Charging times have an upper bound: physics. 250 kW is an insane amount of power and still you'd need around half an hour to fill a 100 kWh battery, to get even close to the 5-10 minutes of charging like at a gas station you'd need megawatts of peak power... and as there are two steps of conversions involved (grid => HVDC => battery voltage), even with 99% efficiency you have 1% (or 10 kW) of heat loss alone. That heat in the small space of a battery pack is a challenge.
Gasoline has about 33kWh per gallon. A typical gas pump is limited to 10 gal/min flow rate (lets say 8gpm just to be conservative).
That means your gas pump takes about a minute to dispense 250 kWh or 23 seconds to dispense 100kWh. That generates effectively no heat. To charge one electric vehicle at the equivalent rate (assuming it could tolerate it) would take a 15 megawatt power source per 'pump'.
Here is the size of a one megawatt AC to DC power substation:
"The complete ABB megawatt station weighs only 20 tons. At 50 m3, the container’s volume is some 15 percent smaller than equivalent solutions."
https://library.e.abb.com/public/52d148c3c4b02ded85257e4c004...
I own an EV (hybrid really, Volt, but I'm 85% electric). I support electric vehicles enormously. But this is a huge huge problem with scaling that no one talks about. My volt can charge, slowly, at 8 amps (~1kW) while I'm at home, a rate my home power can easily take. Most vehicles in the US are static for at least 8 hours once, if not twice, during the day. Using that time to charge slower is a stopgap but I really doubt that the US grid has the excess capacity for this.
Yeah, there are efficiency losses along the way, but two points: - More and more net metering tariffs are homeowner-buys-at-retail-pricing-grid-purchases-back-at-wholesale-pricing... the homeowner value of solar's excess energy is getting less - In a lot of cheaper EV purchases, the car company still owns the battery packs. This is for two reasons: 1) They sell you on a new battery pack when your range starts to decline after a few years, and 2) They're going to use the degraded batteries as second-life storage products... maybe not good enough to power your car, but more than plenty to provide a cheap powerwall alternative.
The points you bring up about mass charging is true, but once pricing starts to reflect that, that's going to make home storage far more economical (it already makes economic sense in some markets).
My parents took us kids on car trips during summer holidays, and usually by the time we needed to stop to refuel the car we also took the time to eat and such.
I'm not disputing your point. It's a HELL of a lot more juice than people are used to thinking on a day to day basis. And it's going to change our infrastructure in fundamental ways.
> the charger delivers exactly what the car needs
You're both right. A Level 3 charger does deliver the right DC voltage the car needs, and it does so using power electronics that convert regular old grid AC into DC.
Level 1 & Level 2 charging: AC grid -> cable -> onboard charger converts to 400V DC -> battery
Level 3 charging: AC grid -> offboard charger converts to 400V DC -> cable -> battery
Same number of steps, same conversion efficiency. Tesla even goes a step further and uses the same hardware, building out the (low volume) Superchargers "simply" by ganging together a dozen (high volume) on-board charger modules and stacking them inside a weatherized outdoor cabinet. This commonality maximizes their economies of scale.
For anyone that's confused, it's because now we're really getting into the weeds of how the grid works. :) It's only fair to look back and compare from the same point in the grid, in order to be an apples to apples comparison. Really we should look at the whole electricity supply chain.
Level 1 & 2 charging: high voltage AC transmission line -> local substation converts to 480V AC -> distribution lines (poles or buried) -> pole-mounted or buried transformer converts to 110/220V AC -> household wiring -> cable -> onboard charger converts to 400V DC -> battery
Level 3 charging: high voltage AC transmission line -> on-site transformer converts to 480V AC -> offboard charger converts to 400V DC -> cable -> battery
However, in regards to cities, you are presenting a situation where the charging station comes to the parked car, rather than the car going to the charging station. While that would be quite convenient, if the charging times are rapidly decreased, there’s no reason car owners in cities would not be able to drive to stations to charge up, as drivers do with gas stations today.