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Comment by Tuna-Fish | Hacker News Reader

Except that you also have to move the electricity into the car, which is actually the limiting factor in Teslas today, not the batteries. So this wouldn't really help at all.

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From Tesla's website it looks like they take ~1 Hr to charge (1C rate). That would make me think they are limited by the maximum charge rate of the cells.

On the contrary, it is limited by the size of the cable going from the electricity distribution grid to the side of the car. With a typical (not a high performance) car engine capable of generating 75kW of mechanical power or so and a typical wall socket (in the UK at least) capable of transferring 3kW (and the average house having a 24kW total limit), there's going to be a problem that can only be solved by upgrading the cabling and using special high power sockets.

That's with a 120 kW charger. Can they increase the power 6 times? 720 kW per car?

At some point the amount of copper needed to carry the current becomes heavier than the batteries themselves. 120kW is already outlandishly strong, at 120V it's 1000 amps!

Are Tesla Superchargers 3-phase 480V on the incoming side? It seems they would need to be to support 120kW charging.

If you had batteries which could accept that (Li-Ion's don't like going above 3C I think) and had the kind of energy density being claimed then it would be a relatively trivial matter to use a larger bank of them to provide the peak capability to charge a smaller bank of them.

Source?

Just read up on any existing quick-charging technology. Tesla's superchargers are the world's highest-capacity quick charging at 130kW, 2x the nearest competitor (CHAdeMO). And this still requires ~one hour to give the battery a full charge. Let's say you want to be able to charge in six minutes. That would mean something on the order of 1.3MW of electric power. So let's say you have a small-ish refueling station like a contemporary gas station, with eight charging spots. To power these, you need to pull ten megawatts from somewhere. The current power grid isn't dimensioned for this kind of demand, especially since the demand is very transient.

Tesla is attempting to solve this by building a massive battery storage capacity into the chargers and then trickle charging these batteries when the charging bays are not in use, so this is by no means a problem that has been solved once and for all.

Distribution level voltage is anywhere from 4kv to 25 kv. Say it's 12. Typical partridge or linnet distribution conductor might do 200 A. P=sqrt(3)IV cos theta = 1.73 * 200 * 12000 * 0.9 = 3.7 mw.

So you are correct your average distribution feeder probably does not have capacity for a 10 mw service. I guess that's not much of a shock.

In the United States the normal distribution voltage, prior to being stepped down for consumer use, 7.6kv phase to ground, 13.2 phase to phase. So yes, you're pretty close, except the 13.2 kv would be 3-phase. For heavy industrial use, 4.4 kv is common for actual end user equipment, but above that would be some pretty serious equipment for an end user. Larger transmission lines operate anywhere from 60kv on up to 1.1 million volts, so lots of power is possible, as long as you don't mind the brownouts.

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