Philo's Lego 9V Technic Motor Comparison page shows that the 9V PF Train Motor has a no-load current of 90 mAH. The PF Medium Motor has a no-load current of 60 mAH, and the PF XL Motor has a no-load current of 80 mAH (both less than the PF Train Motor).
The STALLED CURRENT for the PF Train Motor is 1.3 Amps (higher than the PF Medium Motor's 850 mA, but less than the PF XL Motor's 1.8 Amps). NewBatteryGuy stated on his YouTube video description that a "250 mAh battery Lasted 1 Hr 20 Min at speed 2. Over 30 Mins at full speed. So, one could conclude that since the PF Train Motor draws more current than the PF Medium motor, that one could run a PF Medium Motor for WELL OVER 30 minutes.
I know that 30 minutes is not a long time, but how many minutes do you actually "play" with your MOC? 5 minutes? Think of all of the small PF cars one could make if the battery were small....
Edited by DLuders, 11 December 2011 - 02:29 PM.