Sri, I used my spreadsheet and plugged in your numbers: http://lennonrodgers.googlepages.com/vehicle_calculations_sri.xls
My 5 second calculations show that you will get about 40 miles @ 50 MPH, but that's assuming you get the full 50 AH on your lithium-ion. My lead acids are rated at 44 AH, but I only get 29 AH (66% of rated). Not sure what it is for your lithium-ion. You'll need a gear ratio of 5 to get up to 50 MPH. Your efficiency is approx. 86 Watt-hr/mile @ 50 MPH cruise. But this assumes the same aerodynamic parameters as my motorcycle (yours are probably higher - feel free to modify the parameters in the spreadsheet). I used my motor info, which I think is nearly the same as the Etek-RT. I would build in some buffer for your top speed - my lead-acid system drops in voltage during the last few miles and thus cannot reach the full 45 MPH it was geared to reach. Lennon www.electricmotion.org On Tue, May 6, 2008 at 10:31 PM, damon henry <[EMAIL PROTECTED]> wrote: > > I think you will need closer to 80-100 ahr of those batteries to get 50 > miles. With a 100 ahr pack of Nicads at 48 volts I had a 35 to 40 mile > range at 50 mph. The pack weighed 230 lbs. Your lithiums will be quite a > bit lighter and since you are running at 72 volts instead of 48 you would > have 50% more overall capacity than I did. Weight however is not much of a > factor once you get up to cruising speed. Once you get up to speed it is > mostly aeordynamics, and this is one factor where all motorcycles suck. > > With only a 50 ahr pack you are hoping to do 1 mile per ahr which I think > is a bit over optimistic except for at very low speeds. You should compare > notes with some of the other 72 volt motorcycles and see how many ahrs per > mile they get. I know at 48 volts I average 2.5 - 3 ahr per mile. > > damon > > > > > ________________________________ > > > Date: Tue, 6 May 2008 16:13:07 -0700 > > From: [EMAIL PROTECTED] > > To: [email protected] > > Subject: [ElectricMotorcycles] Before we proceed on the conversion... > > > > > > Hello again, > > > > Thanks for all the advice on bikes and weights. The bike we settled on was > a 250cc 89 Ninja. ((This was a bit of a compromise, as we'd have preferred a > 200 lb ICE > > bike instead of a 300 lb one). > > > > Our goal again, is to do an ev-conversion with 50 mph top speed and a > 40-50 mile range. Doing this project with a like-minded partner, we've > expanded our budget, so Lithium looks like the best bet. > > > > We'd like to get your advice on this configuration: > > > > Batteries: > > 72V, 50AH LFP pack w/BMS from Hipower > > > > Controller+Motor kit which contains: > > E-tek-RT Motor, Alltrax AXE 7234 > > [I know there were some negatives regarding the older version of Etek, but > what about this one?] > > > > Info about batteries: > > > > http://www.chinabatteries.net/www/en/prod.htm > > > > weight is 92 lbs, >1000 cycles > > (>2000 cycles under optimal discharge conditions according to > manufacturer.) > > > > Some numbers: > > > > WH/lb = 39.13 > > [Compare w/ 16.4 WH/lb for an equivalent SLA system using B&B batteries] > > > > approx cost: $2650 for a 24-cell pack, $3500 incl BMS. > > > > Cost/KWH = $730 excl BMS > > Cost/KWH/cycle = $0.73 assuming 1000 cycles > > Cost/KWH/cycle = $0.37 assuming 2000 cycles > > [Compare with $0.61 for an equivalent SLA system using B&B batteries, > assuming 500 cycles] > > > > Total estimated cost (incl bike): $5500. Again sharing the bike with a > friend helps ease the bite on the wallet. > > > > Thanks, > > Sri Subramanian > > Roy Prince > > > > > ________________________________ > Stay in touch when you're away with Windows Live Messenger. IM anytime > you're online.
