75, 85, 95 mph motorway miles per kwh ?

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philnewmerc

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CLS55
I am curious to know if any EV drivers have measured their miles per kilowatt hour reading at higher speeds? Obviously we all now know that EVs have best consumption around 40 miles per hour and are perfect in slow traffic. But at high speed they, for obvious reasons, then tend to lag behind ICE. But it's very hard to find the numbers because car magazines are lazy and just quote the manufacturers figure as they do with MPG. Has anyone got any real-world data at high speed please?

For me 75 is slow, 85 is a good cruising speed, and 95 is a good quiet motorway cruising speed. I'm just curious whether I would have to alter my preferred driving style significantly to cope with an EV on a long trip. (I'm not being facetious when I say the EVs on the motorway I encounter are going somewhere between 55 and 65 ish: I'm wondering if that is truly necessary or if EV drivers just tend to be instinctively hypermiling even when they don't need to because they tend to be very aware of consumption or are paranoid about range unnecessarily???)
 
I don't have any real world data but the laws of aerodynamics will tell you that 95 mph requires double the power compared with 75mph.

I can only imagine that EV range is truly dreadful at high speeds. It doesn't sound like the right type of motive power for you.
 
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For me 75 is slow, 85 is a good cruising speed, and 95 is a good quiet motorway cruising speed. ..................................................
For you, 75 is speeding, 85 is Officer attention zone, 95 is a court appearance not to mention a danger to yourself and others.
 
Hi
On our BMW iX I have measured the range difference on the longish motorway drive between Abu Dhabi & Dubai.
Below are some journeys with the average speed vs electricity consumption.
Abu Dhabi to Dubai 119km 1 hour 13 mins 20.1 kWh/100km 23.9 kw/h total used
Abu Dhabi to Dubai 102km 1 hour 7 mins 20.8 kW/h/100km 21.1kw/h total
Dubai to Abu Dhabi 97km 56 mins 20.4 kWh/100km 19.8 kWh total
Above journeys are basically cruising on motorway with cruise control on.
At speed of 110km/h average speed I can get around 400km range from 100% charge.
Mixed journey 29km 18 mins 24.9 kWh/100km 7.3kWh total
Mixed journey 32km 24 mins 31.6 kWh/100km 10.1 kW/h total
Mixed journey 30km 21 mins 27.9 kWh/100km 8.4kW/h total
On above mixed journeys motorway plus smaller roads or cruise at 140km/h - range drops to around 300km from 100% charge

Heavy right foot on motorways really damages range.
Maximum speed limit allowed on motorway is 140 km/h here - which is around 87 mph
Cheers
Steve
 
I think that what you are asking for is an impossible task.

My own experience is that the m/kWh figure will vary greatly - even using the same car on the same road at the same speed - based on a number of factors, including (but not limited to) ambient temperature, load (passengers & luggage), tyre pressures (my car is quite sensitive to this - inflating the tyres up by 5 psi improves economy noticeably on the motorway) road gradient, electrical consumers used (aircon/heating etc), drive mode configuration (my car has Sport/Normal/Eco/Snow, in addition to various regeneration levels including one-pedal mode), driving style (the 'lead foot' syndrome), whether you are using cruise control or not (cruise control reduces efficiency, but the drive is more relaxing), among others.

All of the above will affect an ICE car too, but to a much lesser degree. With an EV, the above could cause variations from (say) 2 m/kWh to 4 m/kWh - that's a 100% difference (or 50% economy - depending on how you look at it...).

It's just not calculable. But good luck with it....
 
I don't have any real world data but the laws of aerodynamics will tell you that 95 mph requires double the power compared with 75mph.

Not sure that's right? Aerodynamic drag is proportional to the airspeed squared, so doubling speed increases drag by a factor of 4 (2 squared). 95 mph is 1.26 times 75, so the difference in drag would be 1.26 squared = 1.6 (roughly)? You'd need to be doing 105 mph to double the aerodynamic drag compared to 75 mph.

Of course rolling resistance from the tyres/bearings/etc. goes up with speed/rpm as well ... the extra power needed isn't based solely on increased aerodynamic drag.
 
Hi
On our BMW iX I have measured the range difference on the longish motorway drive between Abu Dhabi & Dubai.
Below are some journeys with the average speed vs electricity consumption.
Abu Dhabi to Dubai 119km 1 hour 13 mins 20.1 kWh/100km 23.9 kw/h total used
Abu Dhabi to Dubai 102km 1 hour 7 mins 20.8 kW/h/100km 21.1kw/h total
Dubai to Abu Dhabi 97km 56 mins 20.4 kWh/100km 19.8 kWh total
Above journeys are basically cruising on motorway with cruise control on.
At speed of 110km/h average speed I can get around 400km range from 100% charge.
Mixed journey 29km 18 mins 24.9 kWh/100km 7.3kWh total
Mixed journey 32km 24 mins 31.6 kWh/100km 10.1 kW/h total
Mixed journey 30km 21 mins 27.9 kWh/100km 8.4kW/h total
On above mixed journeys motorway plus smaller roads or cruise at 140km/h - range drops to around 300km from 100% charge

Heavy right foot on motorways really damages range.
Maximum speed limit allowed on motorway is 140 km/h here - which is around 87 mph
Cheers
Steve
So basically at the UK motorway speed limit you're talking about 3 miles per kwh. Assuming a battery of 80 kwh is being charged from 20% to 80%, ie 48 kwh, this would give a range of 144 miles before the next recharge. Interesting.

Would be ideal if anybody knows what the typical consumption might be at 80 miles per hour???
 
I don't have any real world data but the laws of aerodynamics will tell you that 95 mph requires double the power compared with 75mph.

I can only imagine that EV range is truly dreadful at high speeds. It doesn't sound like the right type of motive power for you.
The fuel consumption in my car barely changes from 70 to 90 mph. I assume this is because the engine is working in a super efficient zone on the RPM scale. But though in most cars the consumption will obviously increase, it certainly does not double. However for EVs this does seem to be the case, not that I can find much hard evidence...
 
Out of curiosity..how would you ever know the true miles per KWH on an EV? On an ICE car if you don't believe the gauge you can fill it to the brim.....use it for a bit....refill and calculate pretty accurately your mpg. On an EV you are depending on electronic readings whether you measure the power going in or the rate per mile it goes out. How do we know its accurate?..... Like many ICE cars, I bet not many under read the miles per KWH!!
 
Assuming a battery of 80 kwh is being charged from 20% to 80%...

That's not the optimal use profile - what you should be doing is charge overnight to 100% before departing, then re-charge along the route to 80%. And you can go down as low as 10% if you're charging the battery up immediately after reaching this percentage.

For drivers of simpler cars than Teslas (myself included), there's a great app called A Better Route Planner (ABRP), that connects to your car's BMS and manages the charging stops for optimal / quickest route overall.

There's also a web version if you don't have an EV and want to have a go:

 
Out of curiosity..how would you ever know the true miles per KWH on an EV? On an ICE car if you don't believe the gauge you can fill it to the brim.....use it for a bit....refill and calculate pretty accurately your mpg. On an EV you are depending on electronic readings whether you measure the power going in or the rate per mile it goes out. How do we know its accurate?..... Like many ICE cars, I bet not many under read the miles per KWH!!

How do you know the time on your smartphone is accurate? With my old Doxa watch, I always knew where I stood, but can you trust all this new modern electronic trickery... :D
 
You have an AMG and a motorbike and seriously never break the speed limit? I'm not knocking it, I'm just very impressed.
EVERYONE speeds without exception.......its just the amount over that varies. Very few people have the patience (or want to annoy other road users enough) to be below 30 as they roll past the sign.....or don't start to go before the black and white GLF sign. And that way more dangerous (depending on what's around) than 80 or 90 on the motorway will be.

They used to be a lady called Pam who worked with me at an old job. We were talking about speeding and she swore she never did....NEVER EVER.....and she was a Vicars wife too (and she was.)!! I left just after her that night and she was doing well over 30 before we had even left the industrial estate!!! Next day she flat denied it!!! I think she really did not know.....which is a worry in itself.
 
Out of curiosity..how would you ever know the true miles per KWH on an EV? On an ICE car if you don't believe the gauge you can fill it to the brim.....use it for a bit....refill and calculate pretty accurately your mpg. On an EV you are depending on electronic readings whether you measure the power going in or the rate per mile it goes out. How do we know its accurate?..... Like many ICE cars, I bet not many under read the miles per KWH!!

Seroulsy now - the brim-to-brim calculation only works accurately if you use the same pump as the same ambient temperature.
 
EVERYONE speeds without exception.......its just the amount over that varies. Very few people have the patience (or want to annoy other road users enough) to be below 30 as they roll past the sign.....or don't start to go before the black and white GLF sign. And that way more dangerous (depending on what's around) than 80 or 90 on the motorway will be.

They used to be a lady called Pam who worked with me at an old job. We were talking about speeding and she swore she never did....NEVER EVER.....and she was a Vicars wife too (and she was.)!! I left just after her that night and she was doing well over 30 before we had even left the industrial estate!!! Next day she flat denied it!!! I think she really did not know.....which is a worry in itself.

There's a difference between drivers who speed absent-mindedly, i.e. because they were not watching their speed or not paying attention to the road signs, and drivers who simply decide that they should be driving at a speed higher than the speed limit and do so knowingly.
 
Hi,
What everybody seems to forget is that the performance of my ICE cars got better as I burnt fuel and reduced the cars weight.
On my EVs the maximum power reduces as the state of charge reduces!
A Tesla Model 3 Performance probably has 100hp less at 20% state of charge as it does at 75% state of charge!
Cheers
Steve
 
@markjay Pumps are calibrated regularly to the difference should be irrelevant.
Secondly the fuel you are buying is stored underground a pretty much constant temp.....so as long as you let the warm fuel in you tank get low before filling and refilling the difference in close to nil. But lets say you somehow manage to buy petrol that 20 degrees hotter one day than the next....the expansion rate in petrol for 20 degrees is well under two percent....sub a litre in a 50 litre tank.....so on a 30 mpg car that would make the measurement less than 0.5 mpg out.
 
@markjay Pumps are calibrated regularly to the difference should be irrelevant.
Secondly the fuel you are buying is stored underground a pretty much constant temp.....so as long as you let the warm fuel in you tank get low before filling and refilling the difference in close to nil. But lets say you somehow manage to buy petrol that 20 degrees hotter one day than the next....the expansion rate in petrol for 20 degrees is well under two percent....sub a litre in a 50 litre tank.....so on a 30 mpg car that would make the measurement less than 0.5 mpg out.

They are calibrated electronically... can this be trusted? :D

But joking aside, calibration isn't the issue - the point where the nozzle stops delivering fuel when it senses that the tank is full can vary between pumps, as it's not included in the calibration process.

The ambient temperature does matter, because the fuel in the pipeline and in the pump will be at a different temperature to the fuel in the tank. If you are filling-up 70 litres than the volume change of 2-3 litres might not make a huge difference, but if you are topping-up (say) only 10 litres than it will be more noticeable, especially if there were extreme weather differences between the two filling dates.

My point is that 'accurate' is a relative term, and all that can be said in this context is that a brim-to-brim exercise is potentially less-inaccurate than relying on the car's onboard trip computer.

(I say 'potentially' because I am not actually sure what is the basis for the premise that the onboard trip computer is the less accurate of the two...)
 
Hi,
What everybody seems to forget is that the performance of my ICE cars got better as I burnt fuel and reduced the cars weight.
On my EVs the maximum power reduces as the state of charge reduces!
A Tesla Model 3 Performance probably has 100hp less at 20% state of charge as it does at 75% state of charge!
Cheers
Steve
According to Tesla the power will be the same between 90% and 10% charge. The exception being lots of flat out acceleration one after the other like a day at the strip......the power gets backed off very slightly to protect the car. One owner said it works out a drop of only about 0.3 mph of his terminal speed each run.......tiny and un-noticeable on the road. (From a US Tesla owner Forum.....so who knows if that's correct or not. I'm just the messenger!!)
 
But joking aside, calibration isn't the issue - the point where the nozzle stops delivering fuel when it senses that the tank is full can vary between pumps, as it's not included in the calibration process.
Fair poins in your post.....but in the real world none are enough to affect the MPG by more than a mpg or so. How accurate in the EVs reading and how could you check?

By the way....when I check my mpg there is no point stopping at the click......I fill to exactly the same point in the filler neck to help with accuracy.
 

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