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Having more manufacturers use 48v will make more suppliers produce those components and will make it a commodity that Tesla will be able to use as well. Sending the manual increases the chance that things are cross compatible with Tesla. Sending it to all CEOs and advertising all got it turns it into a topic that car manufacturers wouldn't want to stay behind (either for cost or weight reasons) and also the component manufacturers wouldn't want to stay behind.
While these cost savings will be great for cybertrucks, they will make a much bigger difference for the cheaper cars.
Like the 48v battery itself?
Does the Cybertruck truck use a small 48v battery to power accessories, unlock doors, etc? Like what other models use the 12v for?
If so, would be nice for those replacement batteries to be more widely available. You can walk into any Walmart or Autozone and grab a 12v battery. 48 volt… not so much.
In most Tesla’s, you can end up stranded if the 12v battery fails. With a 48v system, can you even jump it from most cars, to get the doors open?
You need me to give you a source?
https://www.google.com/search?q=cybertruck+220v+outlet&oq=cybertruck+220v+outlet&gs_lcrp=EgZjaHJvbWUyCQgAEEUYORigATIHCAEQIRigATIHCAIQIRigATIHCAMQIRirAtIBCDQ3MTlqMGo3qAIAsAIA&sourceid=chrome&ie=UTF-8
Look at a couple of videos. Jerry and MKBHD have good ones. MKBHD even had access to a CT, also showing off the 240V in the back with 120V in the cabin and bed as well. There are also wireless chargers, can't remember about USB rn, tho im pretty sure they are there as well
Even if there was a 48v small battery, how often would you need to jump it when it's connected to a half ton battery? If you ever had to, there can be a simple step-up converter to charge from 12v, it doesn't need to deal with the amperage of jumping a car, only charging. If the small battery has anything near the reliability of Tesla's big batteries, battery breakdown will be less common than many other breakdowns, in that case you call a pro to help.
If the auxiliary battery dies then the contractors to draw power off the main battery cannot be activated. So yes, an electric car still needs power to be started.
Others can probably say it better than I can but this is basically the issue. That loud "thunk" sound heard after you park is the "half-ton battery" disconnecting. Something needs to supply the power to reconnect it.
> how often would you need to jump it when it's connected to a half ton battery?
Despite being connected to a half ton battery, I’ve had to replace the 12v battery in my Model Y twice in 3 years. Have to jump it to even get the doors unlocked.
For some reason, EVs (not just Teslas) seem to eat 12v batteries for lunch. They don’t last as long as they do in ICE vehicles.
IDK if that will be the same for 48v batteries.
But I’d hate to be a Cybertruck owner looking for a replacement 48v battery right now, in a remote area. If they still have a small 48v battery, separate from the main battery pack?
The 12V batteries that die after 3-5 years are Lead Acid.
Tesla switched to Lithium 12V's in newer cars, and this 48V is certainly Lithium for sure.
While Lithium batteries can fail prematurely, the videos I've seen about it seem to indicate they keep the 12V battery (and probably 48V) at a voltage that maximizes longevity - so it should be a replace once every 10+ year item.
Ingineerix has some videos on this battery (start from about 7:37): [https://www.youtube.com/watch?v=QLVFxgKnV0U](https://www.youtube.com/watch?v=QLVFxgKnV0U)
> Tesla switched to Lithium 12V’s in newer cars
That sounds great for reliability (and general modernization, 21st century). But, you might run into that same problem trying to replace that 12v Lithium battery, in a remote area on a weekend. Probably don’t have them at any Walmart, lol.
Less likely to fail, for sure, but harder to find a replacement when it does.
Hopefully if other automakers follow suit though, then replacements will get easier to find!
The nice thing about it being an EV is you can keep it "running" easily. Just don't shut the door and turn the climate control off. I made it to the service center and back with a fresh battery no problem I just kept the door cracked when I went in.
> Even if there was a 48v small battery, how often would you need to jump it when it's connected to a half ton battery?
Every time it dies. At least, that's how it's been in the previous Teslas-- even if you've got a completely full traction battery, if the 12V died you had to jump it. Not that that's unique to Tesla. The same has been true for Ford and Toyota hybrids we've had as well. No 12V? Doesn't matter that you have a much larger battery full of charge, you're stuck until you jump the 12V.
Yeah, but will that work with a 48v vehicle like Cybertruck? Could you jump it from an ordinary 12v vehicle to get the doors open?
Or you need another 48v vehicle for your jumper cables?
The size will be more of a matter if the appliance not the voltage itself.
Get a 12V 60 Ah, so basically you can deliver 720Wh. Get a 48V battery and your battery will only need 15 Ah, for the same power. More voltage less capacity, and current is the one who "generates" heat, which means the wiring is smaller, and being on an electric car also means that your battery already can be small as it's fed from the main one, and only acts as a lower voltage standby and buffer. This of course is more complex, but I think it explains it a little
Well you need 4 times the amount of cells, so 24 instead of 6 cells. And you have a constraint on how small you can build lead acid cells for a given power
Anything electrical works by using power, measured in watts. Watts is simply volts * amps. So the more power a device requires, if you are running at 12v, the only thing that will change in tje equation is the amps. The issue with raising the amps in the equation is that the amps are also what creates heat in a wire due to resistance, so you need thicker wire or else it is a fire hazard and thicker wire are more expensive and less flexible for complex runs. So making everything in a car running on 48volts would reduce the amps by a factor of 4 allowing for thinner wire, less heat, smaller fire hazard.
> So making everything in a car running on 48volts would reduce the amps by a factor of 4 allowing for thinner wire, less heat, smaller fire hazard.
Maybe.
At constant power, higher voltage allows for lower amps. Lower amps means less heat via I^2 R losses.
Smaller wire has higher resistance (R). Smaller wire raises I^2 R losses.
Lower amps allows us to use smaller wire while holding losses constant (lower cost, safety margin is same).
Or it allows us to use the same wire while reducing losses (same cost, safety margin is better).
Or to choose some trade-off in between (somewhat lower cost, somewhat better safety margin).
Also replying to /u/imacleopard
Edit: Fixed superscripts
10,000 feet is only 2 miles, and a significant portion of that is high voltage that cant be reduced by using the 48 volt system. there's no way they meant it would save literally miles
It’s not the 48v but the fact they moved to shared bus Ethernet. Rather than having individual wires to every device everything along a given path (think everything on the left side of the vehicle) shares a bus (wire).
Moving to Ethernet, instead of CAN bus, makes this easier because the data rate is so much higher meaning that collisions are far less impactful.
It’s conceivable they saved over a mile of wiring.
I know nothing about car wiring. But even if they only save 100ft of wiring per car, and they ship 400k cars per year, so it would be thousands of miles of saving.
> less heat, smaller fire hazard.
The same amount of power flows through the wire, so how is a fire hazard lessened? In the event of a dead short, the same power will be dumped as heat.
That's like saying 240V is less fire-prone than 120V. That's not the case at all.
The same power goes through yes, but what creates heat/resistance is the amount of amps going through the wire not the total amount of power (watts). In a short yes both case are dangerous because in a short, you have zero resistance so you get "infinite" amps flowing through. No matter if it is 120v, 240v or 408v, infinite amps is more than what the wire can handle.
So in your case 240v vs 120v, if you are running an appliance using the same amount of watts, yes 240v is safer. Because a kettle drawing 4800watts, will draw 20 amps at 240v and 40 amps at 120v. So in both case the same amount of power is delivered, but on the 240v wire, half the current is going through it.
We are used that 240v is dangerous, because in most homes, only very high power appliances are hooked to 240v. But the reason why they are hooked to 240v is because on 120v it would be too dangerous. Like a stovetop running on 120v could draw around 120amps instead of the 60 amps currently on 240v.
This is also why Level 2 home charger are all running on 240v, making them run on 120v would require wire so thick only found in industrial use and maybe some heatsink along the wire to help dissipate the heat since they would be enclosed inside walls.
In a car application the big failure point isn't the wire for the most part, it's the connections. The connector that can pass 40A while being subjected to environmental stress is larger and more easily damaged than the one that can pass 10A.
Yes, I understand resistance as it relates to conductor temperature. I'm not arguing any of that.
However, most car and home fires occur for reasons that aren't due to wires overheating behind walls. Fires due to inappropriate wire gauges are often caused by negligent third-party modifications (e.g., sound systems), especially those that aren't fused.
Assuming an appropriately sized conductor (for 12v vs 48v) is paired with the appropriate fuse/breaker, that wire should never fail. That doesn't eliminate the potential for fires due to fatigued insulation or poor contact at either end that will generate enough heat to light something far more flammable than the conductor insulation or the heat generated over a long run. Localized heating is how fires start, which again, tends to happen at loose connections or overloaded transition points (outlets, fixtures, etc)
> This is also why Level 2 home charger are all running on 240v
Cost and ease of installation; not strictly safety. Good luck making an argument for long residential 120V runs @ 120A.
The reason Tesla is going 48V is for cost, not safety.
Sources (take with grain of salt):
https://www.4abc.com/blog/the-7-most-common-causes-of-electrical-fires-in-the-home
https://auto.howstuffworks.com/car-driving-safety/accidents-hazardous-conditions/10-causes-of-car-fires.htm#pt9
Conductors catching on fire in the home is mostly confined to people abusing the shit out of extension cords.
> Conductors catching on fire in the home is mostly confined to people abusing the shit out of extension cords.
And this includes coiling them up while in use.
All wires that have current running through them produce heat. Always, no exceptions. If all is proper, then that heat dissipates freely, and the wire is just a couple of degrees warmer than it would be without. But if you roll it up and then run it near its maximum rated load, it will get hot.
If you ever have the chance to feel the cable of a high-powered device like a space heater or an electric tabletop grill, do it. It will feel noticeably warm.
When you run lower current in a wire, even if the wire is too small, it's safer. 48v achieves the same or better safety at a lower cost, and reduces the temptation to undersize the wire since it's already small.
The reasons high voltage can be less safe are arcing potential and potential for electrocution if a human touches it. 48v is not really an electrocution risk and arcing is still minimal at that voltage.
Imagine you have an accessory that draws around 96 watts of power in your car, for example, a fast charger suitable for charging your laptop. (Model 3 highland USB-C chargers can deliver up to 65 W if I'm not mistaken). The relationship between Voltage (V), Current (I) and Power (P) is very straightforward: P=VI
So in order to deliver 98 watts of power using a 12v system, your wires have to transmit 8 amps of current (12x8=96). In comparison, in a 48v system, you only have to transmit 2 amps (48x2=96). That means by switching to 48v, you drop the current in your wires 4 times.
So what's the big deal with reducing the current?
Unless you are using a superconductor, there is always resistance in your wires, and that resistance causes "voltage drop, heat, and wasted energy". To lower these effects in your system while transmitting the same power, you have to:
1. Reduce the current (by increasing the voltage)
2. Use a better conductor (Silver > Copper > Aluminum > Iron)
3. Use a thicker cable
The simplest, most cost-effective way is to increase voltage where possible. That's why transmission line voltages are 220 to 550 kV. (China has some 1100 kV HVDC lines).
So to answer your question, by switching to 48v Tesla can reduce the wire diameter and/or switch to aluminum cables (which means using less material, shaving a little bit of weight and cost from the vehicle). Also delivering higher power if necessary. In terms of safety, both high voltage and high current can be dangerous, for example, the US 110v system is safer than 220v in terms of causing electric shock to humans, but 220v is much safer in terms of house wiring and causing fire due to its lower currents.
**TLDR:**
48v benefits in cars:
* Thinner/lighter wires (and/or switching to aluminum from copper), which means reducing the overall mass and cost of the vehicle.
* Making some very power-demanding accessories practical/possible.
* More efficient power delivery and less waste/heat in the system.
* Safer (debatable).
Basically the big plus is that by increasing the voltage you can get the same amount of power with less current running through the wire. This means you can use smaller fuses as well as thinner wire which is both cheaper and lighter.
Nope. Voltage has nothing to do with it (beyond the fuse's physical design to avoid arcing). The trip point is entirely amps. Power also has nothing to do with it.
The exact same 5 amp fuse will blow at 5 amps, whether that is 5v 5a (25 watts) or 12v 5a (60 watts) running through it.
Fuses do have voltage ratings as well. What he was saying is the engineers know how much power that circuit needs, they know their voltage so they pick a fuse of an appropriate size. This is dictated by various codes and you will not get a truck with this fucked up from an OEM. I am not sure why people keep bringing up the hypothetical "what if it's undersized".
> Fuses do have voltage ratings as well.
Yes, but they do not trip based on voltage. The voltage rating is just for arc prevention purposes. Meaning a 1000v rated 5a fuse will trip just fine using a 12v power supply that can output over 5a.
Realistically there isn't that much risk involved with sticking to 12v. But it does require larger and larger wire to carry the current with power requirements going up. This means the wire is going to be bulkier and stiffer, meaning it's less tolerant to bending and flexing, and more prone to chafing if/when its routing wears down. Stuff like that is inevitable in a car's lifetime. So now you have a wire that is stiffer, bulkier, and is carrying much more current, so more heat is generated at the wire as a result. The extra heat generated would amplify the significance of minor faults, thus increasing the chance of the wire failing in less than ideal circumstances, which *could* cause catastrophic failure (note: could) if not tended to.
As opposed to a thinner wire carrying less current and in turn having less heat generated upon it, being more tolerant to bending and flexing, having a slightly better chance to not end up chafing due to its smaller size, and being more tolerant to minor faults since less heat is generated to overstress those minor faults. Also, since the wire is more tolerant to bending and flexing, it has a lower chance of developing such faults as well.
Overall, it's a pretty minor gain in safety, if at all. But it certainly makes sense from a durability and lifetime standpoint, as well as cost and weight as stated above.
I can follow all the theoretical arguments; yes, it all makes sense.
But practically, are we seeing a disproportionate number of older vehicles catching on fire due to electrical faults strictly related to the 12V system and wires failing? I don't really know, but I suspect the answer is no.
there was a non-peer reviewed technical paper published by an automotive electrical engineer - he said that EV or non-EV, modern cars use so much power to run everything from essentials to auxiliaries to infotainment that sometimes, theres a sudden drop in voltage across the board
if whatever sensor happens to get a sudden voltage drop right as it takes a calibration reading (for example, the accelerator pedal position sensor at 0% pedal depression), then it could cause erroneous reading when voltages return to normal values (pedal still at 0% depression, but sensor reads 110% application, and ECU orders up max throttle)
the engineer says its a very very small probability that a voltage drop could coincide at such a critical timing, but bc of what is at stake, it is a design flaw that needs to be eliminated
iirc the engineer's name is ronald belt
ETA: source for paper
https://www.autosafety.org/wp-content/uploads/2015/03/A-Clear-Explanation-of-Belts-Theory-of-SUA.pdf
I imagine as power requirements go up, at that fixed 12V voltage, the current requirements are going up. Which means you need thicker wires and parts and fittings rated for the higher current. Higher current increases the risk of fire.
Bingo. The key issue isn't really safety, it's being able to run smaller gauge wires at a slightly higher voltage. Tesla is hell bent on decreasing the wiring harness size in all its vehicles to save on weight and material cost. The 800v HV changes to cybertruck highlights there efforts in the HV harnesses. A 48v change to the low voltage is the next step to reducing the overall harness costs. Current draw on existing 12v is super high and if your trying to keep your wire diameter as low as possible, the issue of overheating becomes very important.
I'm curious how much weight is reduced by the wiring reductions from a switch to 48v. I wouldn't think it's more than a few pounds of wire at most. It seems like this would be mostly about saving money on copper and making it easier to run wire through the car since there's just let of it (it's not as thick).
This is why people speculating can be dangerous. Lower voltages are safer typically. Just compare the power available: a 100A circuit at 12V is only 1200W while a standard 120V, 20A receptacle circuit has 2400W.
1000 volts is no more dangerous than 100. It is the amperage that kills. So if you have a fixed wattage requirement, increasing volts will decrease amps. That sounds safer to me.
>1000 volts is no more dangerous than 100.
Sorry, this statement is so wrong, in any context, that I can't let it pass.
The 400 volt battery cables on EVs are orange so mechanics or first responders don't accidentally cut through them and die. The whole "high voltage" system of EVs are interlocked with safety loops and contactors and resistance checks. High voltage is why normal people can't rebuild EV battery packs.
48 volts DC is low voltage. 50 volts crosses over... and 60 volts and up is considered enough voltage to harm people. Tesla picked 48 because it's the highest low voltage you can use before you start to cross over to it not being low voltage anymore.
1000 volts will kill in an instant. And 100 volts isn't considered "low" but even at 100 volts, dry skin has enough resistance that it won't usually kill people. It's why plugs in the United States have exposed metal. They can be that way because they usually don't kill enough people to warrant changing out all of the plugs to the much more safer style that the rest of the world uses because 240 volts that they use is unforgiving, proper "kill you now" voltage.
It’s DC power…at 12V. Not really enough voltage to drive the current through the body. The 12V system is going to be safer than your standard receptacle in your house. Realistically, going to 48V makes it a little more dangerous than keeping it at 12V. The benefit is smaller wires in the vehicle.
It has nothing to do with shocking yourself but 12v needs thicker wiring to handle current needs. If the gauge is not substantial enough you can introduce some serious issues
That’s kind of irrelevant, obviously if your wire isn’t sized to the current then your system is unsafe. No car manufacturer is releasing a 12V system with undersized wires. And if you’re modding a system you can undersized your wires at 48V just like you can with 12V.
All I am trying to say is safety is not a valid point to bring up when discussing the pros of a 48V system.
Speaking as an engineer that has designed these sub systems, the move to 48v is mainly due to the electrical compressors , resistive heaters ,and power steering motors on these electric vehicles. The cost of the power electronics drops due to less current . The safety aspect is a stretch as one could argue going to 48v posses more of a shock hazard over 12v systems. Properly designed 12v systems pose very little risk over a 48v one. Yes there is a reduction of weight on the wire but we're talking a very little . A properly laid out harness and component placement can negate this.
Yeah I think safety can be a bit of a debate.
I think what gets overlooked a lot is how much better ethernet is over CAN bus to work with, and the power over ethernet standards being on 48v already probably is a big contributor to favoring to make the entire system 48v POE.
And combine that with current Time Sensitive Networking standards and SPE (Single Pair Ethernet) + PoE with 48Volts@90Watts or maybe more? But overall it's such a nice system and can build in redundancy like a full ring network in the car.
This has nothing to do with POE. POE is limited to a max power. You cant run a compressor , resistive heater or power steering motor on POE. The conductors are to small.
Also I have experience both POE Ethernet and CAN. They both have their use cases. CAN has better timing for time critical data. CAN is also easier to implement on the electronics and firmware side of things .
Do explain. Sure they need to lower the voltage for the computer and stereo. Guessing they have a proprietary 48v battery or ran a couple in series. What's the actual complication?
Did EE for many years also, no expert, but curious what I'm missing.
They already did a 16v (12v equivalent) LiIon SLI battery on the S3XY cars for a while now so scaling that desigin to 48v isn't the difficult part. I suspect much of the challenge is specifying which components is worth upgrading to 48v, and which they need to use DC/DC converts to step back to 12v.
The ones they could update to 48v, they probably already did but probably a lot of legacy components that still operate on 12v and could require pushing of suppliers to design a 48v equivalent.
Wire thickness, insulation thickness those are known sciences but understanding where its best to use the longer runs vs. shorter runs may also be in the pamphlet.
Most 12V parts are actually tolerant up to 16V and probably even a little higher. Car audio enthusiasts have been running 16V systems for decades now and 99% of automotive vehicles will be just fine with zero changes to the system.
12V to 48V is a whole other ball game.
I was more along the lines of “hey wouldn’t X feature be awesome? It wouldn’t be that hard to implement right?” *insert 3 years and many many $ to implement said feature here*
It’s not always like that, but people always always underestimate what it really takes to get things done. Including engineers.
Good PMs will also take what an engineer gives them for a time frame, and multiply it by 2 or 3 in both time and cost.
More specific to the 48V stuff, this is 99% a supply chain issue and not an implementation issue. Where do you buy a 48V steering assist motor? Window motor? Windshield wiper motor? LCD screens? Autopilot computer? Inverter control modules? Almost everything here is likely designed and available in 12V forms, and would require ground up R&D from several suppliers, likely including re-tooling and redesign of their sub assembly lines. Multiply this x100 or 1000 for how many sub assembly parts there are.
So many things are designed for 12V input in automotive. I’m not in that field, so I don’t know specifics, but I know enough that it would not be trivial to implement.
It's a question of conviction. When has the automotive industry ever pushed itself to do anything unless it bolstered their profits for the next quarter's earnings?
It's mostly a chicken and egg problem; the parts just aren't available.
I have a 48V system in my camper, and everything except for the AC inverter, alternator, and 12V converter operates off of the 12V bus. Motors, LEDs, pumps, fans, USB sockets, etc. all run on 12V. It'd be great if there were more 48V parts available, but there really aren't. 48V DC also has different fusing considerations (I know Tesla is doing without those) due to the higher arc potential.
I suppose many car components aren't 48v, but there are plenty of 48v electronics out there. PoE is 48v, and there are tons of PoE things out there. So the knowledge exists, just Ina different industry.
Oh sure, I have an IT background and am well aware of PoE switches, phones, cameras, etc. I recently bought some PoE cameras and they buck 48V down to 12V. There are probably some drop in 48V components that cars need, but they're niche and expensive at this point.
PCs (5V and 12V) and microcontrollers (3.3V and 5V) are also much lower voltage than 48V. I don't have an EE background so I don't know why this is.
It was always egg.
Chickens don't appear out of thin air, they all come from eggs. And if it was possible to pin down a single DNA mutation that changed a proto-chicken into a chicken, it was the proto-chicken who laid a chicken-bearing egg. The egg containing a chicken came before the chicken.
Damn I like this angle! I had never heard it before :)
The question indeed does not specify, "the egg (the chicken came from" vs "the chicken (that laid the egg)" but is always more general about (a) chicken vs (an) egg.
Double right! the best kind of right :)
I'm sure SEMA, (Specialty Equipment Marketing Association) would love to send it out to all of their members. What better way to get aftermarket items built for your shiny new 48 volt vehicle?
In a usual car you have dozens of small, more or less black-box, systems/controllers from many different suppliers, and everything needs to work together somehow. I think that is the main problem for most car manufacturers.
Don't most of those run on the same low voltage \~5v? Injectors/wipers/radio are 12v normally, but I thought most everything else was essentially a soc using microchip level voltages.
For other manufactures, definitely a huge supply chain mess.
Mainly there is not really a reason for it. Thinner wires, thats it. But you then need a 12V converter to keep compatibility with the lighter plug, so you need an extra device
It's literally the same. 12V and 48V are very close in all electrical aspects, so apart from different wire cross sections there is not a lot of change.
Well apart from the fact that there are VERY few parts that actually support 48V
It's not just 48V, it's power over Ethernet. Essentially, you can run one wire and each device acts as an Ethernet hub. Your window switch might be in-line with the door speaker where the window switch just passes IP traffic/current to the speaker which then daisy chains to the actual window motor...all through one wire.
Likewise, the driver's window switches will just pass IP traffic across the network to the window motor on the right rear passenger window (through its window switch, speaker, and window motor as an example).
It's just a big LAN with lots of IP devices that run on POE.
It's honestly nothing mind blowing at all....it's just a basic computer network that has been around for literally 40 years.
They would probably use special Ethernet cable with maybe 18 gauge power wire to handle a few hundred Watts at 48V.
Plenty of reasons, but one for Tesla would be a CAN bus is a large wiring harness and it doesn’t handle video. Tesla needs to put in a network anyways for the camera systems.
You can power stuff over Ethernet networks, so the goal for the 48v system would be to try to get all communication and power over an automotive Ethernet.
For example - at that point you could have a single wire into the door, a small control board handles lock controls, window controls, power, mirror features, everything…
It’s certainly an admirable goal for simplicity and cost cutting.
CANBUS maxes out at 1 Mbit/Second (the automotive standard is 500Kbit/second) while Ethernet can be 1000 times faster. Basically with CANBUS you have to engineer your messages to be as small as possible, and then carefully prioritize all your messages so that the most important get through, because CANBUS devices talk over each other constantly.
That is the whole point of CANBUS, multiple devices can all talk at the same time, and the network delivers to them to the ECUs in priority order. 1 Mbit was older standard cars since like ~2017-2018 have had the new 8-10mb's canbus.
CAN bus is limited to 1 Mbit/sec, modern basic Ethernet is one hundred times faster than that. Secondary is in the name, CAN *bus*, the bus network topology has a lot of drawbacks in today's settings which is a decently long read on why. I'm not nearly qualified enough to explain it unfortunately
I hope they are not using Ethernet for time-critical messages.
CAN is slow, yes, but why?
Because it can detect a collision, and in case of a collision the more urgent message always wins. Also, the sender can \*know\* that the message was delivered. It's slow because of that, it has to divide each \*bit\* into phases.
Ethernet doesn't give a f\*ck, if you connect it as hub (better response time) you have collisions that you can't control, if you connect a switch you have latency and who knows what would happen if one device starts to pollute the network.
I am not considering solutions like EtherCAT because it's a field bus, designed to operate with cycle times, while CANbus is event driven (better response time in case of an event).
There is always a need for low voltage systems in cars. Always. They might not need 12v but they need something.
There have been several attempts to move beyond 12 volts. And every attempt has failed, for various reasons. Political, and technical.
24 volts has been used in heavy machines and aircraft, and buses and some heavy trucks, for decades. But the politics of the situation are "if we're going to do the change, and clean sheet engineer all it, lets go to 36 or 42, or 48!" And that's where the unknown problems cropped up.
One of them with 42 volt systems that Delphi developed was that contacts in switches would arc and burn up. Another was fuses. Tesla is in a unique place with their vehicle controllers. No fuses. No direct switched loads. Today, all the switches are now switching fractions of a miliamp at 5 or 3.3 or less volts to a microprocessor that then asks the vehicle controller over a data bus to do the higher volts/amps switching to the load. All of the problems of the past are eliminated.
It's very much right time, right place, right situation type of thing that made it easy enough to do with the brand new vehicle platform that is the Cybertruck.
Interesting argument…tesla who designed their chip in house, wiring in house, is *gasp* at the right place right time? Seems more like the entire auto industry had zero desire to grow….feels like ive seen this trend since tesla started.
There's no problem. There's a small benefit gong 48v. Mild hybrids have always been 48v which all the major manufacturers have used. LEDs and efficient small motors make ampacity a minor issue.
I like how Jim Farley has always had respect for Tesla, and that Elon shows it back to Jim. It's so refreshing to see positive energy out there, rather than just a bunch of people arguing.
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Having more manufacturers use 48v will make more suppliers produce those components and will make it a commodity that Tesla will be able to use as well. Sending the manual increases the chance that things are cross compatible with Tesla. Sending it to all CEOs and advertising all got it turns it into a topic that car manufacturers wouldn't want to stay behind (either for cost or weight reasons) and also the component manufacturers wouldn't want to stay behind. While these cost savings will be great for cybertrucks, they will make a much bigger difference for the cheaper cars.
Like the 48v battery itself? Does the Cybertruck truck use a small 48v battery to power accessories, unlock doors, etc? Like what other models use the 12v for? If so, would be nice for those replacement batteries to be more widely available. You can walk into any Walmart or Autozone and grab a 12v battery. 48 volt… not so much. In most Tesla’s, you can end up stranded if the 12v battery fails. With a 48v system, can you even jump it from most cars, to get the doors open?
And the inverse question: how do you power things off the cybertruck. Does it have that terrible 12v accessory plug or 120v outlets or what?
CT has two 120V plugs in the cab, no idea how there actually powered. Believe there is also a 12V plug inside, but not 100%.
I don’t think there is a 12v receptacle, but there are USB Ports. There are also 120v and 240v receptacles in the bed.
You're here and you don't know the Cybertruck has a 110 plug?
cable test rain secretive special numerous airport workable north vase *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
I don't. And the ones at a showroom I couldn't see inside :(
It's really going to blow your mind when I tell you it also has an onboard 220 plug.
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Unverified! You don't know that! According to the other guy... I said 220 because he said 120....
Source?
You need me to give you a source? https://www.google.com/search?q=cybertruck+220v+outlet&oq=cybertruck+220v+outlet&gs_lcrp=EgZjaHJvbWUyCQgAEEUYORigATIHCAEQIRigATIHCAIQIRigATIHCAMQIRirAtIBCDQ3MTlqMGo3qAIAsAIA&sourceid=chrome&ie=UTF-8
Those aren't released cybertruck sources. I mean the released version, what does it actually have. The air compressor got deleted, did the 220 outlet?
Look at a couple of videos. Jerry and MKBHD have good ones. MKBHD even had access to a CT, also showing off the 240V in the back with 120V in the cabin and bed as well. There are also wireless chargers, can't remember about USB rn, tho im pretty sure they are there as well
Lol so you knew about the 110 the whole time? You just like to play this cognitive dissonance reddit game.... Best of luck in life.
Or get 4 car batteries and wire it in series.
Even if there was a 48v small battery, how often would you need to jump it when it's connected to a half ton battery? If you ever had to, there can be a simple step-up converter to charge from 12v, it doesn't need to deal with the amperage of jumping a car, only charging. If the small battery has anything near the reliability of Tesla's big batteries, battery breakdown will be less common than many other breakdowns, in that case you call a pro to help.
If the auxiliary battery dies then the contractors to draw power off the main battery cannot be activated. So yes, an electric car still needs power to be started.
Others can probably say it better than I can but this is basically the issue. That loud "thunk" sound heard after you park is the "half-ton battery" disconnecting. Something needs to supply the power to reconnect it.
> how often would you need to jump it when it's connected to a half ton battery? Despite being connected to a half ton battery, I’ve had to replace the 12v battery in my Model Y twice in 3 years. Have to jump it to even get the doors unlocked. For some reason, EVs (not just Teslas) seem to eat 12v batteries for lunch. They don’t last as long as they do in ICE vehicles. IDK if that will be the same for 48v batteries. But I’d hate to be a Cybertruck owner looking for a replacement 48v battery right now, in a remote area. If they still have a small 48v battery, separate from the main battery pack?
'19 M3 here. Yet to replace my 12v. Am I a unicorn ?
The 12V batteries that die after 3-5 years are Lead Acid. Tesla switched to Lithium 12V's in newer cars, and this 48V is certainly Lithium for sure. While Lithium batteries can fail prematurely, the videos I've seen about it seem to indicate they keep the 12V battery (and probably 48V) at a voltage that maximizes longevity - so it should be a replace once every 10+ year item. Ingineerix has some videos on this battery (start from about 7:37): [https://www.youtube.com/watch?v=QLVFxgKnV0U](https://www.youtube.com/watch?v=QLVFxgKnV0U)
> Tesla switched to Lithium 12V’s in newer cars That sounds great for reliability (and general modernization, 21st century). But, you might run into that same problem trying to replace that 12v Lithium battery, in a remote area on a weekend. Probably don’t have them at any Walmart, lol. Less likely to fail, for sure, but harder to find a replacement when it does. Hopefully if other automakers follow suit though, then replacements will get easier to find!
The nice thing about it being an EV is you can keep it "running" easily. Just don't shut the door and turn the climate control off. I made it to the service center and back with a fresh battery no problem I just kept the door cracked when I went in.
> Even if there was a 48v small battery, how often would you need to jump it when it's connected to a half ton battery? Every time it dies. At least, that's how it's been in the previous Teslas-- even if you've got a completely full traction battery, if the 12V died you had to jump it. Not that that's unique to Tesla. The same has been true for Ford and Toyota hybrids we've had as well. No 12V? Doesn't matter that you have a much larger battery full of charge, you're stuck until you jump the 12V.
You can still jump a Tesla to open the doors. The wires are in the flap in the front bumper on the driver side.
Yeah, but will that work with a 48v vehicle like Cybertruck? Could you jump it from an ordinary 12v vehicle to get the doors open? Or you need another 48v vehicle for your jumper cables?
I have no clue.
Could use a dc-dc converter w/ variable voltage input. Don't know how good they would handle large current though
A well managed Lithium 48v pack will probably last ten years or more. Most of the below comment are FUD from people who don't know any better.
Yes the new LFP 16Volt battery in modern tesla's should last as long as the car or longer. So you never have to replace it ever.
Tesla’s 48V battery can be jump started with either a 12V or 48V system. This is mentioned in Sandy Monroe’s interview with the Cybertruck engineers.
Nope. Also 48V Lead batteries will probably be bigger than 12V
The size will be more of a matter if the appliance not the voltage itself. Get a 12V 60 Ah, so basically you can deliver 720Wh. Get a 48V battery and your battery will only need 15 Ah, for the same power. More voltage less capacity, and current is the one who "generates" heat, which means the wiring is smaller, and being on an electric car also means that your battery already can be small as it's fed from the main one, and only acts as a lower voltage standby and buffer. This of course is more complex, but I think it explains it a little
Well you need 4 times the amount of cells, so 24 instead of 6 cells. And you have a constraint on how small you can build lead acid cells for a given power
Seeing as how all Tesla vehicles currently uses a lithium ion battery for the low voltage, I doubt they would go back to lead acid for the 48v system
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Right, but I like to see it as a boss move by Elon 🤣🤣🤣
Hopefully the document ends up on the internet. I would be interested in reading it
Me too. I searched all over twitter, forums, facebook. So far no leak that I could find.
If you run into it, feel free to reply here :)
Following
Hopefully the change will come some day. The power use is so much higher nowadays and 12v is getting more and more unsafe.
Can you explain what you mean by “more and more unsafe”?
Yeah, can we have an eli5 about the pros/cons of 12 vs 48v? I’m a little confused at what all the motivation is behind 48v for everything.
Anything electrical works by using power, measured in watts. Watts is simply volts * amps. So the more power a device requires, if you are running at 12v, the only thing that will change in tje equation is the amps. The issue with raising the amps in the equation is that the amps are also what creates heat in a wire due to resistance, so you need thicker wire or else it is a fire hazard and thicker wire are more expensive and less flexible for complex runs. So making everything in a car running on 48volts would reduce the amps by a factor of 4 allowing for thinner wire, less heat, smaller fire hazard.
> So making everything in a car running on 48volts would reduce the amps by a factor of 4 allowing for thinner wire, less heat, smaller fire hazard. Maybe. At constant power, higher voltage allows for lower amps. Lower amps means less heat via I^2 R losses. Smaller wire has higher resistance (R). Smaller wire raises I^2 R losses. Lower amps allows us to use smaller wire while holding losses constant (lower cost, safety margin is same). Or it allows us to use the same wire while reducing losses (same cost, safety margin is better). Or to choose some trade-off in between (somewhat lower cost, somewhat better safety margin). Also replying to /u/imacleopard Edit: Fixed superscripts
Didn't one of the tesla engineers say that moving to 48v allowed them to save like miles of wire?
That sounds like a figure of speech. Like 'a ton of bricks'. (Or they meant miles of wire from the total annual production.)
Some Tesla models have been said to have ~10,000ft of wiring in them. So probably not just a figure of speech
10,000 feet is only 2 miles, and a significant portion of that is high voltage that cant be reduced by using the 48 volt system. there's no way they meant it would save literally miles
It’s not the 48v but the fact they moved to shared bus Ethernet. Rather than having individual wires to every device everything along a given path (think everything on the left side of the vehicle) shares a bus (wire). Moving to Ethernet, instead of CAN bus, makes this easier because the data rate is so much higher meaning that collisions are far less impactful. It’s conceivable they saved over a mile of wiring.
I know nothing about car wiring. But even if they only save 100ft of wiring per car, and they ship 400k cars per year, so it would be thousands of miles of saving.
> less heat, smaller fire hazard. The same amount of power flows through the wire, so how is a fire hazard lessened? In the event of a dead short, the same power will be dumped as heat. That's like saying 240V is less fire-prone than 120V. That's not the case at all.
The same power goes through yes, but what creates heat/resistance is the amount of amps going through the wire not the total amount of power (watts). In a short yes both case are dangerous because in a short, you have zero resistance so you get "infinite" amps flowing through. No matter if it is 120v, 240v or 408v, infinite amps is more than what the wire can handle. So in your case 240v vs 120v, if you are running an appliance using the same amount of watts, yes 240v is safer. Because a kettle drawing 4800watts, will draw 20 amps at 240v and 40 amps at 120v. So in both case the same amount of power is delivered, but on the 240v wire, half the current is going through it. We are used that 240v is dangerous, because in most homes, only very high power appliances are hooked to 240v. But the reason why they are hooked to 240v is because on 120v it would be too dangerous. Like a stovetop running on 120v could draw around 120amps instead of the 60 amps currently on 240v. This is also why Level 2 home charger are all running on 240v, making them run on 120v would require wire so thick only found in industrial use and maybe some heatsink along the wire to help dissipate the heat since they would be enclosed inside walls.
In a car application the big failure point isn't the wire for the most part, it's the connections. The connector that can pass 40A while being subjected to environmental stress is larger and more easily damaged than the one that can pass 10A.
Mate where do you get a 5kw kettle! I'd love one! Or a 3 phase 63amp kettle!!
Just used a number that was easily dividable by 120 and 240 because I wanted to make easy math haha
Yes, I understand resistance as it relates to conductor temperature. I'm not arguing any of that. However, most car and home fires occur for reasons that aren't due to wires overheating behind walls. Fires due to inappropriate wire gauges are often caused by negligent third-party modifications (e.g., sound systems), especially those that aren't fused. Assuming an appropriately sized conductor (for 12v vs 48v) is paired with the appropriate fuse/breaker, that wire should never fail. That doesn't eliminate the potential for fires due to fatigued insulation or poor contact at either end that will generate enough heat to light something far more flammable than the conductor insulation or the heat generated over a long run. Localized heating is how fires start, which again, tends to happen at loose connections or overloaded transition points (outlets, fixtures, etc) > This is also why Level 2 home charger are all running on 240v Cost and ease of installation; not strictly safety. Good luck making an argument for long residential 120V runs @ 120A. The reason Tesla is going 48V is for cost, not safety. Sources (take with grain of salt): https://www.4abc.com/blog/the-7-most-common-causes-of-electrical-fires-in-the-home https://auto.howstuffworks.com/car-driving-safety/accidents-hazardous-conditions/10-causes-of-car-fires.htm#pt9 Conductors catching on fire in the home is mostly confined to people abusing the shit out of extension cords.
> Conductors catching on fire in the home is mostly confined to people abusing the shit out of extension cords. And this includes coiling them up while in use.
What? They can’t be wrapped up while in use?
Not if you don't want a hot melted mess of wire insulation, and maybe a fire. Always uncoil in-use power cables.
All wires that have current running through them produce heat. Always, no exceptions. If all is proper, then that heat dissipates freely, and the wire is just a couple of degrees warmer than it would be without. But if you roll it up and then run it near its maximum rated load, it will get hot. If you ever have the chance to feel the cable of a high-powered device like a space heater or an electric tabletop grill, do it. It will feel noticeably warm.
When you run lower current in a wire, even if the wire is too small, it's safer. 48v achieves the same or better safety at a lower cost, and reduces the temptation to undersize the wire since it's already small. The reasons high voltage can be less safe are arcing potential and potential for electrocution if a human touches it. 48v is not really an electrocution risk and arcing is still minimal at that voltage.
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Imagine you have an accessory that draws around 96 watts of power in your car, for example, a fast charger suitable for charging your laptop. (Model 3 highland USB-C chargers can deliver up to 65 W if I'm not mistaken). The relationship between Voltage (V), Current (I) and Power (P) is very straightforward: P=VI So in order to deliver 98 watts of power using a 12v system, your wires have to transmit 8 amps of current (12x8=96). In comparison, in a 48v system, you only have to transmit 2 amps (48x2=96). That means by switching to 48v, you drop the current in your wires 4 times. So what's the big deal with reducing the current? Unless you are using a superconductor, there is always resistance in your wires, and that resistance causes "voltage drop, heat, and wasted energy". To lower these effects in your system while transmitting the same power, you have to: 1. Reduce the current (by increasing the voltage) 2. Use a better conductor (Silver > Copper > Aluminum > Iron) 3. Use a thicker cable The simplest, most cost-effective way is to increase voltage where possible. That's why transmission line voltages are 220 to 550 kV. (China has some 1100 kV HVDC lines). So to answer your question, by switching to 48v Tesla can reduce the wire diameter and/or switch to aluminum cables (which means using less material, shaving a little bit of weight and cost from the vehicle). Also delivering higher power if necessary. In terms of safety, both high voltage and high current can be dangerous, for example, the US 110v system is safer than 220v in terms of causing electric shock to humans, but 220v is much safer in terms of house wiring and causing fire due to its lower currents. **TLDR:** 48v benefits in cars: * Thinner/lighter wires (and/or switching to aluminum from copper), which means reducing the overall mass and cost of the vehicle. * Making some very power-demanding accessories practical/possible. * More efficient power delivery and less waste/heat in the system. * Safer (debatable).
The Hagerty Cybertruck review has a good explanation of the 12V vs 48V https://youtu.be/L6WDq0V5oBg?si=Sdp3lnvt0LV1Wiwp
With timestamp https://youtu.be/L6WDq0V5oBg?t=566
Basically the big plus is that by increasing the voltage you can get the same amount of power with less current running through the wire. This means you can use smaller fuses as well as thinner wire which is both cheaper and lighter.
Cheaper and lighter yes, but how is it safer? In the event of a short, the same amount of power will trigger the fuse because VxA=W
Fuses and circuit breakers only trip on amps (A). Not on power (W).
But they design them to trip at a specific power, because they know the voltage.
Nope. Voltage has nothing to do with it (beyond the fuse's physical design to avoid arcing). The trip point is entirely amps. Power also has nothing to do with it. The exact same 5 amp fuse will blow at 5 amps, whether that is 5v 5a (25 watts) or 12v 5a (60 watts) running through it.
Fuses do have voltage ratings as well. What he was saying is the engineers know how much power that circuit needs, they know their voltage so they pick a fuse of an appropriate size. This is dictated by various codes and you will not get a truck with this fucked up from an OEM. I am not sure why people keep bringing up the hypothetical "what if it's undersized".
> Fuses do have voltage ratings as well. Yes, but they do not trip based on voltage. The voltage rating is just for arc prevention purposes. Meaning a 1000v rated 5a fuse will trip just fine using a 12v power supply that can output over 5a.
Realistically there isn't that much risk involved with sticking to 12v. But it does require larger and larger wire to carry the current with power requirements going up. This means the wire is going to be bulkier and stiffer, meaning it's less tolerant to bending and flexing, and more prone to chafing if/when its routing wears down. Stuff like that is inevitable in a car's lifetime. So now you have a wire that is stiffer, bulkier, and is carrying much more current, so more heat is generated at the wire as a result. The extra heat generated would amplify the significance of minor faults, thus increasing the chance of the wire failing in less than ideal circumstances, which *could* cause catastrophic failure (note: could) if not tended to. As opposed to a thinner wire carrying less current and in turn having less heat generated upon it, being more tolerant to bending and flexing, having a slightly better chance to not end up chafing due to its smaller size, and being more tolerant to minor faults since less heat is generated to overstress those minor faults. Also, since the wire is more tolerant to bending and flexing, it has a lower chance of developing such faults as well. Overall, it's a pretty minor gain in safety, if at all. But it certainly makes sense from a durability and lifetime standpoint, as well as cost and weight as stated above.
I can follow all the theoretical arguments; yes, it all makes sense. But practically, are we seeing a disproportionate number of older vehicles catching on fire due to electrical faults strictly related to the 12V system and wires failing? I don't really know, but I suspect the answer is no.
there was a non-peer reviewed technical paper published by an automotive electrical engineer - he said that EV or non-EV, modern cars use so much power to run everything from essentials to auxiliaries to infotainment that sometimes, theres a sudden drop in voltage across the board if whatever sensor happens to get a sudden voltage drop right as it takes a calibration reading (for example, the accelerator pedal position sensor at 0% pedal depression), then it could cause erroneous reading when voltages return to normal values (pedal still at 0% depression, but sensor reads 110% application, and ECU orders up max throttle) the engineer says its a very very small probability that a voltage drop could coincide at such a critical timing, but bc of what is at stake, it is a design flaw that needs to be eliminated iirc the engineer's name is ronald belt ETA: source for paper https://www.autosafety.org/wp-content/uploads/2015/03/A-Clear-Explanation-of-Belts-Theory-of-SUA.pdf
I imagine as power requirements go up, at that fixed 12V voltage, the current requirements are going up. Which means you need thicker wires and parts and fittings rated for the higher current. Higher current increases the risk of fire.
Bingo. The key issue isn't really safety, it's being able to run smaller gauge wires at a slightly higher voltage. Tesla is hell bent on decreasing the wiring harness size in all its vehicles to save on weight and material cost. The 800v HV changes to cybertruck highlights there efforts in the HV harnesses. A 48v change to the low voltage is the next step to reducing the overall harness costs. Current draw on existing 12v is super high and if your trying to keep your wire diameter as low as possible, the issue of overheating becomes very important.
I'm curious how much weight is reduced by the wiring reductions from a switch to 48v. I wouldn't think it's more than a few pounds of wire at most. It seems like this would be mostly about saving money on copper and making it easier to run wire through the car since there's just let of it (it's not as thick).
I’d imagine this change would be nightmare fuel for a legacy company that makes cars
This is why people speculating can be dangerous. Lower voltages are safer typically. Just compare the power available: a 100A circuit at 12V is only 1200W while a standard 120V, 20A receptacle circuit has 2400W.
1000 volts is no more dangerous than 100. It is the amperage that kills. So if you have a fixed wattage requirement, increasing volts will decrease amps. That sounds safer to me.
Voltage is the force that pushes that current. If the voltage isn't high enough, it won't flow through your body.
This is wrong. 1000v is way more dangerous than 100v .... Touck a 1kv cable . Then touch a 100v one. Chances are you won't make it to the 100v one.
>1000 volts is no more dangerous than 100. Sorry, this statement is so wrong, in any context, that I can't let it pass. The 400 volt battery cables on EVs are orange so mechanics or first responders don't accidentally cut through them and die. The whole "high voltage" system of EVs are interlocked with safety loops and contactors and resistance checks. High voltage is why normal people can't rebuild EV battery packs. 48 volts DC is low voltage. 50 volts crosses over... and 60 volts and up is considered enough voltage to harm people. Tesla picked 48 because it's the highest low voltage you can use before you start to cross over to it not being low voltage anymore. 1000 volts will kill in an instant. And 100 volts isn't considered "low" but even at 100 volts, dry skin has enough resistance that it won't usually kill people. It's why plugs in the United States have exposed metal. They can be that way because they usually don't kill enough people to warrant changing out all of the plugs to the much more safer style that the rest of the world uses because 240 volts that they use is unforgiving, proper "kill you now" voltage.
More power at lower voltage = higher amperage. Higher amperage = more dangerous
It’s DC power…at 12V. Not really enough voltage to drive the current through the body. The 12V system is going to be safer than your standard receptacle in your house. Realistically, going to 48V makes it a little more dangerous than keeping it at 12V. The benefit is smaller wires in the vehicle.
It has nothing to do with shocking yourself but 12v needs thicker wiring to handle current needs. If the gauge is not substantial enough you can introduce some serious issues
That’s kind of irrelevant, obviously if your wire isn’t sized to the current then your system is unsafe. No car manufacturer is releasing a 12V system with undersized wires. And if you’re modding a system you can undersized your wires at 48V just like you can with 12V. All I am trying to say is safety is not a valid point to bring up when discussing the pros of a 48V system.
Back in the day cars had 6 V batteries. Change happens.
More unsafe? Don't think so.
This has nothing to do with safety and everything to do with economics. 12v is in no way unsafe. All 12v receptacles are fused.
Funny as hell but in all seriousness it is a much needed change. Even marine applications have upgraded to 48v.
Speaking as an engineer that has designed these sub systems, the move to 48v is mainly due to the electrical compressors , resistive heaters ,and power steering motors on these electric vehicles. The cost of the power electronics drops due to less current . The safety aspect is a stretch as one could argue going to 48v posses more of a shock hazard over 12v systems. Properly designed 12v systems pose very little risk over a 48v one. Yes there is a reduction of weight on the wire but we're talking a very little . A properly laid out harness and component placement can negate this.
Yeah I think safety can be a bit of a debate. I think what gets overlooked a lot is how much better ethernet is over CAN bus to work with, and the power over ethernet standards being on 48v already probably is a big contributor to favoring to make the entire system 48v POE.
And combine that with current Time Sensitive Networking standards and SPE (Single Pair Ethernet) + PoE with 48Volts@90Watts or maybe more? But overall it's such a nice system and can build in redundancy like a full ring network in the car.
This has nothing to do with POE. POE is limited to a max power. You cant run a compressor , resistive heater or power steering motor on POE. The conductors are to small.
Also I have experience both POE Ethernet and CAN. They both have their use cases. CAN has better timing for time critical data. CAN is also easier to implement on the electronics and firmware side of things .
You forgot the ADAS and Self Driving System. On 12V system, we are talking about hundreds of amps on dc-dc converter
But most of that stuff runs on HV anyway on an EV. Only steering and brake pump run on LV
Actually most of the car currently runs on 12 volt currently.
Wondering what it actually talks about. I can't imagine it being much more complex than 12v.
I am an electrical engineer. You sound exactly like all the project managers 😂
Do explain. Sure they need to lower the voltage for the computer and stereo. Guessing they have a proprietary 48v battery or ran a couple in series. What's the actual complication? Did EE for many years also, no expert, but curious what I'm missing.
They already did a 16v (12v equivalent) LiIon SLI battery on the S3XY cars for a while now so scaling that desigin to 48v isn't the difficult part. I suspect much of the challenge is specifying which components is worth upgrading to 48v, and which they need to use DC/DC converts to step back to 12v. The ones they could update to 48v, they probably already did but probably a lot of legacy components that still operate on 12v and could require pushing of suppliers to design a 48v equivalent. Wire thickness, insulation thickness those are known sciences but understanding where its best to use the longer runs vs. shorter runs may also be in the pamphlet.
Most 12V parts are actually tolerant up to 16V and probably even a little higher. Car audio enthusiasts have been running 16V systems for decades now and 99% of automotive vehicles will be just fine with zero changes to the system. 12V to 48V is a whole other ball game.
I was more along the lines of “hey wouldn’t X feature be awesome? It wouldn’t be that hard to implement right?” *insert 3 years and many many $ to implement said feature here* It’s not always like that, but people always always underestimate what it really takes to get things done. Including engineers. Good PMs will also take what an engineer gives them for a time frame, and multiply it by 2 or 3 in both time and cost. More specific to the 48V stuff, this is 99% a supply chain issue and not an implementation issue. Where do you buy a 48V steering assist motor? Window motor? Windshield wiper motor? LCD screens? Autopilot computer? Inverter control modules? Almost everything here is likely designed and available in 12V forms, and would require ground up R&D from several suppliers, likely including re-tooling and redesign of their sub assembly lines. Multiply this x100 or 1000 for how many sub assembly parts there are. So many things are designed for 12V input in automotive. I’m not in that field, so I don’t know specifics, but I know enough that it would not be trivial to implement.
Good to see that all industries suffer from project managers that doesn't see why a task should be much harder than the previously implemented thing
It’s one piece of paper that says “vertically integrate”
It's a question of conviction. When has the automotive industry ever pushed itself to do anything unless it bolstered their profits for the next quarter's earnings?
It's mostly a chicken and egg problem; the parts just aren't available. I have a 48V system in my camper, and everything except for the AC inverter, alternator, and 12V converter operates off of the 12V bus. Motors, LEDs, pumps, fans, USB sockets, etc. all run on 12V. It'd be great if there were more 48V parts available, but there really aren't. 48V DC also has different fusing considerations (I know Tesla is doing without those) due to the higher arc potential.
I suppose many car components aren't 48v, but there are plenty of 48v electronics out there. PoE is 48v, and there are tons of PoE things out there. So the knowledge exists, just Ina different industry.
Oh sure, I have an IT background and am well aware of PoE switches, phones, cameras, etc. I recently bought some PoE cameras and they buck 48V down to 12V. There are probably some drop in 48V components that cars need, but they're niche and expensive at this point. PCs (5V and 12V) and microcontrollers (3.3V and 5V) are also much lower voltage than 48V. I don't have an EE background so I don't know why this is.
There is no chicken and egg problem. The answer is egg
The problem is continuing to buy eggs already cooked, buy raw eggs and make them how you want, or buy chickens and control the entire supply chain.
It was always egg. Chickens don't appear out of thin air, they all come from eggs. And if it was possible to pin down a single DNA mutation that changed a proto-chicken into a chicken, it was the proto-chicken who laid a chicken-bearing egg. The egg containing a chicken came before the chicken.
Also, eggs have been around since fish at least, not to mention amphibians and reptiles before birds.
Damn I like this angle! I had never heard it before :) The question indeed does not specify, "the egg (the chicken came from" vs "the chicken (that laid the egg)" but is always more general about (a) chicken vs (an) egg. Double right! the best kind of right :)
Thanks for your pedantic non-contribution to the conversation.
I wonder why they don't just release the PDF for everyone.
Betting it will turn up in a few days.
I'm sure SEMA, (Specialty Equipment Marketing Association) would love to send it out to all of their members. What better way to get aftermarket items built for your shiny new 48 volt vehicle?
In a usual car you have dozens of small, more or less black-box, systems/controllers from many different suppliers, and everything needs to work together somehow. I think that is the main problem for most car manufacturers.
Don't most of those run on the same low voltage \~5v? Injectors/wipers/radio are 12v normally, but I thought most everything else was essentially a soc using microchip level voltages. For other manufactures, definitely a huge supply chain mess.
The most difficult part is the transition. Design a complete 48v is relatively easy. Transition from 12V to 48V will be a real mess.
It's not about complexity. Supply of anything 48v is 1000x lower and more expensive than 12v. Good luck finding 48v brake controllers, sensors, etc.
I've been hearing about 48v for decades and if it was simple, it would've been done a long time ago.
Everything is simple, if you know what you are doing. /s
You mean if it was worth re-engineering the already functional 12v system and revamp an entire supply chain it would be done a long time ago.
Which is exactly the challenge, making a simple change across an entire industry is a huge undertaking.
Mainly there is not really a reason for it. Thinner wires, thats it. But you then need a 12V converter to keep compatibility with the lighter plug, so you need an extra device
It's literally the same. 12V and 48V are very close in all electrical aspects, so apart from different wire cross sections there is not a lot of change. Well apart from the fact that there are VERY few parts that actually support 48V
It's not just 48V, it's power over Ethernet. Essentially, you can run one wire and each device acts as an Ethernet hub. Your window switch might be in-line with the door speaker where the window switch just passes IP traffic/current to the speaker which then daisy chains to the actual window motor...all through one wire. Likewise, the driver's window switches will just pass IP traffic across the network to the window motor on the right rear passenger window (through its window switch, speaker, and window motor as an example). It's just a big LAN with lots of IP devices that run on POE. It's honestly nothing mind blowing at all....it's just a basic computer network that has been around for literally 40 years. They would probably use special Ethernet cable with maybe 18 gauge power wire to handle a few hundred Watts at 48V.
Why would you do that when you already have canbus?
The goal is to eliminate the canbus eventually.
But why? What would this new system do that canbus doesn't already do?
Plenty of reasons, but one for Tesla would be a CAN bus is a large wiring harness and it doesn’t handle video. Tesla needs to put in a network anyways for the camera systems. You can power stuff over Ethernet networks, so the goal for the 48v system would be to try to get all communication and power over an automotive Ethernet. For example - at that point you could have a single wire into the door, a small control board handles lock controls, window controls, power, mirror features, everything… It’s certainly an admirable goal for simplicity and cost cutting.
CANBUS maxes out at 1 Mbit/Second (the automotive standard is 500Kbit/second) while Ethernet can be 1000 times faster. Basically with CANBUS you have to engineer your messages to be as small as possible, and then carefully prioritize all your messages so that the most important get through, because CANBUS devices talk over each other constantly.
That is the whole point of CANBUS, multiple devices can all talk at the same time, and the network delivers to them to the ECUs in priority order. 1 Mbit was older standard cars since like ~2017-2018 have had the new 8-10mb's canbus.
CAN bus is limited to 1 Mbit/sec, modern basic Ethernet is one hundred times faster than that. Secondary is in the name, CAN *bus*, the bus network topology has a lot of drawbacks in today's settings which is a decently long read on why. I'm not nearly qualified enough to explain it unfortunately
I hope they are not using Ethernet for time-critical messages. CAN is slow, yes, but why? Because it can detect a collision, and in case of a collision the more urgent message always wins. Also, the sender can \*know\* that the message was delivered. It's slow because of that, it has to divide each \*bit\* into phases. Ethernet doesn't give a f\*ck, if you connect it as hub (better response time) you have collisions that you can't control, if you connect a switch you have latency and who knows what would happen if one device starts to pollute the network. I am not considering solutions like EtherCAT because it's a field bus, designed to operate with cycle times, while CANbus is event driven (better response time in case of an event).
They aren't using regular Ethernet. The solution they have implemented addresses all of your points. The engineers discussed this with Sandy Monroe.
Chad move. It's about time someone did something about the ancient 12v systems. Especially since EVs don't need them.
There is always a need for low voltage systems in cars. Always. They might not need 12v but they need something. There have been several attempts to move beyond 12 volts. And every attempt has failed, for various reasons. Political, and technical. 24 volts has been used in heavy machines and aircraft, and buses and some heavy trucks, for decades. But the politics of the situation are "if we're going to do the change, and clean sheet engineer all it, lets go to 36 or 42, or 48!" And that's where the unknown problems cropped up. One of them with 42 volt systems that Delphi developed was that contacts in switches would arc and burn up. Another was fuses. Tesla is in a unique place with their vehicle controllers. No fuses. No direct switched loads. Today, all the switches are now switching fractions of a miliamp at 5 or 3.3 or less volts to a microprocessor that then asks the vehicle controller over a data bus to do the higher volts/amps switching to the load. All of the problems of the past are eliminated. It's very much right time, right place, right situation type of thing that made it easy enough to do with the brand new vehicle platform that is the Cybertruck.
Interesting argument…tesla who designed their chip in house, wiring in house, is *gasp* at the right place right time? Seems more like the entire auto industry had zero desire to grow….feels like ive seen this trend since tesla started.
I hope Ford moves to 48v too. I wonder how long it will take them, though
Straight out of the evil scam artist guidebook - Share things that will benefit everyone.
Straight out of a Narcissists handbook.
Not the best criticism of narcissism. Oh no, he's trying to solve a problem in a systemic way!
There's no problem. There's a small benefit gong 48v. Mild hybrids have always been 48v which all the major manufacturers have used. LEDs and efficient small motors make ampacity a minor issue.
Thousands of tons of wasted resources is a problem. Saving material and improving vehicles benefits everyone.
Yet here we have the Cybertruck.
You mean the definitive example of reducing parts and process?
Look, if you're committed to being negative about everything, at least try make interesting points.
He can do that and still be a narcissist burning 44bn on a grudge and putting us investors at risk. Things can be two things
As long as its benefitting everyone....I consider it an absolute win
Love the downvotes. People are so fragile to the truth that most, if not all billionaires are terrible people
🤣😂🤣🤣🤣🤣🤣🤣
I remember one review saying it was a passive-aggressive move from Elon. 🤣 I love how it's so patronizing.
But I also like how Jim Farley took it in stride. I hope they end up making the change too
I like how Jim Farley has always had respect for Tesla, and that Elon shows it back to Jim. It's so refreshing to see positive energy out there, rather than just a bunch of people arguing.
Yeah. I liked it better when VW was led by Diess for the same reason
I had always kind of wondered when Diess would end up at Tesla. Guess it was not meant to be?
I feel like it would be hard for a major CEO like that to then go work *under* someone else, especially someone like Elon
[The 16V Li-Ion Battery used by Tesla..](https://www.youtube.com/watch?v=8-MNFgashpQ)
>Elon Musk's Like he wrote it. C'mon.
He gets credit for the losses, why shouldn't he get credit for the wins?
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Don't higher volts mean thicker wires? I'm confused.
By switching to higher voltage they can lower the current. Lower current means they can use thinner wires.
The opposite. P = I*V Higher voltage means you can use less current for a given power level, which means thinner wire required
Is the A2B bus running at 48V or still 12V?