Weight-reduced oil hoses for tempering batteries

Jon Lawson

ContiTech is developing solutions that increase the efficiency, and thus the range and durability, of the batteries in electric vehicles.

The latest development are hoselines for a customer for battery tempering using oil instead of the more common cooling water. This results in very new requirements for the hoses and hoselines used in e-vehicles.

At the same time, however, it opens up completely new opportunities.

The batteries in electric vehicles work at their most efficient at temperatures between 10 and 30°C. This temperature spectrum enables long ranges, extends battery life and allows the batteries to work more efficiently.

For that reason, the batteries have to be either cooled or heated, depending on the outside temperature.

Some manufacturers are now increasingly relying on oil as the relevant medium or are immersing batteries directly in the oil. The manufacturers expect a significant extension in range for their e-vehicles if an oil bath is used.

Up till now, tempering has largely been achieved by means of cooling water. Classic heating and cooling lines have carried the relevant media.

However, this system also brings risks with it: In the event of a leak, the battery could come into contact with the water which, in the worst-case scenario, could cause a short-circuit, resulting in total failure of the battery. Costly precautions still have to be taken to exclude this risk.

The situation is different with oil since it does not have any charge carriers and therefore does not conduct electricity. This even means that the battery can be completely immersed in oil. As a result of its insulating effect, therefore, it reduces the impact of outside temperature action and thus also the need for regulation.

One challenge faced by the hose developers was the specification to cut weight by up to 25% – while the requirements for under- and overpressure resistance were increased by 50% at the same time.

The tight bending radii in vehicle compartments with restricted space also had to be taken into account.

ContiTech addresses this by using special, harder compounds with reduced wall thicknesses at the same time so that the hoses do not lose the flexibility that is required in the tight package spaces.

On the other hand, the hoses for this application are not subject to the same high pressures as classic oil hoses. That allows the developers to contemplate the use of completely new materials.

After all, completely different requirements in terms of pressure, temperature and acoustics are applicable here.

The connecting systems represent another challenge since the developers cannot use the classic VDA connectors in the tight package spaces available in the electric vehicles. A new, significantly more compact solution therefore also had to be found here.

The search for new solutions is aided by the fact that the type of customer involved in the field of e-mobility is completely new. Specifications as usually encountered with the traditional vehicle manufacturers are generally a thing of the past here, replaced instead by a bold readiness to try something new.

These customers are looking for flexible suppliers who will develop the perfect solutions for and with them – generally before the series-production order is placed. Only a company with extensive material and development expertise and the willingness to think outside the box can deliver this upfront performance.