Efficiency after 16,000 kms

[user-name-required]

Hi all, will make this brief.

Watched @tommolog 's great video about his 3 year review, and in it he has his 70mph (112kmh) range test in his 2022 lightning ER doing 286 miles (458kms). Doing some math, that would mean his efficiency in kwh/100kms would fall around 28.6kwh/100kms.

On my truck - 2024 flash trim, bought Nov 1, 2024 - I averaged 34kwh/100km through the winter, and right now am at about 38kwh/100km in the summer (on account of towing my trailer a lot). But on individual road trips at 112kmh, I am typically showing an indicated efficiency of ~33kwh/100km, or about 15% worse than Tom's figure.

What could be the cause of this? We do live at sea level (my house is maybe at 50m elevation), so maybe that is a factor, but a 15% degradation because of elevation seems like an awful lot. Same for the temps, that efficiency I get when I do the 100km drive with the kids to visit my parents, over a pretty flat freeway at 70mph never seems to be much better than about 33/100kms, no matter the season.

Truck is stock, with the stock AT tires.

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[SpaceEVDriver]

You can easily lose a lot due to lower elevations and higher relative humidity, but a comparison with Tom’s would require knowing the elevation of most of his driving. I don’t know that information.

Check your tire pressure. Ford US recommendation is 36 PSI (248 kPa), which is ridiculously soft for this truck. I run at 48-50 PSI (331-345 kPa).

I live at 7000 ft (2134 meters) elevation. When I drive 72 mph (116 kph) on the freeways, I get 2.4-2.5 miles/kWh (about 25 kWh/100 km) during most trips. When it gets cold (not often less than about 0 ºC, though it does sometimes get colder), I lose efficiency as everyone does. In the cold and wind, I can go down to 2 miles/kWh (31 kWh/100 km). If I push the truck to higher speeds or accelerate hard, I lose more efficiency.

At 112 kph, I would guess that you should be getting closer to Tom's efficiencies. Given 33 kWh/100 km (1.9 miles/kWh), my first guess would be tire pressure. Second would be speeds—are you averaging 112 kph or is that your maximum speed? Third would be acceleration behaviors. Finally would be HVAC use.

 

[user-name-required]

You can easily lose a lot due to lower elevations and higher relative humidity, but a comparison with Tom’s would require knowing the elevation of most of his driving. I don’t know that information.

Check your tire pressure. Ford US recommendation is 36 PSI (248 kPa), which is ridiculously soft for this truck. I run at 48-50 PSI (331-345 kPa).

I live at 7000 ft (2134 meters) elevation. When I drive 72 mph (116 kph) on the freeways, I get 2.4-2.5 miles/kWh (about 25 kWh/100 km) during most trips. When it gets cold (not often less than about 0 ºC, though it does sometimes get colder), I lose efficiency as everyone does. In the cold and wind, I can go down to 2 miles/kWh (31 kWh/100 km). If I push the truck to higher speeds or accelerate hard, I lose more efficiency.

At 112 kph, I would guess that you should be getting closer to Tom's efficiencies. Given 33 kWh/100 km (1.9 miles/kWh), my first guess would be tire pressure. Second would be speeds—are you averaging 112 kph or is that your maximum speed? Third would be acceleration behaviors. Finally would be HVAC use.

Thanks for the response SpaceEVDriver

- I run my tires at 40-42psi I think, could maybe bump them up a bit more and see how that goes.
- I set the cruise control to around 112-115kmh typically, so I am a bit above the speed limit on this particular freeway but not into "get pulled over" territory...my days of speeding tickets are hopefully long behind me. Otherwise in all EVs, I find it hard to keep a consistent speed manually.
- Acceleration, I am pretty chill on the acceleration, definitely not chirping tires.

So, it sounds like the elevation and humidity and the tire pressures might be the ticket. I can't recall from the video if Tom gives his tire pressures or not. And that's nuts that you live at 2130m elevation! That's like the top of the ski resorts in my area!

I know nothing about New Jersey other than the accents of it's people, but being near to the coast, I would think his elevation isn't crazy high, and that his humidity there is also pretty high.


I live in a coastal temperate rain forest region technically, so humidity is always high here, and we are at sea level for most of our freeway driving.

 

[SpaceEVDriver]

The density of air contributes linearly to drag forces, which come into play above about 35-45 mph (56-72 kph). At STP (0 m altitude, 25 ºC, 0% humidity) the density of air is about 101 kPa. At 2100 m, the air density is about 78 kPa (same temperature, same humidity). *IF* drag forces were the only thing that had impact on efficiency, that would be a reduction of about 23% going from sea level to my home. That’s obviously not all that matters (rolling resistance, various electrical and thermal inefficiencies, mechanical inefficiencies, temperature, humidity, etc. matter too).

Humidity impacts on air density are coupled with air temperature because of the nature of how air holds onto water vapor. Below about 25 ºC, the density is mostly temperature-dependent because of that behavior. In this plot they’re using 20 ºC as the reference, but the moist air density difference between 25 ºC and 20 ºC isn’t all that much so you can use the graph to gauge the relative density for the temperatures you’re experiencing. I doubt you’re getting much above 30 ºC except in the very hottest days.

 

[SpaceEVDriver]

This might be of interest. Sadly it’s US-based and doesn’t cover up into BC, but it might give a good idea of how things change throughout the year based on weather, air density, etc.

The animated map about 2/3 down the page is interesting. You could probably compare with coastal areas in the US Pacific Northwest to get an idea of how the relative efficiencies might change throughout the year.

https://www.xweather.com/the-ev-range-report

 

[user-name-required]

This might be of interest. Sadly it’s US-based and doesn’t cover up into BC, but it might give a good idea of how things change throughout the year based on weather, air density, etc.

The animated map about 2/3 down the page is interesting. You could probably compare with coastal areas in the US Pacific Northwest to get an idea of how the relative efficiencies might change throughout the year.

https://www.xweather.com/the-ev-range-report

Oh man, speaking my language here: data, charts, links. Amazing.

Will be clicking around on that later today, thanks!

 

[Heliian]

What tires?

Set your display to mi/kwh for a more accurate comparison.

Grabbers need to be 42psi COLD.

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