Copper continues to rev up usage in automotive wiring applications as additional electrical and electronic components are added to light vehicles, but other factors— moves to smaller-gauge wires and material substitution—are slowing the drive in terms of growth rates.
Overall, the amount of copper wiring in cars and light trucks has increased steadily over the past 15 years or so, especially in luxury vehicles, according to Bob Weed, president of original equipment manufacturing (OEM) markets at the New York-based Copper Development Association.
This is evidenced by the fact that the number of electrical circuits in the average large, high-end car, such as a Buick or a Cadillac, has doubled to about 2,600 in the past 10 years. Midsized vehicles and light trucks have seen similar growth, although perhaps not quite as pronounced, he said.
Kevin Krizman, assistant director of technology at the International Copper Association, also based in New York, estimated that the average light vehicle contains about 45 pounds of copper.
Weed estimated that copper wire accounts for 20 to 25 pounds of this total, although the copper wire content of a large luxury car—with loads of additional options—is as much as 30 to 40 pounds.
In an average vehicle powered by an internal combustion engine, the thick wire cable running from the battery to the alternator accounts for about 25 percent of the copper wire content while the medium-sized power and signal wires that power various components account for another 25 to 35 percent according to Krizman's estimates. The balance comes in the form of smaller wires that are used to power various other accessories, including "infotainment" systems.
The wire harness is one of the most complicated components in light vehicles. It is divided into the engine harness, which typically accounts for the largest portion of vehicle wiring; and the interior harness, which typically uses smaller-diameter wires because of lower power or data transmission requirements, Krizman said.
The demands on the wiring harness continue to grow with the increasingly complex electrical and electronic needs, he said. Among these are starter motors, lights, defrosters, engine management computers, actuators (such as fuel injectors and brake controls), exhaust sensors, braking and suspension electronics (such as antilock brakes), service diagnostics, interior lights, power mirrors, power windows, power seats, heating and air conditioning fans, air conditioning compressors, radio, DVD players, navigation systems and more.
In an effort to make vehicles more energy efficient, a number of recent improvements/additions have been made. These include electronic control of such components as fans, water pumps and power belts vs. the more typical belt-driven method, which uses more fuel.
Infotainment "gadgets"—navigation systems, satellite TVs and radios, and DVD players, many of which are either installed later or are portable, standalone units—are quite popular, although sales have reached a saturation point and are now declining slightly, according to a Consumer Electronics Association spokesman.
Whether these devices are actually installed or not, their popularity is a plus for copper wiring, the spokesman said, as most vehicles now have auxiliary jacks to keep these "anywhere" electronics charged while on the move.
"People aren't satisfied with just one outlet to the electrical system—traditionally the cigarette lighter—anymore," Weed said. "On average they want to have three or four outlets to plug their electronics into."
There is also more "intelligence" being built into the circuits that enable the control of when and how these devices can be used. Just how much this is occurring, however, is based on what consumers want and what they are willing to tolerate, Weed said. "There is a delicate balance. We can offer features that keep them safe, but consumers want to remain in control. If they hate what the automakers offer them, it won't work."
There is some threat of substitution, especially as part of a broader push to reduce vehicle weight to make them more fuel efficient as well as save costs. Some of the larger wires and cables, for example, have been switched to aluminum products, although the smaller wires haven't seen much substitution—at least not yet, Weed said.
"Aluminum has half the conductivity of copper but about a third of its weight," Krizman said, adding that aluminum also has other disadvantages, such as corrosiveness, higher fatigue cracking and a higher coefficient of expansion.
But copper still has an advantage where space is an issue, as thicker aluminum wires are needed to achieve the same conductivity as copper, Weed said.
Copper wire itself is being used in thinner and thinner gauges, resulting in a reduction in the amount of copper per wire length. However, it enables more wire to be used, so it actually results in an overall increase in copper consumption.
"We are seeing about an 8- to 10-percent increase in copper wire and connectors used in automotive applications each year, but the rate of increase would be greater if the gauge wasn't being downsized," Weed said.
"The prognosis for the use of copper in automotive wiring applications is still very good," he said. "The copper industry is working diligently to produce a product at the right price that does the right job. One good thing is that the underlying demand is increasing. That means we don't have to fight substitution and downsizing in a decreasing market."