1. Automotive Wiring – The Evolution from Copper to Aluminum
Traditionally, copper has served as the primary material for wiring of all types, from home wiring to
automotive wiring. This is due to several factors. First, copper offers high conductivity with little
resistance. In fact, the only material that offers better conductivity than copper is silver, which is
certainly not an affordable solution for wiring needs. Copper also offers decent length of life, though
there can be corrosion problems when copper wiring is exposed to the atmosphere.
However, copper is being phased out in automotive electrical systems, particularly in wiring harness
applications and especially for hybrid vehicles. Aluminum is the metal that is replacing copper. There
are a number of reasons for this shift, as well.
Benefits of Aluminum over Copper Automotive Cables
The first and primary benefit of aluminum over copper is the fact that it is far lighter. Even in larger
gauge applications, aluminum is lighter than copper. This is an important consideration for wiring
harness applications with hybrid vehicles. Extraneous weight must be shed from all aspects of design
and production to eliminate unwanted problems and to bring hybrid and electric vehicles into
compliance with government regulations.
Because every ounce of additional weight on a hybrid car or truck affects fuel consumption and
battery life, lighter metals are optimum. The lighter the metal, the lighter the wiring harness and other
automotive cables will be. This translates to better fuel economy, better battery life and other benefits
for end consumers, as well as for the environment.
The second important benefit of aluminum over copper is the fact that aluminum is far more
affordable than copper. Once, copper was the most affordable metal on the planet, but that is no
longer true. Increased demand from emerging nations around the world (India and China,
predominantly), as well as reduced production from mining facilities on a global scale, have combined
to push the price of copper ever higher. Aluminum, which was actually considered a precious metal in
the past, has become more and more affordable as better mining and refining methods have been
developed.
In fact, the cost and weight factors for copper make it very difficult to understand why the metal
continues to be used for wiring harness applications and automotive cable needs. Overall, the use of
aluminum to replace copper automotive wire harness cables promises to offer lower weight, better
longevity, lower costs and reduced emissions from even hybrid vehicles, which are the lowest
emissions vehicles on the market, barring full-electrics.
The Problems with Aluminum
However, the situation is not as simple as it seems. Wire harness manufacturers cannot simply retool
their production lines to use aluminum rather than copper. There are hurdles to overcome here.
The most significant factor here is heat. In high-heat situations, which occur in numerous places in
the modern automobile, including hybrid vehicles, aluminum has the propensity to "creep." Because
of this, connections will not remain stable over time. As the aluminum automotive cables creep and
contract, eventually the connections will come loose. Therefore, the first hurdle to overcome is to
develop a connection method that will not come loose with aluminum "creep."
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2. One solution has been proposed here. That is, the use of aluminum elements for cabling and copper
elements used in connections has been offered. However, there is a problem with this situation, as
well. Copper and aluminum "do not get along well." That is, there is a very high electrochemical
potential between these two metals.
Therefore, if copper connections were used with aluminum cables, the resultant corrosion would
make the entire system ineffective. In addition, joining copper and aluminum is not a simple or
affordable process. As technology progresses, that may change, but the state of the manufacturing
industry today makes this very difficult.
However, there is an intelligent connection method in development. This has been develop by the
BMW Group, in conjunction with the High Voltage Technology and Power Transmission. In essence,
this is a connection concept that uses an aluminum electrical connection, codenamed LEIKO.
LEIKO is essentially a sheet metal cage that enhances the stability of the connection and helps
support the contact pressure spring, as well. This method allows the unwanted "creep" factor to
become a benefit, rather than a detriment. For instance, because the contact elements are not
responsible for holding the connection together in this scenario, the "creep" factor actually stabilizes
the contact. The lifetime of this connection method is expected to be about 10 years, and should
feature constant contact throughout the duration of its lifespan.
In fact, due to unique wedge-shaped connection elements, the connection actually becomes stronger
over time. This is because the "creep" factor actually brings the wedge-shaped elements into closer
and closer contact as high heat is applied. Further innovations including the use of precious metals
as a coating for connectors has resulted in significant advantages.
Of course, there is another problem with substituting aluminum for copper. That is, aluminum has a
lower conductivity rating than copper. Remember, copper is the second best metallic conductor after
silver. Aluminum is several ranks down the list from copper. To combat this lower conductivity,
aluminum automotive cables must be made thicker. The diameter of thickness for high-voltage wire
harness applications is actually about 60% greater than the equivalent copper wiring.
There is no concern here about increased weight, though, as even an aluminum wire with a 60%
greater diameter still weighs in at less than the original diameter copper cable. However, it does pose
a problem for automakers. The concern here is that due to the larger diameter, automakers will need
to manufacture wider openings, or pass-through areas, for automotive cables. Cable ducts would
also need to be larger to accommodate the larger diameter wiring in use.
Yet another factor is the limited knowledge of aluminum's aging behavior in the demanding
environment of an automobile. Current studies are underway, and should deliver results about aging
and the applicability of aluminum automotive cabling some time in 2012.
Finally, safety considerations for aluminum automotive cables must also be addressed. While the
metal has been used in applications for major automakers for decades (notably with General Motors),
there are still safety considerations for the widespread use of aluminum in high-voltage situations
within the passenger compartment. This is largely due to the possibility of fire in high-voltage
situations. Insulation and better technology and manufacturing processes can largely mitigate this
risk, but international safety standards must first be agreed upon and then implemented to make this
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3. application feasible. Certain manufacturers have made strides in creating single-core aluminum
automotive cables that are able to withstand high temperatures (up to 125 ° C).
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IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany
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Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de