I would have to call Mr Mitlin's knowledge into question is he believes all secondary cells require 'several hours' to fully charge. Clearly, they don't! MW
On 14 Aug 2014, at 18:09, Ben Goren via EV wrote: > "As hemp makes a comeback in the U.S. after a decades-long ban on its > cultivation, scientists are reporting that fibers from the plant can pack as > much energy and power as graphene, long-touted as the model material for > supercapacitors. They're presenting their research, which a Canadian start-up > company is working on scaling up, at the 248th National Meeting & Exposition > of the American Chemical Society (ACS). > > "David Mitlin, Ph.D., explains that supercapacitors are energy storage > devices that have huge potential to transform the way future electronics are > powered. Unlike today's rechargeable batteries, which sip up energy over > several hours, supercapacitors can charge and discharge within seconds. But > they normally can't store nearly as much energy as batteries, an important > property known as energy density. One approach researchers are taking to > boost supercapacitors' energy density is to design better electrodes. > Mitlin's team has figured out how to make them from certain hemp fibers—and > they can hold as much energy as the current top contender: graphene." > > http://phys.org/news/2014-08-hemp-nanosheets-topple-graphene-ideal.html > > The full article gives energy density at 12 Wh / kg, which, if I have my > figures right, is an order of magnitude shy of CALB and similar popular BEV > batteries. Still, I imagine that's more than enough for a quarter mile, and I > can't imagine what supercapacitor discharge rates will mean for the drag > racing crowd. A supercapacitor-powered dragster could well mark the end of > hydrocarbon-based racing. > > I can also imagine hybrid battery / supercapacitor systems, if these become > affordable, even if energy density doesn't significantly improve. Use a > supercapacitor with just enough Wh to go all-out for a dozen seconds to power > the motor and to accept regen charge, and have a battery just barely capable > of continuous discharge at freeway speeds uphill charging the supercapacitor. > The battery can be optimized for capacity and density (and price) without > worry about discharge rates. The supercapacitor is already optimized for > discharge; it just needs to be big enough to hold enough to get up to speed. > > Cheers, > > b& _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
