Quote:
Originally Posted by freebeard
The cited article makes the case that watt-hour/mile is a better unit to work with than kilowatt-hours/100 miles.
From the chart, the Leaf weighs 3276lb, and gets 300 watt-hours per mile; a ratio of 11 to 1.
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Yes. I looked over the article. I'll read it more detailed this time.
The problem with rules of thumb is that they don't help when it comes to calculating distance based on actual circumstances nor when modding. For an example, taking the rolling resistance and air drag and calculating how far I could go at what speeds (assuming that the motor/battery efficiency doesn't change from an estimated 80% efficiency) I see I can go only159km/99miles at 100kph/62mph yet reach 229km/142mi at 75mph/47mph.
What I did was take a spreadsheet and put in it all the numbers pertaining to the Leaf (known weight,known drag coefficient, known frontal area, guessed rolling resistance and guessed total efficiency). Then I took all the formulas for physics and put them all together into a total sum of theoretical distances. (i.e. F=V^2*Cd*A*D*0.5, P=V^3*Cd*A*D*0.5, F=a*m, P=m*V^2, P=F*d, etc.)
That's not exactly real life testing, but it's closer to ballpark than using a rule of thumb. The rule of thumb
300w/h per mile would mean that the Leaf gets 80miles, regardless of how and where it's driven, or how it's been modified.
Of course on the other hand, there are numbers that I just guessed at and others I just overlooked completely. For an example, I just guessed the rolling resistance and the total efficiency. I didn't even include other uses of the battery pack's energy, such as air-conditioning, heating, gauges, radio, lights, etc. Also battery degradation on both a used Leaf and over coming years. Also actual air density.
But still, the math is there, and if it says I can go almost 1.5 times the distance by driving at 45mph instead of 60mph, it's close enough to the truth to be believable.
But yes, I need to read that article.