3 ms·

This has been a real head-scratcher for me. BMW and other automakers could have vastly improved their cars by switching to 48V a decade ago, but they still keep

This has been a real head-scratcher for me. BMW and other automakers could have vastly improved their cars by switching to 48V a decade ago, but they still keep just plodding along with 12V. I have no explanation for this.

hulitu 2y ago
> automakers could have vastly improved their cars by switching to 48V a decade ago, The microcontroller still runs at 5/3.3/1.8 V.
theshrike79 2y ago
Tradition, long supply chains etc. Tooling all their shit to 48V is a massive undertaking with pretty much zero advantages.
- cyberax 2y ago
  They don't need to retool all the factories at once. They could have gradually introduced 48V systems in parallel with 12V, slowly phasing in new components as they replaced the old 12V.
  - typewithrhythm 2y ago
    Converting between voltages is not a free action, and running two systems is more complicated than one... You really need some special component that is much better at 48 for it to be worth it, otherwise a delayed platform switch is better; one some competitors have moved and the suppliers exist.
    - Kirby64 2y ago
      The special component was supposed to be the starter. With start stop systems essentially mandatory, the starter runs much much more often and therefore wiring savings on the starter are pretty useful…
    - cyberax 2y ago
      Starter motor, power steering, heated seats, powerful headlights, power-hungry onboard computers. They _all_ benefit from 48V.
      - shiroiushi 2y ago
        On top of all that, almost all the wiring in the car can be made thinner, because of the greatly reduced losses. This saves a bit of weight, but also a lot of cost because copper is expensive.
        potato3732842 2y ago
        There is no free lunch. You need to go to a finer wire strand, better insulation, better loom, better support for the harness etc, if you want that super fine wire to last. Some of those have pretty direct labor cost impacts too. That's gonna kill a lot of your cost savings, especially at lower production volumes where the design cost is harder to amortize. There's no free lunch.
        msandford 2y ago
        > better insulation It's very, very hard to get insulation that's not good for at least 100V and I suspect that just about any generic wire is good for more like 300V. The only exception that comes to mind is wire that's specifically for "household low voltage" like 24V AC for thermostat, doorbell, sprinklers, landscape lighting. Also normal ethernet. But these are almost all what you'd call signalling wiring rather than power wiring. Your average hook-up wire that you could buy at the auto parts store to make some repairs is almost certainly rated for 300V already. Mostly because of chafe resistance. Wikipedia says that the dielectric breakdown strength of PVC is 40 millions volts per meter https://en.wikipedia.org/wiki/Polyvinyl_chloride https://en.wikipedia.org/wiki/Polyvinyl_chloride. Divide both sides by 1 million and you get 40 volts per micron. OK so you need 1/3 of a micron to insulate enough for 12V and you need 1.25 microns for 48V. Now let's have a reasonable safety factor of say 10 or so and we're looking at 3 microns vs 12.5 microns. The only wire I can think of that might have insulation that thin is enamel coated magnet wire for the inside of motor windings. But even that is probably thicker. Any kind of plastic insulation is going to be significantly thicker than this just to be able to be coated onto the bare copper wire and stick. You're not wrong that the insulation needs to be thicker as the voltage goes higher. But you're unaware of just how ridiculously over-insulated everything already is due to other constraints of manufacture.
- vardump 2y ago
  Less copper in the car is not a "zero advantage". Cheaper and lighter.
m463 2y ago
I think it's like any existing vs new tradeoff. Tesla didn't have any existing, so their clean-slate math was clearly in favor of 100% new technology. (Well, they did have 12v existing in their other cars, but they were clean-slate in the truck.)
numpad0 2y ago
care to define "improve"...?
- cyberax 2y ago
  More robust, cheaper (far simpler wiring harness), eventually ability to do zonal assembly.
  - numpad0 2y ago
    Are BMW cars less reliable, expensive, not ready for zonal assembly...? Major car components like doors or front axles are assembled in parallel to miscellaneous parts on the main body, and all .join() at the final assembly. This had been the case for past 30-50 years, possibly more, in case this needs to be said.
    - cyberax 2y ago
      They can be even more reliable. And they definitely _are_ expensive. > Major car components like doors or front axles are assembled in parallel And doors (and tailgates) are the biggest body component that is _sometimes_ assembled independently. Then workers manually route cables through the body. Pre-routing cables inside panels that can then just be welded together can save a lot of labor.
      - numpad0 2y ago
        > And doors (and tailgates) are the biggest body component that is _sometimes_ assembled independently. Sometimes? What and when on Earth is this about? Pre-WWII? They wash and paint and dry the whole body at once _for paint consistency_, then take off doors and trunk lids and bumpers and send them into separate assembly lines. Those major parts flow parallel "threads" in sync and converge near the end, where connectors are plugged in and those major parts are bolted back in and plastic trims are pushed in to tuck everything under. Cars were basically always done that way for a long time everywhere. I think even lots of hand made supercars are like that, only except tact times are magnitudes longer. > Then workers manually route cables through the body. > Pre-routing cables inside panels that can then just be welded together can save a lot of labor. What do these even mean? Are you hallucinating workers crimping cables in-situ? They just clip on harnesses and plug in couplers in "the line". Never seen under a door trim? It sounds like you're either extremely ill-informed, or worse yet, potentially, intentionally misinformed about car manufacturing that what you see is advanced manufacturing. I think you should... look more closely into what "legacy auto" have been doing forever.
phlipski 2y ago
It's a classic chicken and egg economic problem. BMW doesn't make the chips/electronics that support the 48V architecture - Bosch & Continental (with NXP/TI/Infineon/Renesas as their silicon suppliers) do and they're not going to support 48V unless ALL (or a significant majority) of the automakers will. So it's a game of chicken.
- maxerickson 2y ago
  The semiconductors have been available for 20 years.
  - michaelt 2y ago
    Eh, yes and no. I designed some stuff along these lines 15 years ago. At that time, 12 volt stuff was not just available, it was available with great economies of scale and a huge range of options, off the shelf. You need an automotive-qualified relay? A light? A solenoid? A DC-DC converter module? A fan? You'd have 100 choices at 12v, 30 choices at 24v and 3 choices at 48v.
deleted 2y ago
[deleted]

hulitu 2y ago

> automakers could have vastly improved their cars by switching to 48V a decade ago, The microcontroller still runs at 5/3.3/1.8 V.

theshrike79 2y ago

Tradition, long supply chains etc. Tooling all their shit to 48V is a massive undertaking with pretty much zero advantages.

cyberax 2y ago
They don't need to retool all the factories at once. They could have gradually introduced 48V systems in parallel with 12V, slowly phasing in new components as they replaced the old 12V.
- typewithrhythm 2y ago
  Converting between voltages is not a free action, and running two systems is more complicated than one... You really need some special component that is much better at 48 for it to be worth it, otherwise a delayed platform switch is better; one some competitors have moved and the suppliers exist.
  - Kirby64 2y ago
    The special component was supposed to be the starter. With start stop systems essentially mandatory, the starter runs much much more often and therefore wiring savings on the starter are pretty useful…
  - cyberax 2y ago
    Starter motor, power steering, heated seats, powerful headlights, power-hungry onboard computers. They _all_ benefit from 48V.
    - shiroiushi 2y ago
      On top of all that, almost all the wiring in the car can be made thinner, because of the greatly reduced losses. This saves a bit of weight, but also a lot of cost because copper is expensive.
      - potato3732842 2y ago
        There is no free lunch. You need to go to a finer wire strand, better insulation, better loom, better support for the harness etc, if you want that super fine wire to last. Some of those have pretty direct labor cost impacts too. That's gonna kill a lot of your cost savings, especially at lower production volumes where the design cost is harder to amortize. There's no free lunch.
        msandford 2y ago
        > better insulation It's very, very hard to get insulation that's not good for at least 100V and I suspect that just about any generic wire is good for more like 300V. The only exception that comes to mind is wire that's specifically for "household low voltage" like 24V AC for thermostat, doorbell, sprinklers, landscape lighting. Also normal ethernet. But these are almost all what you'd call signalling wiring rather than power wiring. Your average hook-up wire that you could buy at the auto parts store to make some repairs is almost certainly rated for 300V already. Mostly because of chafe resistance. Wikipedia says that the dielectric breakdown strength of PVC is 40 millions volts per meter https://en.wikipedia.org/wiki/Polyvinyl_chloride https://en.wikipedia.org/wiki/Polyvinyl_chloride. Divide both sides by 1 million and you get 40 volts per micron. OK so you need 1/3 of a micron to insulate enough for 12V and you need 1.25 microns for 48V. Now let's have a reasonable safety factor of say 10 or so and we're looking at 3 microns vs 12.5 microns. The only wire I can think of that might have insulation that thin is enamel coated magnet wire for the inside of motor windings. But even that is probably thicker. Any kind of plastic insulation is going to be significantly thicker than this just to be able to be coated onto the bare copper wire and stick. You're not wrong that the insulation needs to be thicker as the voltage goes higher. But you're unaware of just how ridiculously over-insulated everything already is due to other constraints of manufacture.
vardump 2y ago
Less copper in the car is not a "zero advantage". Cheaper and lighter.

m463 2y ago

I think it's like any existing vs new tradeoff. Tesla didn't have any existing, so their clean-slate math was clearly in favor of 100% new technology. (Well, they did have 12v existing in their other cars, but they were clean-slate in the truck.)

numpad0 2y ago

care to define "improve"...?

cyberax 2y ago
More robust, cheaper (far simpler wiring harness), eventually ability to do zonal assembly.
- numpad0 2y ago
  Are BMW cars less reliable, expensive, not ready for zonal assembly...? Major car components like doors or front axles are assembled in parallel to miscellaneous parts on the main body, and all .join() at the final assembly. This had been the case for past 30-50 years, possibly more, in case this needs to be said.
  - cyberax 2y ago
    They can be even more reliable. And they definitely _are_ expensive. > Major car components like doors or front axles are assembled in parallel And doors (and tailgates) are the biggest body component that is _sometimes_ assembled independently. Then workers manually route cables through the body. Pre-routing cables inside panels that can then just be welded together can save a lot of labor.
    - numpad0 2y ago
      > And doors (and tailgates) are the biggest body component that is _sometimes_ assembled independently. Sometimes? What and when on Earth is this about? Pre-WWII? They wash and paint and dry the whole body at once _for paint consistency_, then take off doors and trunk lids and bumpers and send them into separate assembly lines. Those major parts flow parallel "threads" in sync and converge near the end, where connectors are plugged in and those major parts are bolted back in and plastic trims are pushed in to tuck everything under. Cars were basically always done that way for a long time everywhere. I think even lots of hand made supercars are like that, only except tact times are magnitudes longer. > Then workers manually route cables through the body. > Pre-routing cables inside panels that can then just be welded together can save a lot of labor. What do these even mean? Are you hallucinating workers crimping cables in-situ? They just clip on harnesses and plug in couplers in "the line". Never seen under a door trim? It sounds like you're either extremely ill-informed, or worse yet, potentially, intentionally misinformed about car manufacturing that what you see is advanced manufacturing. I think you should... look more closely into what "legacy auto" have been doing forever.

phlipski 2y ago

It's a classic chicken and egg economic problem. BMW doesn't make the chips/electronics that support the 48V architecture - Bosch & Continental (with NXP/TI/Infineon/Renesas as their silicon suppliers) do and they're not going to support 48V unless ALL (or a significant majority) of the automakers will. So it's a game of chicken.

maxerickson 2y ago
The semiconductors have been available for 20 years.
- michaelt 2y ago
  Eh, yes and no. I designed some stuff along these lines 15 years ago. At that time, 12 volt stuff was not just available, it was available with great economies of scale and a huge range of options, off the shelf. You need an automotive-qualified relay? A light? A solenoid? A DC-DC converter module? A fan? You'd have 100 choices at 12v, 30 choices at 24v and 3 choices at 48v.

deleted 2y ago

[deleted]