Temperature control of Batteries

04. August 2020 DRÄXLMAIER ensures efficient thermal management

The number of electrically-powered vehicles on the roads across the globe is increasing. Changing from an internal combustion engine vehicle to an E-car should be as easy as possible for anyone who decides to do so. It requires long ranges, fast charging and powerful performance as well as long service life. In order to fulfill these requirements effectively, correct temperature control of the high-voltage batteries is essential.

Great diversity
And that‘s easier said than done. The wide variety of drive types and the lack of a battery cell standard results in a great diversity of cooling systems. Thus, effective thermal management plays an even more significant role in E-mobility.

Impact on the energy footprint
The fundamental theorem of thermodynamics also applies to the thermal behavior of batteries: The sum of all energies in a closed system is constant. In addition to self-heating, the environment and the transport of energy to a heat sink have an influence on the energy balance of batteries. Special attention must be paid to temperature differences between the coldest and warmest cell. Even minor differences in the internal resistance can cause various distributions of electricity, depending on the interconnection and the cell type. This in turn affects the cyclical aging of the battery cells that is based on usage, and with that, the service life of the battery.

Types of battery cooling
Batteries can be cooled in various ways. There are active and passive cooling systems that depend on the battery type. With the latter, the cells are cooled only by heat conduction, radiation or natural convection. In purely electric vehicles, stationary cooling of six to eight kilowatts must be assumed for the sporty driving mode. Simple passive cooling is generally not sufficient for this purpose. Active cooling, on the other hand, relies on forced convection, in which the heat energy produced is transferred to a heat sink via a medium. Solutions that work with coolants and a heat exchanger are particularly powerful and are therefore frequently used for the temperature control of high-voltage storage tanks.

Coolant considerations
When choosing the ideal coolant, there are numerous advantages and disadvantages that have to be considered. Directly cooled systems currently have the best cooling power but also need larger quantities of coolant than indirectly cooled ones. Systems cooled by refrigerants, on the other hand, can attain lower temperatures. However, in that case, the cell can‘t be heated by the medium. Moreover, things like weight, crash requirements, installation space and adaption to each cell type are an issue.

Simultaneous Engineering
All in all, it is important to analyze not only the battery, but all the heat sources in the vehicle.  This holistic approach also includes parts like high-voltage switchboxes or cables and connectors. It is worthwhile here to evaluate permanent, dynamic loads and simulate them beforehand. Simultaneous Engineering can increase efficiency in vehicle projects, as that will help to avoid unnecessary change loops.

General information

About
DRÄXLMAIER Group

The DRÄXLMAIER Group supplies premium automobile manufacturers worldwide with complex wiring harness systems, central electrical and electronic components, exclusive interiors, and battery systems for electromobility. The combination of core competencies in the interior, electrical, electronic and battery systems areas makes DRÄXLMAIER unique in the industry. The company thereby covers the entire process chain, from the initial idea, through the development and production process, and up to precisely in-sequence delivery of the products to the assembly lines of premium automobile manufacturers. The inventor of the customer-specific wiring harness, the DRÄXLMAIER Group develops pioneering wiring harness technology as well as electrical and electronic components, all directly in-house. These include multi-voltage and high-voltage wiring harness systems, battery management systems and intelligent power distributors. DRÄXLMAIER is working on the future of emission-free mobility with its solution for low-voltage and high-voltage battery systems. As a market leader for interior systems in premium automobiles, the DRÄXLMAIER Group also supplies premium automobile manufacturers with ambient lighting, center consoles, door panels and instrument panels, as well as complete door and cockpit modules.  

The DRÄXLMAIER Group is an international automotive supplier with more than 60 sites in over 20 countries. Founded in Germany in 1958, the company employs more than 75,000 employees throughout the world. For the DRÄXLMAIER Group as an owner-managed business, responsible and long-range thinking has always been the basis for economic success. It is therefore a core element of its strategy to design its business and production processes, as well as its products, in a more sustainable manner and in that way to increase the competitiveness of the company on a long-term basis.

In 2019, the DRÄXLMAIER Group generated sales of 4.9 billion euro. Customers of this member of the Top 100 Automotive Suppliers include Audi, BMW, Jaguar, Land Rover, Maserati, Mercedes-Benz, MINI, Porsche and Volkswagen, as well as Californian automotive manufacturers.