Mercedes-Benz eCitaro fuel cell defies extreme cold and steep passes
The first electric bus in which a fuel cell system extends the range has just undergone one of a range of tests and passed with flying colours: after a night at temperatures far below freezing, the electric drive system and fuel cell started up smoothly.
At the beginning of 2023, a team of Mercedes-Benz test engineers went to the Alps with the eCitaro fuel cell in order to test its cold-starting behaviour in winter temperatures and to try out the newly developed thermal management system. At the same time, the runs at elevations of more than 1700 metres above sea level were intended to provide insights into the function of the fuel cell system at extreme altitudes. The new drive system also had to prove its performance on demanding mountain pass runs with uphill and downhill gradients of as much as 15 percent. Last but not least, the energy consumption was of great interest in these challenging conditions.
On the road with the e-bus test team
“During the journey, test engineers constantly monitored countless measuring points and data,” explained test manager Jonas Steinki. Besides the temperatures of the battery, fuel cell, engines and passenger compartment, these also include the energy consumption of the drive, the heating and other auxiliary consumers, the charge level of the batteries and the fill level of the hydrogen tanks. Test engineers Rainer Bickel, Stephan Lutz and Hannes Mayer continuously checked the most important parameters of the fuel cell system, drive, thermal management and heating on their monitors, looking for anomalies and comparing the data with the calculated target values.
The test run that lasted several days, started with crossing the Alps from Neu-Ulm via Füssen, the Fern pass and the Reschen pass to Bolzano. The combination of battery and hydrogen was designed to be able to cover the 360-kilometre route. Nevertheless, was is difficult to estimate how the energy consumption would develop on the long and steep passes at temperatures below freezing. To err on the side of caution, the team decided to partially recharge the high-voltage batteries at the Allgäuer Tor service station.
Good energy balance thanks to thermal management and high recuperation
On the way across the Fern pass, it soon became clear that the eCitaro fuel cell was capable of dealing with the demanding route even better than expected. “Despite the gradient, the fuel cell operated within the most efficient power range of 20 to 30 kW,” explained Rainer Bickel, pointing to the corresponding value on the monitor. “What’s more, the new thermal management reuses the waste heat from the fuel cell to control the interior temperature. The electric heating is therefore hardly used so that the overall energy consumption of all the auxiliary units, such as heating, steering and compressor, remains at a very low level.”
