The first Mercedes-Benz battery-electric eCitaro bus (earlier post) will be delivered at the end of the year and will go into practical operations in the context of a customer-oriented driving test.

The Rhein-Neckar-Verkehr GmbH, operator of the local public transport system in the Rhine-Neckar metropolitan region, signed a corresponding declaration of intent with the Daimler subsidiary EvoBus GmbH. Series production of the Mercedes-Benz Citaro with all-electric drive will then begin at the end of the year at the Mannheim bus plant. The transport operators in Hamburg and Berlin have already ordered a total of 35 eCitaro buses.

The platform of the new Mercedes‑Benz eCitaro is the Citaro, the brand’s best-selling city bus with more than 50,000 units sold. Lithium-ion batteries with a total capacity of up to about 243 kWh provide the power for the eCitaro. The batteries are divided between as many as ten modules, each supplying around 25 kWh.

In addition to two battery modules on the vehicle roof, the standard equipment includes four battery modules in the rear of the bus. Depending upon customer requirements, another two or four battery modules are mounted on the roof of the eCitaro. With a minimum of six and up to a maximum of ten possible battery modules, transport operators can adapt their usage and charging strategy very precisely to individual needs.

With the maximum complement of ten battery modules, the eCitaro in standard specification weighs around 13.44 tonnes. In conjunction with a gross vehicle weight rating of 19.5 tonnes, this corresponds to a payload of more than six tonnes or around 88 passengers—in line with what is needed in practice even during rush hour.

The eCitaro’s charging technology also allows it to adjust to the individual wishes and requirements of the transport operators. For the start of series production, plug-in charging is intended. To this end, the city bus has a connection for a Combo 2 plug. If opportunity charging is required to extend the range, there will also be an option to charge the eCitaro via a pantograph in future.

However, the battery capacity alone provides little indication of the actual performance capability and, above all, the range of an all-electric city bus—the true measure is that of energy consumption. In the case of a city bus, this is impacted significantly by climatic conditions and consequently by the need to cool and, above all, to heat the interior. The engineers have therefore put a considerable amount of thought into the issue of thermal management.

Compared with the current Citaro with combustion engine, the energy requirement for heating, ventilation and climate control has fallen by about 40% in the eCitaro. This exceptional energy efficiency provides the basis for the eCitaro’s practical operating range even under unfavorable conditions.

According to the SORT2 standardized city driving cycle, the Citaro with a full complement of Samsung NMC Li-ion batteries should be able to achieve an operating range of around 150 kilometers (93 miles) in the summer. In other words, it is already possible to serve some sub-networks within the daily workload of a city bus without opportunity charging.

Without opportunity charging, the eCitaro already covers about one third of all requirements of the transport operators. Under ideal conditions, the eCitaro even drives around 250 kilometers (155 miles) without opportunity charging.

The eCitaro is designed to be transitioned to future battery technology. The next generation of the eCitaro, using the next generation of Samsung NMC technology, will then cover around 50% of all applications. This greater battery capacity also makes a meaningful introduction of an eCitaro G articulated bus with a reasonable range possible.

Additional development steps are already mapped out, including the use of lithium-polymer solid-state batteries from Blue Solutions, a subsidiary of Bolloré Grop, which are characterized by a particularly long service life as well as high energy density. With a rated battery capacity of about 400 kWh in the solo bus and even more in the articulated bus, the eCitaro will then meet about 70% of all requirements without opportunity charging.

Gustav Tuschen, Head of Product Engineering Daimler Buses, discusses battery and fuel cell technology for the eCitaro.

Subsequently, the range of the eCitaro will be increased yet again by a fuel-cell range-extender. It will be designed to allow the eCitaro to fulfil nearly 100% of all requirements on city buses. This technology eliminates the need for opportunity charging and the complex infrastructure required for it in almost all cases—the eCitaro will be able to replace city buses with combustion engine virtually one to one.

Public funding supports development. The development of a marketable city bus transport system using solely battery power takes place via the “SAEBEL” project, funded by the German Federal Ministry of Transport and Digital Infrastructure as part of the electric mobility funding policy with a total of €1.85 million.

The implementation of the funding policy is being coordinated by NOW, the German “National Organisation Hydrogen and Fuel-Cell Technology”. Results of the various funding activities of the BMVI in the context of local public transport are combined within the programme support research as part of the working group “Innovative Powertrains Bus”.

To accelerate the market development for the eCitaro with fuel-cell technology as a range extender, Daimler Buses aims for funding as part of the German “National Innovation Programme - Hydrogen and Fuel-Cell Technology” (NIP).