Speed vs mileage

[jimball]

I know that an electric vehicle is the opposite of an ICE powered vehicle where ICE city mileage is lower than highway mileage.

With the FUV, iirc, the range numbers are calculated based on an average 35 mph city driving speed.  Range decreases at highway speeds.  Range also decreases the heavier the load being carried in the vehicle.

My question:  It there a guideline by how much range will decrease at increased speeds?

I live next door to Pittsburg, Ks. and do a lot of shopping in Joplin, Mo. which is about 35 miles away on fairly level countryside.  25 miles of that trip is on a 55mph highway.  My wife & I are both plus-sized riders.  Once in Joplin, we will drive another 5-10 miles in city driving. 

Will we be be cutting it too close to consider driving the FUV to Joplin?   Joplin has several charging stations, but none are close to anything where  we could occupy ourselves for a few hours while The FUV recharged.  Exception being a Casino west of Joplin a few miles. 

An alternative is to drive paved county roads, avoiding the highway.  It would be possible to drive at 35 mph almost all the way, with only 3-4 miles at 55mph speeds.

[Dan21]

There are 2 considerations that need to be calculated separately. First, the aerodynamic drag force goes up with the square of the velocity. Traveling at 55 mph compared to 35 MPH has the drag going up by 55/35 ^2, or a factor of 2.45. That's a lot. If the FUV range is presented assuming 35 MPH constant speed, the range would drop from 100 miles to 40.5. But you are not traveling the whole charge at 55 MPH. Therefore, if half of your trip is at 55 MPH and half at 35 MPH, range would drop from 100 miles to 70.25 miles.

The other consideration is the vehicle weight. I don't know what the FUV assumes for vehicle weight for their testing (or whether they have single or double occupancy), but the range would be affected linearly with gross weight. Test weight would be vehicle empty plus passenger(s) weight. Compare that to your planned passenger weight and add that to the vehicle empty weight. Therefore the weight ratio used to calculate vehicle range reduction is the ratio of your gross weight divided by theirs. One thing you can do to maximize range is to minimize rolling resistance is to keep your tires pumped up to the maximum recommended by the vehicle manufacturer, not the maximum safe pressure rating printed on the side of the tires. The vehicle manufacturer gets to specify proper tire inflation, not the tire manufacturer.

For example, I run the same tires on my 1400 lb Westfield as my 2400 lb Miata. Recommended tire pressure for the Miata is 26 psi and 15 psi for the Westfield.

[DanCooper]

I made a spreadsheet that includes all these factors. It closely matches the published FUV specifications. It can predict the range for any trip, including speed and elevation change for each segment. E-mail me and I will send it to you. danc19fr@yahoo.com

Wouldn't it be nice if this forum had a place to store files and pictures?

[CharonPDX]

One thing you can do to maximize range is to minimize rolling resistance is to keep your tires pumped up to the maximum recommended by the vehicle manufacturer, not the maximum safe pressure rating printed on the side of the tires. The vehicle manufacturer gets to specify proper tire inflation, not the tire manufacturer.

In good weather, I always over-inflate by a slight amount. (Although never above tire's maximum.) For example, my Subaru Forester when not loaded suggests 35 PSI front and rear (Up to 45 rear when carrying maximum load.) The tires themselves are rated to 60. I put them at 40. It's not enough to cause uneven wear, and it does stiffen the ride a little, but it does bump my mileage by a few MPG.

I never over-inflate in bad road conditions, though. (So, yes, if it's been dry for a month, and we're about to have a few days of nasty rain, I absolutely lower the pressure back down.)