Ten Mercedes-Benz eCitaro G fully electric articulated buses with the new pure hydrogen “H₂ mode” drive mode will be put into operation by the city bus fleet of Stuttgarter Straßenbahnen AG (SSB) in 2025. SSB has been a development partner of Daimler Buses for the Mercedes-Benz eCitaro G fuel cell with H₂ mode.

SSB will no longer be purchasing diesel buses. From 2027, it intends to operate in the city center of Stuttgart exclusively with emission-free buses, and from 2035 to be climate neutral across the entire Stuttgart bus network.

With the new H₂ mode operating strategy, the eCitaro G fuel cell electric articulated buses equipped with a hydrogen-based fuel cell as a range extender can be operated exclusively with hydrogen as an energy source in certain operating scenarios. The pure hydrogen drive mode makes them independent of stationary charging processes. This increases their operating radius compared to hybrid or purely electric technologies. The fuel cell always operates in the efficient operating range between 20 and a maximum of 40 kW, even in H₂ mode.

Compared to a hydrogen-only vehicle with a small buffer battery, the new eCitaro G fuel cell with H₂ mode is much better at fully and profitably storing in its large batteries the energy recovered by recuperation when braking. This boosts the overall efficiency of the eCitaro G fuel cell with pure hydrogen drive, particularly in urban traffic where braking is frequent, but especially in difficult terrain, such as on uphill gradients like the Stuttgart Weinsteige.

Further, the large battery capacity allows high levels of drive power to be utilized over longer distances without the fuel cell having to operate in the inefficient upper power range. The experts from Daimler Buses provided prior advice to the SSB and evaluated the planned routes for the eCitaro G fuel cell in Stuttgart.

The Mercedes-Benz eCitaro G fuel cell vehicles for SSB are equipped with four NMC3 high-voltage battery packs with a total energy capacity of 392 kWh. The compact fuel cell module has a maximum output of 60 kW and is located on the roof of the rear section directly behind the articulation joint. Six hydrogen tanks each with a total capacity of 30 kilograms of H₂ are located on the roof of the individual articulated buses.