Many comments here seem to be confusing the accessories circuit voltage with the electrical vehicle motor and drive system. The vehicle motors have a combined power output of 450KW which requires a high voltage 800V system or the wiring would be so heavy it would not be feasible.
This spec appears to be the accessories circuit with Tesla pushing for a new 48V standard. That’s super smart because it immediately means you need roughly a quarter of the metal in wiring that you needed previously. It’s cheaper, lighter and more environmentally friendly. And it enables the use of higher power devices. If you’ve ever had to wire your 1000W sub woofer amp directly to your battery you know what I’m talking about.
It’s worth noting that newer GA aircraft like Cessna 172 use a 24 volt system. So non 12V systems for accessory power isn’t a totally new idea. And older 172s have 12 volt systems. So the transition was made in that space anyway.
Dumb question but why does deciding to run at a higher voltage decrease the amount of wiring necessary? And why not increase it even further then?
Watts = Amps * Volts (or, more scientifically, P = I * V)
If something draws 48 Watts of power, you can either supply it with 4 Amps @ 12 Volt, or 1 Amp @ 48 Volt.
It's the amps that determine how thick the wiring needs to be, so by lowering the amperage, you lower the amount of wiring needed.
I believe the only reason cars are 12 V is because that's a practical voltage to build lead-acid batteries at (which is actually closer to 14 V in practice). Early car electric systems were only 6 V back when the only accessories were the front lights and the horn, but as more stuff was added on cars moved to 12 V.
This makes such little sense to me. I'm probably just stupid, but if the same amount of power is flowing through the wire, don't you need the same size of wire? A higher voltage system will push more energy through the same component, so you need thicker wires. If you up the resistance of the component to consume the same amount of energy as before, you arrive at the same size of wire you were using before, don't you?
What exactly is magical about higher voltages that makes them suddenly able to carry more power across the exact same wire? I know you just said it's "lower amperage" but I don't understand how amperage can be the only thing dictating the required size of a wire.
A higher voltage system enables the same energy at a lower amperage, so constrained to wanting to do a particular thing (loud stereo, bright headlights, ...), higher voltages result in lower amperages. I'll opt to not try to explain that intuitively, hoping that somebody else chimes in.
For the other half, "why do amps determine wire size?" Amps are coulombs per second -- how much electrical stuff moves through a cross section in a second. The amount of heat produced is directly proportional to amperage (every bit of movement has a chance to whack into something and produce heat, and more movement per second or more seconds generates more heat). Wire size is ultimately constrained by being able to release that heat while still acting like a wire (not melting, not sublimating, still conducting, not setting anything else on fire, ...). The amount of heat released is proportional to surface area (proportional to the square root of diameter, but that difference doesn't matter a ton right now), and the amount of heat produced is proportional to amperage and approximately nothing else. The point where those two terms are equal is the limit for the system (engineers add in huge safety factors to account for conduit and insulation and other imperfections), above which your wire melts and below which it behaves reasonably. Higher amperages require higher surface area to release the extra heat (so much higher thicknesses), so a given amount of power (stuff you want your electrical system to do) requires lower amps or thicker wires to work appropriately, because you can achieve the same power by increasing the voltage on the same amperage, thereby solving your power problems without extra heat.
Edit: Heat released is also proportional to the temperature differential between the wire and the outside world, as well as a constant associated with how well it's thermally insulated. The wire temperature rises till either some sort of breakdown occurs or that rate of heat release balances the rate of heat production. The spirit of that original comment is correct, but this feels like a nuance that might matter to somebody new to the topic.
What matters is energy but what's being carried by the wire is charge. A given amount of charge can have more or less energy, which is what voltage is. So if you give each unit of charge more energy then you can carry more power by only moving the same amount of charge. You get a similar thing in mechanical systems: a shaft is sized based on the maximum amount of torque it can withstand, but the amount of power going through it also depends on the RPM. More RPM = more power, for the same amount of torque, so if you are for some reason limited in the size of the shaft, you can use a gearing mechanism to rotate it faster and then gear down the other side and get more power through a smaller shaft. It's just that in mechanical systems gears are a lot less convenient than changing voltages is in electrical systems.
(RPM and voltage are in fact related in EVs as well: generally speaking a higher voltage motor will be able to produce more power for the same amount of space and materials, but mostly by spinning faster, not producting more torque. You then need to gear it down to be practical in a car. But the trend is that things that make higher voltages and higher RPMs possible (the technology in transistors, insulation, bearings) are already cheap or getting cheaper, while things that make higher currents and torques possible (generally more raw material like copper and steel) are staying the same or getting more expensive. So EVs in general are pushing to higher voltages for lots of things)
Just as further confirmation, remember that long distance power delivery uses high voltage, often measured in kilovolts. Because of reduced losses that way.
The power loss by the resistance scales in the square of the current and linearly to the resistance. So doubling voltage reduces resistance power loss to one quarter so you could lower wire size and increase its resistance to double and still resistance power loss would be halved
Imagine you've got an object you want to move by shooting water at it from a hose.
If the pressure coming from the hose is high, then you don't actually need a lot of water, and so you can use a narrow hose. On the other hand, if the pressure is low, you'll need to use a lot more water at once, so a wider hose.
It's the same thing for electrical components. If you'll excuse the mixed analogy, if you need to push an object with 480 watts of water to get it to move the speed you want it to, you can either do it with 48 volts of pressure with a hose 10 amps wide, or do it with 12 volts of pressure 40 amps wide.
Resistance is proportional to the square of current. This would mean 1/16th the loss instead of 1/4th.
Isn't the resistance of a wire usually modeled as a constant value?
Power dissipated in the wire as heat is proportional to the square of the current. It's equal to the voltage drop times current (P = I * V). Voltage drop is current times resistance (V = I * R). So P = I^2 * R.
Nope. Consumed power is voltage*amperage, and it’s constant, so 4x more voltage means 1/4 the amps. Wire heating is I squared R, so with both I reduced and R increased the losses are just 1/4, not 1/16 of the 12V system. Because you wouldn’t keep the same wire gauges you’ve had in the 12V system, you’d reduce them to actually have some benefits from conversion.
Car electrical systems typically run at 13.8-14.4V while the alternator is charging and drops slightly after the battery is topped off. When the engine is off the battery regulates a 12v output
Things like stator motors were also probably quite difficult to do at 6v.
I know the older Honda CT110 postie bikes came in 6v in the old days. That was a kick start.
60 volts DC is a safety threshold. You start to move current through tissue at higher voltages.
Yes but state of your body/skin (R) and current (I) is what matters with regard to 60 volts being really dangerous (also the current path as the article below states).
60 volts is nothing UNLESS you are completely wet or sweaty.
"It is estimated at 150 ohms for completely wet skin (in water), 1000 ohms for sweaty skin, and 100,000 ohms to 500,000 ohms for dry skin."
Assuming a worst-case scenario with dry skin providing a resistance of 100,000 ohms, fatality becomes a possibility if the current exceeds 50 mAmp.
Therefore, the lethal voltage would be above 0.05 (50 mAmp)×100,000=5000 Volts. [1]
So if you are wet or sweaty, it could be 7.5V to 50V that gets dangerous.
So it makes sense why 60 volts is a safety threshold, especially for those that live in Florida or Arizona.
[1] https://www.scienceabc.com/humans/how-many-volts-amps-kill-y...
Ha, it’s always easy to tell when people have experience with these things.
Doorbell wiring is 48V. Go hold those in each hand and tell me how impossible it is to feel if your hands are dry.
Doorbell voltage in the US is typically 12V or 24V AC in the US. I can’t feel that with dry hands.
You might be confused with POTS (landline phone service) which is 48V DC with all phones not in use.
Just don't be holding on when it rings! That's painful, with 90 VRMS at 20 Hz.
What you stated is incorrect. Anyway, V=IR is a truth. If you touch 48v DV dry. You are going to be fine.
From experience I'm not touching 60v, sweaty or dry as sand - that voltage hurts! And 48v is seriously uncomfortable. People have died from less DC voltage in industrial settings.
Following EN61010, the max safe DC voltage in laboratory equipment is 35v for wet locations. For a car, we ought to assume that being wet is a possibility.
48V is good because a lot of safety standards have the cut off for 'extra-low voltage' at 60V DC, gives you a bit of margin (when battery charging it pushes up to be in the 50s for example). Some battery systems I've seen at 56 volts nominal too. so sometimes people do have a bit higher-voltage ELV systems.
48V still lets you touch both conductors with dry hands and it's still very unlikely for you to be able to get any current to flow through you, you can't even feel it (although with safe working practices you'd only touch either positive or negative at one time, not both). Obviously it's very much not the case to be able to touch the 800V conductors safely in the traction systems in EVs, that side is extremely dangerous and requires extreme caution and safety procedures!
As long as the battery pack is still sealed and the interlock systems are undamaged and working correctly, it's no big deal. You follow the manufacturer's instructions to make it safe, then work on it like there's no voltage present.
If the battery pack is broken or a prototype or whatever, yeah, then you need to think things through carefully before doing them. And have a plan for what you're going to do when things go wrong.
Source: I work in electric aviation and work on battery packs.
GP was talking about the low voltage system (the 12-volt system in most cars) and choosing a voltage for it, not anything about the traction battery.
No, they were comparing the difference in precautions between 12/48v accessory battery and the 400/800V traction battery.
You are correct; thanks; I missed the precise context of the snipped text.
If you can't feel 48 V with your hands I'd recommend moisturizer, because you have very dry skin.
The reason to not keep going higher is purely practicality because stepping down bigger voltage gaps for lower voltage applications begins to become less efficient/more waste heat.
If you design 100v computers, monitor, headlights, seat adjustment motors, window/windshield motors, pumps, etc. you could cut these 48v wires in half again but if you end up stepping everything down anyway it loses its utility.
The safety rules about voltage and the human body are often poorly overstated, as is the addage that 'its the amps that kill you, not the volts.' in reality it takes a whole lot of both [0].
As further research, here[1] is styropyro touching 2 contacts which have more current than the largest bolts of lightning (enough to almost instantly vaporize a crowbar) with his bare hands, but because it is 12V it is not able to pass through him.
[0] https://youtu.be/BGD-oSwJv3E
[1] https://youtu.be/ywaTX-nLm6Y
Just don't try that with wet hands.
Even with wet hands it's hard to get much out of 12v.
Bad analogy: for the electrons, Volts are (inverse) latency, and wire thickness is maximum bandwidth (or max amp). That is, make electrons go faster, instead of pushing more electrons at the same time.
Of course none of this really makes sense, for example you can't increase wire thickness to increase amps etc.
For your first question, power = voltage x current. To transmit the same power, if you double the voltage you only need half the current. This is important because the resistance losses in conductors are related to the current not voltage, so you can use thinner wires without overheating.
As an analogy, if you have a hose squirting out water at a certain rate, and you increase the pressure, then all other things being equal you'll get a higher rate of water. But then that means you could now reduce the size of the hose, keeping the new higher pressure, and achieve the original rate of water delivery with a smaller, cheaper, lighter hose.
It's very similar with electricy: water pressure is voltage and the rate of water delivery is power.
You've already gotten a bunch of answers but to be honest I find all of them a little incomplete if you don't have any electrical background, so here is my attempt to be quite thorough from (almost) first principles.
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The equation for power delivered by an ideal system is P = IV, or power (P) = current (I) * voltage (V). Power is measured in watts, and that is generally the overall number that matters, in terms of what you can run off of your system at the same time.
So to increase the wattage (power) of your system you can either increase the voltage or the current.
- Increasing the voltage of a system increases the amount of resistance it can "break through". In "danger to human" terms, our skin is generally not a great conductor, so voltages lower than 50V usually won't enter the body (read: vital organs) at all. Voltages above 50V will start to enter the body depending on conditions, which is when electricity becomes much more dangerous.
- However even if the voltage is high enough to enter the body, if the current (I) isn't very high it still won't be dangerous. Current is measured in Amperes (A), and the usual number at which a current inside the body becomes dangerous is above 30mA. 30mA can cause respiratory failure if it passes through the lungs, current as low as 100mA can cause cardiac arrest if it passes through the heart. In a car's electrical system, the currents we're operating with are definitely going to be over the 30mA threshold we just established, so we want to keep the voltage under 50V instead.
Anyway back to cars and ignoring danger to humans for a second. Resistance is the main thing you want to overcome when it comes to the efficiency of such a system. The equation for power loss is P = I^2 * R, or "power dissipated (as heat) is proportional to the square of the current times the resistance". So if you increase the current of your system (in order to deliver more watts) you will also increase the amount of power you lose as heat. You can decrease the loss by decreasing the Resistance.
The equation for resistance through a material is: R = ρ * (L/A), or Resistance = resistivity (an innate property of the material) * Length / Area. In other words, the longer your wire is the more current you will lose to resistance. But if you increase the cross-sectional area of your wire (A) by making the wires thicker, you decrease the resistance.
So in short: if you have a high current (amperage) system, you use thicker wires in order to ameliorate resistive heat loss. But you can alternatively just decrease the amperage to reduce your resistive heat loss, which means thinner (and therefore much lighter) wires. But then you need to increase the voltage of your system in order to offset the power you're losing by decreasing the current. If you increase the voltage by 4x, from 12V to to 48V, this keeps it under the human danger zone (of 50-60V) and means your wires can be up to 16x thinner, taking up less space and less weight. Having it be a nice multiple of the previous system (4x) should make upgrading the relevant circuits a little more straightforward as well.
Higher the voltage the lower the amp draw, so smaller wires can be used.
48V has been considered for automotive for decades. The problem was not know how.
It simply has never been worth it before to retool things in practice.
It's also electrically a lot more noisy. The limit of what is considered low volt is like 60v or something.
It was never worth it to retool for decades?
Or was there a pathological lock-in between suppliers and manufacturers that prevented even the most obvious innovations from happening if they required any amount of coordination?
Since car manufacturing, and design, wasn't held back at all by something like auxiliary current, the reason more likely was people not wanting to waste energy to improve on something that is working just fine for everyone.
Well according to Tesla it wasn't working just fine for everyone - they have been able to massively simplify their internal wiring.
Classic example of legacy automakers happy to maintain the status-quo because it is easiest, while the new kid on the block is pointing out that things don't have to be the way they are just because they are that way.
Its the same with aluminum casting. The car makers used the technology once in a while in some specific parts, Tesla was like 'why not make half the car out of one casting'.
Tesla worked closely with a supplier, did lots of its own research and development and continue to work with a supplier to make the technology better over time.
This was considered stupid at first. This is now very widely copied. First automakers from China copied it. And now others are copying it as well. Even Toyota (who everybody believes are some kind of gods of manufacturing) are copying this now.
If you have been doing something one way for long enough, going into a radically different direction is hard. Your whole workforce knows about welding steel sheets together, and nobody knows anything about casting. Your whole workforce knows about V12 and the ecosystem for that.
Its hard to fundamentally change how you do things when you are producing millions of vehicles a year.
A quick search turned up this:
Source: https://www.spglobal.com/mobility/en/research-analysis/gigac...
Obviously not a technical journal, nor did I double check anything.
What the numbers say 15-20% might be replaced by gigastampings (sidenote: I ak surprised Elon didn't rename Twitter to Giga-X). Which, ok, is a thing. But nowhere near the revolution people seem to believe. First, it has to happen. Second, others have to consider it better, read overall cheaper, and continue doing it. Then we can properly judge. Until then, it might as well be in the category of Teslas fully automated factories that ended with Elon doing pyjama parties with his workers on the shopfloor and ad-hoc tents.
And Toyota, as per the linked article, is not copying it, they are "eyeing" it. And believe itbor not, manufacturers are eyeing new production tech all the time.
And Toyotas reputation in car manufacturing is well earned.
You are underestimating how long things take in the car industry. 2030 is really, really soon.
The majority of cars sold then will be existing models with minor updates.
And car companies only upgrade their major platforms every 5-7 years. Many companies are currently planning their second (or first real) EV platform.
But by 2030 even the waste number of EV will be on first generation EV platforms still.
Companies have 100s of million invested in their current body lines. So unless you build a totally new factory you are not gone adopt this technology.
When Toyota came out with their production system it took decades for all the practices to become established.
I'm more an aerospace guy, but I am fully aware of the time scale around production technology changes. Thing is so, 2030 is an estimate, not a commitment. And I didn't find anything about actual investments or announcememts from OEMs around that.
Also, 20% of castings still means a lot of welding before a car body is made.
One thing regarding Toyotas production system so: it is all about management and processes and not about the actual machinery. And it share a lot of principles ranging as far back as Venice's Arsenal in the 16/17th century and, especially, WW2 mass manifavturing of, e.g., planes.
Anothet major difference: TPS is a proven methodology for longer than Tesla, let alone any production tech coming out of Tesla, exists as a company.
Legacy automakers have no need for a 48v system. Most vehicles have an ICEs and they will for the next decade(s) as EV and PHEV adoption rises. 12 years is the average age for cars in the EU/US.
Why would they upgrade a system when they don’t need to? Tesla can be a front runner and companies like Bosch will start creating 48v parts as EVs become more popular for legacy auto to use.
Also 48 V semiconductors are more expensive and not so easily available.
24V is common in trucks, and yet never made it to regular cars because there was never sufficient reason.
Using a higher voltage is not an innovation (it's an obvious change, and we've gone from 6V to 12V to, in some cases, 24V already) - rather it's just a slight efficiency improvement in largely non-critical systems, with not a lot of incentive to take on the cost of transition.
In a a personal ICE vehicle, the only real significant power was to the starter motor and from the generator, and the distance there was short so the copper didn't really matter and thus no one cared for 24V - unlike industry where you might have significant aux systems. With EVs, you have heat pumps and brake boosters on the auxillary power, so you now have a stronger driver for conversion.
Even within 12V, you'd get a larger weight reduction from not carrying an aux battery, and just feeding through a converter from the HV system.
The 12v battery performs the very significant safety feature of allowing the HV battery to be disconnected when the car isn’t ready to move. You’d need to have a converter in the HV battery to avoid that down side, and then you have a new downside of a fault could cause your 12v line to be HV instead.
Fair point, but I imagine disconnecting is mainly to avoid live HV wiring throughout the vehicle, and thus reducing risk of catastrophic shorts or arcing.
If the aux supply is near or in the battery, leaving that connected would while the rest of HV is interrupted would probably not cause any notable increase in risk.
At the same time, vehicle fires have been caused by a shorted auxillary battery (I have personally experienced an entire industrial building burn down because the 12V battery in a parked ICE car shorted and went up in flames), so I imagine only having one battery to worry about is a risk reduction.
I mean there have always been a market for 48V components. The problem is that the market is much smaller so as a customer, you’re paying a lot more and it’s hard to justify raising the price of your car because you decided to go 48V.
Try counting the number of businesses involved in making a vehicle.
Why is it inherently noisier?
Faster slew rate for all switch supplies in the system. Nothing directly runs 48v.
I’m still skeptical. Why can’t it be filtered out
It can, it just requires up to a dollar more per device.
Nothing "directly" runs on 12V either. All electronics will have stepdown converters in both the 12V and 48V use case. Motors, solenoids and incandescent bulbs can be made to work with either voltage (the same way we do for 24V systems in heavy goods vehicles here in Europe).
Motors, bulbs, relays.
Lights and motors can easily take 48V. It's only the digital devices that require switching supplies, and that's still much better that 200-300V rectified mains power.
Not true.
Your motors and actuators operate directly on 48V (in fact, most actuators would prefer a higher voltage like 96V). That's really significant.
Microelectronics is effectively a "don't care" since everything is behind a regulator or a PHY.
Yeah, 48V tolerant switching regulators are going to be a bit more expensive until the volume gets rolling, but that problem solves itself while ethernet and CAN PHY chips are already 48V tolerant.
Mercedes-Benz has been using 48V systems since 2016.
https://paultan.org/2016/10/31/mercedes-benz-reveals-first-d...
This dynamic, where Tesla "announces" something that the rest of the industry has been doing for a while anyway, and a bunch of star-struck enthusiasts and stock manipulators tout it as an example of Tesla' "super smart innovation", is getting tiresome.
That's a complete misunderstanding of what Tesla did. Having a component in the car that is 48V and having the whole car being on a 48V PoE architecture are totally different things. The sad part is that these company actually have the beginning of a 48V system but never actually pushed threw and did it all.
This is like when SpaceX landed a first stage and everybody was like 'DC-X did it SpaceX did nothing new'.
There is a reason lots of people, including experts are exited of what Tesla did here.
Of course Tesla has taken it further which is interesting and could be useful - but it's not quite true that the whole car is on 48V, they've already said that ~20% of the common / supplier-provided components are still 12V. For pure EVs, sticking with higher voltage makes a lot of sense and Tesla was perfectly suited to lead the charge here since they have built so much of their supply chain from scratch and can spec everything to be 48V where other EV manufacturers mostly just reused components from their ICE cars.
Previous 48V systems were only partial for good reason as well - traditional manufacturers have been using "mild hybrid" 48V systems since ~2001. Many of the electrical components on ICE vehicles are parasitic engine loads since they need power than can be provided with 12V, so e.g. the water pump and AC compressor have separate belts that always are 'robbing' the engine power regardless if they're needed or not. Adding that 48V system allows for the engine to be freed from the draw that those components require and adding some light regenerative braking is sufficient to keep the batteries supplying that system charged.
That these 48v systems aren't universal should provide some color on how successful / important the manufacturers had found them to be.
There is still a large benefit to this. Because Tesla is seen as a leader in the EV space it prods others to follow them. In some cases like this it gives people in the supply chain or internally at other automakers justification to make changes they've been prevented from making in the past.
All sorts of people have all sorts of random ideas that never go anywhere until an industry "golden child" says it's the way forward. Without that effect the change can take much longer to happen.
Jup happens all the time. Tesla also made the CyberTruck a drive by wire system, now fans are claiming it has the unique ability to have variable steering angles based on speed which is "far ahead of any other manufacturer"
Except that BMW 5-series and 7-series from 2010 onward have had this option... They've done it in a smarter way using a plantery gear system to keep a physical steering wheel connection as a backup instead of going the cheap and less safe drive by wire way that Tesla put on the CyberTruck.
That is a link to a press release. As best as I can tell from other sources, they started shipping some high end, low volume models the next year that added a separate 48V curcuit in addition to the 12V. Color me impressed...
U mean Apple?
As far as i know, 60 V is the limit for alternating current. For DC it is 24 V.
Depends on the region. 56V AC and 72V DC here. -48V has been the standard voltage in telecoms for +100years, so 48V systems and parts are not that exotic.
How is DC more noisy?
I get this a lot
I work at an electronics store in Australia
This week I had a customer dumbfounded why his 3,500W inverter almost caught fire
He was using 8-gauge wire (~56A max)
He needed 00-gauge (almost 300A max)
If he’d have run the system at 48V instead of 12V he’d have saved $200+ per metre on cabling his inverter
My advice on voltage selection for a vehicle is once you’re needing more than a few metres of 0-gauge, you should possibly increase the voltage of the system
High current cabling means expensive ANL, mega or other high performance fuses or other expensive circuit protection methods
I strongly believe that 48V systems are inherently safer than 12V systems when it comes to the public doing DIY work
Good look doing DIY work on the 48V network of a modern car, ICE or EV or 12, 24 or 48 V doesn't matter.
And the past 12 V systems are dead easy to work on. On older cars that is, as soon as you have electronics and bus systems DIY basically requires deep car electronics knowledge and skills.
Do you have examples of what kind of DIY work is hard?
I haven’t done a ton of work on newer cars, but at least adding wiring for a hitch on my Kona EV was just as easy as any wiring I’ve done on my old truck.
Is a job like adding amps and better speakers trickier?
I have a defender and added a bunch of stuff to it: cruise control, motor pre-heater, rear camera, working lights in the rear. I'll also add a diesel heater and more electrics at some point. On 12V it's easy, can't imagine doing work like that with 48V. Not sure how this works, and if you maybe just can use 12V anyway. But wanted to make the point of camper vans and overlanders and offroaders.
An old or a new one?
Ah right, should've specified that. Of course an old one ;) A Td5. I call the other one "New Defender"
And a TD5 is already modern-ish enough, but very nice regardless! Personally, I would be at a loss working in anything built after the early 80s, so for a Defender that would be the dual-carb V8s, and 200/300 TDis.
My 1982 Range Rover has all of three fuses, so electrically I'm fine! Except the mess previous owners did to the original wiring... No idea why it is so difficult to just make your own wiring for after market accesories instead of butchering the OEM one up beyond recognition. It works, so I don't touch it. I have no idea why it works so...
Yeah I don't touch anything in the box beneath the passenger front seat ;) The previous owner thankfully already fixed the "oil creeps up the wires" issue, so I can leave it. Nothing I'm too keen on, but simple enough I figure.
I know that feeling haha. Adding wiring is so much easier than ripping up existing stuff ...
When a mechanic from Land Rover saw the wiring, he said something along the lines of "just fault location would be 2k, none of the colors I see should be there". A mess... But hey, the 80s and 90s were a wild time, and it is rust free!
Depends on where you connect stuff. Directly to some wiring loom that is already there? Bad idea, not all connected equipment will take the aditional loads well. Going directly to the car battery with dedicated wiring? Doable, but since start-stop is a thing, battery management and other stuff migjt not like that very well neither. Second batery? A bitch since start-stopp.
Hence, one needs some good knowledge around that, what to connect where.
In the old days, well, just go directly to the main battery with your aftermarket wiring and Bob's your uncle.
And none of that, battery management, which equipment can be connected where, has anything to do with the voltage but rather with all the other stuff modern cars have (bus management, battery management, ECus,...) all of which might or might not accept voltage and amp fluctuations very well.
Dead easy is relative I guess, I once tried to track down an issue with the wiring loom of my 400cc motorbike and ended up giving up…
So how is this done on cars? Dores each manufacturer have their own proprietary bus system (what i imagine), or is there a standard that everyone can use?
I guess you work at Jaycar too? Always a fun conversation trying to explain voltage drop to someone who wants to cheap out on cable with our inverters and DC/DC chargers.
I'm sure a 48V bus would solve all those F1 errors too.
That's funny, I assumed the same.
Not an employee, but a very happy reoccurring customer.
How do you integrate the 48V system with the existing 12V system when doing aftermarket/DIY work? Do you add a 48V inverter? A buck-boost DC-DC converter? between the battery (or main fuse block) and the 48V system?
You don't. 48V battery and separate circuits if it's an RV, otherwise forget it.
Thanks for posting this - I only noticed your reply now. Exactly this. Installing inverters for my own projects is what really highlighted the amp/volts/gaugerelationship. I quickly moved to 24V and will push for 48V for my next. As an aside I use Victron gear which I'm very happy with. Biggest install is for a film van and has dual 5KW inverters that can deliver 8KW continuous - and it's a 24V system.
Back in the '80s I was helping a buddy upgrade the stereo system in his RX-7. The teenager down the street comes by and educates us that "you should be using really thin wire, like telephone wire, because otherwise the amp sucks all your power." My buddy was an electrical engineer at Hewlett-Packard.
Given the choice almost any EE would probably pick the higher voltage system for cost saving reasons, but I imagine they were mostly constrained by legacy compatibility requirements here.
It’a “smart”, but there are probably reasons it hasn’t already changed everywhere else.
Yes, the legacy OEMs are constrained by their suppliers, who dictate what they can (not) do.
In automotive, it is usually the other way round. Regardless, what exactly was wrong with the existing 12 and 24 V systems for auxiliaries that absolutely needed to be changed?
The move to 48V means much less power is lost (power loss = (IxI)xR ), cables can be much smaller, cables and terminals can be much lighter and much less copper can be used used.
Basically it's just a more efficient way of doing things.
Elon has said it's not a revolution, or ground breaking in any way, it is simply a step improvement. Anyone could have done it. Tesla did it.
As others pointed out lready, others did it, too.
Re-read the comments, others have not done it.
Audi has a mild-hybrid 48V (as do many others) that also runs some other things like active roll control and the power steering pump.
They still have a 12v system running infotainment, seat heaters, defrosters, powered seats, lights, etc. etc.
As I never knowingly listen to music on 48V, is it reall so much better than 12V?
It's not about making the music sound better anymore than getting rid of an internal combustion engine is about getting you there faster. Have you ever seen the size of the wires in a car that go the amplifiers? They're as thick as your thumb.
The move to 48V means much less power is lost (power loss = (IxI)xR ), cables can be much smaller, cables and terminals can be much lighter and much less copper can be used used.
Basically it's just a more efficient way of doing things.
Of course it didn't 'absolutely' need to be changed. But the same can be said for 1000000 other innovations cars made since the Model T.
In the long term it will safe money while while being more efficient. As cars get more and more electronics it becomes more and more relevant.
Its something everybody has understood for decades, but nobody had a long term enough look to make it happen. Car companies were struggling t show profit. And in the 2000s companies like GM literally went bust.
And yes its true, OEM can tell suppliers what to do. But if you want something that suppliers don't have at hand, your gone pay for development. And if you are say GM, to move to 48v you need to literally coordinate the work of 100ish suppliers to bring the product together.
And remember, these OEM since the 90s have outsourced the majority of all electronics devices and the waste majority of the software. Do they have the internal expertise to manage such a transition?
Look at over-the-air updates, its still not standard. And even those cars that can over-the-air update, that mostly only for some of the core main components. Lots of the supplier delivered parts can still not be upgraded like that.
And the car industry had plenty of troubles in the 2000s so its not surprising they didn't do stuff like that.
High current (amperage) requiring thicker wires, or more wires, thicker/heavier connections, more expensive switches, more cooling etc.
The same thing that was wrong with vehicles that get 10mpg.
The same thing that was wrong with laptops that get so hot they burn your lap and the fan sounds like a jet engine.
The same thing that was wrong with incandescent bulbs getting hot instead of using that energy for light.
This is about making things more efficient.
"super smart" - more like completely obvious to everyone for decades
That’s what Elon said, no innovation, just made the step
Do Tesla have 800 V batteries yet? I thought they were still using 400 V for all the cars.
Cybertruck is the first Tesla vehicle with 800v architecture. The S3XY lineup uses 400v.
48V is also used on some boats (eg. certain trolling motors)
up till now most ev‘s used 400v there are some with 800v and more premium models do get 800v
Stuff like buses have used 24 volt for ages. Basically anywhere with larger accessory loads.
48 volt has been 'on the radar' in automotive spaces for a couple decades.
48V is a dangerous voltage. Better not touch any wire.
A lot of commercial trucks use 24V systems also.
Musk did an interview with Sandy Munro about it. Worth watching.
And FWIW... 24V is very common for DC circuits in industrial control systems. 48V is used too but less common; however, 48V is very common in telecom.
48V is also currently used on the supporting electric traction motor of "Mild Hybrid" cars.