IT’S OFFICIAL: E-CITARO TO MAKE WORLD PREMIERE IN IAA GERMANY

By: Fabian Cotter


IN WHAT IS PROBABLY one of the global bus world’s worst-kept secrets, the Mercedes-Benz eCitaro will make its official world premiere at the 2018 IAA Commercial Vehicles show in September, as announced at a Mercedes-Benz unveiling recently.

IT’S OFFICIAL: E-CITARO TO MAKE WORLD PREMIERE IN IAA GERMANY
The much-anticipated eCitaro will debut to showgoers at the 2018 IAA Commercial Vehicles event in Germany.

Its key attributes include: being a zero-emission bus; a tailor-made exclusive exterior; flexible charging technology - plug-in charging as standard, optional pantograph; thermal management - new approaches for heating and climate control; and a practical range also under difficult conditions, according to Daimler Buses.

Ultimately, as would any electric bus, its big selling points to world markets are that it, "emits zero local emissions and runs almost silently".

According to Daimler Buses it, "combines the thousandfold proven platform of the world's best-selling city bus with new technological solutions."

"The all-electric Mercedes-Benz eCitaro takes electric mobility using city buses to a new level altogether," it’s stated.

The new eCitaro offers a claimed "unprecedented standard in energy efficiency", thanks to its innovative thermal management system that uses "innovative components available for the first time with the launch of the eCitaro", apparently.

"Its performance enables the eCitaro to cover a large part of the requirements of the transport operators right from the start. In addition, it is ready for the battery technology of the near future – the performance capabilities will increase quickly."

"Its design fuses the basic shape of the Citaro with elements of the Mercedes-Benz Future Bus into a distinct appearance. It is also more than just a city bus: Mercedes-Benz takes a holistic view of electric mobility, embedding the eCitaro firmly in its overall eMobility system. In addition, the eCitaro is the starting signal on the road to an electric future," the company stated.

Daimler says the eCitaro will be an important element in any ‘well developed’ local public transport infrastructure, with low-emission and locally emission-free buses.

Based on the concept of a regular Citaro - the world's best-selling city bus with more than 50,000 units sold – the eCitaro joins the large-capacity CapaCity bus, as well as the Citaro hybrid and the Citaro NGT in showcasing Daimler’s "highly sophisticated level of development of powertrains", said to be "characterised by both their efficiency of operation and their low emissions".

"The all-electric eCitaro is now taking the next step from low-emission bus to locally emission-free bus."

EXCLUSIVE EXTERIOR?

Fundamentally, the eCitaro marries exterior design elements of a normal modern Citaro with that of the stylistically boundary-pushing Future Bus Concept, its autonomous bus project.

At the front, a 28cm Mercedes star highlights attractive lighting effects from different angles and in changing sunlight, with the star, the trim elements and the Mercedes-Benz badge embedded into the high-gloss black front panel, integrated with individual LED headlamps. The model logotype with a blue ‘e’ indicates the all-electric powertrain.

Its curved windscreen smoothly transitions into the roof with dark bars on the left and right. At its middle, the roof sports an ‘island’ in vehicle colour that forms the roof membrane. A multi-piece roof-edge ridge hides the roof-mounted equipment

Further ‘optical tricks’ lend the eCitaro "perfect proportions and make it seem light," the company states.

 Related article: Daimler's electric order before world premiere
Related article: Daimler's electric order before world premiere

INSIDE STORY

In the passenger compartment, the eCitaro features a general update of the interior of the entire Citaro family. The ‘coffered’ design ceiling above the centre aisle and the sweeping roof-edge flaps hide a new air circulation system with textile ducts in place of the current plastic air ducts. They are said to be even easier and simpler to install.

In addition to the closed look and the new interior lights, the advantage of the new ceiling is a significantly reduced number of individual parts. Together with the new air circulation system, this lowers the already low interior noise in the passenger compartment even further, which means more comfort, it’s claimed.

Also new is the black trim on the sills and window posts. As a result, the window posts are said to stand out less and the appearance of the side walls is "calmed".

While the new exterior was designed and developed exclusively for the eCitaro, Mercedes-Benz will transfer the changes in the interior to the entire model series.

MOTIVE MACHINATIONS

The new eCitaro uses a ZF AVE 130 electric portal axle with motors at the wheel hubs. The peak output of the motors is 2x125kW, while torque is 2x485Nm.

Lithium-ion batteries with a total capacity of up to about 243kWh provide the power. They are modular in design; the batteries are split between up to 10 modules, each supplying around 25kWh. As well as two battery modules on the vehicle roof, the standard equipment includes four modules in the rear of the bus. In the eCitaro these take the place of a combustion engine and transmission. Depending upon customer requirements, another two or four battery modules are mounted on the roof of the eCitaro, says Daimler.

Each battery module is made up of 15-cell modules, as well as "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 prismatic cells with a capacity of 37Ah each. With a minimum of six and up to a maximum of 10 possible battery modules, transport operators can adapt their usage and charging strategy very precisely to individual needs, it’s claimed. 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 opportunity charging necessary, the company explains.

With the maximum complement of 10 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, it states.

FLEXIBLE CHARGING

For the start of eCitaro series production, plug-in charging is intended. To this end, the city bus features a socket for a Combo-2-plug above the front wheel arch on the right-hand side of the vehicle in the direction of travel as per the provisions of the German Association of Public Transport Operators (VDV). This ensures the simplest, fastest and at the same time cheaper power supply variant, the company says.

If opportunity charging is required to extend the range, there will also be an option to charge the eCitaro via a pantograph in future. This option will be gradually phased-in once series production has started. There will be two possible variants: in phase 1, an integral pantograph on the roof; in phase 2, charging rails on the roof that will allow charging via a stationary pantograph of a charging station. In both cases, the installation space will be level with the front axle.

This intelligent modular concept of battery and charging technology means that Mercedes-Benz is able to offer transport operators the opportunity to configure the eCitaro precisely to the individual requirements of the company or even of individual routes, it’s stated.

In addition, the eCitaro is also able to generate electrical energy through an energy recovery process. In this case, those two electric motors at the wheel hubs of the drive axle act as alternators during braking, transforming the kinetic energy of the vehicle into electricity.

BATTERY HEAT

Batteries at their ideal temperature give maximum performance and service life, so thermal management is important. Mercedes-Benz cools the batteries to ensure that they remain at the ideal temperature, thereby ensuring maximum charging capacity, performance capability, and service life, it’s stated.

"This cooling is undertaken by a separate battery cooler mounted on the roof. At extreme outside temperatures, the standard passenger-compartment climate control system is used to boost the cooling of the batteries."

PRACTICAL RANGE

Operating range figures for all-electric-powered city buses are often difficult to compare and caution is advised, since reference values can be missing and the figures have often been calculated under ideal conditions, says Daimler Bus

For the eCitaro, in the interests of reliable data, Mercedes-Benz prefers to consider a "worst-case scenario" and therefore takes its direction from the challenging standardised city driving cycle known as SORT2. To make things even trickier, Mercedes-Benz also adds the energy requirements of the ancillary consumers into the equation. According to SORT2, the Citaro with a full complement of batteries achieves an operating range of around 150 kilometres in the [European] 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. That is, it can seamlessly replace one in three city buses powered by a combustion engine. Under ideal conditions, the eCitaro even drives around 250 kilometres without opportunity charging, it’s claimed.

eCitaro testing saw engineers also evaluate the compatibility of the bus with different charging systems. It ensures the eCitaro communicates in accordance with ISO 15118 standard, with the charging station communicating with the control unit of the eCitaro.

Start of series production is still planned by the end of 2018, with initial orders already received, it’s stated. First customer deliveries will also start still before the year is out.

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