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Tesla shares 48V architecture with other automakers

electrek.co

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Re: Tesla shares 48V architecture with other automakers

#351

Post by dharma1 »

dmix wrote: post #222
eqvinox wrote: post #202

Earlier quoted context omitted.

It's a bit of an arbitrary determination; 60V is the international common denominator on what various legal or civic (e.g. insurance) regulations consider safe; https://en.wikipedia.org/wiki/Extra-low_voltage#Separated_or... 48V is somewhat of a dinosaur from the days when you designed things with a 20% margin since that's what was cheaply attainable. Regular PoE is 54V these days (10% margin), and some more specific…

What's a commonly produced thing that's 48v? I don't know much about this subject. Is it most industrial type stuff or is there consumer tier products using it?

Pro audio - most condenser microphones (except electret) run off 48v provided via the mixer/audio interface through XLR cables

Re: Tesla shares 48V architecture with other automakers

#352

Post by robocat »

myself248 wrote: post #168
Tuna-Fish wrote: post #108

Earlier quoted context omitted.

And to explain why this hadn't been done before/how we got here: Nothing in a car actually wants 12V DC. Most of the low voltage stuff will run better at 5V or below, while a lot of the higher voltage stuff would benefit from going as high as possible. 12V exists because DC-DC conversion used to be expensive, and you had to make a compromise about the voltage based on losses, wire thickness, and picking a low enough…

12v exists because 6v was too low; wires were impractically thick for even the early accessories being added in the 1950s. The 6v-12v transition happened in 1955/56 for many cars. Some stuff like lightbulbs could be reused by putting two 6v bulbs in series in a 12v car, so it was a very cheap and relatively straightforward transition. If they'd just had some foresight and gone 48v in 1955, we would've saved 50 millio…

A 12-volt battery typically has six cells. A 48 Volt Lead-acid battery would have 24 cells - I'm not sure how that would change the constraints on charge balancing and starter-motor stress.

I can say that the 24 Volt deisel vehicles I have used makes buying two batteries expensive.

Re: Tesla shares 48V architecture with other automakers

#353

Post by hef19898 »

jdewerd wrote: post #338
DannyBee wrote: post #272

Earlier quoted context omitted.

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.

Re: Tesla shares 48V architecture with other automakers

#354

Post by hulitu »

DannyBee wrote: post #272
mmaunder wrote: post #246

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…

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.

> The limit of what is considered low volt is like 60v or something.

As far as i know, 60 V is the limit for alternating current. For DC it is 24 V.

Re: Tesla shares 48V architecture with other automakers

#355

Post by andrewf »

TheLoafOfBread wrote: post #121
KaiserPro wrote: post #111

Earlier quoted context omitted.

> using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car Ethernet isn't a bus, its point to point. PoE over cat5/6 uses 4 pairs of UTP. so it might be used to join aggregate things together, but it won't be a bus. Yes, you can increase the datarate, but ethernet is fundamentally unreliable. So you'll need…

Ethernet can be used as a bus (see CSMA/CD), but if there are more than 2 nodes, performance of whole bus will go to complete shit and there is no guarantee that an ECU will transmit a single packet during its run, because that CD has no automatic arbitration, it is just random disconnection and try again. Not good for critical things like ABS. That's also whole reason why FlexRay was spawned, because even that FR is…

I think that's what 10BASE-T1S (standardized in 2019) is for. It has a non-CSMA/CD arbitration scheme. https://www.electronicspecifier.com/industries/industrial/an...

Re: Tesla shares 48V architecture with other automakers

#356

Post by jeffrallen »

stephen_g wrote: post #282
bigdict wrote: post #256

Earlier quoted context omitted.

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?

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…

> 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.

Re: Tesla shares 48V architecture with other automakers

#357

Post by wayfinder »

jdewerd wrote: post #338
DannyBee wrote: post #272

Earlier quoted context omitted.

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?

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.

Re: Tesla shares 48V architecture with other automakers

#358

Post by the_gipsy »

bigdict wrote: post #256
mmaunder wrote: post #246

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…

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?

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.

Re: Tesla shares 48V architecture with other automakers

#359

Post by teknico »

mmaunder wrote: post #246

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…

> 1000W sub woofer amp Your car subwoofer is surely not so stiff that it needs so much power. But after using it, your ears will definitely be.

Re: Tesla shares 48V architecture with other automakers

#360

Post by mythhabit »

exclusiv wrote: post #317
maxerickson wrote: post #263

Earlier quoted context omitted.

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 provid…

> 60 volts is nothing UNLESS you are completely wet or sweaty.

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.

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