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Discussion Starter · #1 · (Edited)
Pulled out of Exeter services after an 80% charge on return from Cornwall with a string of M5 rapids to choose from and soon arrived behind a very tall artic box trailer. There were lots of big trucks as it was a Tuesday.

It was 22C outside and we had decided to run the aircon when possible to stay fresh on our longest journey so it was set to a more comfortable 19.5C.

The BBC forecast was for 8mph N.Easterly so almost dead in to wind on the M5 northbound.

I often do a short test of the wake of big draggy vehicles by dropping in behind and switching the energy screen on the Leaf and monitoring real time energy consumption. This is most beneficial when in to wind of course.

It soon became apparent that the vehicle in front had cruise control on as we settled at 59mph indicated. The flat bits showed the consumption dial hovering around the 15kw power consumption.

I have been wanting to know what benefit can be gained through sitting in an aerodynamic drag wake on a long run for some time and everything appeared to provide us with the best opportunity.

Before the armchair health and safety police chime in consider this.
If you are going slower than the trucks they all have to change lanes to pass you along with everyone else.
If the gap between you and the vehicle in front is small nobody tries to fill it.
It requires alertness and driving within your limits however given that, there is no way an artic will stop quicker than you so it is completely doable just choose a distance which you are comfortable with.
This was done out of curiosity as a learning experience to try to quantify range extension for those hopefully very few times it could prove useful.
You could say I did it so you don't have to.

How much difference did it make?
Remember
  • Gen 1 down to just under 60Ah capacity battery
  • In Drive mode
  • Aircon on
  • Into an 8mph head on wind
  • Started with a standard Ecotricity charge of 80%.
  • Indicated speed 59mph - occasionally 62mph on a few downhills so about 60mph average.
  • No elevation change from start to finish.
  • Cruise control used the whole way +1 -1 etc.
Blue Text Electric blue Sky Font


We arrived at the next charger with 4 miles on the GOM which I know would provide at least 10 more miles before turtle at this rate of consumption. I was quite pleased with that and at no time were we or anyone else in any danger. Please don't ask how close as it varies and I could have been a lot closer.

So 85 miles at motorway slow lane speed is possible from an 80% charge. That is better than 5.25 miles per kWh. I could have switched off aircon and/or put it in Eco but that would have skewed the results from my normal drive mode albeit adding another 10 miles of range to make 95 miles from an 80% charge.

Leafspy reports a 100% charge to be 19.4Kw so x 5.25=101.85 miles no reserve.
Switch to Eco mode with no aircon and 112 miles would be our best achievable motorway range using the above method. Cheaper, lighter and therefore quieter (tyre noise and reduced wind resistance) than more battery or a REX.

Clearly a fair bit better than 1 mile per % is possible even for an unwashed but much loved Gen 1 in the dry.

Time to run and hide;):cool::p.
 

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That's fascinating data and very encouraging. Thanks for posting.
 

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As a new gen 2 Leaf owner this information is very helpful in the acclimatisation from ICE to battery power. I know you have to change driving style and I have always driven as economically as possible in ICE vehicles.

Thanks for collecting the info and posting as I am trying to find the range **** and this really helps.
 

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Discussion Starter · #4 ·
Here is the start screen shot, a bit less than 80% SOC and Gids from the charger after all.
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So 85 miles at motorway slow lane speed is possible from an 80% charge. That is better than 5.25 miles per kWh. I could have switched off aircon and/or put it in Eco but that would have skewed the results from my normal drive mode albeit adding another 10 miles of range to make 95 miles from an 80% charge. Leafspy reports a 100% charge to be 19.4Kw so x 5.25=101.85 miles no reserve.
Is that also the benefit of using ZIG-ZAG tape on a Gen 1 Leaf? How about covering the rear wheel arches? Max tyre pressure I assume? However, you did have quite a warm (but far from new) battery at the beginning of that experiment in dry summer weather!!
 

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Discussion Starter · #6 · (Edited)
Is that also the benefit of using ZIG-ZAG tape on a Gen 1 Leaf? How about covering the rear wheel arches? Max tyre pressure I assume? However, you did have quite a warm (but far from new) battery at the beginning of that experiment in dry summer weather!!
Nup, no aero trickery on the car on this journey :). It needed a clean too, bug spattered and dusty.
I am in the process of doing a new aero mod test set up for that though to get some better test results. The temporary stuff had too short a life to get enough real data in the wild :(very promising though before it started to fall off with better than 4 miles per kWh achieved in free air (not in a wake) at 70mph indicated with wheels, rear wheel arches and radiator intake covered and an 86 mile non motorway road trip covered with 6 miles left on the GOM on arrival since you asked:p:cool:.
If you want to see how much effort is going in to this from manufacturers take a look at the BMW I8 including the bits you can't see easily especially underside in front of rear wheels. They are claiming drag coefficient of 0.22, better than model S 0.25 if you can believe it.

Our battery is a 2011 build sold in 2012 and it gets warmer due to internal resistance. Dealers storing at 100%, age and 17,500 miles is why it is now under rated capacity of 60A/hr.
I do run tyre pressures higher than Nissan say due to learning on US Leaf forum there is no wear issues.
Some of them go to 50psi but ours are usually checked locally warm set to 44psi strangely I find they hardly ever need air adding though.

Of course your range will reduce in winter or in the wet but the benefit of extending it in a drag wake and reducing heater on time (especially Gen 1) by getting there quicker will increase.
 

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My Nissan Leaf battery is an early 2011 build, sold mid 2011, that's given us 15,000 miles of 100% trouble-free driving (we've never yet seen the turtle). Battery capacity is now 58.3 Amp*Hours (=88% of new) with a Health figure of 77% after >3 years normal use (36 rapid & 870 overnight charges, mostly to 80%). As you say, the Ecopia tyres seem to keep themselves inflated at 40 psi - amazing! Better aerodynamics is what I want next. And then, after that, a 12 kWh supplementary battery (in parallel) when it's 7 or 8 years old...

A BMW i8 (as well as an i3 and several other EVs) will be on show at the Great Malvern ElectrAA meeting Sunday 21st September but I reckon it might be rather difficult to crawl in underneath to see their aerodynamic trickery!
 

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Discussion Starter · #9 ·
I've done a search but can't find GBEV's posting about his aero-trickery. Can anyone point me in the right direction?
I have not posted about it yet. Aerodynamics (of the car and using wakes) was one of the subjects discussed at the Battery Electric Vehicle society meet at Bristol where a few forum members happened to be:).
A second prototype will be properly investigated soon for Leaf:).
 
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