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Cybertruck to use 48V instead of 12V?

EVCanuck

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Since CT is such a new platform compared to any other Tesla it would make a lot of sense (economic sense due to the anticipated volumes, engineering due to benefits of the higher voltage) to use the 48V accessories power system instead of the conventional 12V. Do you think Tesla will make this leap? Cybertruck seems to be the perfect opportunity for this...

Edit: Just a TLDR recap for those that don't want to scroll through the comments: Consensus is Tesla will stick to 12V for the Cybertruck
 
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ajdelange

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The low voltage system powers only low power stuff - no starting motor in particular. The modern lights are all LEDs so their current demands are small. The biggest low voltage loads are probably the computers, a blower here and there, motors that run the windows up and down and coolant circulation pumps. The rest is control valves etc. Thus I don't really see a lot of advantages to going to a 28 V system. What did you have in mind?
 
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EVCanuck

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I am wondering how the cooling system (octovalve?) pumps, FSD computer/entertainment system (probably no benefit from 48V), air suspension/on-board compressor, 110V/240V inverter will be powered? Can those benefit from a 48V?
 

ajdelange

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Clearly the 120/240 inverter will be driven from the main battery (it is essentialy, or could be the on board charger or a copy thereof running backwards). Look at a circulation pump in you house. It is typically 1/25 HP which is 30W which is 2.5A at 12 V. That's not much current even were the pumps in the car that big. The valve actuators will probably draw a similar amount of current but not for very long. As regards electronics - the first thing the incoming supply bus meets is a set of DC/DC converters which supply the voltages the various circuits meet. These work over a pretty wide range of input voltages and are highly efficient so the only real advantage to going to higher bus voltage is smaller wiring to the various loads and at the small sizes needed to carry an ampere or 2 there isn't much savings in going down a couple of gauge.

The onboard compressor: depends on how big it is. For the small amount of air needed to control the suspension system I think the same comments apply. But if the in bed compressor is going to be able to supply worksite nailers, impact wrenches, paint sprayers etc it might be made larger. If its load got to be as big as the HVAC compressor I'd guess they power it directly from the main battery just as they do with the HVAC compressor. Or through the 240 VAC inverter. There are so many options these days.

Going away from 12 V takes you away from a huge supply of automotive components made for the 12V personal auto industry. Going to 24 gets you into the narrower marine and truck suppliers so I really doubt Tesla will go to 24V.
 

OneLapper

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Trucks and buses were 12vdc in the 60's, then some OEM went to 24vdc for cost savings, and we're back to mostly 12vdc for modern trucks and buses. 24vdc starters are still a thing, but that's not even common. The 24vdc starter requires a 24v alternator, two or four batteries, and a Vanner battery equalizer. So much extra expense that the OEMs have settled on 12vdc, especially since LED lights are cheap and common.
 

ProfessorRon

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I thought most EVs used at least 600v whereas the new Lucid use 900v to get quicker acceleration.
 

Crissa

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I thought most EVs used at least 600v whereas the new Lucid use 900v to get quicker acceleration.
900 volts requires special cabling and hardware, standard sheathing doesn't cut it. But it gets you more power for less copper - which is great for charging, voltage sag from battery, and yes, acceleration over time.

Not sure it really gets you more acceleration up front; because it's less heat degradation that the higher voltage gets you. But those special wires require alot of extra cost that you don't get back in less copper.

That's why the Zero uses a 100v architecture and why most EVs have used 200-400 volts. Each step adds cost. More voltage is always better if you can do it - that's sorta why I charge my Zero off 240 instead of 120.

-Crissa
 

ajdelange

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Most use 385 and a couple use twice that in order to attain greater efficiency and thus longer range and access to higher powered chargers.
 

Bill906

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Back in 2017 Musk was looking into ditching the 12V system.

https://insideevs.com/news/332478/t...-12-volt-battery-95-less-wiring-than-model-3/

In general aviation many small prop planes like Cessna 172's use a 24V power system instead of 12V. The idea is if you increase the voltage you can reduce the current but still keep the same amount of power. Wire thickness is determined by current. Thinner wires lower the weight of the plane. A friend of mine is building his own general aviation plane. I remember when he was debating 12V or 24V. 24V is lighter, but 12V is easier to find parts for.

I also remember hearing Musk says how Can bus is a poor idea and would like to use something like Power over Ethernet (PoE) for power and communications with components in a car but I not finding that article anywhere.

One main drawback if the CT ends up using a low voltage system that isn't 12V is that replacement electrical parts may be significantly more expensive and hard to find. If your power window motor fails it might be hard to find a replacement 48V one and it will most likely be significantly more expensive that it's 12V counterpart.

I thought most EVs used at least 600v whereas the new Lucid use 900v to get quicker acceleration.
BEV's use high voltage batteries (like 600VDC) to power the traction motors but they also have a low voltage system for the rest of the electrical needs in the car like blowers, wipers, lights etc. It would be odd to have your electric windows be powered by a 600VDC motor.
 

TI4Dan

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12V systems are very reliable and most of the motors or operating solenoids are not the problem but changing
these components to work on higher would require
engineering and additional cost to operate on higher
voltages. I worked on transportation that operated on
12/24/36V systems. Both 12/24V voltages were side by side components where physically the same in appearance but, not the same you could burn out components which it happens when someone was not careful with replacement parts. I don't think there is a problem with 12V system but the idea of running
a higher voltage throughout the chassis may have some
safety concerns, it is possible to receive a shock from 48V,
I have been shocked on 24V....nothing serious. It will raise the cost of vehicle for 48V components and I can't think of a positive
benefit for us. LED lights run on very low voltages but old
school light bulbs run on 120V, higher voltage bulb is not dramatically better then LED bulbs, both work. For saving on cost
and safety 12V still works, however I would be interested in a
bigger battery pack for dual motor Cybertruck.
 

Luke42

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I am wondering how the cooling system (octovalve?) pumps, FSD computer/entertainment system (probably no benefit from 48V), air suspension/on-board compressor, 110V/240V inverter will be powered? Can those benefit from a 48V?
That's likely to run off of HVDC. No reason to step 300V (or whatever) down to 48V for that.

Just use a DC motor + control which matches the big battery.
 

Luke42

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Using 12V components means you can leverage the existing parts bin provided by automotive suppliers.

Using the same voltage as the big battery means you can deliver a lot of power over a small wires, but the 12V stuff won't work (for more.than a few seconds).

An intermediate voltage like 48V seems like the worst of both worlds. Don't get me wrong, 48V is nice intermediate voltage where the wires aren't too big, and the voltage isn't too dangerous. But I don't see why you'd give up the 12V business ecosystem but still go to all the trouble of stepping down the voltage. Running at 48V seems like the worst of both worlds in an automotive application, even though I'm personally a fan of 48VDC systems.

What I'd expect to see is most of the wiring in the car replaced by a standard-ish wire+connector which delivers HVDC (at the big battery voltage) and CANBUS. With that, you can remove a lot of complexity and deliver both power and control everywhere you need it.

The problem, of course, is that every window regular or whatever needs to deal with the HVDC somehow or other. That's easy if it's an A/C compressor, harder if it's a dome light or a turn signal.

I'll be very interested to see what Tesla actually does. I'm just a rank-and-file embedded systems guy.
 
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ajdelange

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Obviously they are going to continue to use the 12 V system to power all the "normal" automobile type loads such as all the lights, the fans, the blowers, the window regulators, the door latches, the pumps, the valves, the windshield wipers, the computers, the cameras, the displays, the sound system... The 385 V battery will power the traction motors (via the inverters), the air conditioning compressor, the DC/DC converter that keeps the battery charged, the inverter for the in bed AC outlets, the auxilliary heaters (cabin and battery which kick on when the heat pump is insufficient) and maybe the compressor for the bed compressed air port but not the compressor for the suspension if it is separate.

High voltage wiring will be kept separate as is required, I believe, by regulation for safety reasons. It is it jacketed in shrieking orange insulation.

Cars already incorporate Ethernet for diagnostics, downloading etc but up until recently ethernet did not meet the industry's EMI requirements. Progress has been made in this area and I have to think that the multiple cameras in a modern Tesla must be using it. CANBUS will not handle the bandwidth. Doubtless ethernet will eventually supplant CANBUS and at least one BEV startup (can't remember which one) is using ethernet as a brag in its ads.
 
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ldjessee

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Cars already incorporate Ethernet for diagnostics, downloading etc but up until recently ethernet did not meet the industry's EMI requirements. Progress has been made in this area and I have to think that the multiple cameras in a modern Tesla must be using it. CANBUS will not handle the bandwidth. Doubtless ethernet will eventually supplant CANBUS and at least one BEV startup (can't remember which one) is using ethernet as a brag in its ads.
Lucid recently said it was using ethernet for internal car communications.
 

ajdelange

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That's probably who it was then but it could have been someone else too. It is coming to all our cars eventually.
 

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