6 ms·

I don’t see how any car battery charges in 10 minutes. Assuming a 75 kWh battery in the car, charging in 10 minute means providing 450,000 watts for 10 minutes.

by conk 6y ago

I don’t see how any car battery charges in 10 minutes. Assuming a 75 kWh battery in the car, charging in 10 minute means providing 450,000 watts for 10 minutes. At 1000V (higher than any DC charger today) would require 450 amps of current. The wire needed to provide 450A would be unmanageable for a car charger. And this is all assuming 100% efficiency, when in reality there will be various losses from charger to battery. Battery tech aside, how does any auto maker plan to get 10 minute charge time when just getting they much power through a cable is a huge challenge.

koolba 6y ago
Why can’t you have N cables supplying power to N cells in parallel?
- Afforess 6y ago
  heat dissipation. "charging" a battery is an exothermic chemical reaction.
  - Retric 6y ago
    Air can remove a lot of heat. A 98% efficient battery charging at 400kw is only producing 8kw of waste heat. At most you need a modest radiator and some fans. By comparison a normal 200HP engine at 30% efficiency is producing 667kw of waste heat into the air with a tiny percentage of that going out the exhaust pipe.
    - alacombe 6y ago
      Air is a pretty bad thermal conductor. An average ICE is only producing 200HP at a specific RPM, for short period of time. Red-lining any sedan while being stationary will probably overheat the engine pretty quickly, as the on-board radiator fan either electric or mechanical will not provide enough airflow. They are designed to be cooled by incoming air while driving.
      - ferongr 6y ago
        Not really. The actual load on the engine when redlining it while stationary is very small. You can monitor the fuel injector duty cycle, air flow mass or the useful "Load" PID using an OBD scanner like Torque.
        alacombe 6y ago
        Whether or not there is torque applied is irrelevant. For the sake of argument, when talking with a carburated ICE (ie. no electronic optimization), at full throttle, whether you redline with a load or not, at the same RPM, the same vacuum will be produced at the intake, and you will burn the same amount of fuel, thus produce the same amount of heat.
        ferongr 6y ago
        Well, with a carbureted engine that has no mechanism to limit RPM, you're probably not actually producing work at maximum RPM, but rather wasting mixture due to valve float. In essence, you're not burning that mixture. If you did, the RPM would keep increasing until the entire motor disintegrated. With electronic ignition, you usually have a way to limit max RPM by stopping ignition, so you're not producing work (and heat) either way.
        alacombe 6y ago
        There mechanism to limit RPM on carburated engine, it's called a governor.
    - ben-schaaf 6y ago
      > By comparison a normal 200HP engine at 30% efficiency is producing 667kw of waste heat into the air This isn't really a fair comparison. Cooling capacity goes up with the temperature difference to ambient. It's a lot harder to cool 8kw of heat at 20C above ambient compared to 8kw at 200C above ambient.
      - Retric 6y ago
        That is a meaningful difference but we are talking ~1/100th the heat transfer. The majority of that heat is removed via the radiator which uses a liquid coolant which should not exceed 105C even when the outside temperature is 45C so that’s only 60C of wiggle room. Though it’s a fair point batteries have lower maximum temperatures, at worst reducing charging rates when outside temperatures exceed ~(110C or 43C) is hardly deceptive or particularly relevant to most people. High end cars could even use the car’s AC in extreme situations.
- handol 6y ago
  I was thinking I would get bored waiting for it to charge for 10 minutes. But if I can spend half the time plugging in cables, and half the time unplugging them, problem solved.
- elihu 6y ago
  I suppose you could have multiple charge cables, if the car was designed that way. You'd presumably need multiple charge ports and possibly multiple chargers (by which I mean the AC-to-DC or DC-to-DC converter built into the car) and for them to tolerate being connected in parallel with each other. Just to be clear, you'd ordinarily have the cells themselves in series or a bunch of parallel groups in series to reach high voltages, and as far as the charger is concerned it's just one big battery with a single positive and a single negative terminal. On the other hand, if you're suggesting balance charging where you have an individual connection with the charger between each cell, that's not really practical to do with large batteries because the current would be very high and the voltages very low, which, as far as cabling goes, is the worst-case scenario. Charging a single cell at 100 amps and low voltage requires basically the same size cable as charging a bunch of cells in series at 100 amps and high voltage. If you need a big, thick cable for each cell, that gets unwieldy very quickly. Another unpractical option is to switch the battery into a single parallel group during charging and charge the whole group as if it was a single low-voltage high-amp-hour cell. That's unpractical for the same reason; low-voltage charging is an inefficient way to move energy around. Also, switching from series to parallel would require a lot of high-current contactors (basically, electro-mechanical relays), which are kind of expensive.
- octoberfranklin 6y ago
  You can, but that's simply one N-times-thicker cable.
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gpm 6y ago
I'm confused about why you think the wire would be a challenge. I'm not at all knowledgeable about high voltage/power stuff like this so maybe I'm missing something? A quick search tells me that 1000 kcmil wire is rated for 450 amps [1]. Another quick search finds that reasonably sized 1000 kcmil rated for 15000 volts are available and reasonably sized for a vehicle charger [2]. [1] http://wiresizecalculator.net/wiresizechart.htm http://wiresizecalculator.net/wiresizechart.htm [2] (note that kcmil and mcm mean the same things) https://www.lighting-gallery.net/gallery/displayimage.php?pos=-137753 https://www.lighting-gallery.net/gallery/displayimage.php?po...
- alacombe 6y ago
  For reference, a 1000kcmil wire is a 24mm section of copper wire, that alone over any length would be expensive as hell. If you want to go with aluminium wire, you have to bump your wire to 1750kcmil, or 34mm section. Just moving that beast is a workout, not to mention a nightmare to store, as it won't allow to be coiled is sharp bends.
  - octoberfranklin 6y ago
    And stiff! I can't bend a 24mm-diameter solid copper rod with my bare hands. Can you? Going stranded enough to feel even remotely like a "cord" or "cable" will bloat that diameter far, far beyond 24mm. I used to work with ~9mm diameter solid copper and even for that I treated it like EMT and used task-specific benders to shape it.
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- conk 6y ago
  The higher the voltage the faster the dielectric breakdown of insulators. And the cable/plug needs to be designed for 100k+ operations. 1000 kcmil cable x2 +ground and insulation is going to be one beefy cable. I’m not saying it can’t be done, just that it’s not a trivial problem to solve. Add to this an environment with a wide range of ambient temperatures and untrained humans sure to be yanking on stuff. I just would like to see some details on exactly how these claims will be achieved rather than some marketing puff piece. And Toyota is not alone here, GM pulled the same with the hummer EV and “watts to freedom” marketing buzz with no explanation of what that even means.
maxerickson 6y ago
Electric bus 'opportunity' chargers that run at that power are in use: https://insideevs.com/news/429760/siemens-bus-charging-infrastructure-projects/ https://insideevs.com/news/429760/siemens-bus-charging-infra... The contacts are on the roof of the vehicle and the charger drops down onto them. I'm not sure how that adapts for smaller vehicles, but they aren't starting from nothing.
- octoberfranklin 6y ago
  Article makes zero mention of the charging voltages. Since this thing is meant not to charge a single bus, but rather a fleet of buses, it's almost certainly not safe for the general public to get anywhere near it. This thing is in the same class as transmission line transformers.
  - maxerickson 6y ago
    Just search the products named if you want more info: https://new.siemens.com/global/en/products/energy/medium-voltage/solutions/emobility/sicharge-uc.html https://new.siemens.com/global/en/products/energy/medium-vol... The 450 Kw charger can be setup standalone, it doesn't have to be in a charging depot. It charges 1 bus at a time. The design is focused on installation at locations along a bus route where the bus pauses. If the bus automatically charges during the pause, it can operate with a smaller, cheaper battery.
gok 6y ago
Liquid cooled cables would be fine for this; they are already used for 350 kilowatt charging.
clouddrover 6y ago
It shouldn't be a problem. 350 kW CCS chargers are widely deployed. Some CCS chargers today support 400 kW: https://www.greencarreports.com/news/1125436_the-most-powerful-dc-charging-station-in-europe-for-cars-can-deliver-400-kw https://www.greencarreports.com/news/1125436_the-most-powerf...
snoshy 6y ago
I think you raise a valid point, which is that thermal exchange management is a significant issue for fast charging batteries, regardless of capacity. However, Tesla already has deployed 250,000 watt chargers in real world use, so a jump to the 450,000 watt range is within an order of magnitude, and so wouldn't be inconceivable.
elihu 6y ago
450 kilowatts is about 600 horsepower or so. That's a lot, but it's in the range of the sort of power that a high-end electric car motor might draw now, and they somehow manage it with not-too-unreasonably-thick electric cabling. Granted, there probably aren't many electric cars designed to output 600 horsepower for ten minutes: eventually, the cables and the batteries will just get too hot. I'm not an electrical engineer; I don't know what the proper cable size is for this application with all the correct safety margins, but it doesn't seem too terribly unreasonable as long as the voltages are pretty high and the battery can tolerate it. If heat is a problem, then water cooled cables can help.
- octoberfranklin 6y ago
  > it's in the range of the sort of power that a high-end electric car motor might draw ... for a very brief period of time. Please don't use horsepower as a measure of electrical power, it's misleading. All the stuff around us that is commonly measured in horsepower is fossil-fuel-burning equipment with fossil-fuel-levels of energy density at any given cost point. They make hard things seem easy because they don't have to be rechargeable.
  - elihu 6y ago
    Why not? One horsepower is about 746 watts. That's a useful way to compare things sometimes. (Though with the caveat that gas engines generally have horsepower ratings that reflect maximum power, often in an RPM range that you don't normally use in everyday use. Thus an 200 horsepower electric motor might often out-perform a 300 horsepower gas engine, because the former generally has maximum torque from zero RPM whereas the latter has to be in an optimal RPM band. Also the gas engine at the same time produces about 2x or 3x its mechanical power in heat.) With electric motors it seems to be at least fairly common to refer to an electric motor's mechanical power output in kilowatts rather than horsepower. In a lot of ways that makes sense, but horsepower is a unit that more people are familiar with.
aetherspawn 6y ago
Hi, engineer from an electric vehicle company here. This is not an issue because, even if a small wire is used, the efficiency loss is not all that considerable. Energy is cheap, so liquid cooling the cables and dissipating i.e. 5% of the energy into the conductor is a straightforward trade-off. Compare that trivially to petrol, which costs petrol (diesel) to move to petrol stations, and it's actually not that surprising. Additionally, there has recently been a lot of investment into EV chargers with built-in batteries that charge at slower rates when a vehicle is not present, and operate independently from the grid once a vehicle is connected. This answers the obvious question about infrastructure to deliver the power required.
- clouddrover 6y ago
  > Additionally, there has recently been a lot of investment into EV chargers with built-in batteries Two such chargers: https://freewiretech.com/products/dc-boost-charger/ https://freewiretech.com/products/dc-boost-charger/ https://insideevs.com/news/398348/eon-volkswagen-fast-charging-everywhere/ https://insideevs.com/news/398348/eon-volkswagen-fast-chargi...
- AnthonyMouse 6y ago
  > Additionally, there has recently been a lot of investment into EV chargers with built-in batteries that charge at slower rates when a vehicle is not present, and operate independently from the grid once a vehicle is connected. Is this even going to be required in most cases? Charging at that speed is only really useful for road trips where you're sitting there waiting for charging to complete so you can go. If you're charging while the car is parked at home for the night, what does it matter if it's ten minutes or ten hours? So then you only really need the very fast chargers at truck stops on the highway and the like, and then couldn't those chargers just be given a hefty grid connection? The high voltage lines already run parallel to major highways.
- octoberfranklin 6y ago
  You basically dodged his question there. Increasing I^2R heat loss by 5% doesn't let you shrink the cable much. You go from "humongously phat cable" to "really phat cable". The problem remains. Also remember that the cost of the petroleum distribution infrastructure is shared between in-town drivers and road-trip drivers. If these "fast chargers" are only supposed to be used by people who need more than one batteryful of driving in a given day (i.e. people on a road trip), the budget available to pay for the refueling infrastructure is going to be tiny compared to the petroleum infrastructure. EVs will simply never "catch on" for non-commuter use if we go down that road.
amluto 6y ago
Even rather old Model S cars charge at over 300A at a supercharger station. 450A is not a stretch at all. I admit I’m rather impressed that the connectors can handle this amount of current, but they don’t seem to have a problem with it.
matt-attack 6y ago
Pretty sure Tesla’s latest super chargers are around 800Amps.

by conk 6y ago

koolba 6y ago

Why can’t you have N cables supplying power to N cells in parallel?

Afforess 6y ago
heat dissipation. "charging" a battery is an exothermic chemical reaction.
- Retric 6y ago
  Air can remove a lot of heat. A 98% efficient battery charging at 400kw is only producing 8kw of waste heat. At most you need a modest radiator and some fans. By comparison a normal 200HP engine at 30% efficiency is producing 667kw of waste heat into the air with a tiny percentage of that going out the exhaust pipe.
  - alacombe 6y ago
    Air is a pretty bad thermal conductor. An average ICE is only producing 200HP at a specific RPM, for short period of time. Red-lining any sedan while being stationary will probably overheat the engine pretty quickly, as the on-board radiator fan either electric or mechanical will not provide enough airflow. They are designed to be cooled by incoming air while driving.
    - ferongr 6y ago
      Not really. The actual load on the engine when redlining it while stationary is very small. You can monitor the fuel injector duty cycle, air flow mass or the useful "Load" PID using an OBD scanner like Torque.
      - alacombe 6y ago
        Whether or not there is torque applied is irrelevant. For the sake of argument, when talking with a carburated ICE (ie. no electronic optimization), at full throttle, whether you redline with a load or not, at the same RPM, the same vacuum will be produced at the intake, and you will burn the same amount of fuel, thus produce the same amount of heat.
        ferongr 6y ago
        Well, with a carbureted engine that has no mechanism to limit RPM, you're probably not actually producing work at maximum RPM, but rather wasting mixture due to valve float. In essence, you're not burning that mixture. If you did, the RPM would keep increasing until the entire motor disintegrated. With electronic ignition, you usually have a way to limit max RPM by stopping ignition, so you're not producing work (and heat) either way.
        alacombe 6y ago
        There mechanism to limit RPM on carburated engine, it's called a governor.
  - ben-schaaf 6y ago
    > By comparison a normal 200HP engine at 30% efficiency is producing 667kw of waste heat into the air This isn't really a fair comparison. Cooling capacity goes up with the temperature difference to ambient. It's a lot harder to cool 8kw of heat at 20C above ambient compared to 8kw at 200C above ambient.
    - Retric 6y ago
      That is a meaningful difference but we are talking ~1/100th the heat transfer. The majority of that heat is removed via the radiator which uses a liquid coolant which should not exceed 105C even when the outside temperature is 45C so that’s only 60C of wiggle room. Though it’s a fair point batteries have lower maximum temperatures, at worst reducing charging rates when outside temperatures exceed ~(110C or 43C) is hardly deceptive or particularly relevant to most people. High end cars could even use the car’s AC in extreme situations.
handol 6y ago
I was thinking I would get bored waiting for it to charge for 10 minutes. But if I can spend half the time plugging in cables, and half the time unplugging them, problem solved.
elihu 6y ago
I suppose you could have multiple charge cables, if the car was designed that way. You'd presumably need multiple charge ports and possibly multiple chargers (by which I mean the AC-to-DC or DC-to-DC converter built into the car) and for them to tolerate being connected in parallel with each other. Just to be clear, you'd ordinarily have the cells themselves in series or a bunch of parallel groups in series to reach high voltages, and as far as the charger is concerned it's just one big battery with a single positive and a single negative terminal. On the other hand, if you're suggesting balance charging where you have an individual connection with the charger between each cell, that's not really practical to do with large batteries because the current would be very high and the voltages very low, which, as far as cabling goes, is the worst-case scenario. Charging a single cell at 100 amps and low voltage requires basically the same size cable as charging a bunch of cells in series at 100 amps and high voltage. If you need a big, thick cable for each cell, that gets unwieldy very quickly. Another unpractical option is to switch the battery into a single parallel group during charging and charge the whole group as if it was a single low-voltage high-amp-hour cell. That's unpractical for the same reason; low-voltage charging is an inefficient way to move energy around. Also, switching from series to parallel would require a lot of high-current contactors (basically, electro-mechanical relays), which are kind of expensive.
octoberfranklin 6y ago
You can, but that's simply one N-times-thicker cable.

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gpm 6y ago

I'm confused about why you think the wire would be a challenge. I'm not at all knowledgeable about high voltage/power stuff like this so maybe I'm missing something? A quick search tells me that 1000 kcmil wire is rated for 450 amps [1]. Another quick search finds that reasonably sized 1000 kcmil rated for 15000 volts are available and reasonably sized for a vehicle charger [2]. [1] http://wiresizecalculator.net/wiresizechart.htm http://wiresizecalculator.net/wiresizechart.htm [2] (note that kcmil and mcm mean the same things) https://www.lighting-gallery.net/gallery/displayimage.php?pos=-137753 https://www.lighting-gallery.net/gallery/displayimage.php?po...

alacombe 6y ago
For reference, a 1000kcmil wire is a 24mm section of copper wire, that alone over any length would be expensive as hell. If you want to go with aluminium wire, you have to bump your wire to 1750kcmil, or 34mm section. Just moving that beast is a workout, not to mention a nightmare to store, as it won't allow to be coiled is sharp bends.
- octoberfranklin 6y ago
  And stiff! I can't bend a 24mm-diameter solid copper rod with my bare hands. Can you? Going stranded enough to feel even remotely like a "cord" or "cable" will bloat that diameter far, far beyond 24mm. I used to work with ~9mm diameter solid copper and even for that I treated it like EMT and used task-specific benders to shape it.
- deleted 6y ago
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- deleted 6y ago
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conk 6y ago
The higher the voltage the faster the dielectric breakdown of insulators. And the cable/plug needs to be designed for 100k+ operations. 1000 kcmil cable x2 +ground and insulation is going to be one beefy cable. I’m not saying it can’t be done, just that it’s not a trivial problem to solve. Add to this an environment with a wide range of ambient temperatures and untrained humans sure to be yanking on stuff. I just would like to see some details on exactly how these claims will be achieved rather than some marketing puff piece. And Toyota is not alone here, GM pulled the same with the hummer EV and “watts to freedom” marketing buzz with no explanation of what that even means.

maxerickson 6y ago

Electric bus 'opportunity' chargers that run at that power are in use: https://insideevs.com/news/429760/siemens-bus-charging-infrastructure-projects/ https://insideevs.com/news/429760/siemens-bus-charging-infra... The contacts are on the roof of the vehicle and the charger drops down onto them. I'm not sure how that adapts for smaller vehicles, but they aren't starting from nothing.

octoberfranklin 6y ago
Article makes zero mention of the charging voltages. Since this thing is meant not to charge a single bus, but rather a fleet of buses, it's almost certainly not safe for the general public to get anywhere near it. This thing is in the same class as transmission line transformers.
- maxerickson 6y ago
  Just search the products named if you want more info: https://new.siemens.com/global/en/products/energy/medium-voltage/solutions/emobility/sicharge-uc.html https://new.siemens.com/global/en/products/energy/medium-vol... The 450 Kw charger can be setup standalone, it doesn't have to be in a charging depot. It charges 1 bus at a time. The design is focused on installation at locations along a bus route where the bus pauses. If the bus automatically charges during the pause, it can operate with a smaller, cheaper battery.

gok 6y ago

Liquid cooled cables would be fine for this; they are already used for 350 kilowatt charging.

clouddrover 6y ago

It shouldn't be a problem. 350 kW CCS chargers are widely deployed. Some CCS chargers today support 400 kW: https://www.greencarreports.com/news/1125436_the-most-powerful-dc-charging-station-in-europe-for-cars-can-deliver-400-kw https://www.greencarreports.com/news/1125436_the-most-powerf...

snoshy 6y ago

I think you raise a valid point, which is that thermal exchange management is a significant issue for fast charging batteries, regardless of capacity. However, Tesla already has deployed 250,000 watt chargers in real world use, so a jump to the 450,000 watt range is within an order of magnitude, and so wouldn't be inconceivable.

elihu 6y ago

450 kilowatts is about 600 horsepower or so. That's a lot, but it's in the range of the sort of power that a high-end electric car motor might draw now, and they somehow manage it with not-too-unreasonably-thick electric cabling. Granted, there probably aren't many electric cars designed to output 600 horsepower for ten minutes: eventually, the cables and the batteries will just get too hot. I'm not an electrical engineer; I don't know what the proper cable size is for this application with all the correct safety margins, but it doesn't seem too terribly unreasonable as long as the voltages are pretty high and the battery can tolerate it. If heat is a problem, then water cooled cables can help.

octoberfranklin 6y ago
> it's in the range of the sort of power that a high-end electric car motor might draw ... for a very brief period of time. Please don't use horsepower as a measure of electrical power, it's misleading. All the stuff around us that is commonly measured in horsepower is fossil-fuel-burning equipment with fossil-fuel-levels of energy density at any given cost point. They make hard things seem easy because they don't have to be rechargeable.
- elihu 6y ago
  Why not? One horsepower is about 746 watts. That's a useful way to compare things sometimes. (Though with the caveat that gas engines generally have horsepower ratings that reflect maximum power, often in an RPM range that you don't normally use in everyday use. Thus an 200 horsepower electric motor might often out-perform a 300 horsepower gas engine, because the former generally has maximum torque from zero RPM whereas the latter has to be in an optimal RPM band. Also the gas engine at the same time produces about 2x or 3x its mechanical power in heat.) With electric motors it seems to be at least fairly common to refer to an electric motor's mechanical power output in kilowatts rather than horsepower. In a lot of ways that makes sense, but horsepower is a unit that more people are familiar with.

aetherspawn 6y ago

Hi, engineer from an electric vehicle company here. This is not an issue because, even if a small wire is used, the efficiency loss is not all that considerable. Energy is cheap, so liquid cooling the cables and dissipating i.e. 5% of the energy into the conductor is a straightforward trade-off. Compare that trivially to petrol, which costs petrol (diesel) to move to petrol stations, and it's actually not that surprising. Additionally, there has recently been a lot of investment into EV chargers with built-in batteries that charge at slower rates when a vehicle is not present, and operate independently from the grid once a vehicle is connected. This answers the obvious question about infrastructure to deliver the power required.

clouddrover 6y ago
> Additionally, there has recently been a lot of investment into EV chargers with built-in batteries Two such chargers: https://freewiretech.com/products/dc-boost-charger/ https://freewiretech.com/products/dc-boost-charger/ https://insideevs.com/news/398348/eon-volkswagen-fast-charging-everywhere/ https://insideevs.com/news/398348/eon-volkswagen-fast-chargi...
AnthonyMouse 6y ago
> Additionally, there has recently been a lot of investment into EV chargers with built-in batteries that charge at slower rates when a vehicle is not present, and operate independently from the grid once a vehicle is connected. Is this even going to be required in most cases? Charging at that speed is only really useful for road trips where you're sitting there waiting for charging to complete so you can go. If you're charging while the car is parked at home for the night, what does it matter if it's ten minutes or ten hours? So then you only really need the very fast chargers at truck stops on the highway and the like, and then couldn't those chargers just be given a hefty grid connection? The high voltage lines already run parallel to major highways.
octoberfranklin 6y ago
You basically dodged his question there. Increasing I^2R heat loss by 5% doesn't let you shrink the cable much. You go from "humongously phat cable" to "really phat cable". The problem remains. Also remember that the cost of the petroleum distribution infrastructure is shared between in-town drivers and road-trip drivers. If these "fast chargers" are only supposed to be used by people who need more than one batteryful of driving in a given day (i.e. people on a road trip), the budget available to pay for the refueling infrastructure is going to be tiny compared to the petroleum infrastructure. EVs will simply never "catch on" for non-commuter use if we go down that road.

amluto 6y ago

Even rather old Model S cars charge at over 300A at a supercharger station. 450A is not a stretch at all. I admit I’m rather impressed that the connectors can handle this amount of current, but they don’t seem to have a problem with it.

matt-attack 6y ago

Pretty sure Tesla’s latest super chargers are around 800Amps.