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There is a TLDR for this article, but as far as I can tell it cannot be derived from the article itself. Will someone please explain why 48-volt systems are ne

by sowbug 9y ago

There is a TLDR for this article, but as far as I can tell it cannot be derived from the article itself. Will someone please explain why 48-volt systems are newly desirable in cars?

maxerickson 9y ago
The higher voltage means lower amperage, which means smaller components and so on.
- dogma1138 9y ago
  You can use thinner cables or have the same cables with less loss. As for actual component size it’s not that simple the higher the voltage the more clearance you need between conductors. So that is bigger airgaps in PCBs and higher rated insulation where gaps aren’t possible.
  - GeorgeTirebiter 9y ago
    True, however, this can also be achieved by different insulating materials. In general, this is not really much of a problem; I agree, it needs to be considered.
saltcured 9y ago
You want a higher voltage to allow more power without huge cables due to high current. You want low voltage to avoid high-voltage safety issues which increase engineering, assembly, maintenance, and emergency costs. The 48V system sits right at the boundary where you can deliver enough power for more auxilliary systems and some mild-hybrid techniques including frequent start/stop systems, brief acceleration boost, and regenerative braking. Yet, it's not high enough to require switching to a different electrical wiring safety paradigm. This is similar to the reason power-over-ethernet runs at the voltage it does, or "low voltage" lighting exists for home applications where consumers are moving fixtures around and interacting with the wiring.
- sowbug 9y ago
  Thanks. I had always understood PoE's relatively high voltage as helping deal with the attenuation from long runs of thin copper wire. I couldn't find a succinct explanation in the article why cars would benefit from this spot in between merely sending information (digital levels like 1.8, 2.2, 3.3, 5.0, etc.) and using electricity to do "real" work (120V, 240V, 480V, etc.). As I understand your answer, yes, they'd like to use it for work, but not so much as to stray into the range of orange wires. I got the second part of that from the article, but the first part was very hard to extract from it.
  - twic 9y ago
    The specific number of 48V is presumably inherited from telecommunications: https://electronics.stackexchange.com/questions/10851/why-do-pbx-systems-use-48-v https://electronics.stackexchange.com/questions/10851/why-do... There's lots of telecom equipment that works at 48V, so it's presumably cheap and easy for carmakers to find suppliers.
    - GeorgeTirebiter 9y ago
      There is practically no overlap between automotive and telecom. When I was at Tesla, we couldn't find even one manufacturer for common use subsystems (e.g. window motors). It's a chicken and egg problem for now. That's why 'everything' is still at 12V.
      - jaclaz 9y ago
        Canot say in the US, but in EU most trucks have (since I can remember) 24 V circuits, so there is anyway a long list of parts at 24 V manufactured.
        kev009 9y ago
        All US military vehicles (even COTS ones with civilian counterparts like the CUCV and newer) use 24v. So do most heavy trucks.
bsder 9y ago
Other people talk about the power, but there is also the fact that lots of actuators want more voltage to work with. So, any motor, servo, solenoid, relay, etc. works much better at higher voltages. In addition, it is also much easier to convert between high voltages because your transformer/inductor connected to your semiconductor switches is so much smaller.
Theodores 9y ago
I thought the article did a good job of providing examples such as the VW group using 48V to provide 'sportscar' handling in their high end SUV offerings. Having 48V means that these things can be done. Incidentally VW started out with 6V. Early Beetle and bus models have the joys of 6V electrics, usually replaced for 12V. The advantages are clear. And so it is with the move to 48V. With turbocharging there is the problem of the wait, by simply using an electric motor then this problem is solved and a smaller engine can be used to deliver the same power and torque. This is not possible on 12V. But it is on 48V. Stop-start is another area where 48V makes sense. Plus the HVAC. Why don't Americans have kettles? Because of 110V, you need 240V to boil a kettle properly. Clearly 240V needs proper British Style plugs with convoluted earth arrangements and different wiring. So 48V is the happy compromise where there is no need for excessively regulated voltages. The 48V number is a multiple of 12V therefore four 12V batteries in series will get the desired potential difference. Much like how we still have older USB ports for keyboards as well as the fancier ones that do power and multiple monitors, there are plans to run the two power levels in the wiring loom. All the lights on the dashboard will run at 12v for now as will the motors in the doors and seats. However, in time those will possibly become 48V too. Sportscars demand theatre with doors that open in cool ways, so imaginably there will be application here for 48V door locks. Imaginably regular VW hatchbacks will have similar 48V based door mechanisms soon with older models still using the 12V cheaper components. Before these hatchbacks get 48V windows they will probably get the 48V ABS and the 48V power steering along with the 48V stop start. None of this is a waste of time for companies such as Volvo and how they are engineering their platforms to take any one of many power supplies, hybrid or full electric. Volvo have no future plans for making ICE only vehicles and clearly the market is going towards this smart 48V tech whether the future is full electric or not.

by sowbug 9y ago

There is a TLDR for this article, but as far as I can tell it cannot be derived from the article itself. Will someone please explain why 48-volt systems are newly desirable in cars?

maxerickson 9y ago

The higher voltage means lower amperage, which means smaller components and so on.

dogma1138 9y ago
You can use thinner cables or have the same cables with less loss. As for actual component size it’s not that simple the higher the voltage the more clearance you need between conductors. So that is bigger airgaps in PCBs and higher rated insulation where gaps aren’t possible.
- GeorgeTirebiter 9y ago
  True, however, this can also be achieved by different insulating materials. In general, this is not really much of a problem; I agree, it needs to be considered.

saltcured 9y ago

You want a higher voltage to allow more power without huge cables due to high current. You want low voltage to avoid high-voltage safety issues which increase engineering, assembly, maintenance, and emergency costs. The 48V system sits right at the boundary where you can deliver enough power for more auxilliary systems and some mild-hybrid techniques including frequent start/stop systems, brief acceleration boost, and regenerative braking. Yet, it's not high enough to require switching to a different electrical wiring safety paradigm. This is similar to the reason power-over-ethernet runs at the voltage it does, or "low voltage" lighting exists for home applications where consumers are moving fixtures around and interacting with the wiring.

sowbug 9y ago
Thanks. I had always understood PoE's relatively high voltage as helping deal with the attenuation from long runs of thin copper wire. I couldn't find a succinct explanation in the article why cars would benefit from this spot in between merely sending information (digital levels like 1.8, 2.2, 3.3, 5.0, etc.) and using electricity to do "real" work (120V, 240V, 480V, etc.). As I understand your answer, yes, they'd like to use it for work, but not so much as to stray into the range of orange wires. I got the second part of that from the article, but the first part was very hard to extract from it.
- twic 9y ago
  The specific number of 48V is presumably inherited from telecommunications: https://electronics.stackexchange.com/questions/10851/why-do-pbx-systems-use-48-v https://electronics.stackexchange.com/questions/10851/why-do... There's lots of telecom equipment that works at 48V, so it's presumably cheap and easy for carmakers to find suppliers.
  - GeorgeTirebiter 9y ago
    There is practically no overlap between automotive and telecom. When I was at Tesla, we couldn't find even one manufacturer for common use subsystems (e.g. window motors). It's a chicken and egg problem for now. That's why 'everything' is still at 12V.
    - jaclaz 9y ago
      Canot say in the US, but in EU most trucks have (since I can remember) 24 V circuits, so there is anyway a long list of parts at 24 V manufactured.
      - kev009 9y ago
        All US military vehicles (even COTS ones with civilian counterparts like the CUCV and newer) use 24v. So do most heavy trucks.

bsder 9y ago

Other people talk about the power, but there is also the fact that lots of actuators want more voltage to work with. So, any motor, servo, solenoid, relay, etc. works much better at higher voltages. In addition, it is also much easier to convert between high voltages because your transformer/inductor connected to your semiconductor switches is so much smaller.

Theodores 9y ago

I thought the article did a good job of providing examples such as the VW group using 48V to provide 'sportscar' handling in their high end SUV offerings. Having 48V means that these things can be done. Incidentally VW started out with 6V. Early Beetle and bus models have the joys of 6V electrics, usually replaced for 12V. The advantages are clear. And so it is with the move to 48V. With turbocharging there is the problem of the wait, by simply using an electric motor then this problem is solved and a smaller engine can be used to deliver the same power and torque. This is not possible on 12V. But it is on 48V. Stop-start is another area where 48V makes sense. Plus the HVAC. Why don't Americans have kettles? Because of 110V, you need 240V to boil a kettle properly. Clearly 240V needs proper British Style plugs with convoluted earth arrangements and different wiring. So 48V is the happy compromise where there is no need for excessively regulated voltages. The 48V number is a multiple of 12V therefore four 12V batteries in series will get the desired potential difference. Much like how we still have older USB ports for keyboards as well as the fancier ones that do power and multiple monitors, there are plans to run the two power levels in the wiring loom. All the lights on the dashboard will run at 12v for now as will the motors in the doors and seats. However, in time those will possibly become 48V too. Sportscars demand theatre with doors that open in cool ways, so imaginably there will be application here for 48V door locks. Imaginably regular VW hatchbacks will have similar 48V based door mechanisms soon with older models still using the 12V cheaper components. Before these hatchbacks get 48V windows they will probably get the 48V ABS and the 48V power steering along with the 48V stop start. None of this is a waste of time for companies such as Volvo and how they are engineering their platforms to take any one of many power supplies, hybrid or full electric. Volvo have no future plans for making ICE only vehicles and clearly the market is going towards this smart 48V tech whether the future is full electric or not.