I'm interested in building a bike that fits under the 750 Watt limit, but can deliver huge starting torque. It seems that if the mechanical Watts delivered by the motor is limited to 750, the torque at low RPM should be allowed to be huge.
Looking at the ebikes.ca simulator http://www.ebikes.ca/tools/simulator.html for a Crystalyte TC40100 hub motor at 72V/40A, 750 Watts motor power isn't exceeded until about 60 RPM and 5 MPH. The motor amps go from 166 to 140 as torque goes from 140 to 120 Nm.
Looking at the setup instructions for the PhaseRunner http://www.ebikes.ca/product-info/phaserunner.html, there is a power limit that "sets an upper value on the total watts that will be allowed to flow into the hub motor" which might be what I want. It will mean that the motor phase Amp limit will have to automatically adjust down as RPM goes up.
Playing with simulator parameters, it appears that it's quite hard to get big torque without big battery voltage. At low RPM, efficiency is very low, so we might have 3000 Watts from the battery and only 35 W delivered by the motor. I suppose with many cells in parallel with thick bus bars and cables, a low Volt, high Amp battery could also provide high torque without also enabling high speed, but this would be working against where the manufacturers are focusing. I tried 200 Ah, 0.01 Ohm (default is 0.2, so this is unrealistic) 36V battery and still only hit 98 Nm at 1.2 RPM. Better to use high voltage & limit speed with the Cycle Analyst.
US 16 CFR 1512.2 (a)(2) and the California Vehicle Code 312.5 (a) both say an electric bicycle has "an electric motor of less than 750 watts" (they use the exact same wording). So... a motor doesn't really have a Wattage. I'm guessing this hasn't been tested in court yet...
Looking at the ebikes.ca simulator http://www.ebikes.ca/tools/simulator.html for a Crystalyte TC40100 hub motor at 72V/40A, 750 Watts motor power isn't exceeded until about 60 RPM and 5 MPH. The motor amps go from 166 to 140 as torque goes from 140 to 120 Nm.
Looking at the setup instructions for the PhaseRunner http://www.ebikes.ca/product-info/phaserunner.html, there is a power limit that "sets an upper value on the total watts that will be allowed to flow into the hub motor" which might be what I want. It will mean that the motor phase Amp limit will have to automatically adjust down as RPM goes up.
Playing with simulator parameters, it appears that it's quite hard to get big torque without big battery voltage. At low RPM, efficiency is very low, so we might have 3000 Watts from the battery and only 35 W delivered by the motor. I suppose with many cells in parallel with thick bus bars and cables, a low Volt, high Amp battery could also provide high torque without also enabling high speed, but this would be working against where the manufacturers are focusing. I tried 200 Ah, 0.01 Ohm (default is 0.2, so this is unrealistic) 36V battery and still only hit 98 Nm at 1.2 RPM. Better to use high voltage & limit speed with the Cycle Analyst.
US 16 CFR 1512.2 (a)(2) and the California Vehicle Code 312.5 (a) both say an electric bicycle has "an electric motor of less than 750 watts" (they use the exact same wording). So... a motor doesn't really have a Wattage. I'm guessing this hasn't been tested in court yet...
