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Tesla shares 48V architecture with other automakers

electrek.co

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Re: Tesla shares 48V architecture with other automakers

#101

Post by KaiserPro »

panick21_ wrote: post #35

I think the more important change that Tesla made is the change in the databus. Much higher performance ethernet. They changed the whole architecture of the car where there are now very few point to point connection, and its all essentially routed with a few major modules in each part of the car. If you look at current cars there are sometimes huge cable bundles, lots of individual cables for everything. Its a nightm…

> Much higher performance ethernet.

Depends what performance you are after. Ethernet isn't rated for safety critical stuff. It doesn't provide mechanisms for packet loss detection, and in most cases is pretty shit at flow control.

Ethernet is also shit for small sensors/actuators. There are lots of low bandwidth devices that need power and comms, ethernet isn't designed for that. having to route 2 pairs of cables to everything in a star pattern is really impractical.

Its probably ok for linking different zones, of non critical stuff. But running PoE? for all but specialist things, that sounds frankly stupid.

Re: Tesla shares 48V architecture with other automakers

#102

Post by noncoml »

intrepidhero wrote: post #5

Why would a car need a 48V system for accessories? In general the things a car's 12V system powers have gotten less power hungry over time (LED's, heat pump) and in particular, an EV loses the highest power electrical device on the 12V bus, the starter. The typical equipment used for the entertainment and control systems are going to be much more available with 12V supplies, just because that's the industry standard.…

One example is Porsche PDCC. It needs 48V to work so you end up with a car that has both.

Also I think all Mild Hybrids are 48V, so maybe theoretically you could get rid of the extra 12V battery there?

Re: Tesla shares 48V architecture with other automakers

#103

Post by jandrese »

taylodl wrote: post #89
bryanlarsen wrote: post #63

Earlier quoted context omitted.

No benefit? I've seen estimates of $1000 in reduced cost due to reduced copper wiring, and more importantly the labor required to string that wiring. Modern phones charge on 48V these days, so 48V parts are extremely common & cheap.

What you may have saved on wiring is going to be offset by the increased cost of the battery (I'm seeing 2x-3x cost) and the fact you now need a much beefier alternator which is going to have its own cost. You'd think if it were a slam dunk then the bean counters would have insisted on a transition to 48V years ago.

Total current consumption should be about the same (or even less, thanks to lower losses at 48v), so I'm not sure why would you would need a "much beefier" alternator. It will need different windings, but overall it should be about the same size and cost.

Re: Tesla shares 48V architecture with other automakers

#104

Post by KaiserPro »

londons_explore wrote: post #21
intrepidhero wrote: post #5

Why would a car need a 48V system for accessories? In general the things a car's 12V system powers have gotten less power hungry over time (LED's, heat pump) and in particular, an EV loses the highest power electrical device on the 12V bus, the starter. The typical equipment used for the entertainment and control systems are going to be much more available with 12V supplies, just because that's the industry standard.…

Most MOSFETS are 50 volt rated. 50 volts is a sweet spot for switching the most powerful load with the smallest and cheapest switch.

if you're switching 48v, you'd want a mosfet rated for way more than 50v. On a car you'd want 200% headroom at least.

Re: Tesla shares 48V architecture with other automakers

#105

Post by numpad0 »

jnsaff2 wrote: post #83

The "expert" in the article got it wrong. The relationship between the voltage and the losses in the wires is not proportional. They are squared. Going from 12V to 48V is not a saving of 4x rather 16x. 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.

Automotive Ethernet is not 8P8C...that's not how they do it at all

Re: Tesla shares 48V architecture with other automakers

#106

Post by jandrese »

pupppet wrote: post #4

Do more stuff like this, Elon. I really don’t like not liking you.

Don't worry, it will only be a matter of time before he retweets a neo-Nazi and you can go back to hating him.

Some people have way too binary a view of other people. In real life there are rarely outright villains or complete saints. Everybody is a mix of greys. You don't have to agree with everything a person does or says to appreciate their work.

Re: Tesla shares 48V architecture with other automakers

#107

Post by amelius »

jnsaff2 wrote: post #83

The "expert" in the article got it wrong. The relationship between the voltage and the losses in the wires is not proportional. They are squared. Going from 12V to 48V is not a saving of 4x rather 16x. 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.

If you go to a higher voltage, you will typically use smaller wires.

Re: Tesla shares 48V architecture with other automakers

#108

Post by Tuna-Fish »

myself248 wrote: post #60
intrepidhero wrote: post #5

Why would a car need a 48V system for accessories? In general the things a car's 12V system powers have gotten less power hungry over time (LED's, heat pump) and in particular, an EV loses the highest power electrical device on the 12V bus, the starter. The typical equipment used for the entertainment and control systems are going to be much more available with 12V supplies, just because that's the industry standard.…

Hi, automotive electrical is my job. There's quite a bit of very thick wiring in a car, not just the starter wire, but boring stuff like audio amplifiers, rear window defrosters, power seat motors. Those things don't draw a ton of power, like maybe just a few hundred watts, but at 12 volts even modest powers require extraordinarily thick wires, especially when you account for bundle derating. This requires large term…

And to explain why this hadn't been done before/how we got here:

Nothing in a car actually wants 12V DC. Most of the low voltage stuff will run better at 5V or below, while a lot of the higher voltage stuff would benefit from going as high as possible. 12V exists because DC-DC conversion used to be expensive, and you had to make a compromise about the voltage based on losses, wire thickness, and picking a low enough voltage that all the low-voltage stuff doesn't suffer too much.

What's changed is that you can get a single-device DC-DC converter for really cheap these days. Cheap enough that you might as well put it in the light bulbs, and everywhere else that wants a low voltage.

Re: Tesla shares 48V architecture with other automakers

#109

Post by TheLoafOfBread »

yinser wrote: post #39

I liked the interview with auto engineer Sandy Munro discussing the change https://youtu.be/ADwGGEj8sqQ?si=qp6akvy1yyWPTYNe - moving the voltage up means you can drop current - increase the data rate by using ethernet and PoE - using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car - moving the voltage up…

> using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car

You mean like CAN bus is being used since 1990s? I think that Mr Munro little bit fell asleep and missed whole CAN bus and FlexRay evolution in cars.

Re: Tesla shares 48V architecture with other automakers

#110

Post by thot_experiment »

amluto wrote: post #79
jauntywundrkind wrote: post #31

Earlier quoted context omitted.

Extra low voltage is 50v ac or 100v dv. https://en.wikipedia.org/wiki/Extra-low_voltage For some reason people assume it's 48v DC or 50v dc. But it's double that. That said, I feel significantly more scared dealing with 100v DC than I do 48 or 24v.

I find 48V a lot less scary when cars are involved than 12V. Neither is particularly likely to electrocute me, but 48V comes with fuses that will trip at 1/4 the current, giving 1/16 the resistive heating if something shorts, which is a lot less likely to melt or ignite things. Also, the wires are much smaller :)

> 1/4 the current, 1/16 the resistive heating

Really underappreciated safety aspect. The currents required for your average doodad at 48V leave you with a MUCH lower chance of unscheduled welding.

Remember folks, everything is a fuse if you put enough current through it, as a rule of thumb it's good to keep "enough" pretty low.

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