Fully electric Mercedes-Benz eCitaro with innovative technologies: New NMC 3 high-performance batteries and new thermal management increase capacity, extend range and reduce energy consumption

• The locally emission-free, fully electrically powered city bus combines innovative technologies with the genes of the Citaro, which has proven itself thousands of times over
• Mercedes-Benz eCitaro with latest-generation high-performance batteries (NMC 3)
• Long range, individual battery configuration, enormous capacity
• Depot socket charging, optional opportunity charging
• Innovative thermal management drastically reduces energy consumption
• Cockpit and operating concept similar to the conventionally powered Citaro
• The eCitaro features modern design and unrivalled safety features
• Comprehensive advice and service when switching to electromobility

Leinfelden-Echterdingen / Berlin – Launched in 2018, the eCitaro is based on the Citaro with a combustion engine and combines its proven technology with a state-of-the-art electric drive. In the current version with third-generation lithium-ion batteries (NMC 3), the fully electric low-floor city bus represents the highest level of electromobility. What makes it distinctive is its combination of the Citaro's thousand-fold proven platform and a modular battery, charging and drive system technology, a functional yet attractive design and an unrivalled level of safety. It has also been embedded in a comprehensive e-mobility system. As a result, the Mercedes-Benz eCitaro has long since advanced to the model of success among electric buses: In 2022, almost 300 new eCitaro vehicles were registered in Germany alone – almost half of all newly registered e-buses over eight tons. Almost 700 eCitaro buses are currently being operated by German public transport companies, with almost a quarter of these being articulated buses.

New NMC 3 high-performance batteries for the eCitaro

The fully electrically powered Mercedes-Benz eCitaro low-floor city bus with NMC 3 batteries has been available since the end of 2022. Behind the abbreviation NMC 3 is a new generation of high-performance batteries with improved cell chemistry. The modular design of the battery assembly is also new.

The new generation consists of lithium-ion batteries with a new high-energy NMC cathode (NMC: lithium nickel manganese cobalt oxide), a fluid electrolyte and an advanced graphite anode. An outstanding advantage is their enormous capacity, which enables a long range without opportunity charging.

The compact cylindrical cells with their high-energy cell chemistry, combined with an optimised battery pack, result in an increase of the total gravimetric and volumetric energy density of the battery pack. The capacity of 4.93 Ah per battery cell results in a considerable increase in capacity of around 50 percent at the same weight. As before, Akasol is the partner for the production of the batteries.

600 battery cells are installed within each battery module. They have been included in the cooling circuit to ensure the battery's optimum operating temperature of around 25 degrees Celsius. Temperature control provides maximum service life and efficient charging. Nine battery modules combine to form a battery pack with 5,400 cells. This results in a rated energy of 98 kWh per battery pack.

Long range, individual battery configuration, enormous capacity

For both the eCitaro solo bus and the eCitaro G articulated bus, different versions of the battery configuration are possible according to the individual deployment profile. The eCitaro solo bus is available with at least four and no more than six NMC 3 battery packs with a combined capacity of up to 588 kWh. These are divided into three or four packs on the roof and two packs in what used to be the engine compartment. The eCitaro articulated bus has a minimum of four and a maximum of seven battery packs with a combined capacity of up to 686 kWh. Up to five packs are accommodated on the front section and, depending on the bus configuration, one on the rear section as well as one in the former engine compartment.

Under average conditions, the maximum battery configuration ensures a reliable range of 280 kilometres for the eCitaro solo bus and 220 kilometres for the eCitaro G throughout the entire service life of the battery. This means that the eCitaro buses cover the majority of requirements in terms of city buses' daily driving performance. Under favourable conditions, the range is more than 300 kilometres. The distribution of the battery packs results in well thought-out weight distribution down to the last detail. It ensures an appropriate number of passenger seats even with a large number of batteries. Added to this is the weight advantage resulting from the high energy density of the new generation of batteries: Depending on the vehicle configuration, the eCitaro with the new batteries offers a considerably greater range at the same weight and the same number of passenger seats.

Depot socket charging, optional opportunity charging

As a result of its high energy capacity, the eCitaro with the new generation of batteries is also perfectly suited for long routes and subsequent socket charging at the depot with a charging power of up to 150 kW. The familiar positions are available on the left and right above the front axle and at the rear. A maximum of two socket positions per vehicle are possible.

If longer routes are planned, intermediate charging can also be carried out using a pantograph or charging rails (opportunity charging). In combination with charging rails, even the maximum configuration with batteries is attainable. In this case, the charging capacity increases to up to 300 kW.

In addition to their high energy density, the NMC batteries also have other advantages: The new generation already meets the safety requirements according to ECE-R 100-3, which will not become binding until autumn 2023 and includes a large number of tests and inspections. Durability with gentle depot charging is also impressive: Manufacturer Akasol assumes 4,000 charging cycles, depending on factors like the depth of discharge and the individual usage profiles. With daily use and subsequent charging at the depot, this would correspond to a service life of up to ten years.

Innovative thermal management drastically reduces energy consumption

The battery capacity alone does not say enough about the performance and range of a fully electrically powered city bus – the true benchmark is energy consumption. In a city bus, the energy consumption is very strongly influenced by the climatic conditions and thus by the cooling and, above all, the heating of the vehicle interior. Mercedes-Benz therefore places great emphasis on thermal management. Compared with the current Citaro models equipped with a combustion engine, the energy requirement for heating, ventilation and climate control is reduced by around 40 percent. This extraordinary energy efficiency lays the foundation for achieving a viable driving range for the eCitaro even under unfavourable conditions.

The NMC batteries are initially thermally regulated to an ideal temperature of 25 degrees Celsius. This leads to maximum charging capacity, performance and service life. The passenger compartment is heated in an energy-saving manner by a heat pump and is supported by the braking resistor in the event of significant temperature changes. The front heater is equipped with a dual heat exchanger. The heat-dissipating components are interconnected to minimise the energy required to cool them. The power of the heating and air conditioning system varies depending on the vehicle load and the outside temperature. The roof-mounted air conditioning system has an additional heat pump function as standard and heats the passenger compartment very efficiently even at low outside temperatures. CO₂ is used as a highly efficient and environmentally friendly refrigerant.

The vehicle interior can be preconditioned to the desired temperature while the batteries are being charged at the depot. This means that the energy for the required climate control is not drawn from the battery at the start of the journey, thus increasing the range. Even overconditioning is possible, which further reduces consumption during operation. In addition, with an electrical air conditioning system, the necessary performance is available at all times and does not depend on the current speed of the combustion engine.

Proven, powerful portal axle

The drive of the new eCitaro is based on the proven and optimised ZF AVE 130 electric portal axle with electric motors at the wheel hubs. The peak power of the motors is 2 x 125 kW, and the torque is 2 x 485 Nm. Thanks to the gear ratio, a torque of 2 x 11,000 Nm on the axle is fully available from the start thanks to the system and ensures appropriate dynamics even with full occupancy. In the case of articulated buses, the centre and rear axles are powered as standard.

Cockpit and operating concept correspond to the conventionally powered Citaro

The layout of the eCitaro's passenger area corresponds to that of the usual Citaro models. The driver of the eCitaro does not need to adapt any more than the passengers do. The cockpit and operating concept largely correspond to the familiar setup. The direction of travel is selected with the D-N-R pushbuttons. The almost identical operation compared with the Citaro featuring a combustion engine enables the usual quick changeover of drivers.

However, the instrumentation meets the requirements of the electric drive. Here, a power availability display replaces the tachometer. It shows the current power demand or recuperation. The driver also receives information about the state of charge of the batteries. From the central display, the driver can access the range, power availability and a charging indicator. The eCitaro also supports the driver in energy-saving driving by means of an acceleration control: When moving off from a bus stop or traffic lights, whether empty or under full load, the torque is reduced to a comfortable level. This leads to a gentle and passenger-friendly driving style and at the same time reduces energy consumption.

In general, the driving properties are optimised for maximum efficiency without the driver having to pay attention to major differences compared with the Citaro featuring a combustion engine. For example, in the basic setting the bus rolls energy-efficiently and coasts along when the driver takes his foot off the accelerator pedal. As an alternative, the driver can set a basic deceleration as a recuperation rate by means of an electric brake lever in several stages.

Distinctive original design

The characteristic design of the eCitaro skilfully combines the familiar look of the Citaro with independent functional and design elements. This is particularly evident when looking at the face of the eCitaro. The main feature is the large Mercedes star, from which decorative elements radiate to the left and right. The star and decorative elements as well as the Mercedes-Benz brand insignia are embedded in a high-gloss black front mounting plate. LED individual headlamps have also been integrated into the component. The model lettering with a blue "e" indicates the all-electric drive technology discreetly and unmistakably.

The curved windshield blends seamlessly into the roof via dark strips on the left and right side. In the middle, the roof supports a virtually floating "island" in the colour of the vehicle. It is not only a visual feature but also forms the mouth of the roof cover. The eCitaro roof structures are concealed behind an elegant roof edge elevation consisting of a multi-piece extruded aluminum profile. The glossy black bottom segment extends the side glazing of the city bus. The top segment in the colour of the vehicle runs smoothly into the A0 pillar at the front and into the corner pillar at the rear and visually encloses the side.

The rear corner pillars flow at the top with a strong curve into the roof edge elevation. Characteristic are their elegant shape as well as the island that is also suggested here as a trim for the roof structures along with the black bars as a connection between the rear window and roof. These visual tricks give the eCitaro its appealing proportions and take the weight off the high body.

The eCitaro retains the structure of the current model without any changes. This makes, for example, repairing accident damage as easy as possible. The tailgate, rear lamps and bumpers as well as the curved windscreen are spare parts that the eCitaro has adopted from the current model range. The side roof edge elevation is segmented. It can be removed in individual parts and is therefore easy to service.

The unrivalled safety of the eCitaro

In Mercedes-Benz buses, safety does not consist of individual measures. It is based on a comprehensive, integral safety concept. Seating, visibility, ergonomics and climate control are exemplary, and the cockpit also does not require the driver to get used to it. The comfortable and secure chassis with electrohydraulic intelligent eco steering and roll-pitch control has earned a great deal of recognition.

A safety focus includes high-voltage technology with impact-proof mounted battery modules and well-protected high-voltage cables. The batteries are tested and certified according to hazardous goods regulations. Tests of the cell, cell module, battery pack and the battery groups in the vehicle have shown that the battery systems are extremely safe.

The active safety of the eCitaro is unrivalled. The solo bus is fitted ex-factory with the ESP Electronic Stability Program and its many sub-functions. Mercedes-Benz optionally supplies the eCitaro with the Sideguard Assist cornering assistant with pedestrian detection and with Preventive Brake Assist, the first active brake assistant for city buses.

E-mobility system: comprehensive advice and service when switching
to electromobility

eMobility requires specific services. For this reason, the Omniplus service brand from Daimler Buses has converted its range of tailor-made eService contracts to a modular concept with the introduction of the new battery technologies. In addition, the well-known eBasic and ePremium service contracts are still optionally available to public transport companies. They offer package solutions for repair and maintenance work on the high-voltage components as well as on the overall vehicle. The optimum service for the electric bus fleet can thus be put together from the basic warranty, extended battery warranty and service contract modules in a customer-specific manner and in accordance with individual requirements.

In a public transport company, the switch to electromobility is about more than energy consumption and range. Mercedes-Benz uses plug-in charging in the depot as standard. Opportunity charging is also possible on request either by pantograph, which means current collector on the roof, or by combining charging rails and fixed current collectors. Experts at Mercedes-Benz have tested various charging infrastructures. They will provide advice and make recommendations. On request, the eCitaro can furthermore be delivered as a complete package including power supply equipment. In addition, the Omniplus TrainingCenters in Dortmund, Mannheim and Winterthur/Switzerland provide advice about the equipment of an electric bus workshop on request and offer a complete eMobility training concept for employees in driving operation or those employed in the workshop.

The power supply of the buses is the cornerstone of electric mobility in the city. Mercedes-Benz eMobility Consulting will provide support in planning the infrastructure, calculate the necessary power supply, know the routes to distribution network operators and power suppliers and recommend the appropriate charging technology – right up to the organisation of the depot with parking spaces and the power supply to the bus including its battery equipment.

The eCitaro is communicative. It connects to the charging infrastructure using the ISO 15118 protocol. Mercedes-Benz offers solutions for integrating vehicle-specific data into existing management systems. Companies will be able to gain an insight into the operating data of their fleet using the Omniplus On Portal. Mercedes-Benz offers integrated system solutions for maximum transparency from route scheduling to depot management jointly with the industry-renowned ITS software provider IVU Traffic Technologies.