Energy with a System: The Battery Technology of the New City Bus Generation

• New cell chemistry: LFP instead of NMC
• One battery design for all vehicle lengths: the compact battery platform
• Charging flexibility: up to three combinable interfaces
• High-voltage battery: cell chemistry and design engineered for a long service life

With the successor to the eCitaro, Daimler Buses is not only completely redesigning the vehicle architecture, but also the battery technology. The new vehicle generation relies on a newly developed, particularly low-profile high-voltage battery with a modular compact battery concept, a new cell chemistry, and a flexible charging concept, with the aim of improving range, charging performance, and cost efficiency alike.

New Cell Chemistry: LFP Instead of NMC

For the new vehicle generation, Daimler Buses is changing the cell chemistry of the high-voltage battery: instead of the NMC batteries (Nickel Manganese Cobalt) used in the current eCitaro, LFP cell chemistry (Lithium Iron Phosphate) will be used in the future. The new vehicle architecture has been designed around this cell chemistry from the outset and compensates for its somewhat lower energy density through a suitably adapted installation space and packaging strategy.

One Battery Design for All Lengths: The Compact Battery Platform

The next generation of the eCitaro uses a standardized battery pack, known as the compact battery, in varying quantities depending on vehicle length. The 12-meter solo bus can be equipped with either six, eight, ten, or twelve compact battery packs, while the 18-meter articulated bus can be equipped with eight, ten, twelve, or fourteen packs. Each pack has a nominal gross energy content of approximately 50 kilowatt-hours when new.

The vehicle concept, which was designed for electric drive from the beginning, provides for four compact battery packs to be positioned between the axles in the underfloor area. This ensures a low center of gravity and has a positive impact on driving stability, driving dynamics, and ride comfort. In the solo bus, depending on the desired battery configuration, an additional two, four, six, or eight battery packs can be mounted on the roof. In the articulated bus, four battery packs are located in the underfloor area of the front section, while the remaining battery packs, up to ten in total, are installed on the roof, with up to six on the front section and up to four on the rear section. From the minimum to the maximum battery configuration, the battery packs are arranged so that a possible pantograph or charging rails can always be accommodated in the same position at the front section of the roof.

Thanks to the wide range of battery configurations, operators can tailor the battery capacity of their vehicles precisely to their specific operating profile rather than carrying a battery sized for every possible use case. In some operating scenarios, this can result in more than 10 percent higher passenger capacity or, alternatively, lower energy consumption due to reduced unladen weight.

Charging Flexibility: Up to Three Combinable Interfaces

The new model generation has been designed from the ground up for different charging concepts. Up to three charging options are available: the CCS2 connector (Combined Charging System) with a charging capacity of up to 400 kilowatts, as well as a pantograph or charging rail with up to 450 kilowatts. These options can be combined, for example three CCS2 charging ports or two CCS2 charging ports together with one pantograph. This creates a high degree of flexibility for different depot and opportunity charging concepts used by public transport operators. Possible positions for the CCS2 connector are, as before, on the left and right above the front axle, at the rear, and at the front of the vehicle.

The New High-Voltage Battery: Compact Design, Long Service Life

The new high-voltage battery, tailored specifically to the next generation of vehicles, incorporates not only Daimler Buses’ specific requirements but also extensive in-house know-how and development work. The result is the unique, compact design of the individual battery packs, enabling installation both in the underfloor area and as paired units on the roof. The special cell chemistry and battery design are engineered for a long service life.

While individual high-voltage components in the new city bus generation, such as the power distribution unit (PDU), high-voltage cables, charging connector, and compressor, are taken from the truck sector and adapted for bus-specific applications, the compact battery modules, charging rail, pantograph, and drive axle have been specifically developed and configured for bus use.