Efficienct (range) vs. Speed

Is there any data on how the range is affected by speed?

I've noticed that creeping along a level road in a traffic jam often uses more power (as judged by the Instant Energy Economy in the Vehicle Information Display) - around 0.2-0.3 KWh per mile. Yet the efficiency is much higher when you speed up to 30mph, say.

Driving slowly is inefficient, and driving fast is inefficient, so somewhere in between there must be a speed at which the miles per KWh is at a maximum (all other things being constant).

Is there a chart that shows how range changes with speed?

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Swifty said:

...so somewhere in between there must be a speed at which the miles per KWh is at a maximum (all other things being constant).

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As the chart says in some fine print towards the bottom, the most efficient speed is 12mph.

You'll have to turn the climate control completely off for the chart to apply.

12mph, eh? I'll spend more time in the 20mph zone in our local town then. It would be an interesting experiment driving around the UK's crowded roads at 12mph.
We're having an Electric Vehicle day at a nearby airfield in a few weeks time, when the public will be invited to try out our vehicles. I'll try and keep the demonstration rides to 12mph, perhaps. The car is impressively quiet at that speed, as the tyre noise is only just starting to cut in.

I was once driving my old VW Campervan in convoy with a DIY converted VW T4 van along the A849 on the Isle of Mull, Scotland. About 40 miles of single-track road with passing places. Doing a very steady pace. When the T4 pulled into a small parking place, I followed. The driver jumped out and remarked "Mull is the only place in the UK where you could get away with driving so slowly. Except the M25" (For those who don't know the M25, it is London's orbital motorway, frequently clogged with traffic jams. For those who don't know Mull, it is a medium-sized island off the west coast of Scotland with two charging points, just enough so you could go most anywhere).

M25 = "Europe's largest parking lot"

I've driven all over the UK, and almost all of the traffic jams I have encountered were on the M25 :shock:

Swifty said:

I'll try and keep the demonstration rides to 12mph, perhaps.

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Just in case that they had any remaining doubts about EVs being glorified golf carts...

RegGuheert said:

Just in case that they had any remaining doubts about EVs being glorified golf carts...

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Yes, my Leaf could be considered that...
And my ICE car is a glorified go-kart.
My co-worker's Harley is a glorified mini-bike..
Not sure the point, but this is fun...

desiv

The problem is that it is exceptionally difficult to drive smoothly at that speed to reach the required level of efficiency. In the real world, the best speed is undoubtedly higher... You also have to consider parasitic losses at lower speeds...

Swifty said:

12mph, eh? I'll spend more time in the 20mph zone in our local town then.

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TomT said:

The problem is that it is exceptionally difficult to drive smoothly at that speed to reach the required level of efficiency. In the real world, the best speed is undoubtedly higher... You also have to consider parasitic losses at lower speeds...

Swifty said:

12mph, eh? I'll spend more time in the 20mph zone in our local town then.

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Exactly. I want to stress that driving 12 mph is difficult, and giving people rides "at 12mph" will not likely get the same result. It is 12mph at a steady rate, not an average speed.

Just drive the car. Anything under about 35mph will yield fantastic economy.

I've recently done a mix of driving at 12mph, 20mph and 30mph. 12mph is impractical almost anywhere on the public highway. 20 mph is relaxing where circumstances permit. I drove through a 40mph zone at 30mph, meeting no other vehicles, and that was fine.

In my tests I came across something curious.
I live at the top of a 360 foot hill, so my journeys always start with a 2-mile downhill roll. Rolling down the hill, my kWh/mile meter falls to zero, and my range climbs ever upwards. Once at the bottom of the hill, there is a stretch of road which is essentially level for a further 1.2 miles. I've cycled this route, there is almost no gradient at all.
During this 1.2 mile level drive, the kWh/mile meter says almost wholly at zero. I don't see how I can be driving on the level but using no energy.

Swifty said:

I've recently done a mix of driving at 12mph, 20mph and 30mph. 12mph is impractical almost anywhere on the public highway. 20 mph is relaxing where circumstances permit. I drove through a 40mph zone at 30mph, meeting no other vehicles, and that was fine.

In my tests I came across something curious.
I live at the top of a 360 foot hill, so my journeys always start with a 2-mile downhill roll. Rolling down the hill, my kWh/mile meter falls to zero, and my range climbs ever upwards. Once at the bottom of the hill, there is a stretch of road which is essentially level for a further 1.2 miles. I've cycled this route, there is almost no gradient at all.
During this 1.2 mile level drive, the kWh/mile meter says almost wholly at zero. I don't see how I can be driving on the level but using no energy.

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Basing your performance on 1.2 miles, or even 10 miles is not likely to get good results. Also, using the mileage "Guess-O-Meter" (GOM) is a futile endeavor.

Swifty said:

Is there a chart that shows how range changes with speed?

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Had to smile at this, and wonder if a certain someone had put you up to it! ;-)

mbender said:

Swifty said:

Is there a chart that shows how range changes with speed?

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Had to smile at this, and wonder if a certain someone had put you up to it! ;-)

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Not everyone has been reading this forum for 3+ years

Swifty said:

During this 1.2 mile level drive, the kWh/mile meter says almost wholly at zero. I don't see how I can be driving on the level but using no energy.

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For some crazy reason, the LEAF's efficiency meter will read at maximum efficiency until you've burned off all the energy you recently regenerated. So in your case, after the regen you did down the hill, the efficiency meter won't start working normally until you use up all that energy you've recovered.