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Tesla shares 48V architecture with other automakers

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Re: Tesla shares 48V architecture with other automakers

#201

Post by lizknope »

jabart wrote: post #15
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.…

Power steering pumps are electric and have one of the largest wires in my truck. With an EV you also have a heat pump, maybe a heater, coolant pumps now that you don't a constant spinning pulley, windows, lights, headlamps, power doors, seats, radio, amplifier, small PC, etc. From the article "Switching to 48V architecture alleviates a huge number of challenges automakers are facing with 12V. The biggest one, though,…

> Power steering pumps are electric and have one of the largest wires in my truck.

Most new cars don't have hydraulic power steering systems anymore and use an electric motor for power steering. It improves fuel economy as well but the steering feel is generally worse than a hydraulic power steering system.

Re: Tesla shares 48V architecture with other automakers

#202

Post by eqvinox »

elp wrote: post #11

48Vdc is supposedly the highest voltage that is still considered safe. ( https://electronics.stackexchange.com/questions/267789/how-s... ) It certainly sounds like a smart move on the copper savings alone.

It's a bit of an arbitrary determination; 60V is the international common denominator on what various legal or civic (e.g. insurance) regulations consider safe; https://en.wikipedia.org/wiki/Extra-low_voltage#Separated_or...

48V is somewhat of a dinosaur from the days when you designed things with a 20% margin since that's what was cheaply attainable. Regular PoE is 54V these days (10% margin), and some more specific applications creep even closer to 60V. (I've seen 57V and 58.5V, which is of course 5% and 2.5%)

Re: Tesla shares 48V architecture with other automakers

#203

Post by bagels »

CharlesW wrote: post #172
_ea1k wrote: post #161

Earlier quoted context omitted.

Tesla's greatest innovation is simply leadership. Everyone knew castings were the way to go, but noone did it. Now people like Volvo are doing them, and I expect a lot of others to do it as well. 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.

> Everyone knew castings were the way to go… 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?

Car A costs $5k less to manufacture than car B because it uses castings. Car A would be wiser to build because you can get better margins, or lower prices. It'll take a lot longer for buyers to catch on to the fact that the car costs a lot more to repair.

Re: Tesla shares 48V architecture with other automakers

#204

Post by DarmokJalad1701 »

sumeno wrote: post #139
argiopetech wrote: post #47

Earlier quoted context omitted.

Right, but it's a lot easier when you don't have anything someone else might want, much less a billion or more things.

He could give away 99.99% of his wealth, still never have to work another day in his life, and be much less of a target if he wanted to. Boo hoo the poor guy who has more money than almost anyone has ever had in the history of the earth has problems

If he gave away 99.99% of his wealth, that would tank the retirement accounts of millions of people, possibly have his life's work be taken over by some hedge fund ("introducing the Tesla Model V8, now with extra vroom-vroom!"), and then get sued by shareholders for the remaining 0.01%.

Re: Tesla shares 48V architecture with other automakers

#205

Post by DennisP »

hinkley wrote: post #115
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.

Tesla didn’t invent 48 volts either. The EV and hybrid electric world were talking about 48 volts when Musk still worked at PayPal, if not earlier. 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.

Sure, people have been talking about 48 volts for the past 30 years. Somehow most automakers didn't actually manage to do it though.

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.

Re: Tesla shares 48V architecture with other automakers

#206

Post by aidenn0 »

myself248 wrote: post #171
tzs wrote: post #133

Earlier quoted context omitted.

Hold on a second...4x the voltage means you only need 1/4th the current. The power loss in the wire is current^2 x the wire's resistance, so 1/4th the current does indeed mean 1/16th the losses. 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 resistan…

There's also a minimum wire size, based on physical durability requirements. A significant number of wires in the harness already carry no appreciable current and are merely signaling wires, but they can't be infinitely thin. 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.

For very low current wires, I've seen non-metalic (nylon?) strands woven in with the copper for mechanical strength.

Re: Tesla shares 48V architecture with other automakers

#207

Post by DennisP »

GuB-42 wrote: post #196
sitkack wrote: post #2

TIL that 42V fizzled out https://en.wikipedia.org/wiki/42-volt_electrical_system I welcome the move to 48V, as one gets lots of cross over synergies from the 48V telco standard. https://www.servertech.com/blog/48vdc-power-and-the-backbone... https://www.st.com/content/dam/AME/2019/developers-conferenc... https://www.maximintegrated.com/content/dam/files/products/p... https://www.infineon.com/cms/en/applications/infor…

Are you telling us that 42 wasn't the answer after all?

Nah you have the wrong question. You'll need a bigger computer.

Re: Tesla shares 48V architecture with other automakers

#209

Post by reportingsjr »

SigmundA wrote: post #55
elp wrote: post #11

48Vdc is supposedly the highest voltage that is still considered safe. ( https://electronics.stackexchange.com/questions/267789/how-s... ) It certainly sounds like a smart move on the copper savings alone.

Remember a fully charged lithium battery with nominal 48v can be close to 60v just like 12v in your car is actually closer to 14v.

60V DC is the upper limit for circuits that untrained personnel can work on and be exposed to as listed in IEC 62368-1. This is the standard that most consumer goods and IT stuff use to validate and verify electrical safety. 60V isn't going to be hazardous to a person in basically any situation.

Re: Tesla shares 48V architecture with other automakers

#210

Post by elihu »

Tuna-Fish wrote: post #108
myself248 wrote: post #60

Earlier quoted context omitted.

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…

I think another big part of it is that DC switches tend to get expensive above 12V. Cheap AC switches work fine at higher voltage, because the arc is self-extinguishing as it passes through zero twice per cycle, but DC doesn't do that so you can end up with an arc that doesn't extinguish itself, which, aside from not turning the thing off when you want to, burns out the electrical contacts.
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