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January 2009 Posts
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I can't seem to comment under Stuart Irwin's post card on fast-charging systems.
I think we all understand that fast charging is possible with the right battery and something like 480V triple phase power source. It looks like Altairnano and Aerovironment have done this about 8 months ago.
The problem is that we keep seeing claims like 1) 10 minute full charge on 2) 110 V or 220 V standard outlet
This seems to violate the limits imposed by the home circuit breakers and the storage capacity of the batteries in EV's. Perhaps if you can comment on that it would be useful. To me, the numbers do not work.
Thanks
John C. Briggs
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Bo and Ryan, Congratulations. It sounds like you guys are really coming to an understanding of the issues with rapid charging at home.
I was trying to think of an analogy that might be more concrete for people to work with because electricity is so intangible. How's this sound.
Let's assume 1) a car runs on water 2) it has a 53 gallon tank 3) the pipe in your house can supply 10 gallons/hour.
So it is pretty obvious that it will take 5.3 hours to fill your tank each day. Of course this is a pain and someone wants to fix the problem. So they develop the "Rapi-Fill" (tm) tank that allows filling of a Rapi-Fill 53 gallon tank in only ten minutes. The tank is made of nano-structured steel that allows rapid-filling in only 10-minutes from a standard home 10gallon/hour pipe.
Hopefully it is obvious that the problem is not the tank, the problem is the pipe. Changing the physics or the chemistry of the tank will not solve the problem of the 10gallon/hour pipe.
Now if we change gallons to KWH and gallons/hour to KWH/hour we can see the same thing with EVs.
1) a car runs on electricity 2) it has a 53 KWH battery 3) the wire in your house can supply 10 KWH/hour.
So it still takes 5.3 hours to fill up your vehicle.
John is so right : fast charging isn't just a battery problem it's a battery/home electrical/grid problem- in the near future the only way I can see around it is a home energy storage system that would charge relatively slowly but could transfer energy to your car quickly- when eestor had better reputation there was talk of a two eestor energy storage device system, of course this would add extra expense to an already expensive car.
This NY Times article talks about charging.
http://www.nytimes.com/2009/01/25/automobiles/25ELECTRIC.html?ref=automobiles
This could be addressed by having some kind of big capacitor device in the garage that charges itself up all the time and holds the charge until you connect it to an EV and then it transfers the charge into the EV as fast as the EV can take it.
However, this is not very practical. Such a system would be expensive and potentially very dangerous. It would also leak some current thus losing efficiency. And even if you did have one, there are no reasonably priced batteries that can be fast-charged in such a way.
