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> You don't want alluminium wires in your car Why not? I^2*r says that running 75% less current will generate 94% less heat. Existing copper wires would be a
by brookst 4y ago
> You don't want alluminium wires in your car
Why not? I^2*r says that running 75% less current will generate 94% less heat.
Existing copper wires would be a disaster if cars ran on a 3V system. Aluminum at 48V will be fine, as long as it’s sized appropriately the same way copper is today.
- KaiserPro 4y ago> Why not? I^2*r says that running 75% less current will generate 94% less heat. Thats not the argument, you can do that now with copper cables. Aluminium is a good conductor, but it is reactive, brittle and not as malleable as copper. also, copper has almost half the resistance per meter than aluminium. So even for solid bus bars, it doesn't make that much sense, unless you have structural bus bars.
- eimrine 4y ago> copper has almost half the resistance per meter than aluminium. But 4 times the weight
- brookst 4y agoMost car wiring harnesses are affixed to structural members and don’t need to flex. And twice the resistance doesn’t matter. So you go one gauge bigger. If the material is cheaper, more available, and suitable, that’s fine. We don’t insist on gold wires because they’re “better” than copper. It’s all tradeoffs. I don’t see a reason to be philosophically opposed to aluminum other than “it’s possible to do it wrong”, which is of course also true for copper.
- KaiserPro 4y ago> cheaper, more available, and suitable Indeed, but automotive wiring is subject to intense and persistent vibration and heat cycles. so all those ties become stress points for fatigue to cluster around. I'm not saying its never a good idea to use an aluminium wire loom, but I'm struggling to find a situation where its required
- schiffern 4y agoIt's not really the flexible thing you picture with the word "loom." The place Tesla used this was for fixed rigid bus bars, notably the "cable" from the charge port to the battery.[0] Previously they used traditional stranded copper. Now it's a solid aluminum conductor, wrapped in insulation and protected by an outer aluminum tube. These are thick high voltage conductors. I'm sure Tesla did their homework on flex and fatigue. As for resistance, this is why I mentioned conductivity-to-weight as being the critical metric. Copper is over 3x as dense, at 9.0 g/cm³ vs 2.7 g/cm³ for aluminum. It doesn't hurt that aluminum is cheaper and more abundant. [0] https://m.youtube.com/watch?v=hY9cxyvUu6I&t=1115s https://m.youtube.com/watch?v=hY9cxyvUu6I&t=1115s
- deleted 4y ago[deleted]
- cptskippy 4y agoThe switch to 48v is for the low voltage which is normally 12v. The high voltage system is the 300v from the pack.
- albrewer 4y agoAluminum is really easy to fatigue and fracture. In a car that is vibrating and jostling all the time, this could happen surprisingly quickly.
- dv_dt 4y agoAirplanes flying for decades are made of aluminum.
- albrewer 4y agoComparing car design and operating conditions to that of airplanes is kind of silly. The operating conditions of aircraft are far better defined and restricted. Additionally, aircraft airframes are regularly inspected and fully radiographed at certain intervals. Components that develop flaws are changed out when the flaws are detected. The same is not true of cars.
- Snoozus 4y agoTheir cables?
- schiffern 4y agoTesla isn't using aluminum "cables" either. They use the material for large rigid bus bars. https://news.ycombinator.com/item?id=35014013 https://news.ycombinator.com/item?id=35014013