The popularity of the Xiaomi SU7 has not diminished. Recently, the whole network has started a wave of "condemnation" against Xiaomi SU7 wires, which has aroused heated discussions among countless car friends. The reason is: through disassembly, it was found that Xiaomi SU7 actually used aluminum wires instead of traditional copper wires. As for Xiaomi, it responded that it was "needed to lose weight".
As a result, a big discussion began on "Xiaomi's abandonment of copper and aluminum selection, whether it is a tall black technology used to reduce weight, or simply to control costs". Because we noticed that there is no media on the Internet that can compare the reasons in detail, we decided to write a post to explain this matter well.
Copper conducts electricity very well
But aluminum can be made up for by being bold
Let's start with electrical conductivity. The top 4 metals with the best conductive properties in the world are: silver, copper, gold, and aluminum. The corresponding resistivity is 1.59/1.68/2.44/2.82 (-8 ohms in units of 10). It can be seen that the electrical conductivity of copper is about 96% of that of silver (although not as good as silver, but close), and the price is much cheaper than silver. Therefore, in general, copper is a very good wire material.
The conductivity of aluminum is about 1.68 times worse than that of copper, so if the copper wire and aluminum wire of the same thickness are used, obviously, the loss of aluminum wire is greater, and the problem of heat and heat is more serious. ——At this time, someone is about to say, then I make the cross-sectional area of the aluminum wire 1.68 times thicker, wouldn't it be able to make up for the gap in conductivity?
Aluminum wire focuses on lightweight
30% weight reduction with the same electrical conductivity
Of course, this calculation is not rigorous, but it can be roughly understood in this way. However, this leads to a new problem: after thickening, the advantage of light weight of aluminum wire will disappear?—— Actually, this advantage is still there! Because the density of copper is about 8.9 and aluminum is about 2.7, a difference of 3.3 times.
In other words, if the thickness (cross-sectional area) of aluminum wires is 3.3 times that of copper wires, then their weight is roughly the same. The aluminum wire only needs to achieve 1.68 times the cross-sectional area of the copper wire to offset the disadvantage of poor conductivity...... In this way, aluminum wire still has the advantage of light weight. Generally speaking, aluminum wires with the same conductivity are about 30% lighter than copper wires.
The cost of aluminum is much lower than that of copper
Not as flexible as copper
Of course, while choosing aluminum wires, in fact, enterprises choose low cost, after all, the current price of copper raw materials is 80,000 yuan per ton, and aluminum raw materials are less than 20,000 yuan. This cost gap,Anyone should be able to understand it?Several factors are combined,Finally, why Xiaomi SU7Why choose aluminum wires,In fact, it is clear。
In fact, at present, most OEMs use aluminum wire solutions, including Tesla. First of all, the flexibility of copper wire is much better than that of aluminum wire...... Copper has a ductility of about 30%, while aluminum has less than 20%, and the ductility represents the ability of the metal to break easily when it is deformed.
Aluminum wires are not resistant to aging
The stability and life are much lower than those of copper wires
Of course, once the wire is fixed in the car, it will basically not move much in this life, so the disadvantages of aluminum wires in this regard are naturally not obvious, so it is acceptable. So at this point, does it mean that aluminum wires don't seem to have any shortcomings? Of course not!
Copper wires are much more chemically stable than aluminum alloys. In the old houses of the 80s/90s of the last century, there were a lot of aluminum wires, and it was common for them to be oxidized and burned out (the author's old house in Xiangxi, Hunan, has retained some of the aluminum wires. And the copper wires in the city, this kind of problem is much less.
Nowadays most of the industrial products
The total life is pre-set
A Japanese car company, in order to improve the durability of copper wires, even adopted a tin plating process, which is even more "eternal...... In this regard, aluminum wires are indeed incomparable. But today's enterprises have not considered letting you "pass on three generations of one car, and people are still walking in the car", and the current industrial products are "pre-set total life". It is assumed that the ultimate life of the vehicle is controlled at 15 years.
This means that once the car reaches 15 years old, even if there is no problem with the aluminum wire, there will be problems in other places one after another. You fixed it, and in a few days it broke down somewhere else. Bottom line: When the time comes, it is recommended to scrap, so ...... You know.
But it's hard for us to say anything, after all, companies want to survive. Historically, there have been cases of companies going bankrupt because the product was too durable. Besides, now the state advocates "trade-in cars, old houses, and home appliances". You have to count on "one car for three generations, and people are still there"...... After all, people still point to us contributing to GDP.