Fraunhofer IAF has built a compact external charger for 800 V electric vehicles that can also send energy back to the grid. The German institute’s new GaN-based power module is designed for bidirectional charging, but the headline is really the hardware: a 3 kW off-board system small enough to fit into an 8.3-litre enclosure and light enough to carry at 5.7 kg, including connectors.
That puts it in a different category from the usual onboard charger, the chunky 11-22 kW unit that lives inside many EVs and quietly eats cost, weight, and packaging space. Fraunhofer’s pitch is not raw charging speed. It is flexibility: a portable, universal charger that works with CCS and a household Schuko plug, while opening the door to vehicle-to-grid use rather than treating the battery as a one-way bucket.
GaN power module for 1200 V operation
The module sits inside the project GaN4EmoBiL, short for GaN Power Semiconductors for Electric Mobility and System Integration via Bidirectional Charging. Ambibox GmbH integrated the device into a demonstrator for a single-phase off-board charger, and the setup is being tested across battery voltages from 150 to 920 V, which covers modern high-voltage EV architectures.
At the heart of the design are GaN transistors rated up to 1200 V on an insulating substrate. That matters because GaN can switch efficiently at higher voltages, cut heat losses, and shrink the supporting electronics. Silicon can do the job, of course, but it tends to do it with more bulk and more thermal drama.
Why the 3 kW EV charger is slower but more flexible
A 3 kW charger will not win any speed contests against wall boxes and fast chargers. But it is intended for portable or distributed charging, where size, weight, and convenience beat brute force. For fleet operators, emergency use, or locations where a fixed installation is impractical, that trade-off looks a lot less like compromise and a lot more like a useful niche.
- Output power: up to 3 kW
- Battery voltage range in the demonstrator: 150 to 920 V
- Enclosure volume: 8.3 litres
- Total mass with connectors: 5.7 kg
- Connection options: CCS and Schuko
Bidirectional charging and the road to 1700 V
The bigger prize is bidirectional charging. In one direction, the car charges normally. In the other, it can feed energy back during periods of surplus generation or help support the grid during peaks. That is the sort of feature utilities love in theory and only occasionally manage to use in practice, but the hardware has to be compact and cheap enough before the software arguments even begin.
Fraunhofer says the next steps are higher voltage, higher current, larger wafers, and lower cost, with a target of matching silicon economics while keeping the performance edge. The institute also sees a path to 1200-1700 V GaN electronics, which could improve EV efficiency, extend driving range, and reduce charging infrastructure costs. The demonstrator will be shown at PCIM Expo & Conference 2026 in Nuremberg, alongside other GaN systems from Fraunhofer IAF.