I haven't seen a simple formula for Wh/mile vs. speed, I decided to interpolate from a published graph and do some simple curve fitting. From 45 to 80 MPH, I found that

Wh/mile = MPH^2 / 30 + MPH * 5/6 + 120

fits the curve well:

With this data, I can answer simple questions like: should I drive 200 miles at 60 or 75, to minimize the total time, including charging, with my single charger and no supercharger in the area?

At 60, I drive for 200 minutes, and consume 200*0.290 = 58 kWh.

At 75, I drive for 160 minutes, and consume 200*0.370 = 74 kWh.

So, the extra charging time is the time it takes to charge 16 kWh. I saved 40 minutes driving, but my single charger only charges at 10 kW, so it'll take more than an extra hour charging, making 75 MPH slower in total. A second charger would have made it faster.

Useful?

Wh/mile = MPH^2 / 30 + MPH * 5/6 + 120

fits the curve well:

Does anyone have a better curve or data for quick calculations?

MPH Curve Calulated

45 225 225

50 245 245

55 270 266.6666667

60 290 290

65 320 315

70 340 341.6666667

75 370 370

80 400 400

With this data, I can answer simple questions like: should I drive 200 miles at 60 or 75, to minimize the total time, including charging, with my single charger and no supercharger in the area?

At 60, I drive for 200 minutes, and consume 200*0.290 = 58 kWh.

At 75, I drive for 160 minutes, and consume 200*0.370 = 74 kWh.

So, the extra charging time is the time it takes to charge 16 kWh. I saved 40 minutes driving, but my single charger only charges at 10 kW, so it'll take more than an extra hour charging, making 75 MPH slower in total. A second charger would have made it faster.

Useful?

0

## Comments

<pre>

Charging Best Speed Net Speed

Rate (kW) (MPH) (MPH)

9 47 21

18 61 30

36 77 42

72 99 57

120 100+ 69

</pre>

The difference between 9kW and 18kW shows how road trips away from superchargers really benefits from dual chargers, so long as you can find high-current L2 chargers (HWPC or J1772).

The 36kW calculation speaks to the value of 50kW CHAdeMO charging. If we could use those, there would be no reason to conserve energy when traveling, just like when there are superchargers on the route.

To add to hpjtv, given an avg distance b/w SCs of 125 miles, going greater than 65 MPH will still net faster travel times (gain in driving time net of longer charging time) only if the charging station is at least 30 kW. Definitely ++1 on AoneOne's point that "... The 36kW calculation speaks to the value of 50kW (chargers). If we could use those, there would be no reason to conserve energy when traveling.."

@AoneOne, my curve fitting came to:

0.0261905 * MPH^2 + 1.70238 *MPH + 95.3571

I can easily believe that a least-squares fit to my data would give something different. I used a difference-of-differences method and the result fit well enough and was simple enough that I didn't pursue a "better" fit, especially given the errors inherent in extracting the data from the published graph, and that I've included none of the complicating factors like the environment or cargo weight.

Aleks