7 ms·

In terms of rural areas, this will be an interesting challenge. When you drive cross country in the USA, you can expect to find gasoline reasonably close to eve

In terms of rural areas, this will be an interesting challenge. When you drive cross country in the USA, you can expect to find gasoline reasonably close to even the most remote areas. The distance to the next gas station from anywhere in the USA is well below the range of the typical car. 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.

mschuster91 9y ago
> if the charging times are rapidly decreased 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.
- digi_owl 9y ago
  If the range is enough, stopping to charge up for 30 mins means one can also grab a bite to eat. 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.
  - RightMillennial 9y ago
    A problem is not everyone wants to wait half an hour for every charge on a long distance trip. If I'm driving 12 hours, I want to get to my destination with minimal interruption. Having to wait 30+ minutes for each of the 2+ refuelings would be a pain and add a considerable amount of time to the already lengthy trip. I'd avoid that pain point if that's the choice.
    - slouch 9y ago
      How many 12 hour trips do you take? I hear this so much from people who only take one trip a year that would cause this hardship.
      - RightMillennial 9y ago
        I make about 4 trips like that a year. While it is certainly not a regular occurrence it is frequent enough that I would take it into consideration when looking at a vehicle. The point is not that I use the full range of my vehicle all of the time, but that I have the capability to due so. Don't get me wrong. I'm very interested in electric cars. However, the current ranges (which are close to being up to par), and especially the lack of infrastructure and long refueling times dissuades me from actually looking into purchasing one.
- kozak 9y ago
  Is there really a HVDC to battery voltage conversion step? I thought the whole point of quick charging is that you get exactly the DC that the battery needs right from the charger.
  - secabeen 9y ago
    Actually, the superchargers take AC from the grid. The equipment at the supercharger consists of a rack of AC to DC converters run in parallel. That creates the DC that is delivered to the batteries at about 400 Volts.
    - kozak 9y ago
      As far as I understand, the car asks the Level 3 charger for a certain amount of volts and amperes, and the charger delivers exactly what the car needs (being able to vary the parameters for each type of car - and yes, those Level 3 DC chargers are big, complex, and expensive). Then the current goes directly to the battery. And this is why the charging gets so fast: there are no intermediate steps. The car just needs to provide cooling for the battery and control the charging process.
      - schiffern 9y ago
        >> the superchargers take AC from the grid > 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.
        pilom 9y ago
- Diederich 9y ago
  I believe our supercharge yesterday gave us 50kwh in 25 minutes. 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.
- avs733 9y ago
  So this is not a perfect comparison but potentially a useful one. 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/52d148c3c4b02ded85257e4c004b73ed/11779_Megawatt_station_flyer_3AUA0000081847_RevH_EN_lowres.pdf 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.
  - floatrock 9y ago
    Have you thought of putting solar on your roof with storage to collect the extra energy you produce during the day and then dump it into your car at night? 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).

mschuster91 9y ago

> if the charging times are rapidly decreased 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.

digi_owl 9y ago
If the range is enough, stopping to charge up for 30 mins means one can also grab a bite to eat. 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.
- RightMillennial 9y ago
  A problem is not everyone wants to wait half an hour for every charge on a long distance trip. If I'm driving 12 hours, I want to get to my destination with minimal interruption. Having to wait 30+ minutes for each of the 2+ refuelings would be a pain and add a considerable amount of time to the already lengthy trip. I'd avoid that pain point if that's the choice.
  - slouch 9y ago
    How many 12 hour trips do you take? I hear this so much from people who only take one trip a year that would cause this hardship.
    - RightMillennial 9y ago
      I make about 4 trips like that a year. While it is certainly not a regular occurrence it is frequent enough that I would take it into consideration when looking at a vehicle. The point is not that I use the full range of my vehicle all of the time, but that I have the capability to due so. Don't get me wrong. I'm very interested in electric cars. However, the current ranges (which are close to being up to par), and especially the lack of infrastructure and long refueling times dissuades me from actually looking into purchasing one.
kozak 9y ago
Is there really a HVDC to battery voltage conversion step? I thought the whole point of quick charging is that you get exactly the DC that the battery needs right from the charger.
- secabeen 9y ago
  Actually, the superchargers take AC from the grid. The equipment at the supercharger consists of a rack of AC to DC converters run in parallel. That creates the DC that is delivered to the batteries at about 400 Volts.
  - kozak 9y ago
    As far as I understand, the car asks the Level 3 charger for a certain amount of volts and amperes, and the charger delivers exactly what the car needs (being able to vary the parameters for each type of car - and yes, those Level 3 DC chargers are big, complex, and expensive). Then the current goes directly to the battery. And this is why the charging gets so fast: there are no intermediate steps. The car just needs to provide cooling for the battery and control the charging process.
    - schiffern 9y ago
      >> the superchargers take AC from the grid > 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.
      - pilom 9y ago
Diederich 9y ago
I believe our supercharge yesterday gave us 50kwh in 25 minutes. 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.
avs733 9y ago
So this is not a perfect comparison but potentially a useful one. 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/52d148c3c4b02ded85257e4c004b73ed/11779_Megawatt_station_flyer_3AUA0000081847_RevH_EN_lowres.pdf 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.
- floatrock 9y ago
  Have you thought of putting solar on your roof with storage to collect the extra energy you produce during the day and then dump it into your car at night? 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).