Efficiency of Leaf at Bike speed (~10 mph)

[LTLFTcomposite]

Just keeping the LEAF in ready mode, even if not driving, draws significant energy, so that's why there is a break-over point where going slower actually uses more power.

The minimum usually is still several hundred watts!

-Phil

The only thing worse than driving 187 miles @ 12 mph is driving 187 miles @ 12 mph in Florida with no air conditioning, so our max efficiency speed is likely a good bit higher.

 

[LEAFfan]

This idea sprung into my head from another topic: Biking is the most-efficient way to travel (~700 MPGo). I think it's mainly because a bike moves slow, and therefore has very little wind resistance to overcome. QUESTION:

Has anyone ever tried driving the Leaf at a slow but steady speed of 10 mph? I imagine the MPGe would be almost as high as a bike... 500 MPGe or higher. (Perhaps a single seat EV like the Sparrow would be better-suited to this task.)

Yes, I did this on a 2.5 mile loop at sea level on Fiesta Island in San Diego. About 12mph appears to be the peak economy, hence range. Yes, bicycles were outrunning me.

I'm trying to remember the specific data, and I think I remember 8.5 miles per kWh (118 WattHour per mile), for a theoretical range of 8.5 * 21 = 178 miles.

Tony, your m/ kW h was much higher than 8.5 because I drove a 15 mile loop at a steady 15mph and my m/kW h was 9.1 on the console. I think yours was at least 9.2.

 

[theaveng]

Just keeping the LEAF in ready mode..... usually is still several hundred watts!

Ick. I wonder what it's burning several hundred watts on? How much power does the Leaf use when parked? Charging?

 

[theaveng]

good for you, your bicycle riding friends and your amish neighbors whom are residing in a parallel reality at 15 mph.

Ya know, nobody forced you to read this thread. I exercised my freedom of speech to ask a question, and you can choose to exercise your freedom not to listen. No need for the high school behavior. Grow up and act like an adult.

 

[apvbguy]

good for you, your bicycle riding friends and your amish neighbors whom are residing in a parallel reality at 15 mph.

Ya know, nobody forced you to read this thread. I exercised my freedom of speech to ask a question, and you can choose to exercise your freedom not to listen. No need for the high school behavior. Grow up and act like an adult.

hmmm just whom is it exhibiting the obnoxious behavior? you wouldn't be one of those highly degreed know it alls?

 

[theaveng]

you wouldn't be one of those highly degreed know it alls?

You did it again. First you insult bike riders, then my amish neighbors, and now college grads.

 

[Elephanthead]

I am going to insult the entire states of CA and FL because you two are from there. nana nana boo boo.

 

[TonyWilliams]

Tony, your m/ kW h was much higher than 8.5 because I drove a 15 mile loop at a steady 15mph and my m/kW h was 9.1 on the console. I think yours was at least 9.2.

Ya, the 2011 wouldn't go about 8.0 on the dash, but the 2012 did. With thermal management of the Rav4 battery, depending on the outside temperature, the VmaxR (velocity max range) could be well over 20mph.

 

[TimLee]

Has anyone ever tried driving the Leaf at a slow but steady speed of 10 mph? I imagine the MPGe would be almost as high as a bike... 500 MPGe or higher.

You must be kidding :lol: :lol:
Don't you understand what the LEAF weighs compared to a bike? Why would you think it would even come close to the efficiency of a human on a bike?
And people in cars somewhat tolerate people going slow on bikes. People on bikes can't go very much faster.
Just go out in your LEAF and drive down most 2 lane roads in the USA at 12 mph, the ultimate efficiency point, and you are going to come to a very rude awakening of how nasty people can be. :twisted: :twisted: :twisted:
They can be pretty nasty if you're doing the posted speed limit of 30 mph or 35 mph.
I've been working pretty hard the past few weeks to improve miles/kWh in the LEAF.
And I've experienced more rude, discourteous, and downright dangerous drivers than I saw in the past 10 years. :shock: :shock: :shock:

 

[davidcary]

Well - I suspect humans aren't very good energy users. Then there is the need for fuel to taste good. Think how horribly inefficient ethanol production is and you can see how food can really hurt the pipeline of energy. Also weight is not such huge penalty at constant speed - 4 wide tires does really hurt though compared to bicycle tires.

But you could imagine a 10 fold decrease in energy from food production and you could imagine a 10 fold increase in rolling resistance of a car vs a bike, and there you have comparable efficiency.

 

[theaveng]

You must be kidding :lol: :lol: Don't you understand what the LEAF weighs compared to a bike? :lol:

I'm sorry I asked the question. I've experienced as much rudeness from you EV zealots as Alex Jones fans (conspiracists) typically spew: "If you're not a Truther you're a LIAR and a sheeple," is one of their favorite lines. I consider them a hate group. I was trained in science so naturally I question everything and ask "What if".

Children are naturally curious but adults act as if curiosity is a crime, and they will laugh at people ( :lol: ) who dare to stray away from the Party Line/groupthink. So I apologize that I asked "What if" we drove a Leaf at bicycle speed. I won't make that mistake again.

 

[TimLee]

I'm sorry I asked the question. I've experienced as much rudeness from you EV zealots as ... I won't make that mistake again.

I'm sorry if you felt my response was rude, that was not my intent.
I think you asked a perfectly reasonable question.
I was just pointing out that it is not technically practical to think that a very heavy vehicle can even come close to the efficiency of a bike.
And even if it became close, the societal response from other ICE drivers would be horrific.
I am certainly not an EV zealot.
I had never even considered an electric vehicle until a seminar at the University of Tennessee Chattanooga Electric Vehicle Research center caught my interest and I attended. Then came the Nissan LEAF Versa test mule drive event. So now I was intrigued.
But I only bought the 2011 LEAF because an economic analysis showed it would be cost effective compared to other ICE and hybrid alternatives.
But like almost all those who begin driving a LEAF, I fell in love with the sheer joy of the ultra quiet driving and high torque quick response to 30 mph.
So if that qualifies me as a zealot, I plead no contest.

 

[LeafinThePark]

Going back to the original question...comparing the efficiency of the leaf to biking ->

Based on what Wikipedia says about the power required to bike, we can calculate the miles/kWh for a bicycle. According to Wiki, with a 300 Watt output, a 150lb person can propel a bike at a constant 9.3mph. A little math gets us to the impressive efficiency of 312.5 mi/kWh.

Just for fun...I figured out a rough cost/mile. Of course, fuel cost makes a huge difference. I decided on good old pasta for our Bicycle fuel. At about $1.20 for 1lb of dry pasta which has 1600calories, I calculate a cost of about $0.00075/Cal. From a fitness site I see the same 150lb person is going to burn about 400 calories to ride 10 miles, or about 40 cal/mi. The amount of pasta needed to fuel this mile would cost 40 x $0.00075, or $0.03. So the cost of powering the bicycle is 3 cents/mile.

For the Leaf, I will assume 4mi/kWh and a cost of $0.12/kWh. After the straight forward calculation, lo and behold the cost is the same...right at 3 cents/mile. In comparison, and average car getting 25mpg with gas at $3.50 would cost 14 cents to go one mile.

Of course there are a lot of assumptions built into all of this and a whole lot of factors and cost not included....but I find it interesting that at first approximation the cost of energy is the same for the leaf and a bicycle.

 

[BraveLittleToaster]

This idea sprung into my head from another topic: Biking is the most-efficient way to travel (~700 MPGo). I think it's mainly because a bike moves slow, and therefore has very little wind resistance to overcome.

No, that's totally wrong. Biking is the most efficient way to travel because you're only pushing your mass +30lbs, instead of pushing your mass +3000lbs. Driving your Leaf up a hill will always consume more energy than riding your bike up a hill, regardless of wind resistance.

 

[sproqitman]

Going back to the original question...comparing the efficiency of the leaf to biking ->

Based on what Wikipedia says about the power required to bike, we can calculate the miles/kWh for a bicycle. According to Wiki, with a 300 Watt output, a 150lb person can propel a bike at a constant 9.3mph. A little math gets us to the impressive efficiency of 312.5 mi/kWh.

This just seemed wrong to me, so I checked the Wikipedia entry. I think you grabbed the wrong number. 300 watts is for pedaling up a 7% grade. To do 10 MPH on the flat takes approximately 40 watts. Doing the rest of the math, you end up with .04 kWh for 10 miles, or 250 miles/kWh. That equates to 144 kJoules at the pedals. Figuring 25% efficiency for the rider, you need about 140 kcalories of input, or 14 kcal/mile. At $0.00075/kcal, we end up with a fuel cost of 1 cent/mile.

(I'm an amateur bicycle racer, and 300 watts for an hour is a pretty stout effort)

 

[theaveng]

I didn't realize the Leaf was almost 3000 pounds. My insight is only 1900. And I was assuming flat ground where the item's weight is not that important. If you do some basic math: (1/2 mv^2)f - (1/2mv^2)i where initial and final velocities are the same (steady speed of 10 mph) the Delta KE == 0.

You have energy losses from air drag but going 10mph keeps that minimal. In fact I bet the bike has more drag than the semi-teardrop shape of the Leaf. Are there any closed testtracks near L.A. where I could drive a Leaf in circles at 10mph?

 

[GRA]

Graph showing kWh/100 passenger-km for various types of land, sea and air vehicles:

http://www.withouthotair.com/c20/page_128.shtml" onclick="window.open(this.href);return false;

Another source, "Electric Bicycles: A Guide to Design and Use"; by Manchin, William C., claims that depending on what you eat and how far it travels to get to you, in some cases an e-bike may be slightly more energy efficient than one you provide the motive power for.

 

[EatsShootsandLeafs]

I can't imagine why the dislike of this question by anybody in this thread. OP has never indicated it was more than an idle curiosity, and one evidently some of us share. I'm glad he was able to test and come up with a figure. AFAIK a gas car is most efficiently around 30 mph, but perhaps that's old data. I am not surprised the leaf's range goes up massively at low speeds, because wind resistance is mainly out of the equation. If the end of the world ever comes we can keep this knowledge

I have sometimes wondered what the efficiency of the car is at really low speeds. I wondered the same of a Prius, but never got a great answer on what its MPG would be at a consistent say 20 mph. I figured it would pretty darn good.

 

[theaveng]

I think this is a better chart, though it does have some flaws. For example it says a passenger train gets 70 p-mpg but Amtrak & the government's official figures are only 30 (because the trains are often half empty): http://truecostblog.com/2010/05/27/fuel-efficiency-modes-of-transportation-ranked-by-mpg/" onclick="window.open(this.href);return false;

AFAIK a gas car is most efficiently around 30 mph, but perhaps that's old data.

A gas or diesel car is most efficient in its top gear, and most top gears are unusable below 40 or 45, so that would be the most efficient point. I drove a Ford Fiesta last week and it got okay mileage at 30 and 5th gear, but the best mileage was at 40 and 6th gear (>60 MPG).

 

[LEAFer]

I didn't realize the Leaf was almost 3000 pounds. My insight is only 1900.

The LEAF is not "almost 3000 pounds". It is MORE than 3000 pounds: 3,256 - 3,340 (http://sfbayleafs.org/news/2013/01/2013-nissan-leaf-model-overview/" onclick="window.open(this.href);return false.