Last month, Renault announced the development of a bidirectional on-board charger in collaboration with the CEA (Commissariat à l’Energie Atomique). Intended for select Renault electric models from now until 2027, it features innovative power electronics that significantly reduce power losses and shorten charging times. This bidirectional charger will also enable Vehicle-to-Grid (V2G) by injecting the energy stored in the battery into the electrical grid when not in use. Electricity that the motorist can resell to the supplier and thus save on the use of his electric car.

Jean-Francois Salesi, director of advanced engineering at Renault Group, and Philippe Despess, program assistant at CEA’s systems department, answered questions from Auto Plus about the progress this new charger represents and how it will change the way we use the electric car.

Auto Plus: What prompted this collaboration between Renault and CEA to develop a bi-directional on-board charger?

Jean-Francois Salesi: We have been working with CEA in the field of power electronics technology for more than ten years. Renault is a pioneer in the field of electric traction chains and our goal is to improve their efficiency in order to reduce the cost per kilometer for the benefit of the end user.

Philippe Despesse: High-power GaN components have been on the market for several years. But to get the quintessence of their performance, we had to review the electronic architecture of the chargers. CEA supports Renault in this.

Among the advantages of your technique, you mention “reducing the volume and cost of the charger.” What order of magnitude are we talking about?

Jean-Francois Salesi: We worked with CEA both on the implementation of GaN technologies and on the optimization of the charger architecture. This is to achieve compactness and efficiency. Thanks to these innovations, we managed to reduce electricity losses by 30%, which is a significant figure. Current generations of chargers are 90% efficient, which still means 10% loss. With this new bi-directional built-in charger, we achieve 94% efficiency for the direct benefit of the consumer, who will thus save money on charging.

Can you explain what Power Injection molding is, one of the key technologies of this bi-directional charger?

Philippe Despessé: Wideband power components have a high frequency boost capability. But for this, it is necessary that the passive components used in the power converter can support such an increase in frequency, which is aimed at reducing the size of the components. CEA has found ferrite materials that meet this need. Die casting is the manufacturing technique for these ferrites. To give you an idea, on previous components the frequency increase is about 20kHz, while with our new technologies we go up to 100kHz or even 1 megahertz depending on the architecture. Working on passives is essential to unlocking the potential of these high-gap components.

Can you describe the general use case for this type of bi-directional charger for a user and the financial benefits they can expect from it?

Jean-Francois Salesi: With bidirectional chargers, users will be able to resell the electricity stored by the battery when it is not in use. This is called a vehicle-to-grid approach (V2G, editor’s note), in which electric vehicles become grid stabilizers. One of the advantages is the ability to store energy produced by renewable means of production (solar, wind) when it is not required, in order to be able to recover it when needed. In this way, the owner of an electric car will be able to charge his electric car in periods when electricity is most available, and resell it to the network when tariffs are higher. In a certain way, the motorist will become a “merchant” of energy. For the average user who owns a private vehicle, this should allow him to save around €200 per year through this practice.

Renault plans to deploy in 2027

How will this intelligent management be organized?

Jean-Francois Salesi: These are software platforms that will manage this distribution, taking into account the needs of the user according to the phases of vehicle use, the minimum thresholds for battery charge when communicating with energy suppliers to know the needs of the energy company and the applied rates. To successfully deploy these two-way chargers within one to two years, we are working with EDF and Enedis.

We talked about bidirectional charging from the general electrical grid (car to the grid), but when will it be possible to connect the home electrical grid, the so-called car to the house?

Philippe Despessé: We are already working on more than car-to-home, specifically a loading vehicle that can directly deliver any type of equipment. Our teams are working on smart city and smart grid related software to manage this new electrical infrastructure. The SEA is also working on issues of autonomous energy clusters, where one is disconnected from the central grid. Then it is necessary to create an autonomous cluster for a given geographical perimeter, capable of managing the energy mix from various energy sources.

When does Renault plan to roll out this new bi-directional charger and on which models?

Jean-Francois Salesi: The bidirectional charger in question will appear by 2027. But before that, the first generation of V2G-compatible charger will be offered in 2024-2025 on some Renault cars. On which models? Not only on high-end cars, because Renault wants to ensure wide access to these innovations. Energy efficiency is very important to us and we want to ensure that information is disseminated as widely as possible for the benefit of our customers.