Between the consumptions observed in real life, those published by the WLTP approval cycle or even those announced by the manufacturer, there is sometimes a world. We are going to try to see it a little clearer through this article and, we will be able to see it, certain manufacturers like Peugeot play with words to announce very low consumption. Until reality catches up with them.
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When you buy a car, whether electric or thermal, the consumption indicated is always on its technical sheet, noted under the current homologation cycle in Europe, namely the WLTP mixed cycle.
To learn more about how these certifications are carried out and to understand why there are also differences between the different certification cycles around the world (CLTC in China, EPA in the United States, etc.), feel free to consult our folder dedicated .
Surely you have noticed that between the consumption indicated according to the WLTP cycle and reality, sometimes there is a world. It is true that these differences were blurred with the transition from the NEDC cycle to the WLTP cycle a few years ago in Europe, thanks to a new test protocol that was supposed to be closer to reality. But for some models the differences are still quite significant.
As for the electric car, this obviously plays with autonomy, since what is indicated according to the WLTP cycle is usually quite far from reality. During our tests of electric cars, we sometimes noticed deviations of more than 25% in certain cases in mixed use, and without adopting sustained driving.
Even the consumption indicated on the car’s on-board computer is disconnected from reality, since it does not take into account all the parameters, starting with the energy losses during recharging. Losses that do not appear in the calculation of consumption, so they also generate economic losses for the user. Explanations.
How is consumption determined in the WLTP cycle?
He Worldwide harmonized light vehicle test procedure (WLTP) is required for all new registrations as of 1is September 2018. The WLTP cycle replaces the NEDC cycle in Europe. The WLTP cycle is advertised as being closer to reality compared to the NEDC cycle, in particular thanks to new methods for calculating consumption values, in this case, in terms of kWh / 100 km for electric cars. The equivalent to the consumption in liters/100 km for thermal cars.
The WLTP standard changes the conditions of the NEDC homologation cycle towards a more dynamic use of the car. It is based in particular on statistical studies, as well as on a precise assessment of typical driver profiles.. WLTP is based on faster acceleration rates, higher average speeds, and higher top speeds.
The evolution continues at the level of the conditions of use, since instead of simulating traffic in an urban, rural and then mixed cycle, the vehicle is now tested at four different speeds. WLTP was developed from data collected from around the world covering many driving situations. The cycle also contemplates optional equipment that directly affect the aerodynamics, consumption or the total weight of the car.
The protocol is coupled to another complementary cycle called RDE (Real Driving Emissions), which is carried out randomly and on the open road. This makes it possible to take into account all the external parameters that cannot be reproduced in the laboratory, and thus more easily approach the conditions that a user may encounter (climate, temperatures, relief, etc.). The data collected allows us to check the consistency with the results obtained in the laboratory.
The introduction of the WLTP cycle has also set the record straight for certain electric cars. At the time of the NEDC cycle, the data was very ambitious and far from reality. For example, the old electric Hyundai Kona, with its 64 kW battery, was announced at 546 kilometers with the NEDC standard, then at 482 km after a stint on WLTP.
The WLTP cycle has also known how to evolve with the arrival of the electric car and the entire ecosystem that revolves around it. Thus, to establish consumption, the WLTP cycle also takes into account losses during recharge, losses that are not necessarily taken into account by the manufacturer and, consequently, by the on-board computer. In this way, therefore this can change the actual autonomy quite a bit.
What are losses during recharge?
It is a relatively simple process, which the WLTP cycle has obviously not forgotten in its test protocol, but that the on-board computers of all electric cars on the market do not take into account.
These are kWh losses at the level of the electrical installation, the terminal, the on-board charger and the battery. These losses can be cumulative. A recent German study carried out by ADAC pointed out that manufacturers did not mention these losses in the calculation of consumption, which generated financial losses for the user.
Nothing better than an example to imagine the thing: if you recharge the 60 kWh of your electric car battery at home, your energy provider may charge you 70 kWh. This is what happens if your on-board charger has a 20% loss. Therefore, the approved WLTP consumption takes into account your losses, unlike the conventional consumption that manufacturers sometimes advertise.
Therefore, if you have to drive closely imitating the WLTP cycle, you will probably have a lower consumption than the official WLTP consumption on the on-board computer, since it does not take these pressure drops into account.
This is why some organizations ask manufacturers in particular to improve the efficiency of charging systems. It is at this point that Renault has recently worked by presenting a new charging architecture to optimize active (semiconductor) and passive (capacitors and wirewound inductive components) components.
For so-called “slow” charging, i.e. less than or equal to 22 kW, the chargers are not integrated in the terminals, but directly in the car. Thanks to this new architecture, energy losses are reduced by 30% during conversionand correspondingly the heating, facilitating the cooling of the conversion system.
Why don’t on-board computers take losses into account?
It’s a completely legitimate question, but technically it seems very complicated. Although the system that Renault is developing, that is to say, with a charger integrated directly into the car, should open some doors, the losses today depend above all on the charging station and this would imply a review of the consumption calculation system. by the on-board computer
If most manufacturers play and communicate about consumption and autonomy according to the WLTP cycle, some, like Stellantis (and only Stellantis as far as we know today), prefer to play with words and calculation methods.
Thus, during the presentation of each new electric model, electric Jeep Avenger, electric Opel Astra, Peugeot e-208, Citroën ë-C4 X, the brands of the Stellantis group communicate a very low average consumption for electric cars, being careful to specify that this is an “estimate”.
Let’s take an example, the presentation of the new Peugeot e-308. The manufacturer of the lion announced a consumption of 12.7 kWh/100 km, but without specifying in what type of test (mixed or urban WLTP). For having tested several cars of the brands that are part of the group and that share the same motor/battery architecture, so much to tell you that we are far from the advanced figures on the other products.
In fact, Peugeot has divided the size of the battery by the autonomy announced by the WLTP cycle to establish a “theoretical” WLTP consumption before the actual figures, without taking pressure drops into account. For comparison, a Renault Zoé (395 km range with its 52 kWh battery) is given for a consumption of 17.2 kWh. The Peugeot e-208 (400 km of autonomy with its 51 kWh battery) is given for 14.5 kWh/100 km according to official WLTP figures. Again, before the official WLTP figures, Peugeot had announced an estimate of 12 kWh/100 km.
Why can we still consume more on the on-board computer compared to the WLTP cycle?
Since the on-board computer does not take energy losses into account, the recorded consumption should be less than that communicated by the WLTP cycle, which does take them into account.
In fact, it’s not exactly that. During our latest tests, in fact, we noticed (even if the roads were heavily sanitized) that several cars managed to reach their WLTP consumption without too much difficulty (the prize goes to the Nissan Ariya in particular). On the other hand, under more “normal” conditions, regularly we observe a difference of about 2 kWh (it can be more or less, it all depends on the car) more than with the WLTP cycle.
In reality, even if the WLTP cycle is closer to reality compared to the NEDC, there are still too many parameters that come into play that you can’t necessarily integrate. The driving style for example, this also applies to thermal cars, is a determining factor, or even the traffic conditions.
That is to say, if your on-board computer gives you consumption that is higher than the WLTP standards, there is nothing abnormal, on the other hand, knowing that it does not take energy losses into account, note that these same consumptions “at the point of sale” are even higher than what is advertised.
What impact in practice?
This does not change the range of the car., which will be similar with or without losses. It’s just that taking into account the losses, you will know the exact price of a full tank of electricity. Communicating about non-WLTP consumption is therefore a serious blunder on the part of Stellantis, which misleads the client. Worse still, if the latter wants to compare the estimated consumption of the Stellantis cars with that of the competition (in WLTP format), they will think that the former consume much less than the latter. Which is not necessarily true.
By way of comparison, for the e-208, going from an estimated consumption of 12 kWh/100 kWh to 14.5 kWh/100 km, the cost per 100 km with home charge varies from 2 to 2.5 euros. Which is not negligible.
Fortunately, these fanciful consumption figures given by Stellantis are only in press releases. Once the car is for sale on the sites of the manufacturers of the Stellantis group, we find the “real” WLTP consumption figures, which take energy losses into account.
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