I'm not qualified to comment on the power requirements of a particular system, nor the power sources previously discussed, but I would like to make a suggestion to the builder of this vehicle.
Research in-wheel motors (hub motors) before you commit to that design. Look specifically for references to handling and braking. You'll find key words such as un-suspended weight frequently used in this region of expertise. Also consider that a typical hub motor of the kind used for bicycles has a very narrow range of efficiency and a similarly narrow range for power. Range of rpm is the relevant point here. Bicycle hub motors throw away energy as heat when traveling slower than optimum and can get away with it, in part, because the human bean is providing compensatory energy via the pedals. I suggest also to research the Stokemonkey e-assist power system or one of its clones. The Stokemonkey is a slightly modified hub motor which drives the left side of a crankset, allowing the cyclist to select the appropriate gear in the normal bicycle power train, matching the cyclist's cadence preference to conditions. If the system is correctly installed, the cyclist's cadence is closely matched to the motor's narrow range. If efficiency is your goal and it appears that is the case, you may benefit from using a similar design in your EV, including some form of transmission. My first velomobile was equipped with a Stokemonkey. With pedal assistance, I was able to enjoy two watt-hour per mile consumption. Flipped around, that's 500 miles per kwh. Without my pedal assistance the energy use skyrocketed to nearly ten watt-hours, or only 100 miles per kwh. I suspect there are few EVs on the road, other than the hyper-efficient solar models that can get close to those figures. There is a similar design to the Stokemonkey, a one-off for the personal use of the builder that weighs under five pounds with batteries, with a 100 watt motor. He built it solely for the purpose of assisting hill climbs. At that weight and that level of power, it's perfect for his requirements. Your vehicle could do well enough, I believe with a pair of 1 kw hub motors driving a common transmission with suitable gearing. My current velomobile has a Rohloff 14-speed hub transmission, but it is not covered under warranty for electric assist. I doubt that it would tolerate the forces of two 1 kw motors. The big advantage of the Rohloff is the linear progression of the gearing, a 426% range with 12% steps for each click of the shifter. You would not have the space constraints in your EV that exist in a bicycle wheel and might find a more effective transmission design, but I doubt that hub motors are going to be a suitably efficient answer. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140927/34ff71aa/attachment.htm> _______________________________________________ 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)
