A drag racer would want a battery with a high power density. A commuter with a long commute would want a battery with a high energy density. Simplistically, in a high power density Li battery there would be more plates with thinner carbon paste so that the energy can come out quickly and a high energy density battery would have thicker carbon paste and fewer plates so the energy can't come out as quick for a given voltage sag. Similar to the difference between a high power AGM or SLI battery and a deep cycle golf cart battery.
On Thu, May 8, 2014 at 10:20 PM, Jan Steinman via EV <[email protected]> wrote: > On 2014-05-08, at 20:33, Michael Ross wrote: > >> I hear power density discussed...some chemistries have more or less of >> this.... >> Power has a time component so maybe power density has to do with how fast >> you can get the work done with a battery? Probably a structural issue more >> so than a chemistry issue? > > That makes sense, since power is the rate at which energy is transformed, > such as BTU/hr. > > But I'm a bit stymied by the "power density" of a battery. It makes sense in > guesstimating how much acceleration you can get out of a vehicle, but I don't > know what it would tell you about a battery. > > For example, Veggie Van Gogh (http://www.VeggieVanGogh.com) has a 105 > horsepower engine and a gross weight of about five metric tonnes, a power > density of about 16 kilowatts per megagram. That's not far from my diesel > Vanagon, which has 49 HP and 2.4 metric tonnes, for 15.2 kW/Mg. And yet, the > five-ton step van seems "peppier" than the Volkswagen, probably due to more > low-end torque. > > After conversion to electric, the Vanagon will have half the power density, > at 8.7 kW/Mg, from a TransWarP 9 with 28 horsepower and the same gross weight > rating. But I'm hoping it will seem much peppier than that, because a > series-wound motor can give full torque at low RPMs. > > :::: So long as humans were well fed and entertained adequately, they'd > submit to increasingly draconian intrusions into their private lives. -- Thom > Hartmann > :::: Jan Steinman, EcoReality Co-op :::: > > _______________________________________________ > 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) > -- David D. Nelson http://evalbum.com/1328 http://www.levforum.com _______________________________________________ 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)
