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Old 11-16-2009, 11:05 AM
jdcburg jdcburg is offline
Motorized Bicycle Elite Member
Join Date: Jul 2009
Location: massachusetts
Posts: 150
Default Re: Science fair Ideas....

Hi 42blue15 - I can't really argue with your analysis as I don't know what figures you or Bionx used. Because we are talking about a science fair project, it would be good to use the scientific method, that is, quantifiable data obtained in a reproducible manner analyzed without bias. Last month I paid $60.70 for 326 kWh of electricity from the grid. That’s $0.186/kWh. My 6 amp 12V battery charger says the current draw is 1.1 amps at 120 volts, which is 132 watts or 0.132 kW. Normal charge time is 2.5 hours for an average 10 mile ride. That’s for the 2 12v 12ah batteries connected in parallel for charging. Charge time can vary slightly depending on headwinds and load but hasn’t exceeded 3 hours. 3 hrs X 0.132 kW = 0.396 kW. 0.396 kW X $0.186/kW = $0.073 per charge in “fuel costs.” That’s $0.007/mile for a 10 mile ride. If gas is $2.75/gal, then 2.75/0.007 = 392.8, or the equivalent of 393 mpg. However that doesn’t factor in depreciation on the batteries. I paid $18 each for them. If they last 100 cycles, that’s $0.036/mile for the pair for each 10 mile ride. I can’t speak from bicycling experience about that many charges, but my Black & Decker battery-powered lawn mower has 2-12v SLAs that have at least 100 cycles on them, so that is not an unreasonable assumption. $2.75/(0.036+0.007) = 63.95 mpg equivalent. 200 cycles would give 110 mpg. Lithium batteries are reported to have a 1000 cycle life, so although they are more expensive to purchase new they may be a better long term purchase, in addition to being 60% lighter. BTW, my total conversion including SLA batteries, motor, racks, wires, etc added about 30 lbs to the 40 lb bike, so it’s nowhere near 300 lbs - jd
In theory there is no difference between theory and practice. But in practice, there is - Yogi Berra
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