Mercedes-Benz has promoted the all-electric Mercedes-Benz Citaro as taking electric mobility using city buses to a new level altogether.
The 12-metre variant will celebrate its world premiere in September at the IAA Commercial Vehicles, with the start of series production coming before the end of the year. The new Citaro offers an impressive and hitherto unknown standard of energy efficiency, courtesy of its innovative thermal management system.
The intelligent modular concept for its battery and charging technology is a similarly compelling proposition. The electric Citaro is also more than simply a city bus: Mercedes-Benz takes a holistic view of electric mobility, embedding the Citaro firmly within its overall eMobility system.
This comprises services that range from individual and very practically oriented advice ahead of any purchase and recommendations relating to charging infrastructure through to taking on servicing work at the customer’s own workshop.
Citaro: from low-emission bus to zero-emission bus
Back in 2012, this became the first city bus in the world to meet what is currently the most stringent emissions standard, Euro VI.
The Citaro hybrid variant then became a fully recognised low-emission bus. Launched last autumn, it features a hybrid module that further optimises the performance of the combustion engine and reduces the already low fuel consumption by as much as 8.5%. Compared with a city bus meeting the Euro V standard, the CO2 emissions have thus fallen by almost 20% and the nitrogen oxide emissions by as much as 98% in just a few years, while particulate emissions have even reached the limits of detection.
he Citaro hybrid, featuring innovative 48-volt technology, dispenses with the need for a high-voltage network and is available as an option for the majority of Citaro variants, including for the natural gas-powered Citaro NGT. This model is particularly quiet-running and its emissions low, while when fuelled by biogas it is virtually CO2-neutral.
Proven electric axle, new modular battery concept
The drive system of the new all-electric Citaro is based on the tried and tested ZF AVE 130 electric portal axle with electric motors at the wheel hubs, as previously deployed in other variants of the Citaro. Their peak output of the motors is 2 x 125 kW, while torque is 2 x 485 Nm.
Lithium-ion batteries with a total capacity of up to about 243 kWh are responsible for providing the power. These are modular in design: the batteries are split between up to ten modules, each supplying around 25 kWh. As well as two battery modules on the roof, the standard equipment includes four battery modules in the rear of the bus.
Each battery module is made up of 15 cell modules, together with a control unit for monitoring purposes and as a means of balancing the charge of the battery cells. Each separate cell module houses twelve battery cells. Mercedes-Benz uses easily manageable prismatic cells with a capacity of 37 Ah each.
With a minimum of six and up to a maximum of ten battery modules possible, transport operators can adapt their usage and charging strategy very precisely to individual needs. Opting for the largest number maximises the range of the buses, while a smaller number reduces the weight as well as the cost of purchase and allows more space for passengers – but potentially makes time-consuming interim, or ‘opportunity’, charging necessary.
With the maximum complement of ten battery modules, the all-electric Citaro with standard equipment weighs around 13.7 tonnes. In conjunction with a permissible gross vehicle weight of 19.5 tonnes, this corresponds to a payload of 5.8 tonnes or around 80 passengers – even in the rush hour, as is commonly necessary.
The Citaro’s engineering has been future-proofed. Since the development of battery technology is progressing at a rapid pace, provision has already been made for the transition to the next generation.