The first thing you need to determine is the current drawn by the motor. The current drawn by the motor is directly related to the load on the motor.
If the motor draws 5 amps continously then for 1 hour of operation the batteries must be able to supply 5 amps for one hour. One of the specifications of batteries is there rating and this is in AH(amp-hours) Different chemistries of batterys have different AH, and the larger the physical size of any battery the larger the capacity in AH.