Highway Speed?

[ctenidae]

Unless you've got 42 miles to go on 48 miles of range, stressing about efficiency seems counterproductive. Or at least frustrating.

Heck, Geo Metro would top out at around 99mph. That speed was drag-limited. Meaning, you could be redlining that engine and it wouldn't get past 99mph, because every single one of its 55 horses would be pushing to keep you at that speed.

I can verify these facts. I drove my mom's Geo Metro in high school (I got all the ladies). Downhill, with a tailwind, after getting a good push it'd hit 99. Eventually. It would drive for about 4.5 years on a single tank of gas, to be sure, but only because it took that long to get anywhere.

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[mccdeuce]

To the OP, your frustration shouldn't be with EVs in particularl, but the physics of drag. These are the same whether you're driving an EV or an ICE. The difference is, in a ICE vehicle, you just don't notice the inefficiency of driving at 80mph. However, your MPG rate goes down significantly once you go faster than 55mph (give or take).

which is why our speed limits are generally 55…
https://www.history.com/this-day-in-history/nixon-signs-national-speed-limit-into-law
As part of his response to the embargo, President Nixon signed a federal law lowering all national highway speed limits to 55 mph. The act was intended to force Americans to drive at speeds deemed more fuel-efficient, thereby curbing the U.S. appetite for foreign oil.

@GrabberBlueNitePony just because we can drive 80 in 60 zones in NOVA/DC doesn’t mean we should. reaction time is way down, and with all the crazy drivers here I recommend changing the mindset. Speed limit or 5 over. Safer and you will see your efficiency skyrocket. For me, when I do this on my 35mile commute into DC I typically see 3.7 avg speed of 62mph.

 

[Blue highway]

So how's the math work then? With a 91 usable kwh battery on my '23 ER AWD, using 3.1 kwh/mi * 91, the range is theoretically 282 miles, pretty close to the rated 290. I haven't actually topped it to 100% to see what the GOM says yet, but that calculation method seems right.

yes... but (the buts get you every time) the EPA figure is NOT at what most of us consider highway speeds. The EPA is a blend of highway and surface streets and the speeds are much lower than most of us would tolerate without losing the will to live.

It's also warm when the EPA figure is calculated... like 80 degrees +.

if its 80 degrees out, and I'm below 65MPH I'll go a bit further than the EPA number... but if its colder, or if I'm driving normally... nah plan 2.5 miles per kWh... you will likely do better but you will not be stranded.

Fun fact - one of the posters here worked out the capacity of the battery at different temperatures and it aligned pretty well with research papers . Lithium battery 100% capacity is ONLY at 80 degrees F or higher... at 45 degrees, it's down ~10% At 20 degrees F it's down nearly 20%. This has nothing to do with running the heater in the car, it's just that cold impedes the chemical reactions in the battery.

 

[GrabberBlueNitePony]

yes... but (the buts get you every time) the EPA figure is NOT at what most of us consider highway speeds. The EPA is a blend of highway and surface streets and the speeds are much lower than most of us would tolerate without losing the will to live.

It's also warm when the EPA figure is calculated... like 80 degrees +.

if its 80 degrees out, and I'm below 65MPH I'll go a bit further than the EPA number... but if its colder, or if I'm driving normally... nah plan 2.5 miles per kWh... you will likely do better but you will not be stranded.

Fun fact - one of the posters here worked out the capacity of the battery at different temperatures and it aligned pretty well with research papers . Lithium battery 100% capacity is ONLY at 80 degrees F or higher... at 45 degrees, it's down ~10% At 20 degrees F it's down nearly 20%. This has nothing to do with running the heater in the car, it's just that cold impedes the chemical reactions in the battery.

Yeah that’s what I find interesting. I thought in cold, the kWh/mi lowers but the usable capacity remains the same. But this sounds like both lower, that just makes it hard to calculate range while only knowing kWh/mi.

 

[Blue highway]

Yeah that’s what I find interesting. I thought in cold, the kWh/mi lowers but the usable capacity remains the same. But this sounds like both lower, that just makes it hard to calculate range while only knowing kWh/mi.

The "hard to calculate" thing is why the GOM exists. As first released it would pessimistically take these things into account... and in my experience you could really go as far as it predicted... no unpleasant surprises. Actual miles unwound really close to the prediction rate ... but lots of people complained... because their car could only go 100 and something miles in the winter.... so Ford changed the GOM to make stupid people feel better. It worked, judging from the forums complaints of losing range in the winter are way down... and predicted miles unwind faster than actual miles in the cold making the GOM less useful. - end of mini rant.

 

[GrabberBlueNitePony]

The "hard to calculate" thing is why the GOM exists. As first released it would pessimistically take these things into account... and in my experience you could really go as far as it predicted... no unpleasant surprises. Actual miles unwound really close to the prediction rate ... but lots of people complained... because their car could only go 100 and something miles in the winter.... so Ford changed the GOM to make stupid people feel better. It worked, judging from the forums complaints of losing range in the winter are way down... and predicted miles unwind faster than actual miles in the cold making the GOM less useful. - end of mini rant.

Agreed, I miss the old version. Now people are complaining about not getting the actual number. I’d rather have the pessimism to know I am not budgeting more miles than I have on a longer trip.

 

[snowy_91]

since I retired the extra 10, 15 mins on the road doesn't really bother me so I slow down a bit....Now get off my lawn!

 

[mkhuffman]

For me, when I do this on my 35mile commute into DC I typically see 3.7 avg speed of 62mph.

When I pass you tomorrow morning going 80 mph as I drive to my office in Crystal City, I will wave! (I always wave at fellow MME drivers!)

 

[EVandSolar]

I feel bad for folks I see ripping around at 80mph in a frenzy to rush to work on time. Get up 10 minutes sooner. Relax. Leave 5 minutes earlier and enjoy a nice relaxed commute. A lot of the folks rushing around in a frenzy only save 2-3 minutes, while riding bumpers of people already going 15 over, desperate to rip around and speed up even more. What a terrible way to start the day.

Driving fast just for the fun/thrill of it, that's another thing. Have a blast! I'm talking about the folks miserable in their frenzied rush to save 2 minutes on their commute.

I drive on a 55 mph highway, and set my cruise to 63. I get to work 10-15 minutes early. No rush. I've also averaged 3.9 miles/kWh since December(but this is with one of the most efficient EV's made). Our Kia Niro doesn't do quite as good, probably 3.3, but has averaged lifetime 3.6 over the year we've had it, and that includes 70+mph interstate trips over mountains in sub 20 degree weather. It would drop to 2.5 in those conditions! Ouch!!

 

[timbop]

So I think one of my biggest frustrations that I have learned is that despite the Mustang name, going fast is just not good if you want to maintain range. But how fast is fast? It feels like most of the time in varying weather between 50-70 degrees F, for the 1200 miles I've had the car, I cannot get above 3-3.2 kwh/mi. I am in Northern Virginia, most of my driving is highway, usually 10-15 miles for my commute, or the occasional 35-45 miles if I have a longer drive into DC. Only time I get more efficiency is when I have traffic which makes sense. I typically drive between 65-70 mph and that in itself is annoying. I have always gone 75-80mph but since that is so bad for an EV (facepalm), I have gone slower. Just doesn't seem like the efficiency is that great even at 65-75 mph. This along with the horrendous GOM update that is all over the place makes it annoying to try to maximize range while still enjoying the "Mustang" aspect.

What do you guys usually drive at on the highway?

I'm guessing this is your first Mustang? It's my fourth, and with the 3 previous ones I never worried about MPG ?

 

[dbsb3233]

In the roughly 25,000 miles of road trips we've done, we've averaged 2.8 MPK. That's on speed limits mostly 75-80 MPH.

Best trip was summer, 3.0 avg. Worst trip was winter, 2.4 avg. Mostly the same route many times through the last 2 years.

 

[HuntingPudel]

I'm guessing this is your first Mustang? It's my fourth, and with the 3 previous ones I never worried about MPG ?

I don't think I've ever really worried about MPG. The Blazer is a big brick (with a little tiny C#@vy engine) and the T/A has >8 liters of Pontiac with a big cam under the hood. Could be why I never seem to have any pocket change. ??

 

[dbsb3233]

I drive on a 55 mph highway, and set my cruise to 63.

Some would call speeding by 8 MPH "rushing" too. ?

 

[Maquis]

I don't think I've ever really worried about MPG. The Blazer is a big brick (with a little tiny C#@vy engine) and the T/A has >8 liters of Pontiac with a big cam under the hood. Could be why I never seem to have any pocket change. ??

??

I generally drive 5-10 over and every time I get my doors blown off by a 1 ton dually 4x4 or a Suburban, I always think “$4 gas must not really be too expensive.” ?

 

[EVandSolar]

Some would call speeding by 8 MPH "rushing" too. ?

Have to drive that speed to not get run over and passed by all the 18 wheelers!

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