: San Diego, CA

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Thu Sep 16, 2010 1:57 am

DaveinOlyWA wrote: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/busine ... ghtweight/
the article wrote: “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.”
7/00 Dodge Intrepid - 18 MPG - gas $1.72
10/04 Toyota Prius - 35 MPG - $2.40
8/30/10 reserved - $3.09
2/22/11 ordered red SL ETEC - $3.56
3/15/11 delivery est. May - $3.95
4/29/11 delivery est. June - $4.20
2.9 kW PV: >100% of power needs, pre-Leaf

danwat1234
Posts: 41
Joined: Sun Nov 14, 2010 9:19 pm

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Sun Nov 14, 2010 9:39 pm

indyflick wrote: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).

User avatar
turbo2ltr
Posts: 1376
Joined: Fri Jul 30, 2010 11:13 pm
Delivery Date: 04 Feb 2011
Leaf Number: 185
Location: Phoenix, AZ

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Sun Nov 14, 2010 9:54 pm

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.
Silver SL-e
Ford F450 Crew Cab Hybrid Conversion

tps
Posts: 1262
Joined: Sun Sep 19, 2010 7:40 pm
Delivery Date: 07 Feb 2012
Leaf Number: 18044
Location: Philadelphia, PA

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Mon Nov 15, 2010 5:37 am

turbo2ltr wrote: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?

User avatar
garygid
Gold Member
Posts: 12466
Joined: Wed Apr 21, 2010 8:10 am
Delivery Date: 29 Mar 2011
Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Mon Nov 15, 2010 7:52 am

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.
See SOC/GID-Meter and CAN-Do Info
2010 Prius
2011 LEAF, 2014 Tesla S85
2018 & 2019 Tesla Model 3
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
Craigslist: Xm5000Li Electric Motorcycle

User avatar
DaveEV
Posts: 6242
Joined: Fri Apr 23, 2010 3:51 pm
Location: San Diego

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Mon Nov 15, 2010 1:43 pm

tps wrote:
turbo2ltr wrote: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...

User avatar
TomT
Posts: 10645
Joined: Sun Aug 08, 2010 12:09 pm
Delivery Date: 01 Mar 2011
Leaf Number: 000360
Location: California, now Georgia
Contact: Website

Re: Video of LEAF traveling at 98 MPH (157 KPH)

Thu Nov 18, 2010 7:53 pm

LEAFfan wrote:
mwalsh wrote: 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
Leaf SL 2011 to 2016, Volt Premier 2016 to 2019, and now:
2019 Model 3; LR, RWD, FSD, 19" Sport Wheels, silver/black; built 3/17/19, delivered 3/29/19.

Return to “Engineering”