500 test kilometres on ice and snow, double-digit minus temperatures, extreme conditions without compromise: in February 2026, the Mercedes-Benz eCitaro with the new NMC4 battery technology confronted the polar cold in Rovaniemi, Finland. The results of the winter tests are worth listening to.
Magazine
NMC4 batteries: hot performance in freezing cold.
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The new battery generation in the extreme winter test on the Finnish Arctic Circle.
Hardness test at the polar circle.
If cold needed a name - Rovaniemi would be a good choice. The capital of the Finnish landscape, Lapland, is located on the Arctic Circle. Five months a year, the temperatures here remain constantly below freezing point. Tough conditions for an electric bus - batteries are known to be sensitive to cold. Reason enough for Daimler Buses to carry out intensive winter testing of the latest generation of nickel-manganese-cobalt (NMC) batteries in the Mercedes-Benz eCitaro: Components that have proven themselves here are suitable for winter operations all over Europe.
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Hardness test for bus and battery at outside temperatures of up to minus 20 degrees on the Finnish Arctic Circle.
Hardness test for bus and battery at outside temperatures of up to minus 20 degrees on the Finnish Arctic Circle.
Hardness test for bus and battery at outside temperatures of up to minus 20 degrees on the Finnish Arctic Circle.
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500 kilometres on ice and snow.
For the winter testing of the Mercedes-Benz eCitaro G articulated bus equipped with five battery packs, the Daimler Buses team had selected a typical city bus route in Rovaniemi. The test bus covered more than 500 kilometres at continuous double-digit minus temperatures. Every trip was accompanied by a dense network of sensors. Outside and inside temperature, cell temperatures, current consumption, state of charge - all relevant variables were included in the evaluation. The focus was less on consumption than on the performance of the batteries under constant cold conditions. After all, the drive control system must reliably bring all components together, and the weakest link sets the pace.
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The test engineers monitor the performance of the NMC4 battery while driving and during charging stops in icy cold.
The test engineers monitor the performance of the NMC4 battery while driving and during charging stops in icy cold.
The test engineers monitor the performance of the NMC4 battery while driving and during charging stops in icy cold.
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Door openings at every stop made thermal management extremely demanding. Snow and ice-covered roadways caused slippage during every driving-off procedure and every brake application, putting to the test not only the test crew, but also the electronic drive control, the anti-jackknifing protection ATC (Articulation Turntable Controller), the ABS and, last but not least, the high-voltage system control. But despite these extremely adverse conditions, the NMC4 batteries did not show any weaknesses. Even with a low state of charge (SoC) at the end of a long test day, it was possible to call up the full mileage.
Philipp Litzinger, Vehicle Testing Engineer, Daimler Buses
The performance of the high-voltage batteries after a night at minus 30 degrees was incredibly good.
Philipp Litzinger, Vehicle Testing Engineer, Daimler Buses
Confident cold start at minus 30 degrees.
But the toughest test still had to follow: a night in the cold room. How do the batteries work at minus 30 degrees Celsius outside temperature, at minus 20 degrees at cell level? Are there any limitations to performance? The cold start the next morning should show this. No heating, no preconditioning, no compromises. “The performance of the high-voltage batteries at minus 30 degrees was incredibly good,” says test engineer Philipp Litzinger. "The vehicle was immediately ready for use. We accelerated to 60 to 70 km/h without any noticeable reduction in power." The NMC4 battery kept the voltage stable and quickly reached operating temperature. Even the power consumption in the event of recuperation was mastered by the high-voltage batteries completely unnoticeably at these temperatures.
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Snow, ice, minus temperatures: no problem for the Mercedes-Benz eCtiaro G and the NMC4 battery.
Snow, ice, minus temperatures: no problem for the Mercedes-Benz eCtiaro G and the NMC4 battery.
Snow, ice, minus temperatures: no problem for the Mercedes-Benz eCtiaro G and the NMC4 battery.
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From the factory to the Arctic Circle.
The test programme already included the arrival and departure from Mannheim via Sweden to northern Finland. The eCitaro G covered most of the route on its own - a further 3,000 kilometres of data material. Test engineer Philipp Litzinger is completely satisfied with the results of the winter testing under extreme conditions: “The new NMC4 batteries have impressively proven that they can also be used without restrictions at polar temperatures.”