so i've read on my dc motor's datasheet that it can take 6v-18v, but recommended 12v. am i able to use the 6v battery to run the motor?, i assume this will drain the battery fast, but its rechargeble. If i do supply a 12v motor with 6V batteries, does it lower the torque of the motor?, if so how much?
eg. 12kg/cm motor torque for recommended 12v, does 6v reduce it down to 6kg/cm torque? or maybe the relationship is not linear.
Thanks for reading my post.
If you run the motor on 6v then its no-load speed will be about half what it would be at 12v, and its stall torque will be about half what it would be at 12v. [EDIT: I am assuming a permanent-magnet motor.]
Bear in mind that if you plan to control the motor from an Arduino, the control device you use between the battery and the motor may have a significant voltage drop, so the motor will get even less than 6v. The voltage drop is negligible using a mechanical relay, generally very small using a mosfet or mosfet-based h-bridge, and substantial using a darlington or an h-bridge based on darlingtons.
For an ideal permanent-magnet DC motor the voltage controls the speed and the torque controls the current. Real motors aren't ideal - as you increase the load the resistance of the windings causes IR losses and the voltage drop means the speed decreases from the ideal. The working torque will probably be the same as this is limited by the current in the windings and the thermal considerations. For really low supply voltages the stall torque will be less then the normal working torque at the nominal voltage.
Good motors come with datasheets that show the current and torque curve for the motor.
BTW for a series- or shunt-wound motor with field windings ignore the above.