Endurance test in snow and ice: Electric trailer cooling under extreme conditions

Reading time: approx. 3 minutes
Text: Juliane Gringer
Photos: BPW

The ePower generator axle from BPW generates energy while the trailer is moving. The first refrigeration companies are already using the solution to operate the diesel unit of the refrigeration machine in the trailer without emissions. Before going into real operation, ePower was subjected to the endurance test during test drives in Spain and Sweden under extreme temperature conditions. Celine Piepenbrink and Eike Goergen from the project team tell us what the axle had to withstand.

They went to Spain in the summer of 2022 with a refrigerated trailer equipped with ePower ,and then to Sweden in the winter.
Why these two regions?

Piepenbrink: These are typical areas for automotive testing because of the extreme weather conditions. In Spain we were in Sierra Nevada, where it is very hot and dry in summer. In Sweden, in addition to the very low temperatures of down to minus 20 degree Celsius at night, there is also snow and ice in the Arctic Circle, which affect the trailer when driving. There, grit is also used rather than salt. So we look at how our components withstand these extreme conditions. The interplay of all influences is exciting for us – this can hardly be reproduced in the lab.

What do the extremes say about normal operation?

Goergen: The system must function properly under all climatic conditions. Not all forwarding agents drive in temperate climates. The hardware is less sensitive. But we have also developed our own intelligent software control system that has to run flawlessly under extreme conditions. Electronic components are usually more vulnerable in this regard.

Celine Piepenbrink
Eike Goergen
How is such a test planned and implemented?

Goergen: It starts around two years in advance with the testing of individual components and subsystems such as software, electronics or mechanics. This is followed by an examination of the entire system in the vehicle. Due to the good preparatory work, no big surprises are to be expected at this point, but we can still refine details.

Piepenbrink: In the preparatory phase, we determine what exactly is to be examined on site. Then we select the sensor technology that is necessary to monitor the respective components. We decide which routes we drive, how long for and with what load. And last but not least, everything had to be organised for the team on site: from overnight accommodations to a local one Commercial Vehicle –Workshop, that it can be driven to store the vehicle and, if necessary, convert it.

Two colleagues were on site with the vehicles, but their team is larger. What do those who stay at the company headquarters in Wiehl do?

Goergen: I was part of Team Wiehl. Thanks to the built-in Telematics from idem telematics, we were able to view the data collected here by the vehicles in real time and see directly whether challenges were looming or the vehicle was simply running smoothly. This short connection to the countries was really worth its weight in gold: The fact that we were able to be there virtually live helped us a lot.

Piepenbrink: I was in Sweden myself and can say: Of course, small stumbling blocks occurred at first, but we were able to fix them directly, for example by revising the software accordingly. This allowed us to test the improvements again immediately afterwards. I experienced a really goof interaction with the remote team: We were always able to act and didn’t have long downtimes.

Goergen: The good preparation paid off, just like the data connection.

What does serious cold like in Sweden do to battery-powered technology on the vehicle?

Goergen: Longer standing times in extreme cold promote discharge. In the test, we focused on the fact that the customer can always operate his refrigerating machine. Variables such as battery capacity play a role here, but our recuperation strategy is also very important: We must always supply the exact amount on energy needed by the system, including the refrigerating machine, at the right time. And it’s not just the battery that needs to be charged – meanwhile, the refrigeration machine also needs to be charged. It became clear to us that the strategies we developed with Thermo King them are very good. The customer can choose what power he needs depending on the energy demand, the refrigerating machine and the battery charge level.

In Sweden, the refrigerating machine even had to be run in heating mode. Because it was so cold outside?

Piepenbrink: Yes, because the refrigerating machine reduces its output at low temperatures. But we wanted to challenge the system and see a higher performance. Therefore, it was necessary to do just the opposite: We heated the refrigerated case to temperatures of -20, 0 degrees and 15 degrees to deliberately provoke the battery as well as the generator. For example, we were able to observe what happens when cables, generators and the axle itself are loaded with snow and do not thaw. And we wanted to explore: If we demand a lot of power and the ice thaws, how does that work – and could the condensate be problematic? How warm does the generator become then? We varied the conditions within the extremes again: Cold generator, warm generator, hot generator. Then we could see if that had an effect on the whole system, on the Trailer-Axle or on the generators.

Goergen: In the tests, we run through scenarios that happen in everyday transportation: Then, for example, we drain the high-voltage battery, park the vehicle and charge it overnight – just as freight forwarders might do. Or we do ABS braking. They should be realistic use cases.

In your opinion, what do the tests say about ePower?

Goergen: In my view, the stability of the system proves that it is well-developed and ready. After successful trips in Spain and Sweden, we are currently testing the system along with our partner Thermo King and the TIP Group with refrigerated transport companies in the Netherlands. Thanks to ePower, they supply the supermarket chain Albert Heijn with refrigerated goods – emission-free. The series launch will take place later this year.


ePower is an axle module that generates energy while the trailer is moving in order to supply cooling units with electricity in a CO2-neutral and quiet manner during temperature-controlled transport. Two generators ensure double power and reliability. Intelligent energy management ensures that there are always enough battery reserves available for the cooling system – even on longer routes or in traffic jams. ePower is the basis for the latest generation of cooling units from thermo King. The overall systems of the two partners can avoid imminent driving bans and delivery restrictions, conserve resources and improve sustainability in the transport chain.

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