6 ms·

I'm a little confused by fast charging standards, to be honest. 1MW is 20x the maximum draw of a standard house, and 800x the average draw of a US house. The

I'm a little confused by fast charging standards, to be honest. 1MW is 20x the maximum draw of a standard house, and 800x the average draw of a US house. The hydro plant down the road generates 5MW. It just sounds crazy to plan to pull that much power charging a car at a time.

bloggie 3y ago
It is indeed totally insane, but this is what is being worked on, not necessairly for cars but trucks and semi trucks for example that have much larger batteries than a car. Already to achieve 250+ kW charging stations have to have huge cables and watercooled connectors, here's one such installation I saw some years ago https://i.imgur.com/BpG4QAa.jpg https://i.imgur.com/BpG4QAa.jpg and an example of a cooled connector for 0.5 MW https://www.phoenixcontact.com/en-ca/products/dc-charging-cable-ev-t1hpcc-dc500a-50m50ecbk11-1085658 https://www.phoenixcontact.com/en-ca/products/dc-charging-ca...
- rootusrootus 3y ago
  I assume the next jump in power will come from voltage. A Model 3 pulls ~600A when charging at 250kW, because it's relatively low voltage. If they alter the charging design to accept 800 or 1000V we could see over half a MW without a change in cable design. But I'd guess at this point that would be moot because the cell charging rate is the real limit anyway.
  - Kirby64 3y ago
    Migrating to higher voltage doesn't do anything to charge batteries faster. The only advantage is that you can decrease the size of the cabling since current goes down. On the other side though, you need to move all drive circuitry, motors, etc, to handle higher voltage architecture, which may end of costing more overall.
    - cyberax 3y ago
      Not necessarily. Ford uses a 400V-based architecture, but it can charge at 800V by connected two sections of the battery in series.
      - Kirby64 3y ago
        So, you add the complexity of having to have a way to switch between 400V and 800V safely, which costs some amount of money, and the only advantage then is the cabling from the battery to the charging port can be thinner? That really doesn't seem like much savings, and if anything might cost more. The run from the charging port to the battery should already be really short.
        cyberax 3y ago
        800V for charging allows faster charging on CCS, because the existing stations are mainly current-limited. It won't be necessary on NACS. I think that Ford just wants to switch to 800V anyway, and 400V is just a stopgap.
  - bloggie 3y ago
    Yes Porsche has started with this, they have ~800 V batteries, as you said batteries themselves are the practical limit at the moment but both larger batteries (as with trucks) and new battery technology can help to lift that limit. There are enough engineering challenges at 1000 A I don't think we will see higher currents than that for a while!
  - panick21_ 3y ago
    All indication point to that the Cybertruck will be the first new architecture with a 1000V architecture. Many others have standardized on 800V, for example the Koreans.
NickM 3y ago
DC charging stations sometimes have batteries on site so that they can charge up from the grid and then deliver bursts of power from the batteries during charging. Apparently this is often worth it to avoid the high demand fees that utilities charge when you draw a lot of power at once. I assume this will become more ubiquitous as charging speeds continue to increase. (You're right that a megawatt is a high power draw in the context of normal household electricity usage, but keep in mind that if you can pump ten gallons of gas in a minute you're effectively drawing the equivalent of something like 20MW, so in the context of vehicle refueling it's not so crazy.)
- saalweachter 3y ago
  > but keep in mind that if you can pump ten gallons of gas in a minute you're effectively drawing the equivalent of something like 20MW, so in the context of vehicle refueling it's not so crazy If 15 Teslas pass through a stretch of road per minute with full 100kWh battery packs, you could also describe that as 90MW of current, but it's also not really.
  - jorvi 3y ago
    I always forget just how energy dense petroleum and its derivatives are..
    - matthewfcarlson 3y ago
      When charging, the Tesla shows you a little miles per hour figure (how many miles of range you gain per hour of charging) and it can often reach 1000 or so on the super chargers I use frequently. It’s fun to calculate the miles per hour of gas (around 12,000).
    - athenot 3y ago
      This is true. Though the electric batteries do have the advantage of having already paid the "thermodynamics tax". Some of the energy in gas will go towards heat losses; energy that cannot be converted to movement.
philg_jr 3y ago
You'll never need that much power at home. Level 2 AC 240V 30-50A is fine for overnight charging. The way Tesla Supercharging works is by using a large bank of batteries for the heavy bursts of power draw (>100kW) during the initial periods of charging when the battery is warm and at a low percent. The batteries at the station are backfilled with less current from the grid in the background during periods of low use. At least that is how I understand it. but yeah, maybe trucks with huge batteries may be able to take advantage of it down the road.
- vegardx 3y ago
  I don't know about the NA, but that is definitively not the case for most superchargers (or any other brand of fast chargers, for that matter) in Europe. Batteries are expensive so this is only done in very special cases. I know they've used battery banks at some of the electrical ferries in Norway, simply because the cost of running new high-voltage power lines was deemed more expensive and the schedule of the ferries makes it very easy to model. Power grids are quite large, so any fluctuations across the grid is going to be minimal. They are quite good at modeling these things, otherwise we'd have rolling blackouts quite often. For homes it's the last mile that's usually the biggest limiting factor. But I agree with what you said, for /most/ people anything more than 2kW (so 240V/10A) is more than enough to charge up overnight. A perk with CCS2 is the support for 3-phase power delivery. With very simple wiring and some smart(-ish) electronics you can opportunistically deliver around 11kW to a single car, or divide it with other house appliances or other cars. It's fairly common with 400V TN-system in some parts of Europe, which makes the support of 3-phase in CCS2 very handy.
  - claar 3y ago
    Just a nit pick: 10A @ 240V isn't enough to charge my Tesla Model Y overnight from empty - but 30A @ 240V (7.2kW) is.
    - vegardx 3y ago
      Most people don't drive 500km per day, the average is closer to 50 or so. So on average, you could easily top of your battery pack on 240V/10A circuit. That would be around 10kWh, which you'll do in 5 hours. Double the average and you'll still be topped up next morning.
dmoy 3y ago
> It just sounds crazy to plan to pull that much power charging a car at a time. For comparison, a normal gas station pump is like about 4MW of power (fuel).
- bryanlarsen 3y ago
  Electric cars are almost 4X as efficient as a gas car, so 1MW of electricy and 4MW of gasoline are roughly equivalent in miles added per minute. OTOH the only batteries that can absorb 1MW of electricity are those in some Class 8 trucks, and Class 8 diesel trucks are usually filled with pumps a lot faster than a standard gas station pump.
- deleted 3y ago
  [deleted]
- saalweachter 3y ago
  It's a useful comparison for how long it takes to refuel a vehicle, but "moving a liquid storing chemical potential energy through a tube" and "move electricity through a wire [and re-store it as electro-chemical potential energy]" are two such radically different activities that it glosses over a lot to equate the two.
Symbiote 3y ago
For a comparison the other way, high speed trains in Europe are around 10-16MW. Typical railway locomotives used for freight trains in Britain can draw a maximum of around 5MW. Ordinary-speed electric trains (for commuters, regional trains etc) with a limit of about 180km/h (110mph) draw 1.5-2MW. Presumably the full power is only needed when starting off on a hill.

bloggie 3y ago

It is indeed totally insane, but this is what is being worked on, not necessairly for cars but trucks and semi trucks for example that have much larger batteries than a car. Already to achieve 250+ kW charging stations have to have huge cables and watercooled connectors, here's one such installation I saw some years ago https://i.imgur.com/BpG4QAa.jpg https://i.imgur.com/BpG4QAa.jpg and an example of a cooled connector for 0.5 MW https://www.phoenixcontact.com/en-ca/products/dc-charging-cable-ev-t1hpcc-dc500a-50m50ecbk11-1085658 https://www.phoenixcontact.com/en-ca/products/dc-charging-ca...

rootusrootus 3y ago
I assume the next jump in power will come from voltage. A Model 3 pulls ~600A when charging at 250kW, because it's relatively low voltage. If they alter the charging design to accept 800 or 1000V we could see over half a MW without a change in cable design. But I'd guess at this point that would be moot because the cell charging rate is the real limit anyway.
- Kirby64 3y ago
  Migrating to higher voltage doesn't do anything to charge batteries faster. The only advantage is that you can decrease the size of the cabling since current goes down. On the other side though, you need to move all drive circuitry, motors, etc, to handle higher voltage architecture, which may end of costing more overall.
  - cyberax 3y ago
    Not necessarily. Ford uses a 400V-based architecture, but it can charge at 800V by connected two sections of the battery in series.
    - Kirby64 3y ago
      So, you add the complexity of having to have a way to switch between 400V and 800V safely, which costs some amount of money, and the only advantage then is the cabling from the battery to the charging port can be thinner? That really doesn't seem like much savings, and if anything might cost more. The run from the charging port to the battery should already be really short.
      - cyberax 3y ago
        800V for charging allows faster charging on CCS, because the existing stations are mainly current-limited. It won't be necessary on NACS. I think that Ford just wants to switch to 800V anyway, and 400V is just a stopgap.
- bloggie 3y ago
  Yes Porsche has started with this, they have ~800 V batteries, as you said batteries themselves are the practical limit at the moment but both larger batteries (as with trucks) and new battery technology can help to lift that limit. There are enough engineering challenges at 1000 A I don't think we will see higher currents than that for a while!
- panick21_ 3y ago
  All indication point to that the Cybertruck will be the first new architecture with a 1000V architecture. Many others have standardized on 800V, for example the Koreans.

NickM 3y ago

DC charging stations sometimes have batteries on site so that they can charge up from the grid and then deliver bursts of power from the batteries during charging. Apparently this is often worth it to avoid the high demand fees that utilities charge when you draw a lot of power at once. I assume this will become more ubiquitous as charging speeds continue to increase. (You're right that a megawatt is a high power draw in the context of normal household electricity usage, but keep in mind that if you can pump ten gallons of gas in a minute you're effectively drawing the equivalent of something like 20MW, so in the context of vehicle refueling it's not so crazy.)

saalweachter 3y ago
> but keep in mind that if you can pump ten gallons of gas in a minute you're effectively drawing the equivalent of something like 20MW, so in the context of vehicle refueling it's not so crazy If 15 Teslas pass through a stretch of road per minute with full 100kWh battery packs, you could also describe that as 90MW of current, but it's also not really.
- jorvi 3y ago
  I always forget just how energy dense petroleum and its derivatives are..
  - matthewfcarlson 3y ago
    When charging, the Tesla shows you a little miles per hour figure (how many miles of range you gain per hour of charging) and it can often reach 1000 or so on the super chargers I use frequently. It’s fun to calculate the miles per hour of gas (around 12,000).
  - athenot 3y ago
    This is true. Though the electric batteries do have the advantage of having already paid the "thermodynamics tax". Some of the energy in gas will go towards heat losses; energy that cannot be converted to movement.

philg_jr 3y ago

You'll never need that much power at home. Level 2 AC 240V 30-50A is fine for overnight charging. The way Tesla Supercharging works is by using a large bank of batteries for the heavy bursts of power draw (>100kW) during the initial periods of charging when the battery is warm and at a low percent. The batteries at the station are backfilled with less current from the grid in the background during periods of low use. At least that is how I understand it. but yeah, maybe trucks with huge batteries may be able to take advantage of it down the road.

vegardx 3y ago
I don't know about the NA, but that is definitively not the case for most superchargers (or any other brand of fast chargers, for that matter) in Europe. Batteries are expensive so this is only done in very special cases. I know they've used battery banks at some of the electrical ferries in Norway, simply because the cost of running new high-voltage power lines was deemed more expensive and the schedule of the ferries makes it very easy to model. Power grids are quite large, so any fluctuations across the grid is going to be minimal. They are quite good at modeling these things, otherwise we'd have rolling blackouts quite often. For homes it's the last mile that's usually the biggest limiting factor. But I agree with what you said, for /most/ people anything more than 2kW (so 240V/10A) is more than enough to charge up overnight. A perk with CCS2 is the support for 3-phase power delivery. With very simple wiring and some smart(-ish) electronics you can opportunistically deliver around 11kW to a single car, or divide it with other house appliances or other cars. It's fairly common with 400V TN-system in some parts of Europe, which makes the support of 3-phase in CCS2 very handy.
- claar 3y ago
  Just a nit pick: 10A @ 240V isn't enough to charge my Tesla Model Y overnight from empty - but 30A @ 240V (7.2kW) is.
  - vegardx 3y ago
    Most people don't drive 500km per day, the average is closer to 50 or so. So on average, you could easily top of your battery pack on 240V/10A circuit. That would be around 10kWh, which you'll do in 5 hours. Double the average and you'll still be topped up next morning.

dmoy 3y ago

> It just sounds crazy to plan to pull that much power charging a car at a time. For comparison, a normal gas station pump is like about 4MW of power (fuel).

bryanlarsen 3y ago
Electric cars are almost 4X as efficient as a gas car, so 1MW of electricy and 4MW of gasoline are roughly equivalent in miles added per minute. OTOH the only batteries that can absorb 1MW of electricity are those in some Class 8 trucks, and Class 8 diesel trucks are usually filled with pumps a lot faster than a standard gas station pump.
deleted 3y ago
[deleted]
saalweachter 3y ago
It's a useful comparison for how long it takes to refuel a vehicle, but "moving a liquid storing chemical potential energy through a tube" and "move electricity through a wire [and re-store it as electro-chemical potential energy]" are two such radically different activities that it glosses over a lot to equate the two.

Symbiote 3y ago

For a comparison the other way, high speed trains in Europe are around 10-16MW. Typical railway locomotives used for freight trains in Britain can draw a maximum of around 5MW. Ordinary-speed electric trains (for commuters, regional trains etc) with a limit of about 180km/h (110mph) draw 1.5-2MW. Presumably the full power is only needed when starting off on a hill.