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High-Efficiency Bidirectional Onboard Charger Targets V2G

Jan. 30, 2023
CEA and Renault Group are jointly developing a more compact charger claimed to reduce energy losses by 30% and recharge the vehicle's battery faster. It also allows the connected vehicle to inject energy from the battery into the electrical network.

What you'll learn:

  • What are the benefits brought by the new bidirectional charger?
  • The locations and overall scope of Renault's ElectriCity.

Electric-vehicle ownership could soon become more mainstream for numerous reasons. One of the most notable is bidirectionality. While most EV charging systems send energy in one direction—from a power source to a car’s battery—a bidirectional charger can transform the car’s energy back and pass it from the battery into the electrical network.

Known as vehicle-to-grid (V2G), this bidirectional exchange technology will soon enable Renault vehicles to restore part of the electricity stored in the batteries of its future EVs to compensate for the intermittent nature of renewable energy.

The Renault Group together with the French Commissariat for Atomic Energy and Alternative Energies (CEA) are already working on future generations of V2G technologies, which will be deployed by the end of the decade. To that end, the two partners have jointly developed a new electronic power-converter architecture directly integrated into the vehicle's charger.

This power converter is the result of nearly three years of research and the subject of 11 joint patents. Put in simplest terms, it changes the electric energy from one form into the desired form optimized for the specific load. The converter was developed from wide bandgap semiconductor materials—gallium nitride (GaN) or silicon carbide (SiC) by Renault and CEA, who combined their expertise in on-board power electronics.

Features and Functionality of the New Charger

According to Renault, the bidirectional charger will lower energy losses by 30% during conversion and reduce heating by the same amount, making it easier to cool the conversion system, improve the vehicle's recharging time, and ensure the battery's durability. In addition, this will go hand in hand with engineering efforts to optimize active (semiconductors) and passive (capacitors and wound inductive components) parts to reduce the volume and cost of the charger.

In part, this is possible due to the use of ferrite materials dedicated to high frequency, and a shaping injection process called "Power Injection Molding" (injection molding is a molding technology that melts the material with the aid of a screw and an external heating device and then injects it into a mold to form the corresponding product as the mold cools). Taken together, these processes permit the converter to become more compact.

This new converter architecture will offer a charging capacity of up to 22 kW in three-phase mode, allowing for faster charging of the vehicle. It also lets the charger be bidirectional, enabling the energy stored in the battery to be fed back into the grid. The solution is claimed to be compatible with the electromagnetic-compatibility (EMC) standards of the grid networks and the car.

Jean-François Salessy, Vice President of Advanced Engineering, Renault Group, described the venture, "This project with the CEA has exceeded our expectations by confirming the ability to achieve the expected performance in terms of efficiency and compactness. It opens up strong prospects for power electronics, which is a real challenge in the electric vehicle, in order to make the best use of the batteries' capacities. With bidirectional charging, the vehicle serves the electrical network and enables the end consumer to reduce energy costs.”

Added Sébastien Dauvé, CEO of CEA-Leti, "We were able to bring together Renault Group's system vision for the electrification of the vehicle and the drivetrain, and the skills of our teams in converter architectures and components; in the end, we implemented an architecture adapted to the needs and with high added value.”

Renault’s ElectriCity

Renault has set its sights very high for the future of EVs made in France. The birth of Renault Group ElectriCity in June 2021 is the realization of a main ambition behind what the company calls its “Renaulution” plan: Bring together the industrial sites within a single, EV-specific ecosystem. The ElectriCity hub is made up of the factories at Douai, Maubeuge, and Ruitz (in all, nearly 5,000 employees).

Since the beginning of 2022, the Douai factory has been producing its first EV, the Megane E-TECH Electric. A new production line was made especially for the vehicle in January 2021. A new battery assembly workshop is currently under construction and will supply the site starting in 2024. Douai also will take on production of the all-new Renault 5 as of 2024.

Engines that feed into the hub come from Renault’s Cléon plant, which works closely with ElectriCity.

The Maubeuge factory is specialized in making vans. Maubeuge has been manufacturing the electric version of the Renault Kangoo, a leader in the European electric-van segment since it was launched. In addition to the past three generations of Kangoo, Maubeuge makes vehicles for Daimler (the Mercedes Citan panel van, for example) and Nissan’s Townstar. From 2023, all models leaving the factory will be electric.

The Ruitz factory is a manufacturing site for gearboxes. Since March 2022, it’s been the production site of the DB35 gearbox featured on the entire E-TECH range. Ruitz also is turning more to electric vehicles as it will soon produce the battery trays (housing units for EV battery modules) used on electric vehicles made in France, including the future Renault 5.

On top of that, a memorandum of understanding for the creation of a joint venture between Renault Group and the Minth Group, a Taiwanese global leader in auto parts design and manufacturing, was signed in June 2022 to produce battery trays at the Ruitz factory.

A future EV battery gigafactory, born of a strategic partnership between Renault Group and the battery technology company Envision AESC, has been under construction near the Douai factory since the summer of 2022. Renault and Envision AESC plan to set up the $2.4 billion plant to produce batteries at a competitive cost, with a smaller carbon footprint for future electric models such as the Renault 5.

The Cléon plant is a production site for very-high-performance electrical and mechanical components. Since 2015, it has been producing the electric powertrain featured on the Renault ZOE, Twingo E-TECH Electric, Kangoo E-TECH Electric, and Master E-TECH Electric.

On July 5, 2022, the site inaugurated a new production line for the ePT-160kW electric motor that powers the new Mégane E-TECH. As of 2024, the plant will have a yearly production capacity of more than 1 million electrified motors, comprised of 500,000 electric motors and 510,000 hybrid engines.

French startup Verkor will work with Renault Group to co-develop high-performance and low-carbon batteries, with production starting in Dunkirk in 2025. Initial capacity will reach 16 GWh, of which 10 GWh are for Renault Group. The total annual capacity target is 50 GWh by 2030, of which 20 GWh will go to Renault Group

The ambition set for ElectriCity is to become Europe’s most competitive and efficient EV production hub. The objective is to produce 480,000 electric vehicles every year by 2025, with support from the Cléon site near Rouen, which supplies engines for the new Megane E-TECH Electric and new Renault Kangoo E-TECH Electric. Located in the center of Europe, Renault Group’s ElectriCity leverages the company’s longstanding geographical roots in the Hauts-de-France region in Northern France.

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