For some applications you could also consider Power over Ethernet in the car, get both shielded comms and power. Or can and power over twisted pair.
But 1/4th the current means you can use a higher gauge wire. Looking at a table of wire gauge current capacities it looks like if your maximum current is 1/4th you can switch to wire with 1/4th the cross section. And resistance is inversely proportional to cross section, so 1/4th the cross section means 4x the resistance.
Doesn't that then bring the savings down from the 16x you would get if you just upped the voltage down to 4x?
Edit: Smaller wire is also cheaper of course. That's probably a pretty significant upside when talking about a mass-produced vehicle.
Getting most of the power wires down into the range of signal wires is a huge benefit, because it means they can use common terminals and smaller connectors, but that's where it stops.
If you use 4x higher voltage, the temperature rise is much less significant (16x less significant to be precise) so it becomes more or less a non-issue and you can treat resistance as a constant.
One of the examples pulled out at that time was that you could shave a couple pounds of copper off the alternator by running it at 4x the voltage. Much thinner wires.
Everyone knew that 48V would be a big benefit, but noone did it.
TBH, in a few years, we may be saying similar things about drive-by-wire without a mechanical backup. But it is too early to say definitively.
Larger parts were often dipped into liquid, because air cooling resulted the part bending.
Tesla internal materials team worked on new alloys to improve this, while working in coordination with the machine manufacture to get up the cycle times.
And they are continuing to work with them. Tesla is using newer more advanced cooling systems in Texas then they did in the California factory. Because cooling is one of the limiting factors in Cycling these machines.
The jury's still out on whether gigacasting is courageous, or just moves costs from production (which will not be passed to consumers) to repairs (which will).
> Everyone knew that 48V would be a big benefit, but noone did it.
Audi did in 2016 with the SQ7 TDI, no?
You are right, though. The jury is still out in that they haven't really been used in the real world for long.
> Audi did in 2016 with the SQ7 TDI, no?
I didn't know about that one, but it was still a dual architecture. Going full 48V is a bit different, assuming Tesla really did that.
Which is why I was always more of a Triumph fan.
Planes are fly by wire but that's because they literally have to be, no amount of gym time will let you move the rudder on a 737 by hand.
How will that work in the real world? Could there be bugs? Will people get used to it or will it lead to mistakes?
I'm looking forward to getting a chance to try it, TBH.
Totally correct. We were making 48v power steering systems 20 years ago for OEM development projects. They simply don't have the will/commitment/leadership to bring change like that to market.
Elon sets a direction and people go that way. I can imagine someone at GM listing all the obstacles as a reason they can't change, and Elon looking at them and saying "no, you're the obstacle" or something like that.
Sandy Munro just did an interview with Musk, who said they hadn't done anything revolutionary, they just built the car up to general 21st century standards.
You are confounding the two electrical systems in an EV or hybrid (or mild hybrid).
One is used to drive the wheels - these are very commonly 48V in a mild hybrid and something like 200V or 400V or 800V in an EV. This is only used to power the wheels - nothing else.
The other electrical system is used to power literally everything else. The infotainment system, heated seats, power windows, lights, powered seats, electric power steering, electric assist brakes, etc. This has always been 12V in every car ever ^ (ICE/hybrid/EV) (including every Tesla).
The Cybertruck is the first vehicle ever to move the 12V system to a 48V system.
^ Before about 1955 it was 6v. The move to 12v then was the last time it has changed.
You are not talking about high current devices like heated and cooled seats, defrosters, infotainment and audio amps, power windows, power seats, lights, etc. etc.
I was reading an anti-Musk subreddit over on Reddit and I think the cybertruck is doing this? They were mad that the cybertruck uses 48V and Ethernet cables, but to me, that seems perfect for CAN and power. We already use 48V (or similar) for PoE, and CAN needs a twisted pair... so why not buy that off the shelf instead of using a custom wiring harness?
I don't think the cybertruck is a particularly attractive vehicle, but I also don't think they're crazy for trying that. You can do 10Gbps over a cat-6 cable and it works great. So I'd expect that you can easily do CAN.
Nothing wrong with ethernet, but listening to Musks statements, especially in fields I have some not even deep knowledge, alwqys like listening to a very confident, but otherwise clueless, 1st semester student selling you semester 2 basics as the latest and hottest shit under the sun nobody else even considered possible so far...
We get it, you don't like the features of modern cars. Well sure if they built the car you would like, then CAN bus is fine. But that's simply not where the future is going, if you like it doesn't matter. Its simply not relevant when car CEO discuss what is needed for modern cars.
You solution of 'just remove X,Y,Y features' is just a laughable suggestion here. Its like saying 'you don't need a new graphics card', I play 'Star Craft: Brood War' just fine. Ok I agree, I don't play AAA games either but to criticize a Nvidia CEO for saying the need higher performance would be totally absurd.
Cars will get more electronics parts, more cameras, more safety equipment, more communication and so on and so on. Moving to higher voltage and PoE is simply a logical thing to do given that reality.
If Musk is so utterly clueless, what of the things he said is actually wrong? Musk even literally said its not 'hot shit', its just bringing things up to date. But that's the simple facts of the automotive industry, lots of 'we did it because we have always done it' and despite it not being 'hot shit' its really hard to change.
So in the automotive industry, such changes are great because if you are building millions of something, it makes a very bit difference.
Seems to me you are reading into it what you want to read into it.
Honestly, ethernet introduces a degree of non-determinism with respect to time in the link layer, plus increased bringup times, a potentially more costly core switching fabric, and the need for critical revision of latency assumptions on any potentially safety-related control concerns. Also, max current is not high. I would wager these are the reasons it won't be rushing to an EV near you... it's basically only suitable for a subset of uses, and heterogeneous infrastructure costs more in design, installation and maintenance cost than it nominally saves in production volume standards alignment and HR familiarity. (Source: Mechatronic systems design for the last ~8 years, IANAEE)
I guess my main thought was that going to 48V and in the world of low power LED lights and such, combining power and comms into same wires/cables is something that might be appealing.
Automotive reliability is only an issue for your ABS sensor, airbag sensor etc. but these are a minority compared to what's in modern cars these days. Real driver is cost, compactness (cost) and harsh environment (temperature and vobrations) and EM emissions. It mainly adds to qualification time, but actual semiconductor design cycle isn't that long. That being said, data center stuff is also notoriously slow to qual.
The power over data line (PoDL, automotive Ethernet equivalent of PoE) is defined by a separate IEEE protocol and its critical specifications like EM emissions tests, ESD tests etc are supplemented by documents created by a consortium of car, electrinics, comnector, cablr and semiconductor producors called OPEN Alliance: https://opensig.org/ . There are parts available for PoDL. The voltage levels from 6V to 60V with 6V increments are supported.
Source: I design both data center and automotive Ethernet chips.
[1] https://en.wikipedia.org/wiki/Time-Sensitive_Networking [2] https://1.ieee802.org/tsn/802-1dg/
There is nothing to choose there. They're supersets of each other with increasing power budget, each including the previous revision as lower power classes.
(and PoDL is not PoE; PoDL is for automotive ethernet, which has nothing to do with the RJ45 you see everywhere on consumer/business IT. You never choose between PoDL and PoE, the choice is made when you decided between Xbase-T vs. Xbase-T1.)
> ethernet introduces a degree of non-determinism with respect to time in the link layer
That's what TSN is for, cf. sibling comment.
> plus increased bringup times
That's generally an IP problem, not Ethernet.
> a potentially more costly core switching fabric
I guess it depends on your application; a TSN-capable 8-port automotive ethernet switch is $10: https://www.digikey.com/en/products/detail/microchip-technol... (non-TSN non-automotive is cheaper…)
> heterogeneous infrastructure costs
Automotive ethernet is supposed to replace CAN and the various heterogeneous higher-speed interfaces that were added to deal with higher bandwidth requirements with a homogeneous ethernet world :)
(Source: I work on some software remotely related to some of this shit. Which does mean I'm biased since I don't know whether it will in fact proliferate, I just make it work ;)