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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

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.

klysm 3y ago
Why is it inherently noisier?
- horacemorace 3y ago
  Faster slew rate for all switch supplies in the system. Nothing directly runs 48v.
  - klysm 3y ago
    I’m still skeptical. Why can’t it be filtered out
    - yetihehe 3y ago
      It can, it just requires up to a dollar more per device.
  - ferongr 3y ago
    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).
    - hulitu 3y ago
      > Nothing "directly" runs on 12V either. Motors, bulbs, relays.
  - bsder 3y ago
    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.
  - jojobas 3y ago
    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.
jdewerd 3y ago
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?
- hef19898 3y ago
  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.
  - Closi 3y ago
    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.
    - panick21_ 3y ago
      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.
      - 3y ago
hulitu 3y ago
> 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.
- RF_Savage 3y ago
  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.
avalys 3y ago
Mercedes-Benz has been using 48V systems since 2016. https://paultan.org/2016/10/31/mercedes-benz-reveals-first-details-of-new-engine-family-48v-mild-hybrid-and-electric-turbo/ 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.
- panick21_ 3y ago
  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.
  - mikeyouse 3y ago
    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.
petre 3y ago
How is DC more noisy?

klysm 3y ago

Why is it inherently noisier?

horacemorace 3y ago
Faster slew rate for all switch supplies in the system. Nothing directly runs 48v.
- klysm 3y ago
  I’m still skeptical. Why can’t it be filtered out
  - yetihehe 3y ago
    It can, it just requires up to a dollar more per device.
- ferongr 3y ago
  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).
  - hulitu 3y ago
    > Nothing "directly" runs on 12V either. Motors, bulbs, relays.
- bsder 3y ago
  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.
- jojobas 3y ago
  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.

jdewerd 3y ago

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?

hef19898 3y ago
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.
- Closi 3y ago
  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.
  - panick21_ 3y ago
    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.
    - 3y ago

hulitu 3y ago

> 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.

RF_Savage 3y ago
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.

avalys 3y ago

Mercedes-Benz has been using 48V systems since 2016. https://paultan.org/2016/10/31/mercedes-benz-reveals-first-details-of-new-engine-family-48v-mild-hybrid-and-electric-turbo/ 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.

panick21_ 3y ago
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.
- mikeyouse 3y ago
  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.

petre 3y ago

How is DC more noisy?