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This information is worthless for electric vehicle owners who charge mostly or exclusively at home. A Tesla Model Y battery pack is 75 kWh and the highest rate

This information is worthless for electric vehicle owners who charge mostly or exclusively at home. A Tesla Model Y battery pack is 75 kWh and the highest rated connection within the typical American home with 200 amp 120/240 volt split-phase service is 50 amps over both phases: 12,000 watts. 75 kWh / 12 kW = 6.25 hours assuming the battery can be hit with maximum wattage continuously throughout its charge cycle (this is unhealthy). To charge the Tesla Model Y 75 kWh battery pack in nine minutes the 240 volt cable would need to carry 2083 amps. This is hilariously far beyond the capacity of a 50-amp rated wire. 6 AWG copper wire which is rated for 50 amps has an 0.000395 ohms per meter (at 20°C). Assuming a ten meter length of wire, the resistance is 0.00395 ohms. Power dissipation in the wire P = I^2 * R. 2083^2 * 0.00395 ohms = 17,166 watts. Temperature rise in the wire delta T = P / (A * k) where P = 17,666 watts, A = pi * 0.00411m * 10m. Assuming PVC insulation whose thermal conductivity is k = 0.19 W/m·K. Delta T is approx 700,615 degrees K. The surface temperature of the Sun is approximately 5773 K, so our wire would get about 121 times hotter than the surface of the sun if it did not instantly explode.

toomuchtodo 2y ago
It’s for fast DC charging at 350kw+. Home charging is solved, but there is still travel range anxiety to squeeze out of the human, as well as use cases with high utilization and turnaround need (taxi, livery, law enforcement). 9 minutes to charge and a 20 year service life is awfully close to “you have no excuse this is suboptimal compared to liquid fuel refueling.” High level, EVs have almost killed combustion vehicles, we’re almost there [1] [2]. Batteries will only improve over time as EV production scales up. [1] https://news.ycombinator.com/item?id=41191790 https://news.ycombinator.com/item?id=41191790 [2] https://news.ycombinator.com/item?id=41207048 https://news.ycombinator.com/item?id=41207048
- greenavocado 2y ago
  Home charging is "solved" as in my car will always need to be charged all day or all night at best and if you want a truck that tows anything - such as for landscaping - forget it.
GaggiX 2y ago
Safety, long range and lifespan are still important to people who charge their EV at home.
malfist 2y ago
Home charging will not be that fast in the conceivable future. Just too much power for homes. Just thinking about it, my ford lightning with the extended battery has enough capacity to power the average house for something like 8 days. That'd be crazy be be about to demand that much power at home to charge it in nine minutes. But, it doesn't mean it's worthless to those that charge at home. I only own EVs. Even if I do 99.99999% of my charging at home, I still need to be able to charge during road trips. The faster the better. My partner and I have been eyeing the ev6 with it's 18 minute charge time. That's way easier to swallow than the 48 minutes the truck takes. 9 minutes and every seven hours of driving would be a god send, instead of our current 48 minutes every 4 hours
- greenavocado 2y ago
  Having an option to exchange batteries at every gas station would be even better.
  - malfist 2y ago
    Yeah, but that comes with it's own host of issues. I'm not sure that tradeoff makes sense for something heavier than a motorcycle. Batteries to push a car a reasonable distance aren't light and need to be protected during a crash. Hard to balance that with "and easily removable and swapped"
    - greenavocado 2y ago
      They can unhook and attach from below.
      - malfist 2y ago
        Is grandma going to clamber under her car at a battery exchange station and disconnect and remove several hundred pounds of batteries?
tgsovlerkhgsel 2y ago
> 6.25 hours assuming the battery can be hit with maximum wattage continuously throughout its charge cycle (this is unhealthy). Are you sure it's unhealthy if you're already charging this slow? I'd expect 12 kW to still be below the slow part of a fast charge.
- greenavocado 2y ago
  I'm sorry, you're right about 12kW charging. The battery pack is made up of 4,416 individual cells. The cells are arranged in series to achieve the required voltage. If there are 96 cells in series, the pack would have a nominal voltage of around 400 volts (since each cell has a nominal voltage of about 4.2V when fully charged). The pack has multiple strings of these 96-series cells connected in parallel to increase capacity. 12kW/400V = 30A. 30A/(46 parallel strings) = 0.652A per cell or 652 milliamps. This is quite a slow and healthy charging speed.
kccqzy 2y ago
You took a home charging cable that's rated for 50 amps and thought about what if you used that exact cable for DC fast charging. What did you expect?
- greenavocado 2y ago
  80-90% of Tesla charging is done at home
  - kccqzy 2y ago
    So? When you charge at home you are not going to need the fast charging capability of this new battery. The limiting factor is the onboard charger which for Tesla vehicles could be as low as 7kW. So it's moot. All you are doing is to sow confusion about home charging and public DC charging.
    - greenavocado 2y ago
      Many many people will deduce from the headline that maybe their car can charge at home in nine minutes, which is NOT the case, and NEVER will be.
oliwarner 2y ago
I just did a 1400mile round trip in our 9yo Model S. 80→20kW just doing my nut in. At least it was free. This sort of battery makes that sort of trip easy. There are already 3m liquid-cooled charging cables that allow 600kW+ DC charging. Many use more than one conductor per polarity to increase the capacity.
- deleted 2y ago
  [deleted]
thebruce87m 2y ago
> 75 kWh / 12 kW = 6.25 hours assuming the battery can be hit with maximum wattage continuously throughout its charge cycle (this is unhealthy). 12kW is nowhere near the max charging speed. Here is the charging curve with a peak at 250kWh when DC charging: https://evkx.net/models/tesla/model_y/model_y_long_range/chargingcurve/ https://evkx.net/models/tesla/model_y/model_y_long_range/cha...
- greenavocado 2y ago
  It is if you are charging at home. To achieve 250 kW of power, the Supercharger must supply much higher voltage and current than what is available from standard 120/240V circuits. For instance, Tesla Superchargers typically operate at voltages around 400-500V DC and deliver currents of up to 500 amps or more. Unlike residential power, which typically uses single-phase electricity, Superchargers often use three-phase power. Three-phase power allows for more efficient transmission of large amounts of electricity and is commonly used in industrial settings. The voltage supplied to a Tesla Supercharger is typically in the range of 480 volts AC (alternating current) for three-phase power. Inside the Supercharger, this 480V AC is converted to a higher DC (direct current) voltage, typically in the range of 400-500 volts DC, which is suitable for charging the vehicle's battery. The cables used in Tesla Superchargers are specially designed to handle very high currents. For instance, to deliver 250 kW at a voltage of around 400V DC, the current would need to be around 625 amps. To manage the heat generated by such high currents, Tesla employs liquid-cooled charging cables. These cables have an internal liquid coolant system that actively removes heat from the cable as electricity flows through it.
  - thebruce87m 2y ago
    > It is if you are charging at home. I’m not sure why you are focusing on AC vs DC charging when your original assertion was related to the maximum wattage the battery can handle, which as I said is much bigger than 12kW. Also, even the 12kW would be the wrong maximum for home charging. The Model Y has an 11kW onboard charger for converting AC to DC, so if you have a 3-phase supply at home then this is the maximum your car can convert (NOT that the battery can handle as you suggest). If you have single phase then it’s 7kW. https://www.tesla.com/en_gb/support/charging/onboard-charger https://www.tesla.com/en_gb/support/charging/onboard-charger
albrewer 2y ago
> This information is worthless for electric vehicle owners who charge mostly or exclusively at home I need to make a 310 mile 1-way trip fairly regularly through _very_ rural parts of Texas. That trip is specifically why I don't own an EV. At 600 miles, it makes it to where the humans in the car are now the likely limiting factor on how far you can go between stops.

toomuchtodo 2y ago

It’s for fast DC charging at 350kw+. Home charging is solved, but there is still travel range anxiety to squeeze out of the human, as well as use cases with high utilization and turnaround need (taxi, livery, law enforcement). 9 minutes to charge and a 20 year service life is awfully close to “you have no excuse this is suboptimal compared to liquid fuel refueling.” High level, EVs have almost killed combustion vehicles, we’re almost there [1] [2]. Batteries will only improve over time as EV production scales up. [1] https://news.ycombinator.com/item?id=41191790 https://news.ycombinator.com/item?id=41191790 [2] https://news.ycombinator.com/item?id=41207048 https://news.ycombinator.com/item?id=41207048

greenavocado 2y ago
Home charging is "solved" as in my car will always need to be charged all day or all night at best and if you want a truck that tows anything - such as for landscaping - forget it.

GaggiX 2y ago

Safety, long range and lifespan are still important to people who charge their EV at home.

malfist 2y ago

Home charging will not be that fast in the conceivable future. Just too much power for homes. Just thinking about it, my ford lightning with the extended battery has enough capacity to power the average house for something like 8 days. That'd be crazy be be about to demand that much power at home to charge it in nine minutes. But, it doesn't mean it's worthless to those that charge at home. I only own EVs. Even if I do 99.99999% of my charging at home, I still need to be able to charge during road trips. The faster the better. My partner and I have been eyeing the ev6 with it's 18 minute charge time. That's way easier to swallow than the 48 minutes the truck takes. 9 minutes and every seven hours of driving would be a god send, instead of our current 48 minutes every 4 hours

greenavocado 2y ago
Having an option to exchange batteries at every gas station would be even better.
- malfist 2y ago
  Yeah, but that comes with it's own host of issues. I'm not sure that tradeoff makes sense for something heavier than a motorcycle. Batteries to push a car a reasonable distance aren't light and need to be protected during a crash. Hard to balance that with "and easily removable and swapped"
  - greenavocado 2y ago
    They can unhook and attach from below.
    - malfist 2y ago
      Is grandma going to clamber under her car at a battery exchange station and disconnect and remove several hundred pounds of batteries?

tgsovlerkhgsel 2y ago

> 6.25 hours assuming the battery can be hit with maximum wattage continuously throughout its charge cycle (this is unhealthy). Are you sure it's unhealthy if you're already charging this slow? I'd expect 12 kW to still be below the slow part of a fast charge.

greenavocado 2y ago
I'm sorry, you're right about 12kW charging. The battery pack is made up of 4,416 individual cells. The cells are arranged in series to achieve the required voltage. If there are 96 cells in series, the pack would have a nominal voltage of around 400 volts (since each cell has a nominal voltage of about 4.2V when fully charged). The pack has multiple strings of these 96-series cells connected in parallel to increase capacity. 12kW/400V = 30A. 30A/(46 parallel strings) = 0.652A per cell or 652 milliamps. This is quite a slow and healthy charging speed.

kccqzy 2y ago

You took a home charging cable that's rated for 50 amps and thought about what if you used that exact cable for DC fast charging. What did you expect?

greenavocado 2y ago
80-90% of Tesla charging is done at home
- kccqzy 2y ago
  So? When you charge at home you are not going to need the fast charging capability of this new battery. The limiting factor is the onboard charger which for Tesla vehicles could be as low as 7kW. So it's moot. All you are doing is to sow confusion about home charging and public DC charging.
  - greenavocado 2y ago
    Many many people will deduce from the headline that maybe their car can charge at home in nine minutes, which is NOT the case, and NEVER will be.

oliwarner 2y ago

I just did a 1400mile round trip in our 9yo Model S. 80→20kW just doing my nut in. At least it was free. This sort of battery makes that sort of trip easy. There are already 3m liquid-cooled charging cables that allow 600kW+ DC charging. Many use more than one conductor per polarity to increase the capacity.

deleted 2y ago
[deleted]

thebruce87m 2y ago

> 75 kWh / 12 kW = 6.25 hours assuming the battery can be hit with maximum wattage continuously throughout its charge cycle (this is unhealthy). 12kW is nowhere near the max charging speed. Here is the charging curve with a peak at 250kWh when DC charging: https://evkx.net/models/tesla/model_y/model_y_long_range/chargingcurve/ https://evkx.net/models/tesla/model_y/model_y_long_range/cha...

greenavocado 2y ago
It is if you are charging at home. To achieve 250 kW of power, the Supercharger must supply much higher voltage and current than what is available from standard 120/240V circuits. For instance, Tesla Superchargers typically operate at voltages around 400-500V DC and deliver currents of up to 500 amps or more. Unlike residential power, which typically uses single-phase electricity, Superchargers often use three-phase power. Three-phase power allows for more efficient transmission of large amounts of electricity and is commonly used in industrial settings. The voltage supplied to a Tesla Supercharger is typically in the range of 480 volts AC (alternating current) for three-phase power. Inside the Supercharger, this 480V AC is converted to a higher DC (direct current) voltage, typically in the range of 400-500 volts DC, which is suitable for charging the vehicle's battery. The cables used in Tesla Superchargers are specially designed to handle very high currents. For instance, to deliver 250 kW at a voltage of around 400V DC, the current would need to be around 625 amps. To manage the heat generated by such high currents, Tesla employs liquid-cooled charging cables. These cables have an internal liquid coolant system that actively removes heat from the cable as electricity flows through it.
- thebruce87m 2y ago
  > It is if you are charging at home. I’m not sure why you are focusing on AC vs DC charging when your original assertion was related to the maximum wattage the battery can handle, which as I said is much bigger than 12kW. Also, even the 12kW would be the wrong maximum for home charging. The Model Y has an 11kW onboard charger for converting AC to DC, so if you have a 3-phase supply at home then this is the maximum your car can convert (NOT that the battery can handle as you suggest). If you have single phase then it’s 7kW. https://www.tesla.com/en_gb/support/charging/onboard-charger https://www.tesla.com/en_gb/support/charging/onboard-charger

albrewer 2y ago

> This information is worthless for electric vehicle owners who charge mostly or exclusively at home I need to make a 310 mile 1-way trip fairly regularly through _very_ rural parts of Texas. That trip is specifically why I don't own an EV. At 600 miles, it makes it to where the humans in the car are now the likely limiting factor on how far you can go between stops.