Mercedes Benz eCitaro: Premiere for eCitaro fuel cell featuring a fuel cell, even more efficient with the performance package, new assistance and safety systems

• Premiere of the eCitaro fuel cell 12-metre solo bus takes place at Busworld Europe 2023
• eCitaro fuel cell featuring a fuel cell as a range extender: consistent, practical and cost-conscious
• eCitaro with NMC3 high-performance batteries
• Performance package: minor improvements, major impact
• Even more capable assistance and safety systems
• Optionally: MirrorCam instead of outside mirrors
• Daimler Buses Solutions: turnkey eMobility ecosystems from a single source

More than 1000 units of the Mercedes-Benz eCitaro which rolled off the production line in Mannheim since its start of series production at the end of 2018, and a vast number of current orders underline: the all-electric Mercedes‑Benz eCitaro is a milestone in city bus development. Public transport operators benefit from the ongoing evolution of this low-floor electric bus. Covering ranges of around 400 kilometres before having to recharge with an all-electric solo bus or articulated bus in urban traffic and with average demand ‑ the new Mercedes‑Benz eCitaro fuel cell featuring a fuel cell as a range extender makes it possible. It is celebrating its premiere as a solo bus at the Busworld Europe 2023 trade fair. Don't need extra long ranges or planning opportunity charging? Then the eCitaro with NMC3 batteries is what you need. The rapid further development of the vehicle is ultimately documented by the performance package for the eCitaro and a comprehensive range of new safety features.

eCitaro fuel cell featuring a fuel cell as a range extender: consistent, practical and cost-conscious

Vehicle drives with fuel cells are considered the solution whenever all-electric city buses with a very long range are required. After all, they produce the energy for the electric motors on board. The eCitaro fuel cell has been consistently, practically and cost-consciously designed for use as a city bus. As an operating fluid, electricity is significantly cheaper than hydrogen – this is the reason why this is a battery-electric low-floor city bus featuring a hydrogen-powered fuel cell that therefore serves to extend the range rather than act as the main energy source on board.

Fuel cell: highly efficient, compact and durable

The fuel cell of the eCitaro fuel cell is supplied by Toyota and already belongs to the second generation. The heavy-duty unit generates a maximum output of 60 kW. In the eCitaro fuel cell, it is operated very efficiently at its best operating point at around 20 kW to 30 kW and within a voltage range of 400 volts to 750 volts.

It operates highly efficiently, resulting in a comparatively low consumption of hydrogen to generate power. The very long service life of around 40,000 hours when used as a range extender is also remarkable.

Fuel cell drive – how it works

The fuel cell generates electric current and heat as a result of the reaction between hydrogen and oxygen, a process that is also known as cold combustion. Several hundred fuel cells are required to drive an eCitaro fuel cell vehicle. Together they form a fuel cell unit referred to as the fuel cell stack.

Each of the hydrogen tanks for supplying the fuel cell of the eCitaro fuel cell holds five kilogrammes. They comply with the so-called Type 4, featuring an inner container made of plastic and an outer casing made of carbon fibre, and are both light and highly durable.

The tank system boasts a modular design. The solo bus uses five tanks with a total of 25 kilogrammes of hydrogen. The articulated bus features six or seven tanks with 30 or 35 kilogrammes of hydrogen, as required. Refuelling consistently takes place on the right in the direction of travel, above the second axle. Under optimal conditions, the refuelling time in the solo bus, for example, is only around ten minutes.

Latest generation of high-performance batteries

The eCitaro fuel cell uses the latest generation of high-performance batteries. These NMC3 lithium-ion batteries (NMC = nickel-manganese-cobalt-oxide) were introduced in the eCitaro from the end of 2022. They have a very high energy content and are very durable.

Similar to the hydrogen tanks, the batteries are also scalable. There are three battery packs with a total capacity of 294 kWh in the solo bus. The articulated bus has either three or four battery packs with a maximum energy capacity of 392 kWh. These battery configurations already ensure a considerable range.

As both the battery capacity and the amount of hydrogen carried can be configured individually, each transport operator is provided with an eCitaro fuel cell tailored to its individual deployment profile. As a result of the long range, charging is consistently carried out using a plug at the depot with a maximum charging power of 150 kW.

Long range, high number of passenger seats

The weight distribution of batteries, fuel cells and hydrogen tanks has been optimised down to the most minute detail to guarantee a high number of passenger seats. Here are two key models as an example: Daimler Buses calculates that the two-door solo bus with two battery packs and six hydrogen tanks can provide a capacity of around 88 passenger seats. In a three-door articulated bus with one driven axle, three battery packs and seven hydrogen tanks, the number of passenger seats amounts to around 128.

Thermal management uses the waste heat from the fuel cell

When integrating the fuel cell drive, the Citaro once again demonstrates its versatile concept. Transport operators therefore benefit from the familiar passenger compartment as well as a host of identical components and parts in the Citaro, eCitaro and eCitaro fuel cell.

New features include thermal management. The waste heat from the fuel cell can be used to heat the passenger compartment. For this reason, Daimler Buses is now using the compact air-conditioning system on the basis of R134a refrigerant which is also fitted with a heat pump. In combination with the waste heat from the fuel cell, it achieves higher efficiency levels at low temperatures than the CO₂ air conditioning system of the eCitaro. The waste heat from the fuel cell can also be used to control the temperature of the batteries.

Proven low-floor drive axle

As usual, power is transmitted to the ZF AVE 130 low-floor portal axle with wheel hub motors. These deliver a maximum of 125 kW per wheel and generate a torque of 485 Nm. Thanks to the fixed gear ratio, this results in a maximum torque of 11,000 Nm per wheel. In the articulated bus, the centre and rear axles are driven as standard. In easy topography, the rear section's driven axle alone is enough.

eCitaro with NMC3 high-performance batteries

Customers who are happy with medium ranges or rely on opportunity charging on the route or at the depot are ideally set up with the eCitaro featuring high-performance NMC3 batteries. Its outstanding advantage is its vast performance. In addition, the battery equipment is based on modular design.

The batteries of the new generation are still lithium-ion batteries. To be precise, these are cells with a new high-energy NMC cathode (NMC: lithium-nickel-manganese-cobalt oxide), a liquid electrolyte and an "advanced" graphite anode. However, very compact cylindrical cells in standard cell format 21700 (21 millimetres in diameter and 70 millimetres high) with a high-energy cell chemistry are now used instead of the previously used, prismatic battery cells that were the shape and size of a paperback book. The combination of improved cell chemistry and an optimised battery pack leads to a considerable increase in capacity by around 50 percent at the same weight.

600 battery cells are mounted within each battery module. Nine battery modules are combined to form a battery pack with 5400 cells. This results in a nominal energy of 98 kWh per battery pack.

Long range, individual equipment, vast capacity

As has been customary from the start with the eCitaro, different configurations of equipment are possible both for the eCitaro solo bus and for the eCitaro G articulated bus.

-           eCitaro solo bus: a minimum of four, a maximum of six battery packs with a total capacity of up to 588 kWh (distributed between three or four packs on the roof and one or two packs in the former engine compartment).

-           eCitaro G articulated bus: a minimum of four, a maximum of seven battery packs with a total capacity of up to 686 kWh (up to five mounted on the front section of the bus and, depending on the configuration, one on the rear section and in the former engine compartment).

-           eCitaro fuel cell: three battery packs with a total capacity of 294 kWh (one on the roof, two in the former engine compartment).

-           eCitaro G fuel cell: three or four battery packs with a total maximum of 392 kWh (two or three on the front section, one in the former engine compartment).

In average conditions, the maximum equipment scope guarantees 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 batteries. Under favourable conditions, the range is even well over 300 kilometres. This means that the buses cover the majority of the requirements for the daily mileage of city buses.

Prioritising depot charging, optionally opportunity charging

Thanks to its high energy capacity, the eCitaro with the new battery generation is also ideally suited for long route cycles and subsequent charging at the socket in the depot. In this process, a charging power of up to 150 kW is possible. If even longer routes are planned, intermediate charging using a pantograph or charging rails is also possible, which is referred to as "opportunity charging". The combination with charging rails even enables the maximum configuration of batteries. In this case, the charging power is up to 300 kW.

Performance package: minor improvements, major impact

The technology in the eCitaro has not stopped evolving since its world premiere in 2018. In addition to the major advances in battery technology, this also applies to numerous other details. A current example is the eCitaro performance package, making electric buses even more suitable for the job.

The eCitaro already offers three charging positions for CCS charging using a plug. An additional connector position is now being prepared around the vehicle front. Two eCitaro buses can also be charged sequentially, i.e. one after the other, at a charger with two charging points. This avoids charging peaks, saves infrastructure costs and still offers the operator the necessary operational flexibility.

Another new feature is an additional positioning option for pantographs or charging rails in the centre above the front axle. In addition, the charging rails are optionally equipped with an RFID tag to ensure clear vehicle identification during charging at the depot.

For maximum efficiency, the eCitaro has been equipped with a state-of-the-art CO₂ air-conditioning system featuring a sophisticated thermal management right from the start. However, not every transport operator needs this highly sophisticated system. For use at moderate temperatures, Daimler Buses is now using the EvoThermatik HP Basic climate control system as standard, and EvoThermatik HP High Comfort is available for use in hot countries. Both air-conditioning systems are operated with the proven R134a refrigerant and feature a highly efficient heat pump.

Part of the intelligent climate control system of the eCitaro is the preconditioning of the vehicle interior at the depot. It is now also possible without a direct connection to the CCS charger. This is advantageous if the bus arrives at the depot with largely charged batteries or if charging en route is planned. No charging station at the depot will then be unnecessarily occupied just to send a pre-conditioned vehicle out on its scheduled cycle.

Other benefits include: The considerable energy loss at the bus stop is reduced with optional "EcoMode" door control. Depending on the situation, either only one door leaf is opened, or the doors are opened automatically by the driver, as required. This prevents large quantities of conditioned interior air from escaping unnecessarily.

Developers have implemented various measures to reduce weight and achieve maximum passenger capacity. In addition, the three-door solo bus and the four-door articulated bus can optionally be equipped with a new leaning surface on the rear wall. This gain in standing room optimises weight distribution. The total capacity can thus be increased by up to four people.

Even more capable assistance and safety systems

The next step has already been outlined. In the run-up to the future General Safety Regulation (GSR) within the EU and in other European countries, Citaro range vehicles will become even safer.

The Sideguard Assist 2 turning assistant reacts and outputs an even more precise warning if there is a risk of collision with pedestrians and cyclists. Previously available for the door side, it will also be used for the driver's side in the future. Frontguard Assist is completely new. It detects and warns of obstacles or people directly in front of the vehicle. Sideguard Assist 2 and Frontguard Assist combine to create a complete warning system that warns of obstacles and people at the sides and in front of the vehicle. Together with the reversing camera, which is now standard, or even more with the optional 360° camera system, the drivers are provided with a comprehensive warning system for all aspects of their vehicles.

Also new is the intelligent Traffic Sign Assist speed assistant. It warns the driver if the permissible speed is exceeded. Finally, the Tyre Pressure Monitoring system (TPM) and Attention Assist (AtAs) as well as an interface for the use of alcohol testers for the driver's workplace have been adopted as standard equipment.

In addition, the Preventive Brake Assist 2 active braking assistance system is in preparation. It is even more capable.

Optionally: MirrorCam instead of outside mirrors

Another eye-catching feature is the optional MirrorCam instead of the conventional outside mirrors. The images from the cameras are transmitted to 15-inch monitors. They are installed inside the bus on the left-hand side at the A-pillar and on the right-hand side in the centre under the front dome. An additional camera and a second compact monitor ensure a view of the front right-hand corner of the vehicle.

The MirrorCam combines numerous advantages. These include the extended field of vision for the driver, better visibility in the dark, less dirt, less manoeuvring damage and – a key point for the intercity variants of the Citaro range – a further reduction of fuel consumption thanks to a smaller vehicle front.

The Mercedes‑Benz Citaro with combustion engine also benefits from these changes. For these models the standard equipment has now been changed to the ZF Ecolife 2 automatic transmission with torque converter. With the optionally available Voith Diwa automatic transmission with torque converter, the first model variants switch to the new seven-speed Voith Diwa NXT transmission variant offering a broader gear ratio spread. This leads to lower engine speeds at higher vehicle speeds, thus reducing fuel consumption and noise.

Finally comes the appealing rear end which is also particularly noteworthy. The new rear lamps of the Citaro with the new, unmistakable Mercedes‑Benz light signature are really worth a look.

Daimler Buses Solutions: turnkey eMobility ecosystems from a single source

Combustion engine out, electric mobility in – the transformation isn't that easy. If transport operators want to use electric buses successfully, they require a holistic perspective of their electromobility system.

Daimler Buses has already intensively advised transport operators and actively supported them on their way to electromobility. The next step has now been taken with the establishment of the Daimler Buses Solutions GmbH subsidiary. The company specialises in the design and development of electromobility infrastructure.

The company will be commissioned by customers throughout Europe and, together with its partners, will supply the complete infrastructure for electromobility from a single source. Another special feature: if requested by customers, the installation or conversion of the electrified depots is also carried out across brands.

In cooperation with the experts from Daimler Buses Solutions GmbH, Daimler Buses can supply the entire eMobility ecosystem from a single source on request: from individually configured electric buses to the complete electromobility infrastructure for the depot, including construction measures, electrical installations, chargers, battery storage systems, charging management systems and other digital services. In addition, the next step will involve enhancing the portfolio to include services relating to the necessary infrastructure for operating buses with hydrogen-based fuel cell drives or range extenders.

Omniplus: digital is completely normal

Another plus for all Citaro, eCitaro and eCitaro fuel cell vehicles is the comprehensive service offer provided by the Omniplus service brand. This applies to services ranging from changing the oil of low-emission diesel engines to supplying spare parts – now increasingly 3D-printed on site. Dealers can purchase parts 24/7 from the Omniplus eShop. Genuine remanufactured parts optimise the cost balance and the CO₂ footprint. High-voltage batteries are given a second life in stationary use. Tailor-made service contracts provide security and cost transparency, as well as the diverse and continuously expanded digital services of Omniplus On such as the real-time monitoring of Omniplus On Uptime and Uptime pro. Data is transmitted using the standardised TiGR interface. Digital has long been completely normal for Omniplus.