This trip question mi/kWh: Average or semi real time?

[strahanjen]

Hi, we’ve had a 2024 Flash since November. I still cannot figure out if the mi/kWh display is an average for the entire trip or a somewhat real time value to reflect changing conditions (city roads vs highway speeds). Sometimes the value fluctuates quite a bit over just a minute or two, and sometimes it holds pretty steady and the changes are in small increments.

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[bmwhitetx]

I believe it is simply the number of miles you have traveled divided by the kWh used (since you pressed start). That's the definition of average.

It can vary a lot early on in the trip but should settle down. It is not an instantaneous number like some ICE vehicles can show.

 

[Heliian]

"this trip". Is your current trip average.

You can use and reset "trip 1" and "trip 2" while driving to get more recent usage.

Check out the energy usage page for more details of where the energy went.

I find it quite handy while driving distances.

 

[SpaceEVDriver]

As stated, the efficiency is miles driven since starting the truck divided by energy used. If you have lots of hills or lots of starts and stops, the displayed efficiency can change a lot because you might use energy, add some back, etc over a relatively short distance and that changes the average more quickly than you might imagine.

On a similar topic:
The range estimator is not just the current trip's efficiency * battery capacity remaining. It includes a weighted average of something like the efficiency in the last 5-ish minutes, the overall efficiency of the current trip, and your longer-term driving history. If you're using one of the mapping applications that knows what the battery is doing, the app might also include some elevation changes in that weighting.

 

[Firn]

As stated, the efficiency is miles driven since starting the truck divided by energy used. If you have lots of hills or lots of starts and stops, the displayed efficiency can change a lot because you might use energy, add some back, etc over a relatively short distance and that changes the average more quickly than you might imagine.

On a similar topic:
The range estimator is not just the current trip's efficiency * battery capacity remaining. It includes a weighted average of something like the efficiency in the last 5-ish minutes, the overall efficiency of the current trip, and your longer-term driving history. If you're using one of the mapping applications that knows what the battery is doing, the app might also include some elevation changes in that weighting.

I mean, we call it the GOM for a reason, but I think your explanation still gives it too much credit.

For example, I NEVER get over 2.1mi/kwh, yet recently charging to 100% had the GOM showing nearly 340 miles of range. Granted, it is more accurate around 80% SOC.

 

[PJnc284]

I believe it is simply the number of miles you have traveled divided by the kWh used (since you pressed start). That's the definition of average.

It can vary a lot early on in the trip but should settle down. It is not an instantaneous number like some ICE vehicles can show.

I would guess that's how ABRP calculates it as well but it can be up to .5 higher than what the truck shows. Been meaning to check the kWh before and after a trip in CarScanner and see if it matches either.

 

[RickLightning]

In short you have to be careful understanding, or even trusting, some of the numbers. My Trip 1 and Trip 2 efficiencies on my Mach-E reset for no reason on a trip, losing my lifetime efficiency forever.

Trip 1, as stated, can jump around at the beginning of a trip, then settles down as more miles pile on.

You have to remember that its' an average, so that you don't get in trouble. If you're on a trip and it's plugging along at 1.8, and then you hit a 20mph headwind, you might be getting 1.2. But the average might slowly drop to 1.7, then 1.6... In the meantime, you're chewing up range without realizing how fast. That's why I use CarScanner. It shows me the ENERGY in the vehicle as well as the instant efficiency. So you notice you're getting say 1.2 despite a 1.7 trip average, and see you have 50kWh left, so you can do the math and say "I've got 60 miles of range left". You'll learn that way faster than the GOM telling you.

 

[Firn]

In short you have to be careful understanding, or even trusting, some of the numbers. My Trip 1 and Trip 2 efficiencies on my Mach-E reset for no reason on a trip, losing my lifetime efficiency forever.

Trip 1, as stated, can jump around at the beginning of a trip, then settles down as more miles pile on.

You have to remember that its' an average, so that you don't get in trouble. If you're on a trip and it's plugging along at 1.8, and then you hit a 20mph headwind, you might be getting 1.2. But the average might slowly drop to 1.7, then 1.6... In the meantime, you're chewing up range without realizing how fast. That's why I use CarScanner. It shows me the ENERGY in the vehicle as well as the instant efficiency. So you notice you're getting say 1.2 despite a 1.7 trip average, and see you have 50kWh left, so you can do the math and say "I've got 60 miles of range left". You'll learn that way faster than the GOM telling you.

@Ford Motor Company , you really need to throw an air speed sensor (with PIDs) in these vehicles. Maybe you don't care since thr e GOM is so worthless anyways, but for those of us who care air speed plays a huge aspect into efficiency.

I have to imagine you have CFD simulations as to how air speed and direction impact efficiency, it needs to be included as it very well may be the difference between making the next charger and getting stranded.

 

[SpaceEVDriver]

I mean, we call it the GOM for a reason, but I think your explanation still gives it too much credit.

For example, I NEVER get over 2.1mi/kwh, yet recently charging to 100% had the GOM showing nearly 340 miles of range. Granted, it is more accurate around 80% SOC.

Yeah. Agreed.

My summary is of one of the algorithms described by Ford in its patents (and I missed several parameters like ambient and battery temperature). The specific data they incorporate are subject to lots of noise. For example, a 5- or 10-minute running average is likely to be subject to a lot of spikes that result in a poor quality average, which is one reason they blend it with the longer-running averages. But noise can still cause significant deviation from realistic values.

I regularly get over 2.4 miles/kWh on the freeway and my GOM usually bounces between 280 and 320 miles of range at 100% charge. I've never seen it estimate 340 miles at 100% SoC, but I've gone more than 340 miles on a single charge.

/shrug

 

[Firn]

Yeah. Agreed.

My summary is of one of the algorithms described by Ford in its patents (and I missed several parameters like ambient and battery temperature). The specific data they incorporate are subject to lots of noise. For example, a 5- or 10-minute running average is likely to be subject to a lot of spikes that result in a poor quality average, which is one reason they blend it with the longer-running averages. But noise can still cause significant deviation from realistic values.

I regularly get over 2.4 miles/kWh on the freeway and my GOM usually bounces between 280 and 320 miles of range at 100% charge. I've never seen it estimate 340 miles at 100% SoC, but I've gone more than 340 miles on a single charge.

/shrug

Yeah, I'm well versed in multi-variable technical data analysis as that's basically my day job. It's just astounding to me they can be so far off. As you point out, you get roughly EPA testing average efficiency, and your GOM shows EPA mileage or less. And yet I get well below EPA efficiency, yet it shows above EPA mileage.

Probably worse is that they DO show us estimated mileage. That's such a crap shoot since the type of driving you do varies so much. And yet with this fancy digital dash they show us that instead of some meaningful display, chart, or graph we can actually make use out of.

Frankly, it is astounding to me that with all these sensors, this amazing dash display, we get absolutely nothing as for meaningful displays. Heck, go one further and give us an app marketplace where guys can sell displays and apps, I wouldn't even care if Ford took 40% off the top, if I could buy a meaningful display for $5 I absolutely would do so.

 

[hturnerfamily]

...the mi/kWh display is an average for the entire trip ...Sometimes the value fluctuates quite a bit over just a minute or two, and sometimes it holds pretty steady and the changes are in small increments...

in your own question, you've answered your own question.

yes, it is simply dividing your MILES of travel by the KWH of battery usage: Miles / KWH.
- it doesn't matter your speed
- It doesn't matter your drive mode
- it doesn't matter whether you've charged or DCFC during that 'trip'
- it doesn't matter the price you may have paid to charge

- it may be impacted by factors such as air conditioning, heating, or ProPower usage, as these impact the SOC of the battery, whether driving, or while parked, etc.

in our travels this Thurs - Saturday, over 400 Miles over several days, and with several 'hours' of parked while ON, using ProPower for a vast majority of those travel miles/hours, powering our 120v mini-fridge in the bed, making coffee several times, using the microwave several times, and ALSO remaining ON while DCFC Tesla Supercharging, we averaged 2.9mi/KWH, under 'Trip 1'.

Some of these miles/hours were on 65/70mph interstates around/thru ATLANTA.
Many of these miles/hours were on 50/55mph roadways.
Some of these miles/hours were on 40/50mph rural roads and streets.
Several hours were spent parked, while ON, for ProPower to continue, while away from the truck.
House Hunting is exhausting.

but, the amazing machine, called a LIGHTNING, made it comfortable and smooth.

 

[hturnerfamily]

after saying all that, tho....

you have to also realize that this is simply a basic AVERAGE.. it DOES NOT mean that you WILL have those same mi/KWH outcomes the rest of your trip... THAT will depend on any differences versus what you have already experienced, such as wind, speed, terrain, stop-n-go traffic, etc.

I always play the conservative route, REGARDLESS of what the 'averages' tell me. It may say that I am experiencing 2.9mi/KWH since I left on my trip, but my return home might be AGAINST the wind, and therefore, will probably NOT get anywhere near that average: I might decide to calculate my maximum range by using 2.5 instead, especially if I know I might have a faster speed, as well.
On the converse, if I know that my average has been at very high interstate speeds, the rest of my trip on rural back roads may net a much higher average, and therefore more 'miles' than the GOM might expect... The GOM is a friend, yes, and it's nice to have, but it is NOT the end-all to how far you can go, or worse, how far you might NOT be able to go.

As to the GOM and it's 'range' estimation, I will submit that my LIGHTNING is using conservative range estimates, as compared to my own driving mi/KWH averages - meaning that I don't look at the GOM range for anything other than an estimate - my own calculations warrant better range outcomes, usually much farther than the 'scary' estimates that the GOM normally gives.
The farther you are from your destination, at least for me, the farther 'off' the GOM is.
The closer you get to your 0% SOC, the closer those range estimates are to reality.

 

[PJnc284]

Gotta love a tailwind. Normally only get 2.0-2.1 on my usual route from Wilmington to Raleigh NC but got 2.3 per the truck today. Car Scanner shows 45.3 kWh used over 109 miles which comes out to about 2.4.

 

[Hank42]

Let me know when your stuck driving in the mountains
All that math practically goes out the window.

 

[PJnc284]

Ha yeah. Pretty flat here in eastern NC and 70F today. Also helps that the route i usually take is 90% 55 mph highway. Took the interstate last week and only averaged 1.7 @ 75.

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