Efficiency of Electric Cars Measured in Belgium Study

By · December 11, 2013

Peugeot Ion

Peugeot Ion

Electric vehicles are known to be very efficient. Cars with internal combustion engines are not, losing most of their energy as heat. EV advocates have been saying this for years, and there is a ton of data about the efficiency of gasoline and diesel cars. But electric cars are newer and there are few of them, so we've had less documentation...until now. Some Belgians have been given the opportunity to study a fleet of five cars.

There were Peugeot Ion models, exact clones of the Mitsubishi i-MiEV (European version), and the people monitoring them were from Laborelec, with support from Brussels' Vrije University, which has a facility dedicated to automotive technology. The study was funded by Electrabel, the Belgian utility. It lasted two years, but the first part of the story was to define a methodology. A precise, dedicated monitoring system was developed, and things only got started when it received a full approval from the car manufacturer.

Peugeot Ion

Peugeot Ion

Data Dump

This data was recorded from the five cars over two years: battery current, voltage, state-of-charge, odometer, instant speed, GPS coordinates, and ambient temperature. Total distance covered by the five cars was 42,953 miles, and energy consumption in watt-hours per mile for each car was as follows: 289.62 ; 336.28 ; 249.39 ; 291.23 ; 299.27. The different values result mostly because of different drivers—with an average of 293.16 watt-hours per mile for the fleet.

This is the overall energy consumption, but it isn't enough to give a complete picture as regenerative braking has significantly helped to increase the cars' efficiency. For each car, the increase (in percentage) is as follows. 16.1 ; 9.9 ; 12.5 ; 9.1 ; 11.7. That's an average of 11.86%, and it's a clear gain. Regenerative braking was more than sufficient to compensate for the losses of the charging process, where AC electricity from the mains was not converted to DC for the battery.

Peugeot Ion

Peugeot Ion

A very important part of the study then, was to show where the electricity is going: to the motor, or the auxiliaries (for example, heating/cooling, battery management system, and lights). For each car, the share of the energy consumption going to auxiliaries (in percentage) is as follows. 40.1 ; 35.8 ; 21.6 ; 22.0 ; 36.4.

Overall Clear Winner

This is where internal combustion cars shine. Heating is essentially free in a gas car. An internal combustion engine loses so much energy in its normal operation that it costs nothing to get back some of it to heat the car.

We could then conclude that the biggest thing to make EVs more efficient is the heating system. Car manufacturers know that already. The Peugeot EVs tested had a conventional, resistive heater, but the latest models have a heat pump, which is much more efficient technology. There's still room for improvement: some cars from the 1960s have much stronger heaters that EVs have today. Overall, the energy efficiency of each car, plug to wheel, is as follows. 47.0% ; 49.7% ; 63.2% ; 59.1% ; 51.6%. That's much better than any gas or diesel could achieve, even with the addition of a hybrid powertrain.

Another important result is the higher importance of auxiliaries at lower speed, meaning that EVs have better plug-to-wheel efficiency when used on the road outside of the city—but without too much time on the highway where the higher speed reduces efficiency.

Oh, and the test proved convincing. One driver who had an EV as his company car for two years, bought one for himself when the test was over.

Comments

· · 18 weeks ago

I like those efficiency numbers. Do we know what ICE's can do over a period of time? All I see reported is PEAK efficiency, something they don't often reach.

The line that ends laymen arguments; I can drive 3-4x farther on electricity than I can on gas for the same fuel money.

· · 18 weeks ago

Electrabel is not 'the' Belgian utility. It used to be, now it's an open market.

Both Laborelec and Electrabel and Laborelec are owned by GDF Suez which is French of course.

I wish they would continue the study with more modern EVs like the Zoe and i3

· · 18 weeks ago

A good shop for children. http://www.rctopshop.com/

· · 18 weeks ago

"Overall, the energy efficiency of each car, plug to wheel, is as follows. 47.0% ; 49.7% ; 63.2% ; 59.1% ; 51.6%."

This isn't truly a fair measure of efficiency. The car is using energy from the battery to perform useful functions - providing heat, music, instrumentation, etc. That's not the same as energy losses. In fact, with a heat pump, the heater can be greater than 100% efficient (you get more heat out of it than you expend in energy).

The flip side is that ICEs actually get far MORE efficient in the winter than in the summer because all of that heat which is wasted energy in the summer becomes useful in the winter!

· · 18 weeks ago

Brian, I agree. Heating the i MiEv takes almost as much as moving it - my brother and my father each drive one, and we live here in New England.

Typical EV plug-to-wheel efficiency is ~85%. But with a really efficient motor and drivetrain, and with lots of free-wheel coasting, and only using regen when you need to slow down, etc. it can be ~92%+. The Illuminati Motor Works 'Seven' improved it's efficiency from 153Wh/mile (at ~60mph on flat ground with no significant wind) to ~129Wh/mile. They stopped using any BMS, and are now using a custom gear reduction transmission, and always coast first (greatly reducing the amount of acceleration) and only using regen to slow down.

Also, the Cd of the car has a huge effect on the energy used.

· · 17 weeks ago

Heat pumps aren't really the answer. They're fine for cool days in mild climates, but provide only an incremental benefit in really cold places, where they need to be supplemented by more conventional sources (e.g., resistive PTC heaters). For EVs to work in the NE and Upper Midwest, the best bet is to add fossil fuel heaters (e.g, methane, propane, kerosene), allowing each energy source to do what it does best - the batteries move the car, the fuel heats it.

Just on a side note, what's the source for the claim that newer i-MiEVs have heat pumps? I'd point out that Mitsubishi has always referred to the car's PTC heater as a "compressor" heater, which some writers have misinterpreted to mean "heat pump." As far as I know, Mitsubishi isn't doing anything truly new for the i-MiEV - it's as good as it's going to get with the minor (but welcome) tweaks that come with the re-launched vehicle next spring (at least in the U.S.). I figure a big new technical upgrade like a heat pump isn't likely in the cards, but being wrong on this point would make me quite happy.

· · 17 weeks ago

FWIW, I'm not suggesting that heat pumps are a magical answer to EVs' woes, but rather that they can be more than 100% efficient. As it is, a resistive heater is 100% efficient. Even a fuel heater maxes out at 100%. This article is nominally about efficiency, and my point is that efficiency isn't simply miles per unit energy. It is useful work out per unit energy in. Useful work needs to include heating the cabin on a cold day.

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