500 EV miles at Indianapolis Motor Speedway - October 13, 2011

[Norbert]

I utilized my spreadsheet to determine best speed by brute force in 2 mph increments.

If I actually approximate a formula for total time and graph it, as well as the first derivative, the minimum is at 107.9 mph ( where the first derivative intercepts zero ).

In case you are interested what I did to get the optimal speed, I derived the following formula from the assumption that at the optimal speed, accelerating will decrease the driving time by the same amount as it increases the charging time.

And that
charging time = distance * (power/speed) / charging rate
drive time = distance / speed

EDIT: To explain where the term (power/speed) comes from, it is derived from energy_consumption/distance, equivalent to the Wh/mile number usually, but converted to other variables, since that will later allow simplifying this equation.

This results in this formula:
Charging rate = (v1p2 - v2p1) / (v1 - v2)
with v1 = speed in the row above, v2 speed in the row below, p1 = power in the row above, p2 = power in the row below.

This gives me a column of charging rates, and to find the optimal speed, I go down rows until I find the row which has the charging rate in the computed column.

I suppose the equation v = (14.286 * q ) ^(1/3) - 0.97 is derived by curve fitting, so an approximation?


EDIT: I'm referring to the spreadsheet in this blog: Roadster Efficiency and Range | Blog | Tesla Motors
Download here: https://www.teslamotors.com/display_data.php?data_name=range_table

The downloaded file has a table with rows for each speed (including power consumed at each speed). To that I added a column with the charging rate (for which the speed in this row is the optimal speed).

 

[EVFest]

As a fellow EV supporter and enthusiast, Contour Hardening, Inc.(CHI), manufacturer of the Real Power Mobile Level 3 Quick Charge EV Rescue vehicle, would like to invite you to attend the inaugural EV500 event to be held at the Indianapolis Motor Speedway on Thursday, October 13th, 2011.

Video Link from their website - Real Power - News