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> This is an older article but explains it well https://www.greencarcongress.com/2017/06/20170602-audi.html https://www.greencarcongress.com/2017/06/20170602-a

by grecy 3y ago

> This is an older article but explains it well https://www.greencarcongress.com/2017/06/20170602-audi.html https://www.greencarcongress.com/2017/06/20170602-audi.html From the article: > The 12-volt system is connected to the main electrical system via a DC/DC converter > Audi also offers the new MHEV technology with the conventional 12-volt electrical system > 48-volt vehicle electrical system. In a different layout—without MHEV—the 48-volt constant voltage system already entered volume production in 2016 as the Audi SQ7 TDI. In this vehicle, the alternator still operates on a 12-volt basis, and a DC converter couples the 48-volt electrical subsystem > Small consumers such as control units or lights will remain in the 12-volt system well into the future, however The article makes it very clear that what Audi are doing is not similar to what Tesla have done with the Cybertruck. The Cybertruck has no 12v system, everything runs on 48v. The power seats. The seat heaters. The rear defroster, the interior lights, literally everything. They can have much smaller and lighter wires and use way less copper. Using a 48V system for a mild hybrid is very common, even Jeep do that.

maxerickson 3y ago
Realistically, using 12 volt and 48 volt for accessory systems are pretty similar. 48 volts just reduces your current, and you have to design everything for ~56 volts instead of ~14. But it's not really a different exercise.
- grecy 3y ago
  > 48 volts just reduces your current "Just" is doing an awful lot of work in that sentence. Yes, moving from 12v to 48v reduces the current. That means you can have much smaller gauge wires, it means you lose a lot less power ( powerloss = (II)R ), it means you use a lot less copper and it means you save a lot of weight on wiring and connectors. That is literally the point.
  - deleted 3y ago
    [deleted]
  - maxerickson 3y ago
    Right, the reason to do it is obvious and the development work is straightforward, it's a step forward but it isn't something to get all breathless about.
    - grecy 3y ago
      Absolutely, Elon said that himself in the recent Munroe interview. It is just bringing car wiring into the 21st century.
Moto7451 3y ago
At least in the case of Audi it is more than just the starter used for the mild hybrid depending on market and configuration. On my generation/configuration of car it is also used to prespin the Turbo to avoid lag, it powers the active magnetic suspension, the AC compressor, and the power steering pump (annoyingly located between the feet of the driver and the seat where you can feel it when it runs). While you’re right on the accessories voltage, In other comments I’ve made the point that I’m not trying to say anything about the merits of 48v accessories. Jim Farley and Elon’s bromance aside, the tech exists within car companies. It’s nice they shared but it’s not like NACS where a real issue is being solved. Problems of driving aren’t solved with 48v interior lights. Supply lines are a real challenge and why my Audi still has 12v heated seats despite having a 48v system available. The head unit is 12v. I’m guessing the speaker amp is 12v even though 48v would make that less challenging. They have a 12v only model that shares parts and they apparently didn’t want to move everything to 48.
- grecy 3y ago
  Sure, they use the 48v mild hybrid system to act like the ICE when the ice is not running to power some things that would be on the serpentine belt and need to keep spinning when the ICE is off. It's a slightly more fancy engine start/stop system. > the tech exists within car companies Of course. Elon said very clearly in the sandy munroe interview the move to 48v everything is nothing revolutionary, its just bringing vehicle wiring into the 21st century. Anyone could have done it, they just have not been able to pull it off before now. > They have a 12v only model that shares parts and they apparently didn’t want to move everything to 48. They couldn't move everything to 48v because their suppliers dictate what they can do, and that prevented them.

by grecy 3y ago

maxerickson 3y ago

Realistically, using 12 volt and 48 volt for accessory systems are pretty similar. 48 volts just reduces your current, and you have to design everything for ~56 volts instead of ~14. But it's not really a different exercise.

grecy 3y ago
> 48 volts just reduces your current "Just" is doing an awful lot of work in that sentence. Yes, moving from 12v to 48v reduces the current. That means you can have much smaller gauge wires, it means you lose a lot less power ( powerloss = (II)R ), it means you use a lot less copper and it means you save a lot of weight on wiring and connectors. That is literally the point.
- deleted 3y ago
  [deleted]
- maxerickson 3y ago
  Right, the reason to do it is obvious and the development work is straightforward, it's a step forward but it isn't something to get all breathless about.
  - grecy 3y ago
    Absolutely, Elon said that himself in the recent Munroe interview. It is just bringing car wiring into the 21st century.

Moto7451 3y ago

At least in the case of Audi it is more than just the starter used for the mild hybrid depending on market and configuration. On my generation/configuration of car it is also used to prespin the Turbo to avoid lag, it powers the active magnetic suspension, the AC compressor, and the power steering pump (annoyingly located between the feet of the driver and the seat where you can feel it when it runs). While you’re right on the accessories voltage, In other comments I’ve made the point that I’m not trying to say anything about the merits of 48v accessories. Jim Farley and Elon’s bromance aside, the tech exists within car companies. It’s nice they shared but it’s not like NACS where a real issue is being solved. Problems of driving aren’t solved with 48v interior lights. Supply lines are a real challenge and why my Audi still has 12v heated seats despite having a 48v system available. The head unit is 12v. I’m guessing the speaker amp is 12v even though 48v would make that less challenging. They have a 12v only model that shares parts and they apparently didn’t want to move everything to 48.

grecy 3y ago
Sure, they use the 48v mild hybrid system to act like the ICE when the ice is not running to power some things that would be on the serpentine belt and need to keep spinning when the ICE is off. It's a slightly more fancy engine start/stop system. > the tech exists within car companies Of course. Elon said very clearly in the sandy munroe interview the move to 48v everything is nothing revolutionary, its just bringing vehicle wiring into the 21st century. Anyone could have done it, they just have not been able to pull it off before now. > They have a 12v only model that shares parts and they apparently didn’t want to move everything to 48. They couldn't move everything to 48v because their suppliers dictate what they can do, and that prevented them.