Electric cars: Good thermal management increases range by one fifth

An optimized thermal management promises significant development potential in the development of electric vehicles. At an outside temperature of seven degrees Celsius, up to 20 percent more range can be achieved by optimizing battery temperature control and interior air conditioning. This was reported by the supplier Mahle, which includes the radiator manufacturer Behr, at a press conference held on May 16, 2023, in the climate wind tunnel.

It was no coincidence that a Hyundai Kona Electric of the latest generation was exhibited behind the speakers' lectern, as the developers had identified this range potential in it. In their climate wind tunnel, they can determine through autonomously driven test cycles how the individual components react at temperatures from minus 30 to plus 50 degrees Celsius and at humidity levels between 5 and 95 percent, and where the energy flow is not yet optimal. "We have not yet tested an electric vehicle in our climate wind tunnel where we couldn't suggest improvements to the manufacturer," explained Dr.-Ing. Uli Christian Blessing, Head of Global Development Thermal Management. "Sometimes it is small things like the bending angle of hoses which can be changed within one or two years even in the current series, while fundamentally wrong system architectures can only be improved in the long term. An appropriate heating and cooling performance must be provided in the vehicle; otherwise, there isn't much you can do afterward."

Mahle has now combined the components of its thermal management into modules, initially distributed throughout the vehicle. The heart of these components includes an electric air conditioning compressor in the heat pump, a high-voltage auxiliary heater, cooling plates for temperature control, and self-made fans. A combined thermal module for the heating and cooling circuit is today's standard technology. If, among other things, the heat exchanger, the coolant pump, and the inverter are integrated into one unit, this saves installation space in the vehicle and reduces assembly effort for the vehicle manufacturer. Nevertheless, individual modules of the integrated unit can also be replaced in case of damage.

"The centerpiece and driver for further development is the battery cooling system, which is why battery cooling plates are currently among our bestsellers," explained Blessing. "For example, the fan must quickly dissipate the waste heat generated during fast charging and be quiet when charging at home, which is why we continuously optimize it aerodynamically." Another important component is the high-voltage auxiliary heater, which is needed at very low temperatures where the heat pump only works slowly. Therefore, Mahle develops powerful auxiliary heaters itself.

Important: The very low power consumption when "fast charging" with direct current at low outside temperatures in some current models such as the Toyota Bz4X could also be improved through better heat dissipation from the battery. One could then charge significantly faster with higher power over a longer period without compromising the durability of the battery.

Frightening Charging Curves

During their tests in the climate wind tunnel, the developers often observed "very frightening" charging curves. It was quietly mentioned that the Toyota Bz4X is likely one of the worst "benchmarks" and that the Korean brands Hyundai and Kia are quite good—incidentally, like 10 to 15 Chinese manufacturers whom no one wanted to name. Apparently, there is still considerable development potential in Volkswagen models, while Audi should take a more intensive approach to thermal management in its electric vehicles. Mahle had not yet tested the Volvo XC40 Recharge Pure Electric and Mercedes-Benz eVito Tourer or EQV electric models offered as taxis and rental cars in the climate wind tunnel.

The technology shift to replace the refrigerants previously used, which contain the PFAS group of substances facing an EU-wide ban, is imminent. So far, the commonly used refrigerant has mainly been R1234yf, which is also used in combustion engines, although this varies from manufacturer to manufacturer. The future could belong to refrigerants R 290 (propane) or R 744 (carbon dioxide). However, both require different working pressures than today.

The developers are also already considering surface heating. Today, as per good old tradition, the interior air is still heated over glowing wires. Therefore, the engineers are focusing on the efficient management of interior air. Unlike supplied outside air, it does not always need to be reheated.

Largest Business Field at the Supplier

At Mahle, more than 20,000 employees worldwide work on thermal management in the drive and climate technology sectors at approximately 50 locations. Representing 30 percent of the company's revenue, it is the largest business field of the supplier. This was stated by Jumana Al-Sibai, who is a member of the company's executive board responsible for this business area. She described thermal management as the driver of electrification at Mahle, because its revenue potential in electric vehicles is three times higher than in models with combustion engines.