Bike Forums > More Watts or Volts = Faster Speed?
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 04-11-10, 03:20 PM #1 lildragon555 Member Thread Starter   Join Date: Jul 2009 Bikes: Posts: 28 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) More Watts or Volts = Faster Speed? Is it the number of Watts (ex: 1000 W) or Volts (ex: 36V) that determine how fast the electric motor can go up to?
 04-11-10, 03:36 PM #2 yopappamon Senior Member   Join Date: Mar 2010 Location: Tustin, CA Bikes: Posts: 206 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Watts = power More volts usually means more power until you let the smoke out. Watts = volts x amps, so they are directly proportional
 04-11-10, 04:02 PM #3 lildragon555 Member Thread Starter   Join Date: Jul 2009 Bikes: Posts: 28 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) ok thanks a bunch
04-11-10, 06:25 PM   #4
rscamp
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 Originally Posted by lildragon555 Is it the number of Watts (ex: 1000 W) or Volts (ex: 36V) that determine how fast the electric motor can go up to?
The unloaded RPM is the motor speed constant times the voltage. i.e. 80 RPM/V X 36V = 2880 RPM. The motor doesn't start to consume any significant electrical power or produce any mechanical power until it is loaded...

 04-11-10, 08:52 PM #5 morph999  Senior Member   Join Date: Jan 2009 Bikes: Posts: 499 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Also, bigger tire usually means faster speed on an electric bike. Smaller tires usually mean longer range. You can increase your range sometimes up to about 8 miles more just by going to a smaller tire. Like a 26" to a 20". There is a point at which if the tire is too big for the motor to spin easily then it can diminish your results. Going to a smaller tire though decreases your speed though. And going to a bigger tire will decrease your range so there is trade-offs.
 04-12-10, 07:33 AM #6 dumbass  Senior Member   Join Date: Jun 2008 Bikes: Posts: 415 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Morph.....your correct but only when speaking about a hub motor because you can not adjust for the ratio. Whereas, with a non-hub that is driving through the bikes gear system you have the best of all worlds. When you need torque or range you can gear down. When you need more speed you can gear up. Hey, that sounds just like riding a bike!
 04-12-10, 12:51 PM #7 Geekybiker E-Folder     Join Date: Feb 2010 Location: Chicagoland Bikes: Dahon Speed D7 Posts: 86 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Both- sort of on a hub motor Watts is like HP on a car. Ultimately it determines your top aero limited speed Volts works more or less like gearing to a hub motor. Winding out at too low of a speed, but have plenty of power? You need more volts. (Note no mechanical advantage of real gears. Amps work more or less like torque on a car. The more amps, the quicker off the line you are. Just like a car can make HP through RPM or Torque, a electric motor makes watts through volts or amps.
 04-12-10, 03:48 PM #8 lildragon555 Member Thread Starter   Join Date: Jul 2009 Bikes: Posts: 28 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Would 3 12 Volt 18 AH Batteries power a 1000W 36V Motor pulling around 35 amps?
04-12-10, 04:35 PM   #9
morph999
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 Originally Posted by lildragon555 Would 3 12 Volt 18 AH Batteries power a 1000W 36V Motor pulling around 35 amps?
Sure it would. A 36v 18AH SLA would be more like a 36v10AH lfepo4, though. You typically only get about 70 % of the usable capacity out of an SLA battery. You get about 95 % out of lifepo4.

 04-12-10, 05:04 PM #10 lildragon555 Member Thread Starter   Join Date: Jul 2009 Bikes: Posts: 28 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) How long would it last though?
 04-12-10, 05:15 PM #11 yopappamon Senior Member   Join Date: Mar 2010 Location: Tustin, CA Bikes: Posts: 206 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 18AH / 35A = .514hours = ~30.8 minutes The batteries would need at least a 2C rating to supply 35 amps.
 04-12-10, 05:35 PM #12 lildragon555 Member Thread Starter   Join Date: Jul 2009 Bikes: Posts: 28 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Ill just get this 35 AH one, cause I need at least an hour
 04-12-10, 09:02 PM #13 morph999  Senior Member   Join Date: Jan 2009 Bikes: Posts: 499 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) I recommend 36v of lifepo4 from here http://elitepowersolutions.com/produ...products_id=74 cost about \$360 + shipping which is usually about \$20. A better investment than SLA.
04-13-10, 11:22 AM   #14
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 Originally Posted by lildragon555 Ill just get this 35 AH one, cause I need at least an hour
How far you need to go is a better indicator than how long.

AH X Volts = Watt hours.

Most people don't seem to use more than about 22-23ish watt hours per mile from what I've seem (That's all motor, no pedal)

ebikes.ca has great page on choosing your battery.
http://www.ebikes.ca/batteries.shtml