Cybertruck to use 48V instead of 12V?

PilotPete

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Thanks for the post and list.

There's actually a couple on there I have to add to mine....and made me think of Airbags as well:)

I think that patent video Cybergus posted confirmed enough of my assumptions so I could move on to another subject, but here goes a quick recap of my thought process so far.

BTW I'm interested in learning more about it, than just spewing a whole bunch of words, but I also often feel that many don't bother to explain in more detail what they mean to really engage, so I try to be better, which I agree at times can go the opposite way, especially if there is little to no feedback loop.

There might be some additional confusion if one perceives the argument to only be about changing to 48V from 12V as the thread title would suggest. In reality the "WHOLE" system architecture is changing, not just some of the voltages along the line, and these changes are more significant than the change to 48V by itself.

Anyhoo...back to the system architecture. Let me quote my response to Cybergus patent video first as a quick reminder:





1693360728374.png


Now I can imagine from a voltage perspective this distributed setup would have a 48V bus voltage between the distributed controllers, which I believe are all the red nodules on the drawing above, but possibly only the blue line in the drawing. Then at each controller, you could have a few buck converters with enough capacity, and the right voltage to handle the endpoint loads. This way you can aggregate the buck converters into larger more cost effective units together with the controller, which then acts as a distribution hub for the endpoints, and powers and controls them. In some cases those controllers could also have built in motor controllers as well to drive the smaller things, like fans, windows or seat motors, at any voltage that makes sense for them.

This architecture does a few notable things:
  1. It allows for a single high power cable to run as a bus at 48V along the full length of the vehicle. Which makes a worthwhile difference in cable dimensioning, in that it is long, and at 12V would need to be large to handle that amount of power. Probably in the 1-3kW range, unless they run the 110V inverter from it, in which case it would have to be 3x the size at that power level.
  2. It acts as a spine, in that no "long" and "heavy" low voltage cables have to run back to a single central point, rather only back to the nearest bus and controller, from where the endpoint can be supplied with the appropriate voltage. This reduces losses on lower voltages under 48V by shortening the wire length for those, and at the same time aggregates the buck/motor controllers so that having a 48V bus is worth it by running at a higher load.
  3. The controllers could be modular, in that you would possibly only need 1-3 different types, and could reuse them across the vehicle for different things. This would bring down the overall part count, without any loss of features.
  4. It allows the gradual replacement of non-optimised OEM parts with dedicated Tesla parts, and still offers the flexibility to run endpoints that might need a specific voltage that is less than 48V.
Note these are all answers to comments I made against running "everything only" on 48V, and I think the above solution to divide and conquer makes for a better architecture overall, in that it allows all the things to run on the voltages it needs too, without forcing everything to change to 48V.

Overall I'm pretty happy with that, as well as spending some time finding out how they are doing it, and discussing the matter, with future projects of my own in mind. I learnt something. :)
EM doesn’t do “one offs”. So I’m thinking about all the “traditional” 12v motors. Then I’m watching his discussion about Optimus. Made the comment that they had to custom make all the actuators. I wonder if all the actuators are 48v on Optimus. Could the development of those actuators be used on the CT? Don’t see why not. Same for the video and sound functions of the bot. If the CT is using 30X SS off the SpaceX contract, why not use actuators off the Optimus project.

Then I started thinking, is one of the goals of project Highland to move to a 48v architecture as well?
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CyberGus

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I wonder if all the actuators are 48v on Optimus. Could the development of those actuators be used on the CT?

I think giving Cybertruck the Optimus actuators is a bad idea

Tesla Cybertruck Cybertruck to use 48V instead of 12V? IMG_1997.JPG
 

Crissa

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You're a joker, but not worthy of rebuttal. You're sprouting nonsense again.
Enjoy your holiday... I know I did. ;)
So much nonsense that you still haven't named a single component that runs native on 12v.

You can make simpler circuits to change voltage down by half pretty easily. But if you do that with an automotive 12v circuit, your nominal is 6v with a peak of 7v normal and requirement for tolerances of higher.

But things that run on 5v don't want 6v. That'll start popping components. You can harden it a little, but it limits what components and chips you can use. It really wants no more than 5.5v.

By 'nonsense' you mean you have your preconceptions, and I have my experiences and willingness to look up datasheets. But you don't share that latter part. This is why I don't usually read your posts. They act informed, but they're not helpful.

And note, I never said there was no 12v in computers. I build computers. What I said was There's nothing remaining in computers that requires 12v. We no longer have spinning drives operating at 12v. We no longer have peripherals that draw 12v. Basically, only the fans use it.

Your response was to point out that It's used from the power supply in the smallest sector of computing. Literally, most computers are embedded, then mobile, then server, then laptops, and finally, down at the bottom, are legacy desktops and towers. But you never pointed out what component needed 12v.

-Crissa
 
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JBee

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You can make simpler circuits to change voltage down by half pretty easily. But if you do that with an automotive 12v circuit, your nominal is 6v with a peak of 7v normal and requirement for tolerances of higher.
Sorry finally getting around to closing my open tabs on my 12V PC after a hectic 2 weeks. ;)

I think you are assuming to much and not knowing enough to make sense of what your talking about.

If you are referring to a voltage divider circuit, as an easy solution to get half the voltage, you are mistaken in thinking it can deliver any useful current at all. They can't, nearly all the power is burnt up in the resistors, and you're just left with a voltage signal for measuring, but never for powering things.

By 'nonsense' you mean you have your preconceptions, and I have my experiences and willingness to look up datasheets. But you don't share that latter part. This is why I don't usually read your posts. They act informed, but they're not helpful.
Well if you don't know how even a voltage divider works, or where it's used, then I don't think looking up datasheets is going to be helpful for your either.

You read my posts, because you are still looking for something where I could be "technically" wrong. You know it, as do I, that's a long shot. 🤪


And note, I never said there was no 12v in computers. I build computers. What I said was There's nothing remaining in computers that requires 12v. We no longer have spinning drives operating at 12v. We no longer have peripherals that draw 12v. Basically, only the fans use it.
This is where you miss the fundamental reason for having 12V on every desktop PC that exists, and which I have also described before.

It is because the voltage converters for the CPU, that are all in close proximity to the CPU on the mainboard, all are designed to run of 12V, so there is minimal loss between the 12V and 1-2V the CPU needs. The same applies for notebooks, that have dedicated higher voltage converters on the mainboard near the CPU, running at the battery voltages, by which they also reduce consumption of energy, given battery devices are even more sensitive to energy use.

The point here is simply, that in a Tesla there is no need to have yet another, even lower voltage to run the CPU at it's native 1V to 2V, if that can all be reliably supplied from existing 12V supplies and converters that can live on the same mainboard, to ensure stable supply of the CPU. With PCB designs you also must consider the relevant fault tolerances of the individual components, so routing multiple high voltage traces, or adding power from unfiltered source (like the same bus used for rest of vehicle supply) is going to just add a lot of headaches.

My last PCB project was a ardupilot fork autopilot, running off a ESP32 MCU and PiZero. Lots of signal issues, if your power supply is at 6S with noisy ESC's running a custom built eVTOL. Our entry for the SAR competition needed to have min 40km radio range, 120km vehicle range. And we done that all with a sub 2.5kg pureley electric flying platform that could takeoff and land in a 1m radius. The best part was that the whole mission to find the lost person and pickup and deliver the blood sample was all done hands off, with CV, from the initial mouse click to start the mission.

For reference there never has been a CPU that uses 12V, even since the 8086/80286 running in the Mhz range, so throwing in old peripherals into your argument to justify "they don't use 12V for computers anymore" is just a red herring argument, that has no relevance.

The relevant part is that 12V is used on the mainboard CPU converters that power the CPU on Tesla mainboards.

Conversely, there are definitively NO integrated circuits in use today that would benefit running off 48V, which is the whole discussion of this thread, to find out what is better solved at a 48V. CPU's, GPU's, RAM and solid state storage components are all low voltage, under 5V. Installing a 12V floppy disk is a laughable example to prove your mistaken initial post.

There will most definitely be 12V on the CT. Any other notion is just a fantasy of a hype clouded mind.


JBee, you're just wrong on this.

Just like most computers don't use 12v anymore, neither will the Cybertruck.

The wiring harnesses are long. That itself makes it worthwhile, even if the loads are only a few watts. Munro has lists, if you want. But both Tesla and Ford have talked about how much it would save them in weight and copper. It was considerable.

Compatibility with PoE style components makes it all the better and repair easier.

-Crissa
Despite this I think you missed the whole section on how the "bus architecture" of the CT actually does more for efficiency than the upping of the voltage to 48V, by considerably reducing the length of cable used in the first place.

BTW the PoE statement was also countered with the Tesla 4 core connectorless design patent. It's not a off the shelf PoE RJ45 connector or typical bus at all.

G'day to you, from WA! ;)
 

VR Driving

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Then I started thinking, is one of the goals of project Highland to move to a 48v architecture as well?
I don't think the highland is 48v, it didn't even gain the front gigacast and structure battery in this refresh.
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