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Yet somehow my car doesn't take down the grid every time I plug it in and the car tries to draw 150KW to charge the batteries at max rate. Why would grid stora

Yet somehow my car doesn't take down the grid every time I plug it in and the car tries to draw 150KW to charge the batteries at max rate. Why would grid storage configure the cars to supply power at the max battery rate? Even if my car and the grid-tie system malfunctioned and tried to send unlimited power to the grid, the 30A breaker its plugged into would trip before it hits 7500W. It's not like it needs to handle a lot of power because EV's don't have that much power to spare, if I have a 75KWh battery and am willing to give up 30% of my capacity to the grid, that's 25KWh, or around 2.5KW for 10 hours.

falcolas 4y ago
The grid, even if its your connection between your mains and your car, needs to be set up to limit the output of the car's batteries. Or the car (powerwall, etc) does. > if I have a 75KWh battery and am willing to give up 30% of my capacity to the grid, that's 25KWh, or around 2.5KW for 10 hours. That depends on how much current you can push. The battery is quite capable of giving up that 25kWh in 10-20 minutes too.
- Johnny555 4y ago
  The grid, even if its your connection between your mains and your car, needs to be set up to limit the output of the car's batteries. Or the car (powerwall, etc) does. Yes, and it does have those limits in place for charging, some in software (by the EV charge controller telling the car how much power it can use), some hardware (through at least 2 circuit breakers). Why wouldn't the same limits be enforced if using the car for grid storage? Why does the max power output of a car battery have any bearing on whether it can be used for grid storage?
  - falcolas 4y ago
    Because batteries can pump out magnitudes more power in a very short amount of time than solar. The two are not comparable. But ultimately, what speaks more than anything I could ever say is the requirement for backup power generation (including household battery arrays) requires mains power be cut off before engaging - to prevent damage to the grid.
    - Johnny555 4y ago
      Because batteries can pump out magnitudes more power in a very short amount of time than solar. The two are not comparable. The batteries aren't connected to the grid directly, the grid can't absorb DC power, it has to go through an inverter. Even if your batteries can supply 500KW of instantaneous power, if they are connected to a 1KW inverter, the most the grid will ever see is 1KW - there's no failure mode that would let a 1KW inverter pump out 500KW of AC power, even for an instant.

falcolas 4y ago

The grid, even if its your connection between your mains and your car, needs to be set up to limit the output of the car's batteries. Or the car (powerwall, etc) does. > if I have a 75KWh battery and am willing to give up 30% of my capacity to the grid, that's 25KWh, or around 2.5KW for 10 hours. That depends on how much current you can push. The battery is quite capable of giving up that 25kWh in 10-20 minutes too.

Johnny555 4y ago
The grid, even if its your connection between your mains and your car, needs to be set up to limit the output of the car's batteries. Or the car (powerwall, etc) does. Yes, and it does have those limits in place for charging, some in software (by the EV charge controller telling the car how much power it can use), some hardware (through at least 2 circuit breakers). Why wouldn't the same limits be enforced if using the car for grid storage? Why does the max power output of a car battery have any bearing on whether it can be used for grid storage?
- falcolas 4y ago
  Because batteries can pump out magnitudes more power in a very short amount of time than solar. The two are not comparable. But ultimately, what speaks more than anything I could ever say is the requirement for backup power generation (including household battery arrays) requires mains power be cut off before engaging - to prevent damage to the grid.
  - Johnny555 4y ago
    Because batteries can pump out magnitudes more power in a very short amount of time than solar. The two are not comparable. The batteries aren't connected to the grid directly, the grid can't absorb DC power, it has to go through an inverter. Even if your batteries can supply 500KW of instantaneous power, if they are connected to a 1KW inverter, the most the grid will ever see is 1KW - there's no failure mode that would let a 1KW inverter pump out 500KW of AC power, even for an instant.