Range Of Electric Cars

“Ronen Kleiman says he noticed immediately that the electric vehicle he leased in 2014 wasn’t living up to what the carmaker was advertising on its website — it couldn’t travel the distance BMW said it could on a single battery charge.”
 
See Electric car driver finds altered BMW ad lowers range after purchase
Sigh!!! When I was a teacher it was as plain as the nose on my face. Some people may be grown up but still as innumerate as a primary school student…

In this case, linked at the right, BMW advertised a car as having a range of “up to” 200km “depending on driver behaviour”. That’s clearly a maximum, an extremum of the function of range versus driver behaviour. Behaviour could mean stop and go in urban traffic, or high rates of speed on the highway. In neither case would anyone with any knowledge of number imagine 200km could be achieved. Yet, here’s a guy and a national television network broadcasting a complaint that BMW may have misled consumers. Consumers can mislead themselves if they don’t know the ordinary meaning of words and numbers.

In case anyone does not understand, let me explain two ways to achieve maximum range in an electric vehicle:

  • drive at the optimal speed, probably between 20 and 30 km/h, continually, and
  • don’t do lots of acceleration and braking, both of which waste electrical and mechanical energy which come from the charge of the battery.

When one accelerates, energy is being put into increasing the kinetic energy of the vehicle, not travelling down the road. An electrical system will have losses of energy due to production of heat or a drop in voltage due to heavy currents. Some level of energy conversion between off and maxed out will give optimal efficiency. Further, at high speeds, the force on the car from pushing air out of the way is far greater than at lower speeds. The power, KW, required varies with the square of the speed because the car meets air according to its speed and requires a force according to its speed to part the air. So, if you get 200 km at 50km/h you might indeed get only 160km at 60 km/h. 200km is not the same as 160 km but the behaviour has changed. Get it? The air-resistance at 60km/h is (60^2)/(53.6^2) = 1.25 times as much as the air-resistance at 53.6 km/h. The energy required to do the work of pushing air out of the way is Force X Distance, 200 X F is the same as 160 X 1.25 X F, the charge of the battery. There are other factors affecting efficiency more at low speed like the rolling resistance of the tires. Keep them well inflated and the energy used to roll along increases very slowly with speed and is a small part of the whole trip. The drive-train will increase wastage as output increases to some extent. The net result is that efficiency in terms of range per charge increases rapidly at first, peaks at a moderate speed and then declines rapidly as speed increases.

Data has been published for Nissan Leaf in terms of miles/KWH or range per charge and it follows this pattern. So, BMW wasn’t trying to cheat anyone, just assuming people could understand words and numbers. The leaf, with a 24KWH battery can get 82 miles on a charge at 60 mph up to 132 miles at 35 mph. Do the maths before assuming false advertising. My Solo EV has been reported to get “up to” 200 km on a charge of 16.1KWH but the maker advertises 160km because they don’t want this bad PR. Also, the battery deteriorates slowly with age/use so the warranty of ~85% capacity after five years still fits. It’s old technology but new to many. They need to grow up/mature/read/understand/experience these things.

About Robert Pogson

I am a retired teacher in Canada. I taught in the subject areas where I have worked for almost forty years: maths, physics, chemistry and computers. I love hunting, fishing, picking berries and mushrooms, too.

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14 Responses to Range Of Electric Cars

  1. Oh-oh! I missed something. While the Liberals won, they don’t have a majority. To do anything, they’ll need the support of the GREENs. That gives them the power to strengthen green stuff. This should be good for EVs. Amen.

  2. Grece says:

    Of course it is related, don’t act surprised, as I mentioned this sometime ago. Doesn’t make a worlds difference, as you won’t be getting your Solo.

  3. I don’t know whether this is related or not, but Jerry Kroll, CEO of Electra Meccanica, maker of the Solo EV, was a candidate in tonight’s election in the province of British Columbia in Canada. He’s with the Green party and is competitive against the Liberal candidate in Vancouver-Mount Pleasant riding but, unfortunately, the New Democratic Party is running away with the votes… With one third of the polls reporting, Jerry has 16% of the votes, the Liberal, 19% and the NDP, 63%. I guess now Jerry can concentrate fully on cranking out those Solos. If he can’t beat ’em, perhaps he should join ’em or induce them to join him. He could sell them all Solos and they all could be Green. Yeah, that’s the ticket…

    UPDATE Yay! Jerry came in second in his riding but the Green party took 3 seats, much better than last time. Perhaps this is the start of something good. Perhaps selling all those Solos will make a difference.

  4. Grece wrote, “How can something be more efficient, when its not even available to be purchased as this moment?”

    Efficiency has nothing to do with units sold except it’s advantageous to the buyers. There are enough units on the road today that the data is coming in. It only takes one unit being tested if they are copying the things. Each one is only customized as to style of wheel, colour and a few other items that don’t affect range/efficiency.

  5. Grece says:

    Tesla S gets about 455 miles out of 85KWH at a little over 20 mph. That’s 5.35 miles/KWH. My beloved Solo gets up to 200 km out of 16.1 KWH, 7.72 miles/KWH. Solo is more efficient.

    The major factor in your analysis Robert, is that Tesla already has a proven track record and has vehicle on the road. Where as the SOLO has yet to be built in large quantities and Electra Meccanica is a start-up with no revenue to speak of and no prior history.

    How can something be more efficient, when its not even available to be purchased as this moment? Its like all these ARM server motherboards you keep hoping and praying for, but somehow they never come to fruition.

  6. DrLoser wrote, “the energy cost of modern vehicles is basically related to weight and to going up and down slopes”.

    Slopes can be costly but most folks have the good sense to build cities near the sea or rivers which tend to be flat.

    See Tesla’s data

    Tesla S gets about 455 miles out of 85KWH at a little over 20 mph. That’s 5.35 miles/KWH. My beloved Solo gets up to 200 km out of 16.1 KWH, 7.72 miles/KWH. Solo is more efficient. Notice the strong dependence on speed. That’s because air-resistance is the dominant factor above city-speeds.

    Quoting Tesla who are expert in these matters: “Sustained high speeds have the most dramatic effect on driving range, as the first graph above clearly shows. This is because aerodynamic resistance increases with the square of speed, requiring higher forces to push the air out of the way. In contrast slower city driving speeds are more efficient and electric vehicles have a unique benefit in stop and go, low-speed driving due to regenerative braking. If you are ever in doubt about reaching your destination, driving more slowly is the best way to stretch your range. Relative to range at a steady 55mph you can see a 50% increase or 50% decrease in range due to vehicle speed decrease or increase.”

  7. DrLoser says:

    Just to address this “driving on the flat” thing, Robert. With, or without, a feather-footed action on the accelerator.

    As I am sure you are aware, the energy cost of modern vehicles is basically related to weight and to going up and down slopes. Despite your rather weird claims about cross-sectional drag, this is not a generally accepted costing factor unless you are travelling at more than 12 mph, which I suspect is slightly above the cruising speed of your little theoretical plastic bubble, yet to be constructed and delivered.

    Now, let us disregard the potential expense that you, yourself, will incur in this imaginary cynosure of all motability vehicles. You live in a Prairie state. You probably take a vacation every year, five hundred miles away, just to marvel at a 200 metre hill. You do not need to worry about ups and downs and torque and stuff.

    Regrettably, almost every other potential customer for this piece of useless dreck does need to worry.

  8. One of the fools who responded to TFA on CBC wrote, “So here what Winnipeg to Regina would be in the ECO WARRIOR car.
    1) Leave home
    2) Drive for 1 hr, stop in Portage La praire and Charge, 1 hr
    3) Drive for 1 hr, stop we hope in Brandon to charge, 1 hr
    4) Drive to…… nothing. Stop on the Trans Canada and call CAA, wait an hr.
    5) Turn around go back to Brandon and repeat. “

    Well, maybe with a short-ranged EV those “stops” are appropriate, but some of us love Canada and like to visit places through which we travel. You meet some wonderful people and small businesses that way. OTOH, west of Brandon, one finds Virden, MB, with a lovely stone train station/museum for a charging station and easy walking distance to some eateries and flower shops and … 115km further west is the library at WhiteWood, SK. So, the twits base their arguments on lies or ignorance, pick one. EVs make sense, perhaps not to all but definitely to many commuters, errand drivers, and retired folks like me.

  9. Grece says:

    A Amish horse buggy would suit Robert perfectly, but he needs a barn now. I mentioned to him some time ago that he could build a simple barn with poles and stable a few animals in it, but what do I know.

    Eh.

  10. DrLoser wrote, “electricity comes with a carbon footprint when you are parked outside”.

    Where I live the utility is heavily into hydro and wind. A lot of oil was burned in constructing the dams and transmission facilities but that’s dwarfed by the energy delivered over the decades. Our electricity ultimately comes from Sun.

  11. DrLoser says:

    Oh, and if you can’t afford a horse, a donkey would do.

    And if you can’t afford a donkey, oiaohm is only two or three steps down the evolutionary ladder.

  12. DrLoser says:

    I’m coming to the conclusion that a souped-down electric tricycle doesn’t really fit your needs, Robert — irrespective of whether you can get one, or not. (Clue: you can’t.)

    Now, the thing about electric buggies is that the electricity has to be generated somehow. I think we both know that. And that electricity comes with a carbon footprint when you are parked outside, say, Ikea. I think we both know that.

    Either I am a genius, or some Supernatural Being has sent me the perfect solution for your problems here:

    You need a horse and buggy.

    Very stable (four legs, four wheels) and with as much hauling capacity as you are likely to need.

    Better still: you can feed the horse from the produce of your back yard, and you can use the “exhaust” — which is by definition carbon capture — to recycle the source of fuel.

    I love the smell of horse manure in my back yard, Robert. It smells … it smells of … well, it smells bloody awful, really, but it’s a darned sight more realistic than your nincompoop senile dreams of “free as in I don’t have to stump up money” electrically powered transportation.

  13. Grece says:

    People are too dumb to understand your ramblings Robert. This is why a man with the word START was able to conquer the computer realm. This is why Linux has never gone anywhere in the same market, there is no START button. Fairly simple to comprehend really, unlike you and your never-ending torturous paths in life, never accomplishing anything.

  14. Old Bill says:

    Around here the endurance of electric vehicles is measured in holes played. 37 is way more than most people need. People use them around the neighborhood for other tasks, too. You can get to a Winn-Dixie or CVS or Walgreen’s safely and conveniently or else get to the tennis courts or rec center — all of which can negate the need for a conventional vehicle. Up in the Villages, people even go to the doctor or hospital that way.

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