German car maker Volkswagen is piloting an electric vehicle charger that allows power to flow in both direction so it can be integrated into a smart grid.

Following flexible charging stations and mobile charging robots, the company has introduced the DC wallbox, which charges up to 22kW. Operation will be starting at five sites as part of a pilot phase.

The goal is to gather practical experience to develop the wallbox quickly so it can move into series production.

“An extensive and needs-based charging structure is the key to the success of electric vehicles,” said Mark Möller, head of technical development for VW’s electric mobility division. “That is why we are working on various approaches that enable customer-oriented, intelligent and flexible charging. Like our flexible quick charging station and the visionary prototype of a mobile charging robot, the DC wallbox is one of the future innovations of the DC charging family for electric vehicles.”

With the wallbox, electric vehicles can be charged with direct current (DC) up to 22kW, at about double the speed of a typical wallbox working with AC. With DC, the electricity flows directly into the lead traction battery, provided that the electric vehicle has a combined charging system (CCS) charging port.

Unlike systems based on AC, electric vehicles are charged independently of their integrated on-board chargers that limit charging capacity. Charging the lead traction battery with DC, on the other hand, increases the potential charging capacity compared with AC. The charging process can therefore be shortened.

The wallbox is already prepared for bi-directional charging. Thus, power can flow in two directions so the power stored in the lead traction vehicle battery can be returned to the grid, if necessary, thanks to intelligent charging management. In future, electric vehicles with this function can, for example, serve as a power storage unit for private homes or as a buffer for the power grid.

To gather experience with the product, Volkswagen has started the pilot phase at its own factory sites in Wolfsburg, Braunschweig, Hannover, Salzgitter and Kassel with twenty wallboxes. This also means the existing charging infrastructure will be expanded at the factory grounds.