Battery power VS DC motors

Kris Cardoen

Hi,
I would like to power 4 GHM-04 Lynxmotion Spur Gear Head Motors and controle them via Parallax HB-25 DC Motor Controller.
Is there a formula to know how much amps your battery pack should be able to provide to the motors?
the motor specs are:

- Voltage Operating Range: 6-7.2vdc (this is clear )
- Speed at Rated Load (1.0Kg-cm): 146 RPM+/- 10%
- No Load Current at 7.2vdc: < 221mA
- Current at Rated Load (1.0Kg-cm): < 556mA
I guess the more weight the more amps? correct?
Let's say that the robot has a weight of 7kg/using 4 motors, how much amps does the battery pack require?
Any help would be great
Regards,
Kris

photomankc

The load on the platform definately will relate to the current draw the specs I believe are giving you the current draw for a motor that is loaded to it's maximum rating. So figuring 4 of those motors you're looking at 2.25A if they are loaded to the maximum and about 1A if they are free running. So if you had a battery rated at 2.2 Amp/Hours (2200mAh) you could probably expect a bit less than 60 minutes run time if they are fully loaded and possibly a good deal more if you have something between. Somewhere I believe RobotShop has a calculator to help size your motors.

Of course this is all a gross generalization, duty cycle, speed of the platform in getting here-to-there, effienciecy of the drive components all come into play.