Daimler Buses launched the Mercedes-Benz eCitaro last week. It claims that the zero-emission bus will, by 2020, be able to handle most urban duties through use of solid state storage and a range extender
The electric bus market is soon to see a challenge from Daimler, which formally launched the zero-emission Mercedes-Benz eCitaro last week.
One thing is clear with the eCitaro. At least initially, it will not rely on headline range figures to justify its existence and generate interest, because Daimler did not get carried away with such things during development.
The manufacturer remains wedded to the line that the bus will, in its early years, go through a series of incremental improvements.
By 2022, those will culminate in a ‘worst case scenario’ range of 400km with a small hydrogen fuel cell range extender and solid-state batteries, or 250km on batteries alone. First generation eCitaros will offer a realistic range of 150km.
In terms of distance between charging, 400km is a lot. And as with all of those figures, it is a real-life total. The draw of heating and air-conditioning has been taken into account.
But that’s for the future. The eCitaro starts life with a more modest range, but its passenger capacity is not constrained. With a 19,500kg GVW giving over six tonnes of payload, a theoretical maximum of 88 people can be carried on the 12m model.
‘A special bus’
Daimler has introduced revised external styling that is exclusive to the eCitaro. Inside, there is no difference to a diesel model from a passenger’s perspective, although the rear ‘shower cubicle’ may go later. Currently, it is occupied by batteries.
Hub motors permit a full low floor layout, and work has been done to the ceiling to reduce its weight. The eCitaro is compatible with existing telematics systems, and it is able to transmit its state of charge among much other data via that connectivity.
In a thinly-veiled shot at some other parties, Head of Daimler Buses and Trucks Martin Daum says that it had no interest in being first to the electric bus table. “We do not seek quick headlines or fair-weather solutions. We want reliable buses that work under all conditions.” The eCitaro is thus part of a comprehensive electromobility offering that includes consultancy to help design a package that best suits the buyer’s needs. When doing so, particular attention is paid to the charging method.
Daimler does not hide the fact that it incorporated compatibility with opportunity replenishment only very reluctantly. That is perhaps understandable, given what it is promising in terms of incremental range gains.
Indeed, the major announcement – that solid-state batteries will arrive in the eCitaro in 2020 – is related to that. Solid-state chemistry is not suitable for rapid charging; it will work only with depot replenishment and it is significantly different to lithium-ion.
“Why would we pursue a second technology path?” asks Head of Product Engineering Gustav Tuschen. “Because solid-state batteries deliver longevity and energy density that is superior to lithium-ion.”
Solid-state will allow 400kW/h of energy storage on the eCitaro, for a range under difficult conditions of 250km – accounting for around 70% of urban bus duties.
Evidence of Daimler’s confidence in solid-state technology is the 10 years that it will warrant such batteries for. That is double the period offered with lithium-ion chemistry.
Later, with the hydrogen fuel cell range extender added, the useable range will grow to 400km and the eCitaro will be able to take over 100% of urban workings, Daimler claims.
Covering bases
Alternatively, where range is not the priority, use of solid-state technology will allow an increase in passenger capacity. But solid-state will complement, not replace, lithium-ion, and Daimler will introduce progressive developments in the latter sector, too.
As unveiled, the eCitaro uses first generation lithium-ion storage with a capacity of 243kW/h. Second generation lithium-ion batteries, set to debut in 2020, will permit 330kW/h of storage within the same envelope, increasing the realistic range to 200km.
Heating and cooling of both the saloon and the batteries is handled by a single unit that incorporates a heat pump. When compared on a like-for-like basis to a diesel-powered Citaro, that cuts energy consumption for climate control by 40%.
Clever technology
It is not just the batteries where Daimler is grasping technology by the horns. The entire Citaro range, including the eCitaro, will from 2019 be available with Sideguard Assist. It will warn the driver of pedestrians, cyclists and other objects when turning, although it will not be able to initiate automatic braking. Nevertheless, Daimler says that it will contribute to “an unburdening on the driver in his or her work.”
No concrete pricing for the eCitaro has been revealed, but Head of Marketing, Sales and Aftersales Ulrich Bastert says that it will be between 2-2.5 times that of a comparable diesel.
Daimler has already secured orders for the eCitaro in left-hand drive form. If it delivers what is promised, it will be in strong contention in the UK in due course, too.
