EV drag force analysis

The EPA shares the Test Car Data which has metrics for all vehicles. Of particular interest are the roll down coefficients:

• Target Coef A (lbf)
• Target Coef B (lbf/mph)
• Target Coef C (lbf/mph**2)

By doing the math using different speeds, we can get the expected drag force for any vehicle. The drag force and speed has a direct relationship to the drive train energy needed. To simplify the metrics, three speeds give an accurate drag force in common operational ranges:

• 35 mph - an expected urban only, home, work, and errands vehicle
• 50 mph - expected urban usage plus some high-speed, cross town expressways
• 70 mph - cross country speed, often used by some reviewers

CAUTION: drag force is not electric drive train efficiency! For example, silicon power electronics are less efficient than silicon-carbide power electronics.

So here are the top six vehicles at these three speeds from best to worst.

35 mph



50 mph



70 mph



Discussion

The Lucid and Ioniq 6 show up in all speed ranges, 35, 50, and 70 mph. The Teslas show up in the 50 and 70 mph range. The i4 shows up in the 35 mph, urban range. Given the reported price differences, the lower cost Ioniq 6 should take sales from the more expensive Lucid. The Teslas need to reduce their low speed drag which can be done by better tires and lower weight.

I've attached the OpenSource spreadsheet in the attached PDF file. Sorry, I can't attach a ZIP or OpenSource spreadsheet.

Bob Wilson