Voltage vs runtime ?
 

Hi !


I have a slash 4x4 with an feigao 9l motor runing on 3s lipo and i think i'm getting about 30min+ of runtime/pack geared 18/54. and i'd like to know how much more runtime i would get if i stepup to 4 and gear fore the same speed as i have now with 3s ? And if i would use a 6s lipo and gear for the same speed how mutch smaller batttery can i use ? if i whant the same runtime as a 3s 5000mah pack ?

You are using power (Watts) which is Volts x Amps. The power used over a period of time is the energy (Watt-hours, or W·h). You want to know the energy a particular pack will provide, so multiply its Volts x Amp-hours to get Watt-hours. A 3s 5000mAh pack is 11.1V and 5.0Amp-hours, so 55.5 W·h. A 6s pack (double the voltage) would need to have a capacity of 2500mAh (half the capacity) to give you the same amount of energy.

If you where to use 6s I hope you realize you would also need a different motor. That feigao 9L surely wouldn't last long spinning that fast. If you where to do that save up and get a quality motor that is more efficient, that will also help your runtime

Indeed, the feigaos work best in the 30-40,000rpm range- if you used a 9L on 6s lipo and geared down that much it would overheat due to undergearing ( not enough load on the motor ). 4s sounds fine though, but for 6s you'd want a much slower motor & gear for the same speed- should be able to use a smaller batt as a result due to increased effociency to get the same runtime as before ( or use the same sized lipo as before mah wise & get more runtime ).