What's the optimal driving speed to maximize EV range?
KentuckyKen
Well-Known Member
Aerodynamic drag increases with the square of speed, so lower speeds give more range. Driving styles like lead foot acceleration and non-motive loads like heat, defrost, a/c, etc will also decrease your range and have to be considered.
Since there are no gear ratios for the electric motor I would think that there is no sweet spot on the efficiency curve like there is for a traditional ICE vehicle.
So I guess it all depends on how slow a speed you can put up with and how safe the low speed is for the conditions.
Since there are no gear ratios for the electric motor I would think that there is no sweet spot on the efficiency curve like there is for a traditional ICE vehicle.
So I guess it all depends on how slow a speed you can put up with and how safe the low speed is for the conditions.
jdonalds
Well-Known Member
I haven't seen any charts yet. Some people put a lot of energy into plotting the optimal speed for Prius Hybrids. I'm guessing the maximum range may be in the 20-30 mph area. What really impacts the maximum range, in addition to a certain speed, is steady speed. Accelerating is where power is used most.
dstrauss
Well-Known Member
I can confirm this in spades - there's a straight flat stretch of my drive to work where I can hold 35-40 mph for almost a mile and it chews about 0.3-0.4 EV miles - the power gauge barely lifts off neutral using little power and "gliding" most of the way.
As noted, nobody has run a curve yet so there's no hard data other than that it's probably somewhere between 20mph and 40mph; exactly where will depend on the car's parasitic load, optimization of the electric motor, aerodynamics, and characteristics of the tires. Heck, it probably changes depending on weather--I know my last car got noticeably less electric range when it was raining, so the peak of the curve will probably shift too.
That said, climate control will definitely be a factor; the more energy climate control is using, the higher the most efficient speed will be.
Logic: If the car had perfectly efficient electronics, it would use 0W of energy other than the power going to the wheels, and the most efficient speed is probably near zero because that's when air resistance is the lowest. More realistically, the parasitics use 500W, then at very slow speeds, because it takes longer to get where you're going, you are wasting more power during that time. So a somewhat faster speed will be most efficient.
If it's really cold out and you're dumping 5000W into the climate control, then driving faster will provide a significant benefit, because you will be wasting less of that energy the less time it takes you to cover the distance. I ran across some numbers for a different EV that showed with the climate control off the most efficient speed was around 20mph, but with the heater cranked up it was around 40mph.
That said, climate control will definitely be a factor; the more energy climate control is using, the higher the most efficient speed will be.
Logic: If the car had perfectly efficient electronics, it would use 0W of energy other than the power going to the wheels, and the most efficient speed is probably near zero because that's when air resistance is the lowest. More realistically, the parasitics use 500W, then at very slow speeds, because it takes longer to get where you're going, you are wasting more power during that time. So a somewhat faster speed will be most efficient.
If it's really cold out and you're dumping 5000W into the climate control, then driving faster will provide a significant benefit, because you will be wasting less of that energy the less time it takes you to cover the distance. I ran across some numbers for a different EV that showed with the climate control off the most efficient speed was around 20mph, but with the heater cranked up it was around 40mph.