Minus 30 degrees Celsius in the Arctic Circle, plus 40 degrees in the Sierra Nevada, extreme urban traffic in Istanbul and Izmir: before the new eCitaro was ready for the start of serial production, it had to pass extreme endurance tests.
Omnibus Magazine
Ice and heat
Mercedes-Benz eCitaro in testing.
Ice and heat.
Mercedes-Benz eCitaro in testing.
The little town of Rovaniemi in Finland is considered to be the home of Father Christmas. And in winter, it is the second home of the Daimler Buses test engineers. The eCitaro has completed two winter tests here. Once it even drove to the far north under its own steam to endure almost minus 30 degrees Celsius there.
Winter tests in the Arctic Circle lead to valuable findings. For example, that despite the icy outdoor temperatures, it takes days until a battery is fully cooled down. And that an electric bus with the three-pointed star can start no problem even then. It only gets difficult at icy temperatures when charging outdoors. In this case, the electric bus fares like an athlete who is expected to put in top performances with cold muscles. Driving in the winter, on the other hand, is a pleasure. Andreas Dingler, Head of Testing at Daimler Buses: “The eCitaro, thanks to its individually controllable electric motors on the hubs, has an outstanding starting ability in ice and snow.” The test engineers have also discovered fine details, such as preconditioning and even over-conditioning for starting purposes, which can be used to optimise the range. Such findings cannot be acquired in a cold chamber. Instead, you have to go to the endless ice in the Arctic Circle.
“The eCitaro was not spared because of its drive unit. The tests are at the same level as for the Citaro with a diesel engine.”
Or to a hot summer in Spain. The destination is Granada where the thermometer creeps towards 40 degrees Celsius. Anyone who then loads up the interior and also uses room heaters and humidifiers to generate conditions like those in a fully occupied urban bus will make an e-bus face the highest demands. More so than ever in tough urban traffic with wideopen doors at the bus stops. As if that was not enough, the test engineers took the eCitaro up the nearby Pico del Veleta mountain pass in the Sierra Nevada. The ascent here is nonstop for almost 35 kilometres climbing to 2,550 metres. Among cyclists, the route is considered to be the queen of mountain roads. Also among testers: uphill, the cooling system is tested at full capacity. Downhill, then the deceleration, including the braking resistance of the electric brake.
2,800 kilometres east in Istanbul, another endurance run awaited. An eCitaro with 35,000 kilometres on the clock travelled from the urban traffic in Mannheim in order to then launch itself into the hustle and bustle of the city on the Bosphorus for another 60,000 kilometres. Around the clock, interrupted only by the charging times. It carried on to Izmir, a city of over a million inhabitants on the Mediterranean coast: 400 metres of altitude difference, partly more than 70 per cent humidity and hot temperatures. Another 60,000 kilometres. “It is constantly uphill and downhill, always alternating between a full and empty battery, which is pure stress,” explains Andreas Dingler.
Whether it is a winter or summer test, there must be two test periods in each case. Dingler elucidates: “The first time, we gain insights, then develop the concept further and verify the result the second time.” That is why an eCitaro takes a bit longer than other buses to be ready – but the results speak for themselves. The bad surface trial alone on the group’s own test route in Wörth near Karlsruhe allows the test engineers to ultimately assume a certain relentless character. A few thousand kilometres there equate to a vehicle’s entire life. An acid test in fast-forward mode.
Finally, the eCitaro and a Citaro with a diesel engine even drove on a racetrack for an acceleration duel. It was not about getting the fastest time, but about reducing the starting torque of the eCitaro to the level of the diesel drive – the passengers will be grateful.
All in all, the Daimler Buses test engineers grilled a dozen eCitaros. Added to this were numerous individual tests on components. Andreas Dingler therefore stresses once more: “We tested the eCitaro according to just equally strict criteria as the Citaro with a combustion engine. It reached Citaro level.” And hence, the road is open to serial production and operation at transport companies. Everywhere between Rovaniemi in the Arctic Circle and Granada in Spain.
