48 Volt Semi?

[VIKING26]

Tesla announced 48 volt architecture in the Cybertruck. Assuming that the Semi is the largest vehicle and thus the longest runs of electrical wire, jumping to a higher voltage and reducing the size of wires would have the most cost savings to the Semi. Also, once the 48v components are sourced it would make it easier to jump to 48v in the Semi.

If/when will Tesla make the change?

 

[TSemi]

If/when will Tesla make the change?

For sure all Tesla Semi's manufactured in 2024 will have 48v system. Even current Tesla Semi's may have the 48v, no one knows outside of Tesla. Could be one of the reasons why such a long delay in production and delivery of the Semi, they were testing the 48v components

 

[VIKING26]

For sure all Tesla Semi's manufactured in 2024 will have 48v system. Even current Tesla Semi's may have the 48v, no one knows outside of Tesla. Could be one of the reasons why such a long delay in production and delivery of the Semi, they were testing the 48v components

Maybe the Semi already has 48v architecture, but I’d find it a little odd that Tesla wouldn’t have mentioned this at Investor Day or at any other point.

 

[TSemi]

Maybe the Semi already has 48v architecture, but I’d find it a little odd that Tesla wouldn’t have mentioned this at Investor Day or at any other point.

I guess you haven't noticed that Tesla is tight-lipped about a lot of things, Tesla Semi specs included.

It seems Tesla lives by "Loose lips sinks ships"

 

[dbeiler]

ICE semitrucks use 24 volts. I would assume the existing Tesla Semis uses 48 volts already.

 

[Nack]

Outside North America its 24V, in North America its 12V for the most part. Some areas have either or depending where the truck design originated.

I don’t really see the point of 48V components. You would need to step down the voltage which would lose efficiency or have another circuit and storage. Honestly it just makes more sense to run the high voltage even if its overkill as the motors can be smaller size and you have enough torque to do what you need.

48V works decently for cars because they are small and light and their components are also small and consume little power. For heavy duty you are still somewhat limited with 48V.

Only real advantage is if you do not have a high voltage system on the vehicle and you want to stay under the high voltage threshold but need more voltage than 12V (or 24V if equipped).

 

[VIKING26]

You would need to step down the voltage which would lose efficiency or have another circuit and storage.

Can’t all components just be 48v? Then no need to step voltage down.

For heavy duty you are still somewhat limited with 48V.

Help me understand what you mean by this. Why is 48v limiting? We are only talking the voltage for infotainment, sensors, window motors, etc. The drive motors, inverters, charger, and battery are still running high voltage (350-1000V depending on vehicle design).

Whether it is 12, 24, or 48v on the low voltage architecture, we still need to step down the voltage from the HV battery. 48v can use smaller gauge cables, but is currently not that common so is more expensive to source 48v components.

 

[TunaBug]

Outside North America its 24V, in North America its 12V for the most part. Some areas have either or depending where the truck design originated.

I don’t really see the point of 48V components. You would need to step down the voltage which would lose efficiency or have another circuit and storage. Honestly it just makes more sense to run the high voltage even if its overkill as the motors can be smaller size and you have enough torque to do what you need.

48V works decently for cars because they are small and light and their components are also small and consume little power. For heavy duty you are still somewhat limited with 48V.

Only real advantage is if you do not have a high voltage system on the vehicle and you want to stay under the high voltage threshold but need more voltage than 12V (or 24V if equipped).

The point of 48 is reduced weight: 4x voltage means 1/4 current which means 1/16 of the loss due to resistance. So a weight and cost savings on wire. Having step downs everywhere would defeat the purpose.

The switch to 48 is taking a long time because there is not yet a great industry around 48V native parts. I think EM said as much in a video interview, I think with Munro.

Higher voltage isn’t an option: internationally 50V is the boundary between “low” and “high” : once things are high voltage then working on them requires separate training, tools, etc, due to regulations.

 

[TunaBug]

Hmm, I'm probably off a bit on the details of the 50V threshold. I thought that was an EU limit, but the Low Voltage Directive is 50V AC and 75V DC. Also, if the limit is near 50V then it's probably more likely at 55V, as that would give a 48V +/-10% supply the sufficient wiggle room. Regardless, there are upper limits on voltage before extra safety protocols are required.

 

[Nack]

Even if all components are 48V you still need to step it down or up from the lower voltage circuit to get it. For the things you propose running there would really be no advantage to 48V. 12V does that just fine and its cheap. You could use 24V if you wanted as there is already a supply chain set up.

With the 48V “accessories” usually mean power steering, heat pump, coolant pumps, etc. because they draw enough to benefit from 48V. If you already have HV on board, just use that.

I know upping the voltage reduces current and resistance losses. It also means less copper (more insulation) but still the juice is not really worth the squeeze here. This is the main reason everything did not switch to 42V or 48V in the early 2000s, the benefit just wasn’t worth it. Motor technology got better and 12V could do a lot more without completely retooling everything.

48V is the essential nominal voltage max thats under the threshold that requires extra protection. Its also a multiple of 12V so you can just link 4 12V batteries in series to power 48V and it can charge off a 12V alternator if needed (switching to parallel connection). This was the main advantage over 42V as new batteries were not an absolute requirement for the system.

I get what you are saying, but also know the cost/benefit does not pan out.

 

[Nack]

Well I saw an article on the 48V architecture in the cybertruck so it seems they are doing away with the 12V system in favor of 48V. Still interested to see how it pans out, but seems we will get a chance to see of its a one hit wonder or something that catches on.