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by aidenn0 5258 days ago
Charging a 300mile electric car in 5-10 minutes is not going to happen any time soon, and it's not because of battery technology:

The model S uses 85kWh to go 300 miles (at 55 mph, remember which is way slower than you'll go on the freeway in California). 10 minutes is 1/6 of an hour so:

85kWh * 6/h = 510kW. Do you really think we are going to have 1/2 MW charging cables? Obviously this is not going to happen with home charging. Can you think of a way of even getting 1/2MW to a commercial charging station in a populated area? What about on e.g. labor day when large numbers of people want demand. If 10 people want to do a 10 minute charge in the same city at the same time, thats 10MW, which is a lot of coal we are burning to supply that (or if you want green power, about 100 acres of photovoltaics)[1].

I'm all for electrics, but I know the power grid is going to need an overhaul if more than about 1/8 the population adopts them, and on top of that current trends indicate that most of the new capacity is going to come from coal plants, which largely negates the environmental advantages of electrics.

1: http://en.wikipedia.org/wiki/Nellis_Solar_Power_Plant

2 comments

I'm not very experienced in electronics, but couldn't you constantly store the source electricity in some sort of storage (battery, capacitors) and then dump it quickly into cars? This may not be feasible due to the efficiencies or safety factors involved, but the car wouldn't necessarily have to draw directly from the source line. The recharging stations could draw line power to recharge their storage overnight while the use of their charging terminals is low. However, I imagine the storage would be extremely pricey for the home market.
The most economical way of storing electrical energy on-site is probably the lead-acid battery. Enough lead-acid batteries to store 100 car recharges would be 1200 cubic meters. I found estimates from $0.17 to $0.50 per watt hour which would put the cost at over $1M to handle 100 car recharges. Charging that up continuously would put the energy requirements at 440kW assuming 80% round-trip efficiency.
Thanks for the numbers. It looks like we still need plenty of breakthroughs or drastic shifts in society for this to be realistic.
> 1/2 MW charging cables

Cables are rated by the current they support, not by the power of the devices connected to it. A cable up to 10 Ampères supports 1100 watts on a 110V mains, or 2200W on a 220V mains. Quick charging on electric vehicles probably is done at high voltages.

http://en.wikipedia.org/wiki/Ampacity

EDIT: you are right about home charging not possible. And to the sibling, the best storage systems for fast charging are http://en.wikipedia.org/w/Supercapacitor and http://en.wikipedia.org/wiki/Flywheel_energy_storage