Image: Fraunhofer IAFBidirectional charging is gaining momentum. However, the first bidirectional DC wallboxes on the market still rely on power semiconductor components that are not yet ideally suited to the application. Manufacturers currently use either efficient but expensive silicon carbide components or lower-cost silicon-based alternatives with lower efficiency.The GaN4EmoBiL research project (GaN Power Semiconductors for Electric Mobility and System Integration via Bidirectional Charging), which launched in 2023, has set itself the goal of reducing the cost of bidirectional charging by using alternative materials in power electronics. This aims to make the technology more affordable for the mass market.The concept behind bidirectional charging is familiar to most readers: an electric vehicle’s battery can serve as an intermediate storage system for electricity, for example, from a private photovoltaic system or excess energy in the public grid. Later, this energy can be fed back from the EV into the home network (Vehicle-to-Home, V2H) or the public grid (Vehicle-to-Grid, V2G) when needed, such as during periods of low wind and solar energy generation. This also enables users to earn money through price differentials and compensation for grid-supporting behaviour.Gallium nitride as the key materialThe innovative approach of the GaN4EmoBiL project lies in its use of GaN, the chemical formula for gallium nitride. This compound comprises two elements: gallium (a metal) and nitrogen (a non-metal). Fraunhofer IAF and Ambibox have now used GaN to develop a novel power electronic module for bidirectional DC chargers in the 800-volt class. The GaN components themselves belong to the 1,200-volt class and are applied to a special insulating substrate.At the PCIM Expo & Conference 2026, taking place from 9 to 11 June in Nuremberg, Fraunhofer IAF will present a demonstrator of a bidirectional, single-phase 800-volt DC charger for electric vehicles featuring the aforementioned GaN power electronics.“The single-phase demonstrator of an off-board EV charger with up to 3 kW of bidirectional power addresses an existing gap in the trade-off between cost, flexibility, efficiency, and compactness for bidirectional charging,” explained Jun.-Prof. Dr Stefan Mönch, coordinator of the GaN4EmoBiL project.Charger outside the EVAccording to Fraunhofer IAF, the off-board charger developed by the project partners offers a more cost-effective and flexible alternative to conventional on-board chargers. Unlike on-board systems, which convert alternating current (AC) from an AC charging point into the direct current (DC) required by the electric vehicle, the charging unit is located outside the vehicle. Although its charging capacity of 3 kW is significantly lower than the 11 or 22 kW typically offered by on-board chargers, the system is mobile, considerably more compact and lighter, and supports both CCS and Schuko plugs. The demonstrator has a total volume of 8.3 litres and weighs 5.7 kilograms including the plugs.For clarity: the off-board charger developed in the GaN4EmoBiL project is not a charging station itself, directly connected to the grid like the DC wallbox in the V2G offering from E.ON and BMW for the new iX3. Instead, it is a highly compact power electronics module that functions as a standalone, mobile converter. While conventional V2G solutions integrate the AC/DC conversion technology into a bulky DC wallbox, this new approach outsources the entire bidirectional conversion technology.fraunhofer.de