4 ms·

Presuming an 80 kWh battery and 80% efficiency: 80 kWh / 0.8 = 100 kWh To charge in nine minutes: 100 kWh * 60 min/hr / 9 min = 667 kW A 400 V DC setup is c

Presuming an 80 kWh battery and 80% efficiency: 80 kWh / 0.8 = 100 kWh To charge in nine minutes: 100 kWh * 60 min/hr / 9 min = 667 kW A 400 V DC setup is common for this sort of application, so: 667 kW / 400 V = 1667 A How physically large do the cables and related apparatus need to be in order to deliver this sort of current? What sort of training and personal protective equipment will people need in order to plug and unplug these cables? (Hint: Arc flashes are no joke!) What sort of service would you need to order from the electric company to be able to power just one of these installations?

deepsun 2y ago
Arc flashed are no problem I think, because these cables don't unleash the whole power before everything is connected and protocol negotiation finished. But agree with the rest. Regardless of voltage and current, you still need half-megawatt delivery somehow.
- foxyv 2y ago
  I think the Hyundai Ioniq 5 uses an 800 volt battery. So you can get half a megawatt at 625 amps. Although most new fast chargers are about 350kw (Usually charging around 230kw on average) right now so you are only pulling about 435 amps.
jve 2y ago
Why you limit yourself to 400V? Today 250kW chargers are available: https://en.wikipedia.org/wiki/Tesla_Supercharger https://en.wikipedia.org/wiki/Tesla_Supercharger so we need 2.7 times of that. > The voltage range was increased to 1000 V and it supports up to 615 A (charging cable) / 1000 A (charging pole) for power delivery.[14][15] However, they are currently software limited to 250 kW.[12][16] v4 charger already features thermally conductive liquid to dissipate heat. Maybe one could get rid of cables and car could park near charger and some serious metal rods could automatically connect somewhere under the car. Anyways, that 1000Vx615A already supports 615kW so very close as far as we consider cables/connectors.
Retric 2y ago
400V is hardly the limit… Anyway, if you’re just interested in big connectors/cables MCS targets up to 3.75 multi megawatts for commercial vehicles. https://en.wikipedia.org/wiki/Megawatt_Charging_System https://en.wikipedia.org/wiki/Megawatt_Charging_System Though 3.7MW is mostly theoretical there’s already 700kw chargers in the wild. The cables end up thick, but they can be supported by an overhead gantry which helps.
kccqzy 2y ago
The CCS standard supports 1000V. Furthermore charging cables are locked while charging. (The latch is on the cable for CCS, and the latch is inside the car for NACS.) Unless the lock mechanism is mechanically broken, it's impossible to unplug a cable that's charging.
- goodcanadian 2y ago
  The latch is on the car for CCS. It is only on the cable for chademo. Regardless, the main issue with high current is the cable resistance. You need very thick cables or they will melt. Higher voltage helps, but cable weight is a real issue at higher power. P.S. NACS is just CCS with a different connector.
  - lazide 2y ago
    It isn’t just that higher voltage helps, higher voltage is the key factor. Heat dissipation is a factor of amperage (solely) in the wire, and higher voltage means lower amperage for a given amount of power. Literally. [https://en.m.wikipedia.org/wiki/Ohm%27s_law https://en.m.wikipedia.org/wiki/Ohm%27s_law] The challenge here is that above a certain voltage, insulation gets prohibitively difficult (and bulky), which makes solid state electronics to control and manage it also prohibitively difficult. And leakage current becomes dangerous. For example, we could run chargers at 1 million+ volts, and use standard 12 awg stranded cables to do it with very low losses (and low heat) at megawatt charging rates. But the insulation would be crazy thick (inches?) and if there was any damage or minor leakage, it would be very dramatic very quickly. Like ‘mini nuke’ type arc flashes. And because the distance you can strike an arc in air with 1 million+ volts is measured in multiple feet.
- sebazzz 2y ago
  Even if the lock is broken, the pilot connector of the CCS connector is longer, so it would disconnect before the DC connectors would disconnect. Similar to how the D+ and D- lines of USB-A are shorter than the VCC/GND lines.
oezi 2y ago
DC charging at 350 and 500kw is getting rather common on highway chargers. Why stop there? Heat management is the key limitation.
Tade0 2y ago
Your typical tram is powered by four 150kW motors. It's not an unusually high amount of power.
bearjaws 2y ago
Almost all cars are moving to 800v architectures for this reason.
thebruce87m 2y ago
Note that charging curves usually have a drop in charge rate as the battery gets closer to 100%, so it’s probably an even higher peak than this for this to be the average.

deepsun 2y ago

Arc flashed are no problem I think, because these cables don't unleash the whole power before everything is connected and protocol negotiation finished. But agree with the rest. Regardless of voltage and current, you still need half-megawatt delivery somehow.

foxyv 2y ago
I think the Hyundai Ioniq 5 uses an 800 volt battery. So you can get half a megawatt at 625 amps. Although most new fast chargers are about 350kw (Usually charging around 230kw on average) right now so you are only pulling about 435 amps.

jve 2y ago

Why you limit yourself to 400V? Today 250kW chargers are available: https://en.wikipedia.org/wiki/Tesla_Supercharger https://en.wikipedia.org/wiki/Tesla_Supercharger so we need 2.7 times of that. > The voltage range was increased to 1000 V and it supports up to 615 A (charging cable) / 1000 A (charging pole) for power delivery.[14][15] However, they are currently software limited to 250 kW.[12][16] v4 charger already features thermally conductive liquid to dissipate heat. Maybe one could get rid of cables and car could park near charger and some serious metal rods could automatically connect somewhere under the car. Anyways, that 1000Vx615A already supports 615kW so very close as far as we consider cables/connectors.

Retric 2y ago

400V is hardly the limit… Anyway, if you’re just interested in big connectors/cables MCS targets up to 3.75 multi megawatts for commercial vehicles. https://en.wikipedia.org/wiki/Megawatt_Charging_System https://en.wikipedia.org/wiki/Megawatt_Charging_System Though 3.7MW is mostly theoretical there’s already 700kw chargers in the wild. The cables end up thick, but they can be supported by an overhead gantry which helps.

kccqzy 2y ago

The CCS standard supports 1000V. Furthermore charging cables are locked while charging. (The latch is on the cable for CCS, and the latch is inside the car for NACS.) Unless the lock mechanism is mechanically broken, it's impossible to unplug a cable that's charging.

goodcanadian 2y ago
The latch is on the car for CCS. It is only on the cable for chademo. Regardless, the main issue with high current is the cable resistance. You need very thick cables or they will melt. Higher voltage helps, but cable weight is a real issue at higher power. P.S. NACS is just CCS with a different connector.
- lazide 2y ago
  It isn’t just that higher voltage helps, higher voltage is the key factor. Heat dissipation is a factor of amperage (solely) in the wire, and higher voltage means lower amperage for a given amount of power. Literally. [https://en.m.wikipedia.org/wiki/Ohm%27s_law https://en.m.wikipedia.org/wiki/Ohm%27s_law] The challenge here is that above a certain voltage, insulation gets prohibitively difficult (and bulky), which makes solid state electronics to control and manage it also prohibitively difficult. And leakage current becomes dangerous. For example, we could run chargers at 1 million+ volts, and use standard 12 awg stranded cables to do it with very low losses (and low heat) at megawatt charging rates. But the insulation would be crazy thick (inches?) and if there was any damage or minor leakage, it would be very dramatic very quickly. Like ‘mini nuke’ type arc flashes. And because the distance you can strike an arc in air with 1 million+ volts is measured in multiple feet.
sebazzz 2y ago
Even if the lock is broken, the pilot connector of the CCS connector is longer, so it would disconnect before the DC connectors would disconnect. Similar to how the D+ and D- lines of USB-A are shorter than the VCC/GND lines.

oezi 2y ago

DC charging at 350 and 500kw is getting rather common on highway chargers. Why stop there? Heat management is the key limitation.

Tade0 2y ago

Your typical tram is powered by four 150kW motors. It's not an unusually high amount of power.

bearjaws 2y ago

Almost all cars are moving to 800v architectures for this reason.

thebruce87m 2y ago

Note that charging curves usually have a drop in charge rate as the battery gets closer to 100%, so it’s probably an even higher peak than this for this to be the average.