I have the drain brain (high current model) you mentioned, and I consistently read around 75 Watt-hrs/mile on average for low and medium speeds.
I did not calibrate the current measurement, though the instructions say it's good to a few percent out of the box. I think it is fairly consistent across low to medium speeds because there are two different losses at low/medium speeds: 1. At low speeds (<25 MPH) I have less aero-drag loss, but my motor is less efficient. See this curve: http://lennonrodgers.googlepages.com/eMoto_motor_performance.pdf 2. At medium speeds (>=25 MPH <= 45 MPH) I have higher aero-drag loss, but my motor is approaching peak efficiency. Note: I assume peak efficiency in my spreadsheet (see previous message) for all speeds. -Lennon On Wed, May 7, 2008 at 9:31 AM, Garret Maki <[EMAIL PROTECTED]> wrote: > Mark, > 88whr/mile just seems lower than everyone else. Do you actually have > instrumentation in place to count watt hours out of your pack or are you > guessing based on what you think the SOC is? I have built several bikes > with a current shunt and have used the emeter/Link 10 and also the cycle > analyst to measure/ calculate actual whr/m and at 45 mph with a lighter bike > I'm well over 100 with an etek and 300# bike and on a more similar bike to > what you mention, around 117 whr/m with a series wound motor 50 psi in the > tires and ducking behind the windshield with a fresh brake rebuild and new > grease in the bearings. > > If you are using is cheap state of charge meter which is just a volt meter > and going by the printed specs on the capacity of your batteries you are > really just taking a poke in the dark about what the energy usage is and I'm > afraid you'll be giving other builders false hope about what their range > will be. I just want to keep it real here, and I don't think a lead bike > converted from a gas bike will do better than 100 whr/mile avg. in 45 mph > stop and go riding. Call me pessimistic, but I'd be happy to be proven > wrong. > > I highly recommend this for $150 http://ebike.ca/drainbrain.shtml > > Garret, in Minneapolis now. > > Mark Eidson <[EMAIL PROTECTED]> wrote: > I get 88whr per mile with my 72V bike. I have 6 PC1500 ~50aH AGM > batteries. I figure about 30 miles to 80% DOD. The most I have > driven is 24 miles to ~65% DOD. Typical speed is about 45MPH. I agree > you will need more than 50aH. me > > > > On 5/6/08, damon henry 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: listserv@electricmotorcycles.net > > > 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. > > > > > ________________________________ > Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it > now.
