inchman254
Member
- First Name
- Dave
- Joined
- Sep 16, 2024
- Threads
- 1
- Messages
- 10
- Reaction score
- 14
- Location
- Collingwood, Ontario, Canada
- Vehicles
- F150 Lightning Lariat, Kia Telluride
- Occupation
- Retired
- Thread starter
- #1
I find many of the stories of range, low or high, frustrating to read. They often contain just one, or a few, of the many variables that affect range. I've only had my Lightning for 2 months and I've seen a very wide range of mileage and there seems to be a wide range here on the forum, as well.
The most common listed are speed, outside temperature (if it's cold), cabin temperature and preconditioning. But often one or more of these is left out and almost universally, Wind and elevation change are not referenced.
So, if I may be so bold as a relatively new member, I would propose a checklist for people to use when reporting mileage or range. It would help both the poster and reader to understand what is going on.
First the checklist, then you can read the explanations if you want, or TLDR it. There is a rough calculation included that lets you figure out relative mileage due to wind. No temperature corrections.
If you want to use it, just cut and paste the checklist , then fill in the relevant info. There no rule that you have to fill everything in and you can add any description of your trip that you want.
Comments are welcome and I'll add relevant items or pull this down if people think it's too anal. Would also appreciate it if someone could tell me if I screwed up the math at the end.
Change the font to Courier New after pasting if it looks weird.
Year/Model/SR/ER
Trip Speed
Mileage (m/kwh) achieved
Distance traveled
Cruise Control (on/off)
Wind (speed,head/tailwind)
Outside Temperature (f)
A/C/Heat on?(heat pump?)
Cabin Temp setting (f)
Seat/Steering wheel heat?
Preconditioning
This Trip info (C/D/A/ExT)
Interstate/county road/?
Traffic conditions
Net Elevation Change (+/-)
Terrain (hilly/flat)
Tires (snow?, inflation)
Percent Start
Percent End
Range Start
Range End
Vehicle mileage
Other
Wind speed and relative direction is rarely listed, but we all know wind has a great effect. Nobody would be surprised with a difference in mileage comparing between 60 and 80 mph, but seem to disregard the entire point of why that difference exists when it's external (wind).
The math at the very bottom of this message shows that, if the zero wind mileage at 60 mph is 2.2 m/kwh, the mileage will be 3.4 m/kwh with a 20 mph tailwind and 1.5 m/kwh with a 20 kt headwind (no corrections except for wind). I was not expecting this outcome in the math, to be honest. I thought the headwind would hurt a lot more than the tailwind would help.
To calculate the mileage values for any windspeed (car speed plus headwind) when your zero wind consumption at 60 is 2.2.
1/((speed**2/1600)*0.12+0.17).
**2 means squared
You can put this into any calculator by starting with speed squared, don't worry about the brackets then do a 1/x at the end.
For example, 90 mph windspeed results in mileage of 1.29 m/kwh and 50 mph results in 2.79.
It ain't perfect, I'm sure, but it gives some relative numbers and only takes into account wind.
Traffic. (a bit of speculation here) If you're on the interstate all by yourself, you're moving all the air by yourself. If you're surrounded by cars moving the same speed, you're all creating a bubble of moving air and sharing the load. Stop and go traffic won't fully regen what you're using to accelerate.
Net elevation change. Moving 6300 lbs uphill 1000 ft burns 2.4 kwh in the perfect world of physics. Probably closer to 3 kwh. So you lose ~8 miles of range by going up that hill. On a 150 mile trip it's only 0.1 m/kwh overall. On a 50 mile trip, you lose 0.4 m/kwh. You won't get all of that back when you go back downhill.
Hilly or not. Some people think that the regeneration from ups and downs improves mileage vs a flat road. Hills are better in an EV with regen relative to an ICE vehicle, but I understand there's only about an 80% energy regeneration coming down relative to energy used going up. Regeneration can only be so efficient. Plus it's not like you'll get back the losses due to wind drag, road friction, A/C or battery temperature losses, either. So, if you go up and down a bunch of hills, even if they're only a couple of hundred feet each, you will almost surely see a reduction in mileage.
Cruise control on or off. Some people are pretty wild with the accelerator pedal. We've all been behind drivers that go between 50 and 70 for no apparent reason, and I'm sure they don't know it. One thing that I have noticed is that the lack of engine noise and frequency in my Lightning removes my subconscious awareness of my speed and it wanders a bit more than it used to. Speed variations will have some effect on mileage, even with regen.
Tires (Snows, inflation, age)
'Nuff said.
Other.
Anything you want to add.
(skip this part if you're not into math)
On a 72f day, going 60, no A/C, no wind, you're probably getting about 2.2 m/kwh. Let's invert this for ease of math. 1/2.2 = 0.45 kwh/m. We know that about 10% is used for non-driving stuff. So net 0.4 kwh per per mile. We'll add the 0.05 back in later.
Audi says that, for any vehicle, aerodynamic drag exceeds inertial and rolling resistance loads ("other") starting at ~40 mph . Probably at a bit slower equalization speed for a brick. But let's go with Audi. The rolling resistance values are probably higher on the F150 than an A6.
(all speeds from here on in are wind speeds)
So, first we have to figure out what the wind drag at 40 is. We'll say that "other" are 1 total and the wind drag is 1 at 40 mph. At 60, the wind drag will be 2.25. Total drag, 3.25. 2.25/3.25 = 0.7. So aerodynamic drag makes up 70% of the 0.4 kwh/m, or 0.28 kw/m. That means that 0.12 kw/m goes into "other" which will be constant for all three wind scenarios.
That means that, since "other" is 0.12, the aerodynamic load at net 40 is also 0.12. 0.12 +0.12+0.05 = .29 kwh/m = 3.44 m/kwh
We already know we're at 2.2 m/kwh at 60, but we can prove it... (2.25*0.12)+0.12+0.05 = 0.44 kwh/m = 2.27 m/kwh (rounding error)
And with a 20 mph headwind (net 80), we'll be 4 times more drag than at 40. (4*0.12)+0.12+0.05 = 0.65 kwh/m = 1.5 m/kwh.
Bottom line, the difference in mileage between a 20 mph tailwind and a 20 mph headwind at 60 mph is more than double.
You lose 0.77 m/kwh with a headwind but you gain 1.2 m/kwh with the same tailwind. Surprizing.
The most common listed are speed, outside temperature (if it's cold), cabin temperature and preconditioning. But often one or more of these is left out and almost universally, Wind and elevation change are not referenced.
So, if I may be so bold as a relatively new member, I would propose a checklist for people to use when reporting mileage or range. It would help both the poster and reader to understand what is going on.
First the checklist, then you can read the explanations if you want, or TLDR it. There is a rough calculation included that lets you figure out relative mileage due to wind. No temperature corrections.
If you want to use it, just cut and paste the checklist , then fill in the relevant info. There no rule that you have to fill everything in and you can add any description of your trip that you want.
Comments are welcome and I'll add relevant items or pull this down if people think it's too anal. Would also appreciate it if someone could tell me if I screwed up the math at the end.
Change the font to Courier New after pasting if it looks weird.
Year/Model/SR/ER
Trip Speed
Mileage (m/kwh) achieved
Distance traveled
Cruise Control (on/off)
Wind (speed,head/tailwind)
Outside Temperature (f)
A/C/Heat on?(heat pump?)
Cabin Temp setting (f)
Seat/Steering wheel heat?
Preconditioning
This Trip info (C/D/A/ExT)
Interstate/county road/?
Traffic conditions
Net Elevation Change (+/-)
Terrain (hilly/flat)
Tires (snow?, inflation)
Percent Start
Percent End
Range Start
Range End
Vehicle mileage
Other
Wind speed and relative direction is rarely listed, but we all know wind has a great effect. Nobody would be surprised with a difference in mileage comparing between 60 and 80 mph, but seem to disregard the entire point of why that difference exists when it's external (wind).
The math at the very bottom of this message shows that, if the zero wind mileage at 60 mph is 2.2 m/kwh, the mileage will be 3.4 m/kwh with a 20 mph tailwind and 1.5 m/kwh with a 20 kt headwind (no corrections except for wind). I was not expecting this outcome in the math, to be honest. I thought the headwind would hurt a lot more than the tailwind would help.
To calculate the mileage values for any windspeed (car speed plus headwind) when your zero wind consumption at 60 is 2.2.
1/((speed**2/1600)*0.12+0.17).
**2 means squared
You can put this into any calculator by starting with speed squared, don't worry about the brackets then do a 1/x at the end.
For example, 90 mph windspeed results in mileage of 1.29 m/kwh and 50 mph results in 2.79.
It ain't perfect, I'm sure, but it gives some relative numbers and only takes into account wind.
Traffic. (a bit of speculation here) If you're on the interstate all by yourself, you're moving all the air by yourself. If you're surrounded by cars moving the same speed, you're all creating a bubble of moving air and sharing the load. Stop and go traffic won't fully regen what you're using to accelerate.
Net elevation change. Moving 6300 lbs uphill 1000 ft burns 2.4 kwh in the perfect world of physics. Probably closer to 3 kwh. So you lose ~8 miles of range by going up that hill. On a 150 mile trip it's only 0.1 m/kwh overall. On a 50 mile trip, you lose 0.4 m/kwh. You won't get all of that back when you go back downhill.
Hilly or not. Some people think that the regeneration from ups and downs improves mileage vs a flat road. Hills are better in an EV with regen relative to an ICE vehicle, but I understand there's only about an 80% energy regeneration coming down relative to energy used going up. Regeneration can only be so efficient. Plus it's not like you'll get back the losses due to wind drag, road friction, A/C or battery temperature losses, either. So, if you go up and down a bunch of hills, even if they're only a couple of hundred feet each, you will almost surely see a reduction in mileage.
Cruise control on or off. Some people are pretty wild with the accelerator pedal. We've all been behind drivers that go between 50 and 70 for no apparent reason, and I'm sure they don't know it. One thing that I have noticed is that the lack of engine noise and frequency in my Lightning removes my subconscious awareness of my speed and it wanders a bit more than it used to. Speed variations will have some effect on mileage, even with regen.
Tires (Snows, inflation, age)
'Nuff said.
Other.
Anything you want to add.
(skip this part if you're not into math)
On a 72f day, going 60, no A/C, no wind, you're probably getting about 2.2 m/kwh. Let's invert this for ease of math. 1/2.2 = 0.45 kwh/m. We know that about 10% is used for non-driving stuff. So net 0.4 kwh per per mile. We'll add the 0.05 back in later.
Audi says that, for any vehicle, aerodynamic drag exceeds inertial and rolling resistance loads ("other") starting at ~40 mph . Probably at a bit slower equalization speed for a brick. But let's go with Audi. The rolling resistance values are probably higher on the F150 than an A6.
(all speeds from here on in are wind speeds)
So, first we have to figure out what the wind drag at 40 is. We'll say that "other" are 1 total and the wind drag is 1 at 40 mph. At 60, the wind drag will be 2.25. Total drag, 3.25. 2.25/3.25 = 0.7. So aerodynamic drag makes up 70% of the 0.4 kwh/m, or 0.28 kw/m. That means that 0.12 kw/m goes into "other" which will be constant for all three wind scenarios.
That means that, since "other" is 0.12, the aerodynamic load at net 40 is also 0.12. 0.12 +0.12+0.05 = .29 kwh/m = 3.44 m/kwh
We already know we're at 2.2 m/kwh at 60, but we can prove it... (2.25*0.12)+0.12+0.05 = 0.44 kwh/m = 2.27 m/kwh (rounding error)
And with a 20 mph headwind (net 80), we'll be 4 times more drag than at 40. (4*0.12)+0.12+0.05 = 0.65 kwh/m = 1.5 m/kwh.
Bottom line, the difference in mileage between a 20 mph tailwind and a 20 mph headwind at 60 mph is more than double.
You lose 0.77 m/kwh with a headwind but you gain 1.2 m/kwh with the same tailwind. Surprizing.
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