EV Road Trials


100% Electric Vehicles Peugeot Ion Charging Up

Published on November 8th, 2017 | by Andy Miles

7

EV Road Trials – Different Levels of Range Under Different Conditions.

Peugeot Ion Charging Up

Introduction

On 1 October this year, I published an article in Cleantechnica, in which I shared my experience of driving an EV. I explained the facts, and theory, behind getting the best range out of an electric vehicle. The title of the article was “Electric Car Range Tips, & How An Electric Car Works”. I originally intended to call it “EV Experience”, but the longer title was chosen for the sake of search engine optimisation.

Discussion below the line

There was much interesting discussion below that article. One person insisted that a particular pattern of braking, using the brake pedal, optimised regenerative braking, where, in reality, the two are entirely unconnected. Regenerative braking is optimised by not using the brake pedal at all. He had made the age-old logical error of confusing correlation with cause. He had observed that regenerative braking is greatest when slowing from higher speeds, and then made the incorrect assumption that braking gently at the beginning would somehow result in more regenerative braking, which is not the case.

His braking technique was not the cause of higher regenerative braking, but just something occurring concurrently with it. Using the brakes, at all, is, simply, robbing your regenerative braking system of the opportunity to convert your motion back into electricity.   The only way to maximise regenerative braking is to not use the brake pedal, at all.   There is a certain truth in what he was saying, however, as if you are going to rob yourself of regenerative baking by using the foot brake, doing this the least when initially slowing from higher speeds, where regenerative braking gains are at a maximum, would make some sense. Not using the brake at all would make even more sense.

Correlation Confused with Cause

That particular type of mistake is very common.  It can be seen in both professional research conclusions, inadvertently, and propagandist news sites, deliberately. Whenever you see something cited as the cause of a particular outcome, it is always worth asking yourself, is it really the cause, or just correlation.

Any real-life examples might be controversial, so I will not quote any. A good illustration of the principal, is an experiment where someone drops an egg onto the floor, and shouts “splat”, just before the egg hits the floor. Having done this a number of times, they come to the conclusion that shouting “splat” is essential for the egg to break. Well, we all know it is not, and this could simply be proved by dropping the egg without shouting “splat”. In the same way, whether we believe a certain pattern of using the brake pedal will optimise regenerative braking, or not, the truth of the matter is just as easily proved by slowing down, not using the brake pedal at all.

The Discussion-Question This Article Answers

Another useful part of the discussion was someone asking me for precise figures in the difference, in range, between driving slower, driving faster, and driving behind a large vehicle, to reduce air resistance. I had to confess that I couldn’t give him precise figures, as I had based my article just on my experience of driving an EV for a couple of years, and noticing a definite difference in range in those three scenarios. I decided that, rather than leaving it open, I would perform some road trials to see exactly what the difference was.

Trial protocol.

My electric car has an indicator for battery charge level, which mimics a fuel gauge, using bars, slowly disappearing, one by one, as the level goes down. When they get to the last three, they start to flash on and off, to tell me that I am nearly running out; as if I did not already know. That would not be much use for giving precise figures for battery level, and ranges.

Getting the Figures

I have noticed that when I charge up, using Ecotricity fast-chargers, on the motorway, (Freeway), the display on the charger includes a precise figure for state of charge, expressed as a percentage. What I decided to do was to drive from my home to a fast charger on the M1 motorway, not far from where I live, and to connect my car to the charger, and charge it to 80%. This is the point at which it automatically switches off in any case, so that it was easy to get a precise starting point of 80%.

I took photographs of the charger display, and I then drove south, on the motorway, until I reached the next charging point, about 23 miles away.  There, I connected the car to the charger again, and photographed the display on the charger, showing the precise percentage of charge remaining at the beginning of that charge session. By comparing the two, I was able to provide a precise figure for the percentage of charge used in travelling the 23 miles.

Getting the Comparisons

I performed this operation on three separate occasions. The first time, I drove behind various large vehicles including a bus, at speeds of between 60 and 65 mph. On the second occasion, I drove at speeds between 60 and 65 mph, in roughly the pattern of variation that I remembered, but avoiding travelling behind any other vehicle. On the third occasion, I drove at 70 mph, the maximum speed allowed on the motorway, again, without travelling behind any other vehicle. By doing this I arrived at the precise figures that I had been asked for.

I also made images of the e-mails from Ecotricity, detailing a record of each particular charge event. Those e-mails provide independent corroboration of my statement that I did charge at those particular places, on those particular days, and times.

Before anyone starts to think how dedicated I must be to do all of this driving just to get figures for my readers, I did this on three separate days, when I had other reasons for driving along that stretch of the M1. The only extra trouble was in making the extra charging stop to charge up to the 80% first, and in photographing the displays. I was interested to find out for my own sake, too, just to make sure that I was not, unnecessarily, restricting my view of an otherwise panoramic motorway landscape, to the back end of a bus. I also wanted to know just how much difference it would make to be driving at the maximum motorway speed, rather than slower, range-saving, speeds.

Limitations

The Ideal World

I would be the first to admit that this is not a precise scientific study. To get something more precise I would have needed to drive on a circular test track, all on the same day, where no wind and temperature differences could affect the figures, and where speeds would be very precise and constant, and any shielding vehicle, constantly present or not.

The Real World

Obviously, driving on the motorway on three different days, there might have been some small differences in wind direction and strength and in the air temperature, but not significantly so. Also, I would have been very lucky to have found a large vehicle to drive behind from the start, and to remain behind it constantly throughout. There was a short period with no vehicle in front, at the start, and as the first vehicle I found was driving rather slower than I required, I switched to another, after a few miles.

When trying to drive without any vehicles in front, but at the same average speed as before, and having due consideration for other drivers on the road, I was not always able to do so. As these defects reduce, rather than increase any differences, I am not too concerned about them. Finally, one last problem was that on the last occasion the charger comms failed. As I did not get the usual e-mailed bill, you will have to take my word for it.

The Data

Copies of images of figures used

The Peugeot Ion has a 16 KW/H battery, which is where the “16” comes from.  The “Distance in Miles”, of 23 miles, is the 22.6 miles taken from the sat-nav, and the car’s own trip counter, and rounded up. The “80” is the % of charge at the beginning of each trip, and the “End %” figures are taken from the charger display, at the end of each trip. The photo of the sat-nav display shows the starting point with the distance to travel to the end point.

Date
Battery Capacity KW/H
Start %
End %
Distance in Miles
Driving Style
12/10/2017
16
80
49
23
Shielded 60-65 mph
25/10/2017
16
80
41
23
Unshielded 60-65 mph
02/11/2017
16
80
36
23
Unshielded at 70mph

The Results

The “% Used” is simply 80% minus the “End %”.  The “KW/Hs Used” is calculated as the “% Used” of 16KW/H.  The “Miles per KW/H” is the 23  miles, divided by the “KW/Hs Used”.  The “Calculated Range in Miles” is the range from 100% charge, assuming 16 KW/Hs is available from the battery, and so is 16 multiplied by the “Miles per KW/H”.

Date
% Used
Calculated
KW/H Used
Miles per KW/H
Calculated Range in Miles
Driving Style
12/10/2017
31
4.96
4.64
74.19
Shielded 60-65 mph
25/10/2017
39
6.24
3.69
58.97
Unshielded 60-65 mph
02/11/2017
44
7.04
3.27
52.27
Unshielded at 70mph

 

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About the Author

As a child at school, I had the unrealistic expectation that I would learn about, and understand, absolutely everything, during the course of growing up. Now, at the other end of life, I am fully aware of how much I have not learnt, and do not understand, and yet, I remain interested in everything. My education, starting with an arts degree, and going on to postgraduate studies, in everything from computer science, to hypnotism, reflected my broad interests. For work, I ended up working as a senior officer in local government, and built my career on being a legal eagle for the obscure branch of law, governing the work of my department. I am retired now, and am currently living in North Leicestershire in the United Kingdom, with plenty of time for doing whatever I like. I have always had a keen interest in everything alternative, which includes renewable energy and energy efficiency and, of course, electric vehicles. So, naturally, I have taken ownership of an EV, now that they are affordable and practical forms of transport. Writing is also one of my great pleasures, with various articles and a novel to my name, so writing about EVs is a natural evolution for me.



  • Guy Hall

    Nice article, but please be careful about generalizations. Different EV makes behave differently. The LEAF increases regeneration when the brakes are applied.

    • daddygnu

      I don’t know the details of how the Leaf works, but physics tells me that to slow from one speed to another a certain amount of kinetic energy is converted to different forms – some stored in the battery and some lost to waste heat. If the brakes are used more energy is lost as heat and less is saved in the battery. The rate of regeneration may go up but the time to slow down is shorter and the total energy saved to the battery is less than if you don’t use the brakes.

      • Guy Hall

        You’re correct. The user interface varies from model to model. In the tesla all regen is controlled through how one uses the accelerator pedal. The brake pedal is only to apply the brake pads. In the LEAF, a mild regen is available through the accelerator pedal and when using the “brake” pedal, the car software may first use various levels of regen, then apply brake pads. Tesla and now the 2018 LEAF make available “one pedal driving”. The 2017 LEAF and several others blend the regen across both pedals to make the driving experience similar to gas cars.

    • Andy

      Yes, I did wonder about that possibility, though it seemed illogical to have less than the full amount of regeneration available on easing off the acceleator pedal. I did do some internet searches on that subject, but couldn’t find anything definitive.

  • Clarence Dold

    I would think that most electric cars don’t apply the mechanical brakes early in the pedal travel. My Ford Escape certainly didn’t. I could sometimes hear when the mechanical brakes were being applied because they were rusty. I could drive around the city, come to a stop, and touch the brake rotors with my finger. That isn’t an experiment I would suggest without regeneration.

    I have presumed that some portion of the “bubbles” indicating regeneration in my Nissan LEAF are showing regeneration with no mechanical braking. If I have the option, I will apply the brake pedal while keeping an eye on those bubbles, and avoid hitting the maximum.

    • Andy

      I did consider that, but with my car, going by the regeneration level indicator, it is at maximum when I take my foot off the accelerator pedal, except when going at slow speeds, and does not increase, according to the indicator, if I lightly touch the brake. The principle remains the same, though, that any use of the friction brakes is robbing you of regeneration. I drive without using the foot brake, at all, except for unexpected events, and when I need to come to an actual dead stop.

    • Clarence Dold

      The program LeafSpy shows the amount of regen versus friction braking on a separate screen that I didn’t have enabled.

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