Some friends of mine actuallybuilt out an electrical vehicle some years back and in the process gained a lotof knowhow. One tidbit was that thecable harness made from copper grabbed sixty pounds of weight right away. Thus an EV does need to shed as much copperas possible. Aluminum is an obviousalternative. It is also likely to beeasy to make safe in an automobile which was its problem in house wiring inwhich long term creep caused increasing resistance and failure.
I suspect that EVs will use aluminumextensively for the heavy duty current load once the manufacturers get used todoing so.
I also suspect that good designwill minimize even that quite easily.
Aluminum to replace copper as a conductor in on-board power systems
February 7, 2011
This CAD drawing shows an innovative electrical connector based onaluminum conductors instead of copper. It's part of a project to removeobstacles to using this lighter, less expensive material in electric cars andother vehicles. Credit: Copyright TU Muenchen
Electric power and electronics are playing an ever-increasing role inall kinds of vehicles. Currently copper is the conductive material of choice.But in comparison to aluminum copper is heavy and expensive. In particular forfully electric vehicles the switch to the cheaper and lighter aluminum would bean interesting option. That is why the optimization of intricate power supplynetworks is now in the focus of engineering research. Scientists from theTechnische Universitaet Muenchen (TUM, Germany
At first glance it is not at all clear why copper is still used as conductor in modernelectric or semi-electric vehicles – when aluminum is lighter and significantlyless costly. However, before aluminum can replace copper inpower supply systems,a number of technological challenges need to be surmounted. When temperaturesare high – and there are many places in a car where that is the case – aluminumdisplays a distinct creep behavior. Conventional connectors could thus not beused, as they would become loose with time.
One possible alternative – the use of aluminum-based elements in cablesand copper-based elements in connection areas – also entails problems. Becausethere is a high electrochemical potential between a copper contact and analuminum cable, this kind of wiring would be very prone to corrosion. Besides,joining copper to aluminum is rather demanding with the current state oftechnology. In order to counteract the aforementioned difficulties, scientistsof the chairs for High Voltage Technology and Power Transmission and for MetalCasting and Forming, in cooperation with the respective departments of the BMWGroup, developed an innovative aluminum-based electrical connection concept inthe project LEIKO.
A sheet metal cage, which is an electromagnetic compatibilityrequirement anyway, enhances the mechanical stability of the plug andguarantees the long-term support of the contact pressure spring. Because thenecessary contact force is no longer provided by the contact elementsthemselves, the originally problematic creep behavior of aluminum turns into acontact stabilizing, and thus, positive property. This, in turn, alsoguarantees a constant contact force over a lifetime of ten years.
To this end the researchers came up with a special wedge-shapedgeometry for the aluminum contacts. The aluminum creep now leads to the twocontacts snuggling closer and closer together over time, thereby rendering theelectrical connection better yet. Moreover, the consistent use of aluminumalloys and the ingenious application of precious metal plating made it possibleto relocate the formation of corrosion-prone local elements to less criticallocations in the system.
A further problem with substituting aluminum for copper is its lowerelectrical conductivity. In the case of high-power on-board systems inparticular, the cable cross-sections, which are about 60 per cent larger, needto be taken into account in the construction of cable ducts and feed-throughs.One positive thing the scientists discovered was that because aluminum is verypliable, the standard values from copper cable processing, where bending radiiare set based on the diameter, could also be used for aluminum.
In order to determine the long-term behavior of the coated aluminumcontacts under even the rough conditions typical for motorized vehicles, theproject partners, together with leading suppliers, have successfully initiateda further research project. Funded by the Bavarian Research Foundation (BFS),this project will deliver evidence on the aging behavior and thus thesuitability of the concept by 2012.
Initial results indicate that the material substitution will lead tosignificant improvements in weight, cost, and ultimately emissions. "Weexpect the high-voltage on-board systems of most electric vehicles tobe based on aluminum by 2020. Aluminum will find its way into low-voltageon-board systems as well, because the price of copper will rise significantlywith increasing demand," says Professor Udo Lindemann from the Instituteof Product Development at the TU Muenchen.
The project finds its theoretical counterpart in the Collaborative Research Center
Another aspect of the research conducted within SFB 768 is a studentproject to develop an electrically driven go-cart. In order to experience themanifold challenges of innovation management first-hand, the students startedwith a standard base structure and went through the entire development processfor all subsystems of the vehicle. The results of the LEIKO project are alsointegrated into the student project – the entire high-voltage on-board systemis implemented in aluminum.
The results are to be incorporated in the TUM electro vehicle MUTE,which will be presented at the IAA 2011.
More information: Langer, S.; Lindemann, U.: Managing Cycles inDevelopment Processes - Analysis and Classification of External ContextFactors, in 17th International Conference on Engineering Design, M. N.Bergendahl, M. Grimheden, and L. Leifer, Eds. Stanford University , California , USA
Provided by Technische Universitaet Muenchen
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