## Can electric cars get more range if driven more slowly?

Question
8 months 1 Answer 116 views

1. Originally Answered: Can electric cars get more range if driven slower?
The first weekend I had my all-electric BMW i3 I ran a series of speed vs. ranges tests to see how far I could go on a charge (this was very helpful in mollifying my range anxiety.) At typical driving speeds, the relationship between velocity and range is quite linear (as Waleed’s graph shows)

My results:

72 MPH -> 52 miles range
67 MPH -> 63 miles range
52 MPH -> 91 miles range
Quite a difference! I found I could simplify my range calculation to 55 miles at 70 MPH with an increase of 2 miles range for each MPH under 70. By that formula if I’m going 60 MPH I could expect a range of around 75 miles.

(A caveat: these tests were conducted in December. Even though it’s not “cold” in Northern California, it’s certainly cool and the system uses some of the charge to keep the battery pack warmed. My summertime range has gone up by 10% or more)

A real-world example: I drove to SFO on a cool Sunday morning. It was very early and there were no cars on the road so I made good time doing 75 MPH most of the way. That required 120% of the battery charge (I needed to stop at a fast charge station midway there – nobody in line at 7 AM…) The return trip was mid-afternoon on a weekday and I ran into a lot of traffic. The average speed was closer to 45 MPH with some areas of stop-and-go traffic. I arrived home with 30% charge remaining on the battery for having traveled the same distance.