Even more capacity, even more range: Mercedes-Benz eCitaro ahead of the game with the next generation of high-performance batteries

• Transport companies benefit from the latest generation of batteries
• NMC 3: Compact round cells with high-energy cell chemistry
• Long range, individual battery loading, enormous increase in capacity
• Priority: Depot charging via socket, optional opportunity charging
• Used in the eCitaro, eCitaro Range Extender and in the Brazilian eO500U chassis

The abbreviation is NMC 3: Behind it is a new generation of high-performance batteries for the all-electric low-floor Mercedes‑Benz eCitaro urban bus. An outstanding advantage is its enormous capacity, which results in a long range without having to charge on the go. In addition, there is the modular design of the battery equipment. The first eCitaro buses with the new battery generation are expected to be delivered before the end of 2022.

Transport companies benefit from the latest generation of batteries

The promise remains unchanged: At the world premiere of the Mercedes-Benz eCitaro in 2018, Daimler Buses had already promised that its buyers would always benefit from the latest battery technology. They would benefit from the rapid advances in the development of energy storage systems.

This was already the case when the NMC 1 battery type was changed to the second generation NMC 2, as well as when revolutionary solid-state batteries were introduced. Now the next step is to gradually replace NMC 2 with the third generation, called NMC 3. With its performance capability, the new battery generation is an important tool for the vigorous progress of the switch to electric mobility via buses in cities. As before, Akasol is the battery production partner.

Compact round cells with high-energy cell chemistry

The new generation are also lithium-ion batteries. Precisely formulated around cells with a new high-energy NMC cathode (NMC: lithium nickel manganese cobalt oxide), a liquid electrolyte and an advanced graphite anode. The common abbreviation NMC (nickel, manganese, cobalt) also comes from battery chemistry. However, instead of the previously used prismatic battery cells in the shape and size of a pocketbook, very compact cylindrical cells with the designation 21700 (a format of 21 mm in diameter and 70 mm in height) with high-energy cell chemistry are used. The combination of improved cell chemistry and an optimized battery pack leads to an increase in the overall 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 for the same weight.

600 battery cells are mounted within each battery module. They have been integrated into the cooling circuit to ensure the battery’s optimum temperature of around 25 degrees Celsius. Temperature control ensures maximum service life and efficient charging. Nine battery modules combine to form a battery pack with 5400 cells. This results in a nominal energy of 98 kWh per battery pack.

Long range, individual battery charging, enormous increase in capacity

As was customary from the start with the eCitaro, different equipment versions are possible for both the solo bus and the eCitaro G articulated bus. This means that even with the new battery generation, every transport company will receive an eCitaro made-to-measure according to its individual usage profile. This is accompanied by an enormous increase in energy. With the eCitaro G, for example, it increases by more than 70 percent when moving from NMC 2 to NMC 3.

• eCitaro solo bus: A minimum of four, a maximum of six battery packs with a total capacity of up to 588 kWh (spread between three or four packs on the roof and one or two pack in the former engine compartment).
• eCitaro articulated bus: A minimum of four, a maximum of seven battery packs with a combined capacity of up to 686 kWh (up to five on the front body and, depending on configuration and one on the rear body as well as in the former engine compartment).
• eCitaro range extender solo bus: A minimum of two, a maximum of three battery packs with a combined capacity of 192 or 294 kWh (one on the roof, two in the former engine compartment).
• eCitaro range extender articulated bus: A minimum of three, a maximum of four battery packs with a total of up to 392 kWh (three on the front body, one in the former engine compartment).

Under average conditions, the maximum equipment 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 buses cover the majority of the requirements of the daily driving performance of city buses. In favorable conditions, their range is well over 300 kilometres.

In view of the division of the battery packs, a weight distribution that has been thought through down to the last detail becomes apparent. It ensures an appropriate number of passenger seats even with a large number of batteries. Added to this is the weight advantage from the high energy density of the new batteries: Depending on the vehicle configuration, the eCitaro with the new generation of batteries offers a considerably greater range for the same weight, and thus the same number of passenger seats.

Priority: Depot socket charging, optional opportunity charging

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

If longer routes are planned, charging on the go via pantograph or charging rails is also possible, known as opportunity charging in technical terms. In combination with charging rails, even maximum configuration with batteries is possible. In this case, the charging capacity goes up to 300 kW.

In addition to their high energy density, the batteries also have other advantages: The new generation already meets the safety requirements according to ECE R 100–3, which will only become binding in autumn 2023. This specification includes a large number of tests and inspections. Durability with gentle depot charging is also impressive: The manufacturer Akasol assumes 4,000 charging cycles, depending on factors including the depth of discharge and usage profile. This would correspond to a service life of up to ten years with daily use and subsequent charging in the depot. 

Carrier system and connections redesigned

The different design of the battery packs prevents a simple plug and play solution when adapting the new batteries. As a result the battery packs are approximately twice the size of the previous generation. The developers at Daimler Buses have completely redesigned the carrier system, housing, wiring and piping. The batteries have also been specially adapted to the electronics of Daimler Buses.

The eCitaro with the new NMC 3 battery generation will be available in a left-hand drive version as a solo bus with a length of around twelve metres, and as an articulated bus with a length of around 18 metres. The solo bus is also available as a right-hand drive vehicle. At the same time as the launch in the European eCitaro, Daimler Buses will also be using the new battery generation for its all-electric chassis in South America.

Use in the eCitaro, eCitaro Range Extender and in the Brazilian eO500U chassis

The new NMC 3 battery generation is used in a variety of ways. In addition to the Mercedes-Benz eCitaro and eCitaro Range Extender as a solo and articulated bus, this also applies to the Mercedes-Benz eO500U bus chassis produced in Brazil. With this, Daimler Buses is entering the era of electric mobility for buses in Latin America. The two-axle low-floor chassis was developed in Brazil and serves as a platform for city bus bodies with a length of up to 13.2 metres and a permissible gross weight of 21.2 tonnes. It offers the same high technological standard as the eCitaro.