title_body: Does the RC transmitter control power consumption? This might be a little off topic, please be understanding.
  In case of an RC car toy (specifically, for children) you can control the speed of the car via the transmitter. I am wondering, if I were to customize the transmitter and limit the maximum speed of the car, let's say, to half of the original, do I (or the kids) get to enjoy playing for double the time with the same batteries?
  (for the sake of simplicity, let's say that the throttle on the customized transmitter can only be pushed half way)
  So does the transmitter control the power consumption of the RC car, or it's only a torque to rpm conversion?
  Cheers,
  John
upvoted_answer: Yes, sort-of.
  The speed controller switches the motor on and off in very rapid pulses, and the width of these pulses (and the width of the 'off' period) is controlled by the throttle. It's so fast that the motor just sees it as a varying voltage.
  So if you cut a piece of card and stuck it on the transmitter to prevent full throttle being used, the speed controller would only run the motor at partial power. The car would accelerate more slowly, have a lower top speed and the battery should last longer. It should break less when you crash too.
  However, voltage supplied to the motor is only part of the story. The current drawn from the battery is what's actually important, as battery capacity is measured in Amp-Hours (i.e. a 1AH battery can supply 1 amp for an hour, or 2 amps for half an hour, etc). The current decreases as the motor speed increases. A motor running at full throttle with no load will spin quickly but draw little current but the same motor struggling through grass will be running more slowly and drawing more power.
  So if you want longer run time, drive on a smoother, lower-grip surface or change gear ratio to a lower gear so the motor can reach its top speed with less power. Or buy some extra batteries...