Cybertruck to use 48V instead of 12V?

[PilotPete]

There's nothing that is 48V,

I thought that too, and then I remembered... PoE is 48V. So IF the network for the CT is UTP, then they can use PoE as the default source of power. And all you gotta do is have an RJ45 plug on everything. Talk about inexpensive, ease of assembly and repair...

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[JBee]

I thought that too, and then I remembered... PoE is 48V. So IF the network for the CT is UTP, then they can use PoE as the default source of power. And all you gotta do is have an RJ45 plug on everything. Talk about inexpensive, ease of assembly and repair...

They might call it POE but there are different standards (18-57V) and a RJ45 connector would last a week in an automotive environment. Let alone most are limited to under 90W which is a massive downgrade from standard 12V automotive wiring.

It also won't be running a LAN protocol rather a CAN variation, like most cars, as this allows for redundant paths and loops, meaning each point can remain connected even if one part of the loop is cut. I think 4, maybe even only 2-3 cables would be enough for signal and power depending on how they modulate the signal (like LAN over power point), no need for 8 core CAT 5/6 LAN cable. In electronics even one wire buses are used.

 

[TyPope]

All of the semiconductors used for processing, be that MCU/CPU/GPU are all under 3V and typical off the shelf PC hardware is all 12V/5V. There's nothing that is 48V, and running a few hundred watts over 12V is easy and light enough that 48V won't make a difference for it.

The main items will be all the medium power consumption items, like HVAC compressor or accessories like winches etc. But I doubt we will see a 48V window or light, 12v works just fine for that as well.

48V systems run at lower amperage, use smaller wires, and run more efficiently. Having the HVAC run more efficiency might help with range a bit. I don't know anybody who thinks "No, I want less range." More efficient motors, lighter wiring... Count me in.

A wire of a given size can carry four times as much power at 48 volts as a 12-volt system. In a DC system, power (watts) equals the volts times the amps. A 12-volt wire controlled (limited) by a 15-amp fuse could carry 180 watts. That same wire can carry 720 watts with the same 15-amp fuse.

 

[Mini2nut]

Tesla will be breaking new ground with Cybertruck's 48v electrical architecture.

As Elon stated, the CT will be stuffed with technology. RWS, front/rear aluminum alloy Giga castings, 48-volt architecture, no steering wheel stalks, possibly steer-by-wire technology, etc.

 

[Ryan95738]

All of the semiconductors used for processing, be that MCU/CPU/GPU are all under 3V and typical off the shelf PC hardware is all 12V/5V. There's nothing that is 48V, and running a few hundred watts over 12V is easy and light enough that 48V won't make a difference for it.

The main items will be all the medium power consumption items, like HVAC compressor or accessories like winches etc. But I doubt we will see a 48V window or light, 12v works just fine for that as well.

Mark my words, you are wrong

Airplanes are 28 volts or 26 volts depending on how you ask. It is saved tons of weight in those areas, and they use even less electrical power than a small compact car. This is going to be a big game changer and also allow way easier repair, not to mention diagnostics that actually work and don't malfunction nearly as often

 

[JBee]

Guys thanks for all the lectures, but I'm well versed in the difference a higher voltage makes on cable sizing.

My point was "not" if 48V was worth transitioning car electrical to, rather that even if you did 48V, not everything in the car could run off 48V, so some things wouldn't be connected to 48V at all.

In particular anything that has an IC in it, cannot run on high voltages like 48V without a buck converter down to 3-5V which is the voltage they need to operate. CPU/GPUs are all under 2V and represent a significant vehicle load (except for drivetrain) that will not benefit from 48V. This will run from 5-12V, because all the PC/electronic hardware is at that voltage, and to make CPU'S fast you need to keep the voltage low otherwise they will overheat.

For 48V to make a difference it would have to draw more than 10-20A, so would be a large appliance, say the size of the heat pump used for the HVAC.

 

[HaulingAss]

How many models of cars and trucks are being made as we speak? (I'd guess over 100.)

What's a primary goal of every maker? (I'd guess cost-cutting in the manufacture.)

How many of those models use a 48v system? (I'd guess NONE.)

If my guesses are reasonably accurate, how would you account for the word in caps?

It looks like you are assuming legacy auto is good at bringing value to new car buyers and is not afraid of making fundamental changes to the way they do things. Neither is true. If these two things were true, the average cost of legacy cars, using legacy technology, would not be pushing $50K, a price most consumers cannot even afford.

It takes a disrupter like Tesla to make big changes when entrenched interests think the way they have been doing it for the last several decades is clearly the best way. They would have remained at 12V forever because their customers end up paying for it anyway and all automakers have this additional cost so it's no skin off their noses. Until, that is, a disrupter like Tesla comes along.

Most people here don't even understand just how much of a disrupter little ol' Tesla is (as evidenced by the concensus being that Cybertruck will stick with 12V). The disruptions will not stop there, they will accelerate.

 

[JBee]

How about someone make a list which devices on a vehicle consume enough power to warrant a 48V system, then compare that to a 12V setup.

Don't be fooled though, Tesla won't be the first to use higher DC voltage. Semi's and full size trucks have always been 24V, and there's a whole series of manufacturers that run 48V hybrids as well.

But none have gotten rid of 12V, and neither will Tesla with the CT. It will still have 12V. It will just have 48V for the heavier energy consuming devices.

 

[Crissa]

Very little needs 12v, though. Just legacy hardware.

It's not like the fans on the computer boards need 12v. Or the flash memory. It's all at the level of the processors.

You have loads of motors in the car - wipers, windows, vault, fans - and several resistive heaters and a heat pump. So there are things that draw alot of power but don't care the voltage.

But the thing is, a buck converter for those tiny electronics like cameras and sensors will weigh less than the difference between a meter of 12v wire and 48v wire for the same load.

This is all part price and convention. And with PoE (Power over Ethernet) being so popular, the parts are out there now.

-Crissa

 

[JBee]

Very little needs 12v, though. Just legacy hardware.

It's not like the fans on the computer boards need 12v. Or the flash memory. It's all at the level of the processors.

You have loads of motors in the car - wipers, windows, vault, fans - and several resistive heaters and a heat pump. So there are things that draw alot of power but don't care the voltage.

But the thing is, a buck converter for those tiny electronics like cameras and sensors will weigh less than the difference between a meter of 12v wire and 48v wire for the same load.

This is all part price and convention. And with PoE (Power over Ethernet) being so popular, the parts are out there now.

-Crissa

PoE is only good for small stuff under 100W with existing standards, so not useful as a bus with multiple loads on the same wires. There's also 24V PoE.

Besides they will use CAN not LAN protocols, much more resilient in a vehicle conditions, plus you can run it in a loop circuit. In their case the PoE is just a moniker to describe comms and power over the same cable system. Ideally they'd only need 3-4 cables for this, seeing its all low bandwidth stuff anyway. Essentially you could just have one 4 core wire loop that connects to everything. A lot less cables then.

 

[PilotPete]

PoE is only good for small stuff under 100W with existing standards, so not useful as a bus with multiple loads on the same wires. There's also 24V PoE.

Besides they will use CAN not LAN protocols, much more resilient in a vehicle conditions, plus you can run it in a loop circuit. In their case the PoE is just a moniker to describe comms and power over the same cable system. Ideally they'd only need 3-4 cables for this, seeing its all low bandwidth stuff anyway. Essentially you could just have one 4 core wire loop that connects to everything. A lot less cables then.

Tesla has stated in an official statement that much of the CT will be "connected by Ethernet".

 

[HaulingAss]

How about someone make a list which devices on a vehicle consume enough power to warrant a 48V system, then compare that to a 12V setup.

There is no low-power cutoff point below which there is no advantage for 48V over 12V, the advantage is always similar in terms of how much less copper conductor is needed for 48V vs. 12V (as a percentage of what a 12V circuit requires). It's like Crissa said, the only reasons automotive has stuck with 12V are convention and availability. Just because the advantages of higher voltages scale with size, is no reason to abandon those advantages as they approach zero.

The voltage conversion from the high-voltage pack to 48V will be done centrally. There will also be a 12V converter, like all Tesla have now, but it will be smaller and only used for 12V outlets and those loads for which Tesla found it more cost effective to source 12V components rather than more custom 48V components. The only reason for that is convention and volume efficiencies. As 48V systems become more common, those vestige 12V components will fall away also, regardless of how little power they require.

 

[JBee]

There is no low-power cutoff point below which there is no advantage for 48V over 12V, the advantage is always similar in terms of how much less copper conductor is needed for 48V vs. 12V (as a percentage of what a 12V circuit requires). It's like Crissa said, the only reasons automotive has stuck with 12V are convention and availability. Just because the advantages of higher voltages scale with size, is no reason to abandon those advantages as they approach zero.

The voltage conversion from the high-voltage pack to 48V will be done centrally. There will also be a 12V converter, like all Tesla have now, but it will be smaller and only used for 12V outlets and those loads for which Tesla found it more cost effective to source 12V components rather than more custom 48V components. The only reason for that is convention and volume efficiencies. As 48V systems become more common, those vestige 12V components will fall away also, regardless of how little power they require.

As I said "if" someone would bother making a list, they'd soon see 48V is going to make less of a difference than running everything from a single line bus that has comms and power.

It's the combination of adding comms to the 48V that makes it work better, not just the 48V, and all the small stuff will still be 12V anyway.

 

[Crissa]

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

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